Synthetic auxotrophy reveals metabolic regulation of plasma cell generation, affinity maturation, and cytokine receptor signaling
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The authors addressed a significant biological question, namely the role of glutamine metabolism in humoral responses, and they obtained solid conclusions. The strength of this study is that the authors used state-of-the-art transgenic mouse models together with in vitro analysis, thereby providing important insights into the question posed. The manuscript has been further substantiated by adding more appropriate experimental controls and describing more in-depth functionality/physiological relevance.
https://doi.org/10.7554/eLife.107627.3.sa0Important: Findings that have theoretical or practical implications beyond a single subfield
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Abstract
The proliferation and development of activated B lymphocytes into antibody (Ab)-secreting plasma cells are critical determinants of humoral immunity and sustain certain autoimmune diseases. Specific pathways and substrate supplies in intermediary metabolism influence lymphocyte differentiation and function. We now show that although stringent restriction of glutamine supply decreases B cell proliferation and differentiation into plasma cells, glutaminolysis – a major metabolic use of this amino acid – was only conditionally crucial in B cells and the Ab responses derived from them. Gls, the gene encoding the main glutaminase of lymphocytes, promoted anti-NP Ab responses at the primary and recall phases if either glucose uptake into mouse B cells or pyruvate into their mitochondria was also impaired. Otherwise, it was dispensable. This synthetic auxotrophy, that is, the conditional requirement of glutaminase for processes in addition to survival, involved supporting progressive expansion of mitochondrial respiration followed by plasma cell differentiation. Surprisingly, impairment of glutaminase and the mitochondrial pyruvate channel decreased IL-21 stimulation of STAT3 phosphorylation as well as interferon stimulation of STAT1 activation. Together, our findings establish a powerful collaboration of metabolic pathways in programming increased respiration and the development of Ab-secreting cells, but also reveal modulation of cytokine receptor signaling by metabolism.
Introduction
Circulating antibodies (Ab) are crucial mediators of protection against potentially pathogenic microbes, but Ab also can cause tissue damage or cellular dysfunction (Geyer et al., 2021; McGettigan and Debes, 2021; Olsen and Karp, 2014; Suurmond and Diamond, 2015; Tsokos et al., 2016). In both adaptive and pathological settings, Ab functions depend on their heavy chain class, affinity, and concentration (reviewed in Rajewsky, 1996; Lu et al., 2018; Alemán and Rosales, 2023). Increased affinity after initial and repeated immunizations can be selected in several ways, one of which involves processes that occur in the microanatomy of germinal centers (also known as secondary follicles; reviewed in Boothby et al., 2019; Elsner and Shlomchik, 2020; Victora and Nussenzweig, 2022). Progeny cells that survive a gauntlet of programmed death in selecting for continued clonal proliferation ultimately can generate either memory B cells (MBCs) or an end-stage descendant of the B lineage, the plasma cell (PC) (Victora and Nussenzweig, 2022; Good-Jacobson and Shlomchik, 2010; Adachi et al., 2015; Leach et al., 2019; Inoue and Kurosaki, 2024). The magnitude of PC output (the numbers generated after B cell activation) and their rates of immunoglobulin secretion (Inoue and Kurosaki, 2024; Ise and Kurosaki, 2019; Eyer et al., 2017; Eyer et al., 2020) determine the net output and steady-state concentrations of Ab. Accordingly, understanding mechanisms that regulate the qualities or quantities of Ab, and that reduce or enhance the efficiency of generating PC, are important goals.
To elicit protective Ab, immune exposures such as vaccination activate B cell proliferation, and some progeny of such activated B cells develop into Ab-secreting PC (Shapiro-Shelef and Calame, 2005; Robinson et al., 2020; Bhattacharya, 2022). Specificity is fostered by a reliance on signal initiation through the BCR, the clonal Ag receptor on mature B lymphocytes (Paus et al., 2006; Phan et al., 2006; Benson et al., 2007). The capacity to be activated, survival efficiency, rates of proliferation, and propensity to yield GC B cells or PC depend on an array of other signal-initiating receptors, among them CD19, co-stimulators such as CD40 (reviewed in Elgueta et al., 2009; Rathmell et al., 1996), the death receptor Fas (Rathmell et al., 1996), pattern recognition receptors in the TLR family (Eckl-Dorna and Batista, 2009; reviewed in Celhar et al., 2012; Fillatreau et al., 2021), and cytokine receptors (King and Mohrs, 2009; Pignarre et al., 2021; Duan et al., 2021; Ozaki et al., 2002; Ettinger et al., 2005). One consequence of activation is that B lymphoblasts dramatically increase expression of an array of nutrient transporters that include those for amino acids and for glucose (Caro-Maldonado et al., 2014; Cho et al., 2016; reviewed in Boothby et al., 2022). Beyond this general picture, however, the effects or outputs of receptors likely are scalar and conditional, that is dependent on other signals. For instance, antigen with a high affinity and high valency of the BCR epitope signals differently from a monovalent, lower-affinity antigen (Kurosaki, 1999; Marshall et al., 2000; Puffer et al., 2007; Mukherjee et al., 2013; Pone et al., 2022; Kato et al., 2020, reviewed in Kwak et al., 2019), and may influence generation of PC. Moreover, increased expression of TLR7 or type 1 interferon (IFN) receptor stimulation each reduces the capacity of B cells to maintain self-tolerance (Banchereau and Pascual, 2006; Green and Marshak-Rothstein, 2011; Hamilton et al., 2017; Domeier et al., 2018), presumably involving changes in the quantitative balance among signal transducers and transcription factors. At a later stage, the IL-21 receptor is crucial for PC differentiation (Ozaki et al., 2002). Moreover, IL-21 has recently been reported to promote affinity maturation of GC-derived PC (MacLean et al., 2025). Little is known about the relationships between signal strength and metabolism. In vitro experiments showed that hypoxia or genetically mediated stabilization of hypoxia-inducible transcription factors (HIFs) blunted activation-induced increases in amino acid uptake and transporter gene expression as well as GC and Ab responses (Cho et al., 2016; Li et al., 2021). However, it remains unclear if metabolism can modulate signaling.
Nonetheless, a substantial and increasing body of evidence indicates that nutrient supply, uptake, and intermediary metabolism influence the properties of adaptive immunity, in part by their effects on differentiation and function of cells that mediate host responses (reviewed in Pignarre et al., 2021; Edinger, 2007; Johnson et al., 2016; Ripperger and Bhattacharya, 2021). The bulk of evidence is from analyses of the differentiation and functions of T cells, macrophages, and dendritic cells and documents condition and cell type specificity of findings. Nonetheless, several analyses point to important effects on B cells as well. In addition to a function during B cell development, expression of the glucose transporter (GLUT)1 on mature B cells supported the initial GC size, the Ag-specific Ab responses derived from B cells, and affinity maturation (Caro-Maldonado et al., 2014; Brookens et al., 2024; Bierling et al., 2024).
Among nutrients, only the distribution and sufficiency of oxygen are readily measured, but such analyses consistently reveal evidence of functional hypoxia in follicles, most accentuated in GC (Cho et al., 2016; Li et al., 2021; Jellusova et al., 2017; Nakagawa et al., 2024). Consistent with and potentially as a result of the hypoxia, GC B cells can exhibit higher rates of glucose uptake with several-fold increased glucose oxidation as well as utilization in the pentose phosphate pathway (Cho et al., 2016; Brookens et al., 2024; Bierling et al., 2024; Jellusova et al., 2017). Moreover, the ability to feed intermediates into one-carbon metabolism via increased expression of the enzyme phosphoglycerate dehydrogenase was reported to be crucial for germinal center size and normal degrees of high-affinity antibody production (D’Avola et al., 2022). Cell-type- and stage-specific inactivation of Slc2a1, the gene that encodes GLUT1, indicates that the increased glucose uptake is crucial for both GC homeostasis and the capacity of B cells to yield antibody-secreting PC (Brookens et al., 2024; Bierling et al., 2024). Metabolomic analyses suggested that increases in anaplerotic conversion and usage of amino acids may be evoked in GLUT1-deficient B cells as a potential compensatory mechanism (Bierling et al., 2024). In parallel, however, a remarkable degree of metabolic flexibility was suggested by the in vitro finding that although glucose is essential for PC development and Ab production in the absence of other hexoses, mannose, and galactose together could substitute for glucose (Brookens et al., 2024). Thus, the reduced influx and availability of glucose reduced Ab responses and affinity maturation, but the decrease in these outputs fell short of what likely could be therapeutically meaningful. Moreover, the importance of feeding the increase in B cell-intrinsic generation of serine with diversion of 3-phosphoglycerate away from generating pyruvate raised the question whether the capacity of mitochondria to use this latter metabolite was important in promoting greater quality and quantity of Ab after immunization.
To explore these issues, we used both immunizations and in vitro analyses that leveraged genetic and pharmacological approaches to test the importance of glutaminolysis – on its own or in combination with a second pathway – in Ab responses. Glutamine concentrations in vitro were found to be crucial for class switching as well as PC and Ab production, and B cell type-restricted inactivation of the Gls gene, which encodes the glutaminase expressed in post-natal cells outside the liver, impaired the response to ovalbumin in one immunization model. Surprisingly, however, the anti-NP response in a hapten-carrier model was unaffected. However, a synergistic impact resulted when GLS depletion was combined with targeted loss of function for either GLUT1 (Slc2a1) or an essential subunit of a mitochondrial pyruvate import carrier (Mpc2) (Zangari et al., 2020; Lam et al., 2016). Thus, glutaminolysis promoted the anti-NP response only if glucose intake or pyruvate flux was impaired, revealing one limit imposed on the metabolic flexibility of B cells in their mediation of Ab responses. The combined restriction of two pathways that feed mitochondrial metabolism represented what can be termed ‘synthetic auxotrophy’ rather than synthetic lethality (Farmer et al., 2005; O’Neil et al., 2017), in that effects on differentiation were observed beyond the impacts on death or proliferation. Gene expression signatures in GC B cells highlighted a requirement for GLS in metabolic reprogramming, that is both amplification of glucose-stimulated proton secretion and a major increase in mitochondrial respiration between the first and second days after B cell activation. Surprisingly, MPC2 and GLS were found to promote not only IL-21-stimulated STAT3 activation but also an IFN response signature in addition to promoting increased respiration. Together, the results reveal that an interplay between two metabolic pathways unexpectedly converged on programming not only IL-21R activation of STAT3, PC differentiation, and high-affinity Ab responses, but also the tyrosyl and serine phosphorylation of STAT1 induced by type 1 and type 2 IFNs. These findings have important implications for diseases, such as systemic lupus erythematosus (SLE), in which B cells and their response to IFN are crucial elements of pathogenesis.
Results
Alpha-ketoglutarate can alter threshold glutamine concentration requirements for B cell responses
B lymphoblasts subjected to persistent stabilization of the HIFs took up amino acids at lower rates in vitro and exhibited decreased mTORC1 activity (Cho et al., 2016). mTORC1 promotes Ab class switching by a mechanism beyond effects on the rate of proliferation (Cho et al., 2016; Raybuck et al., 2018; Jones et al., 2016), and extracellular glutamine influences class switch recombination in B cells through a mechanism involving the action of mTORC1 on proteins regulating translation (Chiu et al., 2019). Other work has provided evidence that plasmablasts developing in the setting of plasmodial infection are glutamine avid (Vijay et al., 2020). The admixture of red and white pulp in spleen precludes accurate measurement of amino acid concentrations surrounding B cells in lymphoid follicles. Instead, we adapted a technique used for tumor masses (Haslene-Hox et al., 2011; Sugiura et al., 2022) to measure glutamine in the fluid eluted from transected lymph nodes, revealing a strikingly lower concentration than in plasma (Figure 1a). This apparent glutamine gradient was not a universal feature of the lymph node, in that neither leucine nor pyruvate differed substantially between plasma and interstitium (Figure 1a). To test the dependence of B cells on extracellular glutamine concentration in vitro, and to align with later immunization experiments in which IgG1 is conventionally used as the main readout for isotype-switched Ab responses, we measured both class switching and PC differentiation. Titrations of glutamine in media showed that proliferation, PC differentiation, and the Ab class switch to IgG1 were impaired (Figure 1b and c; Figure 1—figure supplement 1a–c). Although not pursued herein, it is intriguing that some aspects of the immune microenvironment appear to support robust switching and PC generation at a glutamine level that would be insufficient in vitro, suggesting that the required concentration is affected by the signals or nutrients in vivo.
Glutamine and glutaminolysis promote antibody response to ovalbumin.
(a) Reduced glutamine concentration in LN relative to the bloodstream. Shown are the results from measuring concentrations of glutamine, leucine, and pyruvate in the centrifugal eluates (Haslene-Hox et al., 2011; Sugiura et al., 2022) of lymph nodes or plasma of mice (n=3), as described in the Materials and methods. (b, c) B cells from WT B6 mice were activated and cultured together with anti-IgM, BAFF, IL4, and IL5 in the presence of the indicated concentrations of Gln. Shown are the mean (± SEM) frequencies of CD138+ B220lo PC (b) and IgG1+ B cells (c) after culture for 5 days. (d, e) Effects of cell-permeable α-ketoglutarate precursor, dimethyl-α-ketoglutarate (DMK), on the impaired PC differentiation and IgG class switching caused by Gln restriction. CellTrace Violet-labeled B cells were activated and cultured as in (b), with the addition of supplemental DMK as indicated. Shown are mean (± SEM) frequencies of % CD138+ (d) and IgG1+ B cells (e) within each division-counted peak. (b–e) Results aggregated from three biological replicate experiments. p-Values were calculated by Mann-Whitney U test. *p<0.05. Related data are presented in supplement 1 to this Figure. (f–k) An anti-ovalbumin Ab response is promoted by B cell expression of GLS. (f) Schematic of the immunization with priming and sensitization of tamoxifen-treated mice of the indicated genotypes [huCD20-CreERT2+ and either Gls +/+ (WT) or Gls f/f], followed at week 3 by challenges with intranasal instillations of sterile ovalbumin solution. (g) Mediastinal LN were collected from harvested mice and the frequencies of IgG1+ events in the GL7+ CD95+ B cell gate were measured by flow cytometry. Each dot represents an individual mouse, with bars denoting the mean values. (h–k) Single-cell suspensions of lung and bone marrow were analyzed by ELISpot assays with ovalbumin-coated filters to capture secreted Ag-specific Ab detected using anti-mouse IgG1. Shown are (h) representative wells from the indicated sources (organ; genotype of B cells) and aggregated frequencies of anti-ova IgG1+ ASCs in lung (i) and marrow (j). (k) Anti-ova IgG1 in sera of the mice with B cell-restricted depletion of GLS (GlsΔΔ) or controls, as indicated. Shown are data from ELISA with serial fourfold dilutions using individual samples from each mouse. The likelihood of each null hypothesis (no true difference between two samples) was calculated as noted in the Materials and methods (two-tailed and non-parametric testing where conditions not met for Student’s t-test). *p<0.05, **p<0.01, *** p<0.001, ****p<0.0001.
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Figure 1—source data 1
sRaw numbers or other primary info used in preparation of figure panels.
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Figure 1—source data 2
Calculation modes for use of proton NMR to measure indicated metabolites.
- https://cdn.elifesciences.org/articles/107627/elife-107627-fig1-data2-v1.zip
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Figure 1—source data 3
Excel file as source data with raw numbers used in preparation of the graphs in Figure 1d.
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Figure 1—source data 4
Excel file as source data with raw numbers used in preparation of the graphs in Figure 1d.
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Figure 1—source data 5
Excel file as source data with raw numbers used in preparation of the graphs in Figure 1d.
- https://cdn.elifesciences.org/articles/107627/elife-107627-fig1-data5-v1.xlsx
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Figure 1—source data 6
Excel file as source data with raw numbers used in preparation of the graphs in Figure 1e.
- https://cdn.elifesciences.org/articles/107627/elife-107627-fig1-data6-v1.xlsx
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Figure 1—source data 7
Files with data used for panels g-j of Figure 1.
- https://cdn.elifesciences.org/articles/107627/elife-107627-fig1-data7-v1.zip
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Figure 1—source data 8
Files with data used for graph of Figure 1k with anti-ova IgG1.
- https://cdn.elifesciences.org/articles/107627/elife-107627-fig1-data8-v1.zip
Among uses of glutamine after its uptake into cells, glutaminolysis is the first step in generation of α-ketoglutarate (αKG) from the amino acid for usage in the Krebs (TCA) cycle (Altman et al., 2016). To screen whether this process might be of functional significance in the molecular regulation of the class-switch or PC differentiation, and to test if the observed effects were purely division-related, we used dye partitioning combined with additions of dimethyl-ketoglutarate (DMK) in vitro. This cell-permeable molecule can bypass glutaminolysis yet supply αKG. The glutamine requirement for switching to IgG1 was almost completely substituted by DMK (Figure 1d; Figure 1—figure supplement 1b). Moreover, development of CD138+ cells involved a process beyond just the proliferative effect, in that the %CD138+ was lowered by glutamine restriction for multiply-divided cells (division peaks 5, 6, and 7; Figure 1d). Interestingly, DMK in the same cultures as used to score switching to IgG1 effected a definite but incomplete reversion of the glutamine requirement in both division rates and in frequencies of switching and differentiation at equal division numbers (Figure 1d; Figure 1—figure supplement 1b–g). These findings suggest that although other mechanisms likely also apply, B lymphoblasts need glutaminolysis to supply sufficient αKG to the B lymphoblasts.
Glutaminolysis in B cells promotes an anti-ovalbumin Ab response
Glutamine can be taken up via many distinct transporters, and reduction in one can be compensated by increases in others (Sugiura et al., 2022). However, the in vitro data supported testing to what extent immunization-induced Ab responses are affected by glutaminolysis. To bypass potential developmental effects in the B lineage as well as the complex roles of glutamine in T cells and other cell types (Klysz et al., 2015; Liu et al., 2017; Johnson et al., 2018), we introgressed a transgene that encodes B lineage-specific expression of a chemically activated recombinase onto a Gls f/f background (Johnson et al., 2018; Khalil et al., 2012). Inactivation of the Gls gene in mature B cells (Figure 1f; Figure 1—figure supplement 2a, b) and their descendants, hereafter termed GlsΔΔ, by deletion of a segment flanked by loxP sites, could then be initiated at different times after establishment of a normal pre-immune B lineage. Mice (all huCD20-CreERT2+/-, and Gls+/+ or f/f) in which tamoxifen was administered prior to immunization were sensitized to ovalbumin followed by antigen (Ag) challenge in the airways. Lack of GLS (Figure 1—figure supplement 2a, b) led to reduced class-switched GC B cells in lymph nodes draining the lung (Figure 1g) as well as the populations of ovalbumin-specific Ab-secreting cells (ASCs) in the lung and bone marrow (Figure 1h–j). In line with these data, anti-ovalbumin IgG1 and IgM concentrations in sera of B-specific GlsΔΔ mice were ~0.25 x those of CreERT2 controls (Figure 1k; Figure 1—figure supplement 2c). We conclude that in these experimental conditions, glutaminolysis within B cells promoted the development of Ag-specific ASCs and an anti-protein Ab response.
Glutaminolysis is mostly dispensable for anti-NP responses yet synergizes with other metabolic needs
Mitochondrial oxidative metabolism appears to promote affinity maturation in the classic hapten-carrier model of an Ab response specific for nitrophenolic (NP) adducts (Chen et al., 2021; Urbanczyk et al., 2022; Yazicioglu et al., 2023). In contrast to the impact of Gls inactivation on an anti-protein response after ovalbumin inhalation (Figures 1 and 2a-c), the anti-NP Ab response and affinity maturation were unaffected (Figure 2a and d–i). Notably, however, B cell-specific inactivation of Gls synergized with loss of GLUT1. Thus, combining inducible B cell-specific gene targeting that restricted glucose import into B cells (Caro-Maldonado et al., 2014; Brookens et al., 2024; Bierling et al., 2024) with GLS depletion caused dramatically greater decreases in anti-Ova and anti-NP ASCs than iB inactivation of Slc2a1 alone (Figure 2b–i). Combined Gls and Slc2a1 inactivation had a relatively modest impact on IgM anti-NP compared to samples with Slc2a1ΔΔ B cells (Figure 2g). In contrast, a synergism was evident in the effects on circulating Ag-specific IgG1, for which B-specific inactivation of both Gls and Slc2a1 dramatically compromised the humoral response, whereas GLUT1 depletion reduced anti-NP Ab to 1/2 - 1/4 levels of WT controls and a single loss-of-function mutation for Gls had no effect (Figure 2g–i). The synergism was most striking for high-affinity IgG1 (Figure 2i), though it also impacted all-affinity IgG1 (Figure 2h). The modes of eliciting Ab responses differed for ovalbumin- and NP-specific B cells, but the data indicate that the need for glutaminolysis depended on Ag and immunization. Even for the anti-NP response, glutaminolysis within the B cells was important for their function if glucose import was restricted.
Glutaminolysis only conditionally supports the anti-NP Ab response.
(a) Schematic of the immunization with priming sensitization and inhaled challenge of tamoxifen-treated mice of the indicated genotypes [huCD20-CreERT2+ and the indicated combinations of either Gls +/+ (WT) or Gls f/f and either Slc2a1 +/+ (WT) or Slc2a1 f/f], followed at week three by challenges with intranasal instillations of sterile ovalbumin solution. (b–f) ELISpot analyses of cells secreting IgG1 anti-ovalbumin (b, c) and anti-NP (d-f) Ab in mice of the indicated genotypes. Shown are counts from the lung suspensions (b), bone marrow (c, d, f), and spleens (d, e) from each individual mouse, with means (± SEMs) for the aggregate data denoted as bar graphs. (d) Representative ELISpot wells scoring the frequencies of IgG1 anti-NP Ab-secreting cells in spleen and marrow of mice whose B cells were converted to the indicated genotypes [wildtype (
), GlsΔ/Δ (
), Slc2a1Δ/Δ (
), and GlsΔ/Δ Slc2a1Δ/Δ (
)] after immunization and rechallenge. (e, f) Aggregate data with ASC counts for IgG1 anti-NP-secreting cells in spleen (e) and marrow (f). Data were pooled from two independent experiments (seven wildtype, six GlsΔ/Δ, four Slc2a1Δ/Δ, and six GlsΔ/Δ Slc2a1Δ/Δ mice). * p<0.05, ** p<0.01, *** p<0.001 (Mann-Whitney U test).(g–i). Shown are the mean (± SEM) absorbances of aggregated results of ELISA analyses of the IgM (g) and IgG1 (h, i) responses in the immunized mice of the two independent experiments, comparing all-affinity (h) to high-affinity (i) anti-NP, using serial threefold or fourfold dilutions when detecting IgM and IgG1, respectively.
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Figure 2—source data 1
One tranche of a collection of data files used in preparation of Figure 2 (split due to size limits).
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Figure 2—source data 2
Second tranche of a collection of data files used in preparation of Figure 2 (split due to size limits).
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Figure 2—source data 3
Excel files with numerical data used in preparing graphs of Figure 2.
- https://cdn.elifesciences.org/articles/107627/elife-107627-fig2-data3-v1.xlsx
Glucose oxidation rates are several-fold higher in GC B cells than in their naive counterparts (Brookens et al., 2024). However, the effects of eliminating GLUT1 on a GLS-deficient background could be due to glucose usage in serine generation (D’Avola et al., 2022), the pentose phosphate pathway (Brookens et al., 2024), or glycosylation (Lam et al., 2016) rather than from reduced pyruvate flow into mitochondrial metabolism. Directly to interfere with pyruvate import into mitochondria for generation of acetyl-CoA, we used a previously characterized allele for inducible inactivation of Mpc2, a gene encoding an essential subunit of the mitochondrial pyruvate channel (Figure 3a; Zangari et al., 2020; Lam et al., 2016). Although IgG1 is conventionally a primary read-out, it is established that these immunizations can elicit IgG2c. This paralogue of human IgG1 can play particularly salient roles in control of pathogens and in auto-Ab-mediated organ damage during auto-immunity (Cunningham et al., 2007; Rubtsova et al., 2013; Luan et al., 2026). Levels of class-switched anti-NP antibodies in sera after the second immunization were modestly reduced after inducible Mpc2 targeting in B cells (Figure 3b; Figure 3—figure supplement 1a), as were the concentrations of anti-NP Ab after the boost and the ratio of high- to all-affinity Ab (Figure 3c; Figure 3—figure supplement 1b, c), one aspect of affinity maturation. Whereas GLS depletion had no effect on its own, the combined loss-of-function synergized and dramatically reduced Ag-specific IgM (Figure 3—figure supplement 1b) and several switched isotypes (Figure 3b and c; Figure 3—figure supplement 1a). The capacity to produce a spectrum of Ab with higher affinities after secondary immunization was reduced further (Figure 3c–e), and high-affinity IgG2c anti-NP in mice with doubly deficient B cells was ~0.02 x controls, while the all-affinity was ~1/8th of the control values (Figure 3—figure supplement 1a). The disruption of glutaminolysis in B cells reduced their capacity to yield anti-NP IgG1 prior to secondary immunization ("boost"), an impact most striking for high-affinity Abs (Figure 3d and e; Figure 3—figure supplement 1d, e). Moreover, compound loss of function yielded dramatically fewer cells secreting high-affinity anti-NP Ab (Figure 3f; Figure 3—figure supplement 2a, b). Consistent with decreased proliferation in vivo (Figure 3—figure supplement 2c), GC-phenotype B cells (GCB) were reduced as well (~1/2 control numbers) (Figure 3—figure supplement 2d, supplement 3). In contrast to our findings with conditional targeting of Slc2a1 in B cells, in which a substantial degree of counterselection was evident (Brookens et al., 2024), the mRNA encoding both Gls and Mpc2 were far lower in flow-sorted GC B cells (Figure 3—figure supplement 2e, f). Although the magnitude of overall decrease in GC B cells was modest and probably less than the underrepresentation of ASCs producing anti-NP Ab (Figure 3f), the frequencies of NP-binding GC B cells were lower when Gls was disrupted (Figure 3—figure supplement 3e). Although the genetic impact on cellular metabolism was restricted to B cells, substantial decreases were measured for CD4+ T cells of Tfh- or GC-Tfh-phenotype (Figure 3—figure supplement 4a, b). We conclude that glutaminolysis in B cells promotes GC B cell numbers, function, as well as affinity maturation, the production of Ag-specific ASCs, and levels of Ag-specific Ab.
Synthetic auxotrophy – glutaminase support of anti-NP response is dependent on mitochondrial pyruvate channel subunit 2.
(a) Schematic of the immunization with priming and a recall boost of mice of the indicated genotypes [huCD20-CreERT2+ and the indicated combinations of either Gls +/+ (WT) or Gls f/f and either Mpc2 +/+ (WT) or Mpc2 f/f], treated with tamoxifen prior to the initial immunization. (b, c) Results of serological analyses performed on sera from the time of harvest. Shown are the mean (± SEM) absorbances measured in ELISA for detection of all- and high-affinity Abs (α-NP20 and α-NP2, respectively) of the IgG1 (b) and the relative strengths of affinity maturation (c). Impacts of altered metabolic pathways in B cells on relative extents of affinity maturation in the recall responses are shown as mean ratios of absorbances for high- (NP2) / all-affinity (NP20) ELISA at two serum dilutions for the IgG1 isotype. The analogous serologic measurements of IgM and IgG2c anti-NP Ab are shown in Figure 3—figure supplement 1. (d, e) Altered glutaminolysis and pyruvate import collaborate in support of the response to primary immunization as well as the Ab after a secondary immunization ('boost'). All- and high-affinity anti-NP IgG1 was measured in the sera of mice whose B cells were converted to the indicated genotypes by tamoxifen injections and then immunized as in (a). Shown are mean (± SEM) absorbances for (d) all- (αNP20) and high- (αNP2) IgG1 at a single dilution of sera before ('Pre-Boost') and a week after ('Boost') the second immunization. Data represent three temporally distinct cohorts, each including two mice of each of the four genotypes. Probabilities of the null hypothesis applying (P values) for differences in pairwise comparisons are indicated. (f) Shown are mean (± SEM) frequencies of splenocytes producing IgG1 anti-NP Ab of the indicated affinities at harvest after the booster immunization as in (a), with genotypes as shown and each dot representing an individual mouse. Data on IgG2c and IgM isotypes are presented in Figure 3—figure supplement 2. (b–f) Results are aggregated from four temporally separate immunization experiments with mice of each genotype, totaling eight individual controls [(WT, i.e. only CreERT2+) (
)] and eight mice with each type of induced B cell type-specific deletion [GlsΔ/Δ (
), Mpc2Δ/Δ (
), and GlsΔ/Δ Mpc2Δ/Δ (
) genotypes]. Related and additional results – affinity maturation (NP2/NP20 ratios), frequencies of GC B cells and the NP-binding population therein, MBCs, BrdU uptake rates in GC B cells, as well as Gls and Mpc2 mRNA – are presented in Figure 3—figure supplements 1–3. (g, h) Functional requirements for GLS and MPC2 in B cells in a recall phase after secondary immunization. (g) Schematic of the priming immunization without deletion of the conditional alleles, followed by tamoxifen injections ~3 weeks later, and only then a recall boost of mice of the indicated genotypes [huCD20-CreERT2+ and the indicated combinations of either Gls +/+ (WT) or Gls f/f and either Mpc2 +/+ (WT) or Mpc2 f/f]. (h) Shown are serologies of the all- and high-affinity IgG1 anti-NP Ab elicited by a boost when Cre activation was initiated only after the primary response. Results are aggregated from three temporally separate immunization experiments with mice of each genotype, totaling nine individual controls [(WT, i.e. only CreERT2+) (
)] and nine mice with each type of induced B cell-specific deletion [GlsΔ/Δ (
), Mpc2Δ/Δ (
), and GlsΔ/Δ Mpc2Δ/Δ (
) genotypes]. Figure 3—figure supplements 4 and 5 show additional results, with IgM, IgG2c, and IgA isotypes; frequencies of ASCs, total and NP-binding GC B cells as well as Tfh / GC-Tfh cells.
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Figure 3—source data 1
Excel file with the numerical data from ELISA measurements used to graph Figure 3b.
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Figure 3—source data 2
Excel file with the numerical data used to graph Figure 3c based on ratios of values in ELISA measurements.
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Figure 3—source data 3
Excel file with the numerical data from ELISA measurements used to plot dots in Figure 3d.
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Figure 3—source data 4
Excel file with the numerical data from ELISA measurements used to plot dots in Figure 3e.
- https://cdn.elifesciences.org/articles/107627/elife-107627-fig3-data4-v1.xlsx
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Figure 3—source data 5
Excel file with the numerical data from ELISpot measurements used to plot Figure 3f.
- https://cdn.elifesciences.org/articles/107627/elife-107627-fig3-data5-v1.xlsx
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Figure 3—source data 6
Excel file with the numerical data from ELISA measurements used to plot dots in Figure 3.
- https://cdn.elifesciences.org/articles/107627/elife-107627-fig3-data6-v1.xlsx
We next tested how these losses of function impact a recall process by delaying tamoxifen treatments until several weeks after the priming immunization, with the initiation of deletion followed by the second immunization and harvest (Figure 3g). In this setting where the primary response from a pre-immune repertoire was unperturbed, we once again observed that Gls gene inactivation reduced Ab responses primarily when Mpc2 also was disrupted (Figure 3h; Figure 3—figure supplement 4c–e). High-affinity anti-NP Ab of several switched isotypes were drastically reduced: IgG1 to <1/4 of control values (Figure 3h), with IgG2c and IgA almost undetectable (Figure 3—figure supplement 4c–e). Moreover, frequencies of anti-NP ASCs among splenocytes were lower (Figure 3—figure supplement 5a–f). Since high-affinity, class-switched (IgG or IgA) Ab are undetectable 1 week after a primary immunization, we infer from these results that the rapid generation of the ASCs producing these Ab required glutaminolysis and pyruvate import. The splenic ASC pool and high-affinity IgG anti-NP Ab in sera 7 d after a recall challenge can arise from two main sources. Ag-specific MBC can rapidly differentiate into PC without need GC re-entry (Mesin et al., 2020; Kometani et al., 2013). Some GC B cells in persisting follicles may receive additional Ag exposure after secondary immunization, despite the Ab-specific Ab (Mesin et al., 2026). In several models, however, re-activation of MBCs that directly differentiated into PCs after the second immunization was the primary source of the Ab (Leach et al., 2019; Schiepers et al., 2024; Wong et al., 2020; reviewed in Victora and Nussenzweig, 2022; Inoue and Kurosaki, 2024). Nonetheless, some of the effects of GLS and the MPC on Ab levels and ASC generation in these experiments with delayed gene inactivation may be due to impairment within the GC B cells. Irrespective of this latter possibility, the findings reveal a B cell-intrinsic process that acts well after an initial priming immunization and promote both affinity selection and differentiation toward a PC fate through the collaboration of pyruvate influx rate and glutaminolysis.
Synthetic auxotrophy of progressively increased respiration and PC differentiation
Glutaminolysis and mitochondrial pyruvate import each can be inhibited by a well-characterized pharmaceutical compound – CB839 (Johnson et al., 2018) and UK5099 (Zangari et al., 2020; Lam et al., 2016), respectively. We tested the effect of these agents – in combination, or each one singly- on physiology and differentiation of B cells activated via CD40. CB839 reduced the production of CD138+ progeny (Figure 4a and b), ASC (Figure 4c and d), and Ab (Figure 4e). Glutaminase inhibition substantially reduced production of CD138+ plasmablasts/PCs when B cells were co-activated with anti-IgM along with CD40 cross-linking, and co-inhibition of with CB839 and UK5099 further reduced differentiation (Figure 4—figure supplement 1a, b). In part, this effect of glutaminase inhibition was due to decreased efficiency of dividing (Figure 4—figure supplement 1c), which was accompanied by lower cell numbers (Figure 4—figure supplement 1d) with a more modest effect on viability (Figure 4—figure supplement 1e). Consistent with its ability to inhibit glutaminase, this agent decreased intracellular glutamate and the calculated glutaminolysis rate while increasing the glutamine pool (Figure 4—figure supplement 2a–c, e). On its own, UK5099 had no effect on development of CD138+ cells, yet addition of UK5099 to CB839 substantially intensified the inhibition of ASC generation and Ab production. Of note, UK5099 reduced neither glutamine nor glutamate, yet substantially reduced intracellular alanine, which is generated in mitochondria by glutamate-pyruvate transaminase 2 (GPT2) conversion of glutamate and pyruvate to alanine and αKG (Figure 4—figure supplement 2d). Further, the frequencies of ASCs and spot sizes were substantially reduced when metabolism was inhibited only during the differentiation phase, followed by washout of the inhibitors (Figure 4—figure supplement 3). These data indicate that glutaminolysis and mitochondrial pyruvate import promote the differentiation process. Nonetheless, results from applying inhibitors only during the ELISpot culture, that is after 4 days of differentiation in vitro, suggest that glutaminolysis also non-redundantly supports the synthesis and/or secretion of Ab (Figure 4—figure supplement 3b, d).
GLS and MPC2 collaborate in supporting progression to plasma cell (PC) development.
(a) B cells were activated and cultured under conditions promoting PC differentiation in the presence of the indicated combinations of vehicle (DMSO) or inhibitors of GLS (CD839) and the MPC (UK5099). Shown are representative histograms from flow cytometric analyses of CD138 within the live cell gate, with inset numbers denoting the %CD138+. The bar graph shows the mean (± SEM) results for generation of CD138+ cells under each treatment condition, pooling data from three temporally independent experiments, each with three to five independent B cell pools purified from separate mice (each dot represents a distinct sample). (b) Shown are the mean (± SEM) calculated numbers of PC generated in temporally independent replica experiments with a total of eight independent B cell pools cultured in vitro in (a). (c) Representative ELISpot results measuring the frequencies of IgM- and IgG1-secreting PC, as indicated, produced in the differentiation cultures under each treatment condition. (d) Bar graphs with mean (± SEM) ELISpot results pooled from the replicate experiments illustrated in (c), with each dot representing an individual sample. Shown are data normalized to the vehicle (DMSO) control for each set of cultures using an individual B cell pool. (e) Bar graphs show the mean (± SEM) absorbance values from ELISA measurements of IgM and IgG1 secreted into the media during the cultures as in (b). Additional data quantifying ASCs are presented in Figure 4—figure supplement 1a. (f) Prdm1 gene expression promoted by GLS and MPC2. B cells were activated and cultured as above, but harvested after 3.5 d culture in BAFF, IL-4, IL-5, and the indicated inhibitor(s) or vehicle followed by qRT2-PCR to quantitate Prdm1 RNA encoding Blimp1. Shown are the results from four biologically independent mouse pools, B cell purifications and cultures, with the Prdm1-encoded RNA then normalized in each experiment to the level in the vehicle (DMSO) control (in each sample, relative to the averaged CT values of cyclophilin A and GAPDH). (g, h) Global gene expression identifies PC identity as a main target of synthetic auxotrophy. Using three biologically independent replicate pools for each condition, RNA-seq was performed with the B cells cultured as in (f). Enriched genes identified by DESeq2 comparison were analyzed using the MyGeneset tool from ImmGen. (g) Genes enriched in vehicle treated cultures compared to cultures treated with both CB839 and UK5099 are shown as a W-plot with defined stages for mature B cells and PC indicated. (h) Genes enriched in CB839-treated cultures compared to cultures treated with both CB839 and UK5099 are shown as a heatmap of z-scored relative expression, with specific gene identities and defined stages for mature B cells and PC indicated. (i) Metabolic mitigation of the block imposed by synthetic auxotrophy. Graphs of aggregate results from six biologically independent B cell preparations (two biological replicates in each of three independent experiments, presented as in (a), are shown for differentiation assays performed with B cells purified, activated, and cultured as in (a), except that the cell permeable αKG analogue DMK was added as indicated. (j–l) Gene set enrichment analyses (GSEAs) were performed on RNA-seq data generated using RNA from flow-purified GC B cells and hallmark gene sets of the Mouse Molecular Signatures Database. CreERT2 -transgenic mice of each of the four genotypes (Gls +/+or f/f; Mpc2 +/+or f/f) were immunized with SRBC after being treated sequentially with tamoxifen to activate huCD20-CreERT2 as diagrammed in Figure 3a. One week after immunization, RNA was isolated from viable GC-phenotype B cells purified by flow sorting, as well as from IgD+ B cells. RNA-seq data were quality-controlled, processed, and organized into GSEAs as described in the Methods. Shown is a selected subset of analyses with high normalized enrichment scores (NES) for the indicated gene sets (j) oxidative phosphorylation (WT vs GlsΔΔ, Mpc2ΔΔ GC B cells); (k) regulated by c-Myc (Mpc2ΔΔ vs GlsΔΔ, Mpc2ΔΔ GC B cells); (l) oxidative phosphorylation (Mpc2ΔΔ vs GlsΔΔ, Mpc2ΔΔ GC B cells). Additional GSEA and other data are in Figure 4—figure supplement 5).
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Figure 4—source data 1
Data of Figure 4a.
- https://cdn.elifesciences.org/articles/107627/elife-107627-fig4-data1-v1.zip
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Figure 4—source data 2
Data in support of relative IgM production in Figure 4e.
- https://cdn.elifesciences.org/articles/107627/elife-107627-fig4-data2-v1.zip
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Figure 4—source data 3
Data in support of relative IgG1 production in Figure 4e.
- https://cdn.elifesciences.org/articles/107627/elife-107627-fig4-data3-v1.zip
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Figure 4—source data 4
Data in support of the time point for analyses of levels of mRNA encoding Blimp-1 during differentiation of activated B cells into PB/PC for Figure 4f.
- https://cdn.elifesciences.org/articles/107627/elife-107627-fig4-data4-v1.zip
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Figure 4—source data 5
Data for individual replicate experiments measuring relative levels of the mRNA encoding Blimp-1 under various conditions, Figure 4f.
- https://cdn.elifesciences.org/articles/107627/elife-107627-fig4-data5-v1.zip
Progression from B cell activation to the differentiation of plasmablasts and PCs requires several rounds of cell cycling and a division-counting mechanism (Barwick et al., 2016). When the frequency of CD138+ progeny was measured as a function of division number, the results showed that CB839 reduced the capacity to become CD138-positive at equal divisions (Figure 4—figure supplement 4a–d). Moreover, whereas UK5099 on its own did not reduce differentiation efficiency at equal divisions, its addition intensified the inhibitory effect of CB839 (Figure 4—figure supplement 4a–d). Recent work with profound B cell-depletion therapy in chronic autoimmune disease indicates that disease activity depends on continual production of new auto-Ab-producing cells (Müller et al., 2024, reviewed in Taubmann et al., 2024). Hydroxychloroquine (HCQ) is the standard of care in SLE; while effective, it incompletely reduces pathogenic auto-Ab concentrations and disease activity, and often is not sufficient (Olsen et al., 2013). We explored the interplay between HCQ and CB839 (glutaminase inhibition), alone or along with UK5099. Strikingly, whereas HCQ alone slightly increased the %CD138+ at each division and overall, the addition of HCQ to metabolic inhibition caused more substantial reductions in PC differentiation (Figure 4—figure supplement 4a–d).
Levels of Prdm1 mRNA, which encodes a transcription factor that determines PC fate and identity [reviewed in Boothby et al., 2019; Ripperger and Bhattacharya, 2021], were lower in inhibitor-treated cells at a time in the cultures when the CD138+ population just started to develop (Figure 4f). This finding is consistent with an effect on differentiation beyond simple division-counting and with the pattern of results with metabolic inhibition. Moreover, analyses of cell-type modules in RNA-seq data from B lymphoblast cultures at this inflection point yielded evidence that the main systemic impact of combined inhibition was on plasmablast–PC gene expression programs (Figure 4g and h). We further found that DMK, the cell-permeable αKG precursor, partially reversed the inhibitory effects of CD839 and UK5099 on B cell differentiation to a CD138+ plasmablast/PC status (Figure 4i). While not the entire mechanism, these findings indicate that αKG generation via glutaminolysis promotes PC differentiation.
The serological data highlight an impact on affinity maturation of class-switched Ab after a secondary immunization. T cell help drives greater proliferation of both extrafollicular- and GC-B cell-derived plasmablasts that bore higher-affinity BCR (MacLean et al., 2025; Chan et al., 2009), but the findings (Figure 3b and c; Figure 3—figure supplement 2c, d; Figure 3—figure supplement 3) demonstrate effects on GC B cells. Since in vitro systems cannot faithfully recapitulate GC B cell physiology, we performed RNA-seq analyses of flow-purified GC B cells. Immunization with SRBC was performed after B cell type-specific gene inactivation was induced by tamoxifen injections into subjects of each genotype, including matched controls (CreERT2 transgenics with +/+ alleles at the Gls and Mpc2 loci). The analyses of GC-phenotype B cells harvested a week after immunization consistently showed major reductions in the mRNA encoded by the targeted genes (Mpc2; Gls), indicating both that deletion of the alleles flanked by loxP sites (‘floxed’, designated as ‘f’) was efficient and that the GC were not dominated by selective outgrowth of the B cells that retained functional genes (Figure 3—figure supplement 2f, g). Gene set enrichment analyses (GSEA) of the impact of GLS on the relative RNA levels in GC B cells highlighted modules for the interconnected functions of Myc-regulated genes, those connected to mTOR signaling and oxidative metabolism (oxidative phosphorylation; fatty acid [FA] oxidation; Figure 4j–l; Figure 4—figure supplement 5). Moreover, the abnormal metabolism led to reduced expression of RNAs linked to proliferation (E2F-responsive genes and those associated with the cell cycle G2-M transition; Figure 4—figure supplement 5a–c). These effects could be discerned when comparing GlsΔΔ B cells to CreERT2, +/+ controls but effects were heightened when Mpc2 inactivation was compared to Mpc2ΔΔ, GlsΔΔ samples or in comparing doubly-deficient B cells to WT controls (Figure 4—figure supplement 5a–c).
The gene modules pointed to proliferation, c-Myc (a central mediator of metabolic reprogramming), and oxidative metabolism. Oxidative metabolism is vital for PC differentiation (Price et al., 2018). Accordingly, we measured respiration by B lymphoblasts of each genotype on 2 successive days after activation and culture in conditions promoting development into ASC. Of note, rates of mitochondrion-dependent oxygen consumption by WT cells quadrupled between days 1 and 2 after mitogenic stimulation (Figure 5a–d). Consistent with the GSEA data, the increased respiration was blunted in GLS-deficient B cells (Figure 5a and b). In addition, the inactivation of Mpc2, while not affecting respiration on its own, further reduced both the absolute rate and the capacity to increase this core mitochondrial function during the second day when GLS was deficient (Figure 5a and b). To explore if these effects were attributable either to abnormal naive B cells prior to stimulation, or simply to a failure to provide sufficient substrates to the mitochondria, we added CB839 or UK5099 to cultures of normal B cells after activation but performed the metabolic flux assays in the absence of inhibitors. Strikingly, the impacts on respiration caused by pharmacological inhibition initiated at the time of B cell activation matched those obtained using genetic loss of function (Figure 5c and d). Further consistent with altered mitochondrial metabolism, the inhibition of glutaminolysis also impacted the acetyl-carnitine/ratio that is central to the provision of substrates for FA oxidation, with reduced L-carnitine and increased acetyl-carnitine as well as computationally inferred rates of FA oxidation (Figure 4—figure supplement 2h–j).
Synthetic auxotrophy of B cell metabolism that supports a progressive post-activation increase in mitochondrial respiration.
(a) Pools of purified B cells from WT mice or those with the indicated gene-targeted loss(es) of function were activated and cultured (1 and 2 d) with αCD40, BAFF, IL-4, and IL-5. Metabolic functions were then assayed by a metabolic flux analyzer. (b–f) As for (a), except WT cells were treated with inhibitors (CB839; UK5099) alone or in combination, as indicated by the color coding, and then subjected to mitochondrial stress-tested measurements of respiration (b), biochemical assays of [ATP] (g–i), flow cytometry (j, l), or qPCR (k). (a) Oxygen consumption rates (OCR) during mitochondrial stress testing of B cells, comparing loss-of-function B cells of the indicated genotypes, color-coded as in Figure 3. (b–d) Changes in basal respiration and maximal respiration of B cells from day 1 to day 2 after activation (b), calculated from assays in (c) and (d). OCR values at day 2 were used for statistical analysis. (c, d) As in (a) except that purified WT B cells were used, with additions of vehicle (DMSO) or the indicated inhibitor(s) (CB839, 1 µM; UK5099, 10 µm), with each B cell pool assayed on both days 1 (c) and 2 (d) after purification and activation. (e) Extra-cellular acidification rates (ECAR) during glycolytic stress tests of WT B cells activated and cultured in the presence of the indicated agents after 2 d cultures as in (d). (f) ECAR during glycolytic stress test of B cells inducibly rendered GlsΔΔ and/or Mpc2ΔΔ, then activated and cultured as in (a). (g, h, i) Intracellular [ATP] in lysates of B cells activated and cultured (2 d) as in (c). (g) Metabolic inhibitors were present throughout the period of culture (2 d) and assay. (h) Cells were activated and initially cultured in the presence of the indicated metabolic inhibitor(s), then washed, and assayed (90 min) in medium without inhibitors. (i) After activation and 2 d culture with no inhibitor present, the indicated agent(s) were added to block glutaminolysis and/or mitochondrial pyruvate import during the 90 min assay. (j) Mitochondrial membrane potential determined by tetramethylrhodamine (TMRE) staining analyzed by flow cytometry. Shown are mean fluorescence intensity (MFI) values from each independent experiment after activation and culture (2 d) as in (c), then normalized to DMSO-treated condition in each experiment. (k) Flow cytometry results comparing inhibitor-treated cells vs controls after staining for ROS with DCFDA in three independent replication experiments, with each dot representing one experiment, normalizing as in (i).
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Figure 5—source data 1
Data compendium, experimental results in Figure 5 and Figure 5—figure supplement 1.
- https://cdn.elifesciences.org/articles/107627/elife-107627-fig5-data1-v1.zip
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Figure 5—source data 2
Prism file with quantitative data from Seahorse assays of Figure 5.
- https://cdn.elifesciences.org/articles/107627/elife-107627-fig5-data2-v1.zip
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Figure 5—source data 3
Additional numerical data on quantitative analyses of metabolic flux analyses (Figure 5).
- https://cdn.elifesciences.org/articles/107627/elife-107627-fig5-data3-v1.zip
Rates of extracellular acidification rates (ECAR) were measured to test if B lymphoblasts compensated for the reduced respiration by increasing ‘aerobic glycolysis’ – the hallmark of which would be to generate and excrete lactate from pyruvate. Targeting glutaminolysis led to striking decreases in ECAR that were even greater when in concert with interference with the MPC (Figure 5e and f). These decreases indicate that the interference with glutaminolysis broadly reprograms metabolism in the activated B cells. Although activated B cells perform FA oxidation (Weisel et al., 2020; reviewed in Boothby et al., 2022), the inhibitors decreased steady-state ATP concentrations in the CD40-activated lymphoblasts (Figure 5g). Of note, the main cause of these decreases appeared to be interference with the capacity of B cells to increase their respiratory capacity during growth (Figure 5h) rather than the modest impact of acute inhibition of glutaminolysis and pyruvate import in blasts cultured in the absence of inhibitors during 2 d prior to adding inhibitors (Figure 5i). The reduced respiration, lower signals from TMRE staining (Figure 5j), together with normal signal after MitoTracker Green staining and qPCR for mitochondrial DNA content (Figure 5—figure supplement 1a, b), indicate that decreased respiration was linked to a reduction in mitochondrial membrane potential rather than a failure to increase mitochondrial mass or DNA. This decrease in turn was associated with an increase in reactive oxygen species (ROS) (Figure 5k).
Metabolic regulation of interferon cytokine receptor responsiveness
To gain further insight into molecular consequences of synthetic auxotrophy, we analyzed how Mpc2 gene inactivation affected GLS-depleted GC B cells using the RNA-Seq data. Surprisingly, a Jak-STAT3 signature was reduced not only in GC B cells deficient GLS and MPC2 but also in the comparison of Mpc2ΔΔ to combined loss of function (Figure 6a; Figure 4—figure supplement 5a). IL-21R, acting in large part via STAT3, is crucial for PC differentiation (Ozaki et al., 2002; Ettinger et al., 2005; Avery et al., 2010; Rodríguez-Bayona et al., 2013). Cytokine receptors activate STAT3 via Jak1-mediated tyrosine phosphorylation (Asao et al., 2001). Of note, ROS can alter STAT3-dependent gene transcription either directly or through increasing reactive nitrogen species followed by S-nitrosylation of signaling proteins such as STAT3 (Li et al., 2010; Kim et al., 2014; Butturini et al., 2020). We found that the tyrosyl phosphorylation of Jak1 and STAT3 stimulated by IL-21 treatment of activated B cells was attenuated in cells cultured in CB839 and UK5099 (Figure 6b).
Metabolism in B cells promotes B cell proliferation via IL-21 signaling to STAT3.
(a) Enrichment of the IL6-stimulated Jak-STAT3-induced gene set. (b) Immunoblot analyses of IL-21-induced tyrosine phosphorylation of STAT3 in B cell blasts, showing representative results from one individual experiment representative of three independent replications. Purified B cells were activated with anti-CD40 and BAFF, cultured for 16 hr in the presence of vehicle (DMSO) or inhibitors (CB839 and UK5099), as indicated, then stimulated (15 min) with IL-21. (c, d) CB839 and UK4099 attenuate IL-21-induced B cell proliferation. B cells were stained with CTV, stimulated with anti-CD40 and BAFF with and without CB839 and UK5099 for 3 days in the presence or absence of IL-21. (x=4; n=8). (c) Shown are the representative flow plot of CTV partitioning in viable B cell gates. (d) Aggregated mean (± SEM) frequencies of IL-21-induced proliferation of B cells calculated by subtracting CTVlow frequencies of without IL-21 from with IL-21. p-Values were calculated by Mann-Whitney U test. (e, f) Expression of a STAT3 gain-of-function mutant reverses the impact of GLS and MPC2 deficiency on B cell proliferation. WT and GlsΔΔMpc2ΔΔ (designated here as ‘dKO’) B cells purified from tamoxifen-injected huCD20-CreERT2 mice were transduced with replication-deficient virions of either the MIT retrovector or MIT-STAT3-Y640F (Pilati et al., 2011), as indicated, stained with CTV, stimulated with anti-CD40, anti-IgM, BAFF, IL-4, and IL-5, and cultured 5 days. Shown are the flow-cytometry results of a representative analysis of CTV partitioning in Thy1.2-positive transduced cell gates (e) and mean (± SEM) frequencies of B cells that divided ≥3 times, aggregating data from three biologically independent replicate experiments (f), comprising five separate pools each of WT and GlsΔΔMpc2ΔΔ (‘dKO’) samples. p-Values were calculated by Mann-Whitney U test.
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Figure 6—source data 1
Archive of image and Excel files with source data in support of Figure 6.
- https://cdn.elifesciences.org/articles/107627/elife-107627-fig6-data1-v1.zip
We next tested for evidence that the decreased effectiveness of coupling IL-21 stimulation with induction of P-STAT3 when metabolic pathways were impeded has functional significance. As noted above (Figure 1d and e), generation of plasmablasts and PCs includes a division-counting process (Barwick et al., 2016). Thus, outputs of CD138 progeny depend on both proliferation and on the efficiency of converting gene expression programs within tranches of cells that have divided a set number of times. Accordingly, we assayed the efficiency of generating CD138+ cells from a naive pool of splenic B cells with and without addition of exogenous IL-21 after activation. In the absence of inhibitors, IL-21 far more substantially increased the partitioning of CTV between progeny cells in such cultures (Figure 6c and d). In sharp contrast, this cytokine increased the division barely if at all when cultures included CB839, alone or especially in combination with UK5099 (Figure 6c and d). To evaluate the relationship of STAT3 activity to the metabolic dependence of IL-21-induced proliferation, we then exploited a gain-of-function STAT3 mutant (Pilati et al., 2011) in experiments using transduction of B cells that were wild-type or GlsΔΔ, Mpc2ΔΔ (Figure 6e and f). While the division rates of B lymphoblasts deficient in GLS and MPC function were reduced, the subset of GlsΔΔ, Mpc2ΔΔ B cells transduced with constitutively active STAT3 (i.e. the Thy1.1+ cells) exhibited a substantial albeit incomplete restoration of their proliferation (Figure 6e and f).
Unexpectedly, computational algorithms identified the IFN-stimulated gene signature as the most prominently impaired pathway in the Mpc2, Gls1 double-deficient GC B cells (Figure 7a). Thus, the effects of MPC2 in the setting of GLS depletion were to promote IFN response signatures and Jak-STAT signaling, as well as suites of RNA linked to respiration (Figure 7b; Figure 4—figure supplement 5a, d). Among processes that could lead to such a strong effect on mRNA levels, a straightforward possibility was that the metabolism in B cells affects their IFN-elicited signal transduction. Strikingly, IFN-induced phosphorylation of the conserved tyrosine was attenuated when activated cells were treated with CB839 and UK5099 prior to stimulation with type 1 or 2 IFN (IFN-β and -γ, respectively) (Figure 7c and d). This effect was observed in B cells 3 days after initial activation via CD40 crosslinking, and inhibition was observed when the pharmacological agents were present only for the final 16 hr, or when anti-CD40-activated blasts were analyzed the day after activation (Figure 7c and d). Decreased IFN-stimulated phospho-STAT1 was also observed in comparisons between WT and GlsΔΔ Mpc2ΔΔ B cells from tamoxifen-treated mice (Figure 7—figure supplement 1a–d). One consequence of STAT1 nuclear translocation and chromatin association is that the C-terminal transcription activation domain (TAD) can become phosphorylated at S727, an event that depends on the Jak/Tyk2 tyrosyl kinase action (Sadzak et al., 2008). Of note, IFN-induced STAT1(Y727) phosphorylation also was attenuated when GLS and MPC2 were impeded in activated B cells (Figure 7c and d). We conclude that altered intermediary metabolism in B cells can, within less than a day, change IFN receptor induction of phospho-STAT1.
Metabolic programming in B cells modulates interferon signaling to STAT1.
(a) Results from an over-representation analysis of differentially expressed protein-coding RNA in WT versus induced double-deficient (GlsΔΔMpc2ΔΔ) B cells, as counted in the RNA-seq analyses with GC B cells of SRBC-immunized mice (as in Figure 4, (j–l)). Additional GSEA and an overview of gene set comparisons for pairs of genotypes are presented in Figure 4—figure supplement 5. (b) Selected analyses of gene sets enriched in WT GCBs compared to their counterparts subjected to disruption of both Gls and Mpc2 (GlsΔΔMpc2ΔΔ GCBs) using the Hallmark Pathway database. Shown are enrichment of IFN-α- and IFN-γ-associated pathways in WT GCBs compared to the GlsΔΔ, Mpc2ΔΔ samples. (c–h) Immunoblot analyses of IFN-induced STAT1 phosphorylation in activated B cells, showing representative results from individual experiments, each representative of three independent replications. (c, d) Purified B cells were activated with anti-CD40 and BAFF and cultured for 64 or 16 hr in the presence of vehicle (DMSO) or inhibitors (CB839 and UK5099), as indicated, then stimulated (15 min) with IFN-β (c) or IFN-γ (d) followed by immunoblotting using Ab specific for p-STAT1(Y701) or p-STAT1α(S727) along with anti-cyclophilin B Ab as a loading control. (e, f) Inhibition of mitochondrial ETC attenuates STAT1 activation. B cells were activated and cultured as in e and f but for 16 hr, in the presence or absence of metformin (2 mM; 16 hr) or rotenone (0.5 µM; final 2 hr of the cultures) as indicated, then stimulated (15 min) with IFN-β (g) or IFN-γ (h) and analyzed as for panels c and d. (g, h) ROS inhibit STAT1 activation. B cells were activated and cultured for 16 hr, in the presence or absence of menadione (2 µM; all 16 hr) or H2O2 (100 µM; the final 2 hr), and then stimulated with IFN-β (g) or IFN-γ (h) for 15 min.
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Figure 7—source data 1
Archive of image and Excel files with source data in support of Figure 7.
- https://cdn.elifesciences.org/articles/107627/elife-107627-fig7-data1-v1.zip
Finally, we tested models of mechanisms that could mediate the observed ability of metabolism (i.e., glutaminolysis and mitochondrial pyruvate import) to increase STAT1 phosphorylation in activated B cells. Flow cytometry results indicated that a simple model in which surface expression of IFN receptors was reduced is unlikely (Figure 7—figure supplement 1e), suggesting instead an impairment of receptor signaling to STAT1. One observed effect of the combined metabolic reprogramming was to increase steady-state ROS in both B and GC B cells (Figure 5k; Figure 5—figure supplement 1a). Of note, ROS can reduce function of complex I of the electron transport chain (ETC) by modifying reactive sulfhydryl groups in the complex, and elimination of complex I from the mitochondrial ETC decreased IFN-γ activation of STAT1 in a genome-wide loss-of-function screen with an immortalized macrophage-like cell line (Weisel et al., 2020). The absence of complex I was mimicked by the ETC inhibitor rotenone (Kiritsy et al., 2021). Longer rotenone treatments were highly toxic to B cells, but we found that p-STAT1(Y701) induction in activated B cells was dramatically decreased by a remarkably short (45 min) exposure to this agent prior to IFN stimulation (Figure 7e and f). Metformin also inhibits complex I, albeit at higher concentrations than are achieved clinically (Larsen et al., 2012; Fontaine, 2018). When tested with activated B cells, this pharmaceutical agent also decreased p-STAT1 elicited by IFN stimulation (Figure 7e and f).
Dysfunction or chemical inhibition of ETC complex I causes increased mitochondrial production and export of ROS (Li et al., 2003), so it was possible that these results were in part attributable to elevated ROS. Using an approach that had provided evidence of ROS inhibiting STING-dependent IFN-β production (Tao et al., 2020), we increased ROS in activated B cells by applying either menadione or H2O2 prior to IFN treatment. Menadione substantially reduced induction of P-STAT1 by receptors for both IFN-β and -γ, which was almost completely abrogated by a short-term pre-treatment with H2O2 (Figure 7g and h). We conclude that increased steady-state ROS and mtROS in B cells, which arise when GLS and MPC function are impaired, contribute to an unexpected defect in IFN-R signaling to STAT1. All together, the results reveal that an interplay between two metabolic pathways progressively reduced the expansion of mitochondrial respiration in B cells. A key functional effect of the combined impairment of two metabolic pathways is the establishment of a block to PC differentiation and high-affinity Ab responses. Unexpectedly, however, the mitochondrial dysfunction and elevated ROS also converged on IFN-receptor signaling and the programming IFN-response functions.
Discussion
We and others have published examples of a metabolic flexibility in B lineage cells that appears to allow limit or negate the effects of loss-of-function mutations in key steps of intermediary metabolism (Brookens et al., 2024; Bierling et al., 2024; Li et al., 2024). These findings raise questions as to whether or not there are interventions that could more substantially interfere with the ongoing production of PCs secreting Ab or, conversely, which pathways might need to collaborate for promoting full-strength Ab responses. The work presented here supports three central insights. First, we have identified conditions under which the anti-NP response is relatively glutaminase-independent, both in the primary phase and upon recall stimulation of B cells. Despite this apparent independence, this enzyme central to processing of glutamine and to anaplerosis takes on a vital role if mitochondrial pyruvate import is impeded. A related point is that the findings underscore the fallacy in stating conclusions as if universally applicable, inasmuch as the effect of B cell specific loss-of-function for GLS depended on the nature of the immunization. Thus, the anti-ovalbumin response derived from GLS-depleted B cells was substantially reduced under one set of conditions where the anti-NP responses after multivalent hapten-carrier immunization with NP were not similarly reduced after isolated Gls gene inactivation. Mechanistically, the findings revealed that glutaminase activity promotes a progressive increase in mitochondrial respiration in a manner enhanced by pyruvate import, an alternative pathway for providing substrates to the TCA (Krebs) Cycle. A third major finding is that the efficiency of coupling IFN receptors to the tyrosyl and serine phosphorylation of STAT1 – and IL-21 stimulation to STAT3 – depends on the programming of intermediary metabolism in a manner linked to ROS homeostasis. Taken all together, the findings reveal not only new insights into how intermediary metabolism can modulate differentiation and receptor signaling, but suggest the potential for new interventions in autoimmune diseases driven by IFN effects and auto-Ab.
Although the impetus to this work is a basic question about the interplay of intermediary pathways of intracellular metabolism, a major practical implication of the findings presented here is translational. A self-reinforcing network of increased IFN production and pathological levels and persistence of auto-Ab production is characteristic of several autoimmune conditions of humans. SLE and rheumatoid arthritis (RA) are most common and studied, but this pairing also is involved in inflammatory myopathies and primary Sjogren’s syndrome (Rönnblom and Eloranta, 2013; Higgs et al., 2011). Effectiveness of therapeutic mAb for B cell depletion is best established in RA; unimpressive results in SLE raised concerns that disease might be perpetuated by long-lived PC that secrete auto-Ab, do not need BAFF, and are CD20neg. However, dramatic results of testing CD19-directed chimeric Ag receptor T cells in patients with SLE and myositis showed that targeting B cells reduced clinical disease, IFN levels, and those of pathologic auto-Ab [(Müller et al., 2024), reviewed in Taubmann et al., 2024]. These effects imply that ongoing production of PC from B cells maintains IFN production and disease activity. Cost, production complexity, and risk profile mean that a need to identify other approaches that restrict the ongoing differentiation of B cells into PC remains, despite the dramatic results in patients with severe disease. The capacity of CB839 to collaborate with UK5099 to suppress both PC differentiation and responsiveness to IFNs suggests that this agent and glutaminase-specific inhibition in general merit further analysis. Since CB839 appeared safe in patients during phase 2 clinical testing (Lee et al., 2022), our finding of an interplay between the standard-of-care agent HCQ and CB839 in the inhibition of PC development in vitro similarly militates in favor of translational investigation. Which B cells are major sources of the PC that secrete pathological auto-Ab, and the extent to which SLE susceptibility might involve a distinct relationship between intermediary metabolism and PC differentiation, are important issues beyond the scope of the present study. Although the atypical MBC that are implicated in SLE pathogenesis (Dörner and Lipsky, 2024) were not specifically tested and one cannot exclude some contribution of Ag being presented to the remnant GC that persisted after primary immune challenge, our data suggest that inhibition of the pathways impacted MBCs that rapidly differentiated after a secondary challenge.
Another finding of the work bears both on consideration of the intersection of B cell metabolism and function after immunization, and perhaps on the relationship of our findings to SLE. Our data show that although the Ag-specific Ab response elicited by a protein, ovalbumin, was reduced by B cell-specific depletion of GLS in an allergic lung inflammation model of immunization, the anti-NP response was normal. Our finding that the metabolic requirements for Ab responses differed according to Ag or type of immunization raises questions that merit being worked out in future research. A key point is that immunization to elicit anti-NP responses usually is carried out with heavily haptenated carriers, that is many NP-groups on each protein molecule. In sharp contrast, a particular epitope in the carrier protein (ovalbumin, KLH, gamma globulin) will be monovalent unless part of an aggregate. Valency and the extent of BCR cross-linking influence signaling by the BCR, which in turn can affect metabolic regulators such as mTORC1 and c-Myc. A related possibility derives from the characteristics of the anti-NP response, which is dominated by a limited Ig heavy chain repertoire (Cumano and Rajewsky, 1985). Thus, intrinsic biochemical characteristics of VH125:VLλ BCR interactions with NP might lead to programming metabolic requirements that differ from what is elicited by the BCR repertoire responding to ovalbumin. The issue of valency has a bearing on the pathological Ab in auto-immunity in that so many auto-Ab of SLE are directed against multivalent Ag such as dsDNA and ribonucleoprotein complexes (Olsen and Karp, 2014; Suurmond and Diamond, 2015; Tsokos et al., 2016; Caielli et al., 2023). Finally, the specific immunization regimen might affect the results. General issues of valency in engagement of BCR at the cell surface remain incompletely clarified despite years of papers, so extensive further studies will be needed to understand better the relationship to a specific step in intermediary metabolism. Nonetheless, a striking finding herein is that a vital requirement for glutaminolysis is cryptic in the anti-NP response until uncovered by reduced import rates of either glucose into cells or pyruvate into mitochondria.
Our findings directly connect to questions of metabolic flexibility, which is a central issue for the potential translatability or implications of intermediary metabolism in targeting immune responses or auto-immunity. Targeting a particular process is less likely to be efficacious to the extent that GC B cells, or B cells in general, can use alternatives and achieve normal responses or outputs. For instance, although there is evidence that the majority of energy generation by activated and GC B cells involves FA oxidation, most of it in mitochondria (Weisel et al., 2020; Li et al., 2024), elimination of a key step in mitochondrial acquisition and use of FAs had no impact on Ab responses or discernible reduction in GC or affinity maturation (Li et al., 2024). Alternatively, restricting cell-intrinsic generation of serine from a glycolytic intermediate represents one potential point of vulnerability that was not compensated by flexibility (D’Avola et al., 2022). Depletion of a major glucose transporter – and inferentially of reduced supply of glucose for some combination of NADPH regeneration from NADP, serine biosynthesis, oxidation, and perhaps other uses of glucose – also reduced GC size, Ab responses, and affinity maturation (Brookens et al., 2024; Bierling et al., 2024). However, the effect magnitude (reduction to ~1/4 normal) appeared less promising from the standpoint of potential treatment of autoimmunity. Metabolomic data suggested that increased anaplerosis was a compensatory mechanism that might have limited the severity of the defect in ASC generation and Ab responses of GLUT1-depleted B cells (Bierling et al., 2024). Our findings support this inference in that the defects with Slc2a1ΔΔ or Mpc2ΔΔ B cells were each dramatically amplified by impedance of glutaminolysis. The size of the differences, the impact on the IgG2(a/)c isotype that is particularly important in SLE pathogenesis (reviewed in Bonanni et al., 2015), and the vital functions of STAT1 induction by IFN receptors in autoimmune models (Domeier et al., 2016; Domeier et al., 2018) indicate that this synthetic auxotrophy merits translational consideration. Inasmuch as cancer cells commonly have increased ROS levels at steady state (Akter et al., 2026).
The finding that metabolism regulates cytokine receptor coupling to Jak-STAT pathways raised a subsidiary question. Might there be conditions in health or disease, independent from genetic or pharmaceutical loss of function, where reduced rates of αKG production co-exist with decreased glucose import or pyruvate import into mitochondria? Some tumor masses had low interstitial glucose (Ho et al., 2015; Chang et al., 2015), and insufficient dietary protein intake causes a substantial reduction in circulating glutamine (Nohr et al., 1986; Andrews and Griffiths, 2002; Taylor et al., 2013; Raybuck and Boothby, unpublished data). Thus, decreased glutamine and glucose utilization may co-exist during short-term protein malnutrition after surgery of patients with residual tumor masses. A related circumstance could be for B cells in hypoxic regions of a tumor mass in cancer. Hypoxia tends to activate pyruvate dehydrogenase kinases, enzymes that decrease the generation of Ac-CoA from pyruvate, and indeed may also decrease mitochondrial pyruvate import (Golias et al., 2016; Ruiz-Iglesias and Mañes, 2021). Although hypoxia tends to increase glutamine uptake in cancer cell models, our prior work indicated that this stimulus and HIF stabilization in B cells decreased their uptake of a.a. such as glutamine. Moreover, decreased glutaminolysis by cancer cells (i.e. their glutamine use) increased micro-environmental glutamine and the functionality of tumor-infiltrating lymphocytes – indicating that glutamine was limiting in the TME (Edwards et al., 2021) – as has been reported for glucose (Ho et al., 2015; Chang et al., 2015). Since IFN-γ responsiveness is crucial in anti-tumor immunity and B cells tend to contribute to checking tumor growth (reviewed in Ikeda et al., 2002; Sarvaria et al., 2017; Laumont et al., 2022), the findings here have potential implications for one means by which cancer cell effects on nutrient micro-environments may assist in immune evasion.
Materials and methods
Mice and immunizations
Request a detailed protocolAll animal protocols – reviewed and approved by Vanderbilt University Institutional Animal Care and Use Committee – complied with the National Institutes of Health guidelines for the Care and Use of Experimental Animals. Mice were housed in specified pathogen-free conditions. Both male and female mice, aged 6–10 weeks, were used; sex-specific subgroup analyses did not reveal any significant differences and yielded the same conclusions. To enable tamoxifen-induced, B cell type-specific inactivation of GLS, GLUT1, and/or MPC2 coding potential, Glsf/f (Johnson et al., 2018) Slc2a1f/f (Caro-Maldonado et al., 2014), and Mpc2f/f mice (Lam et al., 2016) were crossed with huCD20-CreERT2 (Khalil et al., 2012) transgenic mice; for confirmatory in vitro work with purified B cells, some experiments used Rosa26-CreERT2 (as in Cho et al., 2016). Tamoxifen was administered as reported previously (Cho et al., 2016; Brookens et al., 2024). To control for potential Cre toxicity in B cell responses or GC B cells, age-matched Gls+/+, Slc2a1+/+, and Mpc2+/+, huCD20-CreERT2 mice were co-housed with huCD20-CreERT2 mice that had conditional alleles [Glsf/f, Slc2a1f/f, and/or Mpc2f/f], alone or in combination, and used as wild-type controls.
Mice were immunized, or immunized and boosted, by one or two intraperitoneal (i.p.) injections of 100 μg of 4-hydroxy-3-nitrophenylacetyl hapten (NP) conjugated to ovalbumin (NP-ova, Biosearch Technologies, Novato, CA), emulsified in 100 μL alum Imject alum (Thermo Fisher Scientific, Pittsburgh, PA), as described previously (Cho et al., 2016; Brookens et al., 2024; Raybuck et al., 2018), or after this product was discontinued, Alhydrogel 2% (InvivoGen, San Diego, CA). For mucosal challenges to elicit an anti-carrier Ab response, ovalbumin (50 μg dissolved in 20 μL PBS) was instilled intranasally (i.n.) once daily across seven consecutive days starting 3 weeks after i.p. initial sensitization of mice with NP-ova. Mice were harvested 12 h after the final inhalation. Alternatively, mice were immunized with sheep red blood cells (SRBC) as described (Cho et al., 2016), and harvested at seven days after immunization. Harvested spleens in some experiments were used to purify GC B cells for RNA-seq (detailed below) after tamoxifen injections and SRBC immunization (Figure 4j–l). To assess proliferation rates of GC B cells in vivo, intravital BrdU incorporation measured by injecting mice with 2 mg BrdU (Sigma-Aldrich, St. Louis, MO) 16 hr and 4 hr before harvesting spleens from SRBC-immunized mice. Single-cell suspensions, prepared as described above, were stained for surface markers (B220, IgD, GL7, CD38; dump channel markers as specified in the Flow Cytometry section) followed by cell fixation, permeabilization, and staining BrdU-containing DNA using the APC BrdU Flow Kit (B-D Pharmingen, San Jose, CA) according to the manufacturer’s protocol. GC B cells were defined as B220+ GL7+ IgDneg CD38neg, as control analyses have shown that a CD138+ pre-PC population is <2% of this gate.
Flow cytometry
Request a detailed protocolFluor-conjugated mAbs were purchased from BD Pharmingen (San Jose, CA), Life Technologies, eBiosciences (San Diego, CA), or Tonbo Biosciences. For detection of GC- and memory-phenotype B cells in the spleens of immunized mice, samples were stained as previously described (Paus et al., 2006). In brief, 3x106 splenocytes were stained with anti-B220, -GL7, -Fas, -IgD, -CD38, NP-APC, and a dump channel containing anti-CD11b, -CD11c, -F4/80, -Gr-1, and viability marker (7-AAD or Ghost-Brilliant Violet 510) in 1% BSA and 0.05% sodium azide in PBS. For detection of PC in products of in vitro cultures, viable cells (gated via FSC, SSC, and Ghost e450) were stained with fluorophore-conjugated anti-CD138, -B220, -CD19, or -TACI. For flow analyses of mitochondrial and total intracellular ROS, cells (1–3 × 106) were washed in PBS and stained with 40 nM MitoTracker Green, 10 nM TMRE, 5 μM MitoSOX, or 1.25 μM H2DCFDA, respectively, along with Ghost-780 in PBS (20 min at 37 °C), then washed again (1% BSA in PBS) and further stained with anti-B220, -CD19, -CD138, or -TACI. Samples were analyzed using a FACS Canto flow cytometer driven by BD FACS Diva software or as part of preparative flow purification with a FACS Aria flow sorter. Data were processed using Flow-Jo software (FlowJo LLC, Ashland, OR).
Cell cultures and reagents
Request a detailed protocolB cells were purified from mouse spleens using negative selection with biotinylated anti-CD90 and an iMag system (BD-Pharmingen) or positive selection with anti-mouse B220 nanobeads (Miltenyi Biotec, Auburn CA). To induce PC differentiation, B cells (seeded at 5×105/mL) were cultured with 1 μg/mL anti-CD40 (Tonbo, San Diego CA), 10 ng/mL BAFF (AdipoGen, San Diego, CA), 10 ng/mL IL-4 (Peprotech, Rocky Hill, NJ), 5 ng/mL IL-5 (Peprotech), and, if derived from inducible gene deletion models, 50 nM 4-hydroxy-tamoxifen (4-OHT) (Sigma-Aldrich, St. Louis MO) and re-fed at day 3. When cultured 2 d or less, cells were in the same conditions after plating at 2×106/mL. Alternatively, B cells were cultured and analyzed as for anti-CD40-activated cells after activation with both Fab2' anti-mouse IgM (Southern Biotech, Birmingham, AL; 1 µg/mL) and anti-CD40 (1 μg/mL). Glutamine supplementation analyses, with or without added DMK (5 mM), were performed using glutamine-free RPMI (Thermo Fisher, Waltham MA) supplemented with 10% dialyzed Gibco FBS (Thermo Fisher), 100 U/mL penicillin (Invitrogen, Waltham MA), 100 μg/mL streptomycin (Invitrogen), non-essential amino acids (NEAA, Invitrogen), with or without 10 mM HEPES (Invitrogen), and 0.1 mM 2-mercaptoethanol (Sigma). To test how inhibitors affected in vitro proliferation, cytokine receptor signaling, or PC differentiation, cultures were supplemented with 1 µM CB839, 10 µM UK5099, and/or 3 µM HCQ (all from Cayman Chemical Co, Ann Arbor MI), individually or in combinations, and 1 mM DMK was used to supplement some cultures subjected to glutaminolysis inhibition by CB839. To analyze proliferation in vitro, B cells (2×106, purified as above) were labeled with 5 μM CellTrace Violet (CTV; Invitrogen, Waltham, MA) and then activated and cultured as above. To test the impact of ROS and ETC inhibition on activation of STAT transcription factors, cultures of B cells activated with anti-CD40, BAFF, IL-4, and IL-5 were supplemented with 0.2 mM H202 (Sigma-Aldrich), 2 µM menadione (Sigma-Aldrich), 2 mM metformin (Sigma-Aldrich), or 1 µM rotenone (Calbiochem, San Diego CA).
Retroviral transduction
Request a detailed protocolPlasmids encoding the bicistronic retrovector MIT (Mitchell et al., 2001) or a construct encoding STAT3-Y640F (Pilati et al., 2011) inserted into MIT were transfected into ΦNX ecotropic packaging cells, whose supernatant media were then used for ‘spinfection’ of B cells as described (Cho et al., 2016). For retroviral transduction to test the reversion of GLS1 and MPC2 deficiency on B cell proliferation and differentiation, splenic B cells from tamoxifen-treated huCD20-CreERT2+ ("WT") or Gls1f/f; Mpc2f/f; huCD20-CreERT2+ mice were purified by Thy1.2 depletion and transduced with retrovirus MIT or the gain-of-function mutant MIT-STAT3-Y640F (Pilati et al., 2011). The B cell pools were then stained with 5 μM CTV, activated, and cultured in the presence or absence of IL-21 as above, and analyzed by flow cytometry.
ELISA and ELIspot
Request a detailed protocolRelative NP-specific Ab concentrations in sera, and secreted Ab in culture supernatants, were measured using capture ELISA as described previously (Cho et al., 2016; Brookens et al., 2024; Raybuck et al., 2018). All- or high-affinity hapten-specific Ab were measured using plates coated with NP20-BSA or NP2-PSA (Biosearch Technologies), respectively. Ovalbumin-specific antibodies were measured using serial dilutions of sera incubated on ovalbumin (1 μg/well)-coated 96-well plates (16 hr at 4 ° C). Total secreted Ab were captured using an anti-Ig(H+L) reagent. Captured Ab retained after rinsing were detected in an isotype-specific manner using HRP-conjugated anti-IgM, -IgG1, IgG2c, or -IgE incubation and colorimetric development with Ultra TMB Substrate (Thermo Fisher Scientific).
The frequencies of antibody secreting cells (ASCs) in the bone marrow, lung, or spleen after immunization were measured as described previously (Brookens et al., 2024; Raybuck et al., 2018). Briefly, high protein binding plates (Corning Life Science, Corning NY) were coated with NP20-BSA (for all-affinity ASCs) or NP2-PSA (for high-affinity ASCs; Biosearch Technologies), then seeded with splenocyte suspensions (0.5–1×106 cells/well [IgM], 1–2×106 cells/well [IgG1], and 2×106 cells/well [IgG2c]), cultured in medium with 10% FBS (16 hr), and probed with biotinylated anti-IgM, anti-IgG1, or anti-IgG2c antibodies (Southern Biotechnologies, Birmingham AL). For the detection of IgM or IgG1 ASC in day 5 in vitro cultures, high protein binding plates were coated with anti-Ig(H+L) (Southern Biotechnologies), seeded with suspensions of cultured cells (20 hr, with 100, 200, and 500 cells per well [IgM] or 1000, 2000, and 5000 cells/well [IgG1]), then probed with biotinylated anti-IgM or -IgG1 antibodies (Southern Biotechnologies, Birmingham AL). ASC numbers and spot sizes were quantified using an ImmunoSpot Analyzer (Cellular Technology, Shaker Heights, OH) and the densities based on dilutions with readily resolved spots.
Nucleic acid analyses
Request a detailed protocolRNA was isolated from sorted B cells or in vitro-generated B lymphoblasts using TRIzol reagent following the manufacturer’s instructions (Life Technologies, Carlsbad, CA). RNA from cultured B cells purified from TriZol and processed for bulk RNA-seq by the VANTAGE Core of the Vanderbilts. To assess the extent of the loss-of-function in B cell populations, gene expression was analyzed using quantitative real-time RT-PCR (qRT2-PCR). After cDNA synthesis by reverse transcription with an AMV Reverse Transcriptase kit (Promega, Madison, WI), amplifications were performed using SYBR Green Power UP PCR master-mix (ThermoFisher Scientific) and primer pairs specific for Gls (Forward 5′-GGGAATTCACTTTTGTCACGA-3′; Reverse 5′-GACTTCACCC TTTGATCACC-3′), Mpc2 (Forward 5′-TGTTGCTGCCAAAGAAATTG-3′; Reverse 5′-AGTGGACTGAGCTGTGCTGA-3′), and β-actin (Forward 5′-GGCACCACAC CTTCTACAATG-3′; Reverse 5′-GGGGTGTTGAAGGTCTCAAAC-3′). The relative level of gene expression was calculated using the 2-DDCT method after each sample was normalized to β-actin. Libraries for low-input bulk RNA-seq analyses with flow-purified GC B cells were generated and sequenced essentially as described (Scharer et al., 2020) and sequenced at the Emory Integrated Genomics Core. In brief, for each sample, 1000 cells were sorted directly into RLT buffer (79216; Qiagen) containing 1% (v/v) 2-mercaptoethanol. RNA was isolated using Zymo Quick-RNA MicroPrep Kit (11–328 M; Zymo Research). Synthesis of cDNA was performed using SMART-Seq v4 Ultra Low Input RNA Kit (634894; Takara Bio) kit. Final libraries were generated using 200 pg of cDNA as input for the NexteraXT kit (Illumina, FC-131–1024) with 12 cycles of PCR amplification. Final RNA-seq libraries were quantitated by QuBit (Life Technologies, Q33231), size distributions determined by bioanalyzer (Agilent 2100), pooled at equimolar ratios, and sequenced at the Emory Genomics Core on a NovaSeq6000 using a PE100 run. The RNA-seq samples of a biologically independent replication set of flow-purified GC B cells from immunized mice representing the four different genotypes were sequenced at Novogene on a NovaSeq X Plus using a PE150 runBulk RNA-seq. RNA from cultured B cells was performed by similar methods at the Vanderbilts' VANTAGE core.
To analyze sequencer outputs of each core, Fastq files were assessed for quality using FastQC. Adapters were trimmed using TrimGalore, followed by FastQC to validate adapter removal. hisat2 was used to align fastq files to the mm10 genome downloaded from UCSC genome browser. Qualimap was used to analyze the aligned sequences for quality. Subread’s featureCounts was used to count and normalize sequence counts in groups being compared. featureCount outputs were then used for DESeq2 analysis to identify fold change and significance of observed differences in gene expression. Normalized RNA-Seq counts were analyzed using GSEA 4.3.2 (Broad Institute) and the Hallmark gene sets collection from the Molecular Signatures Database (MSigDB) to identify changes in biological pathways. Differentially expressed genes identified by DESeq2 were analyzed using the MyGeneset tool from the Immunological Genome Project (Immgen) to identify B cell subsets associated with genes affected by intervention in metabolic pathways. The web-based gene set analysis toolkit (WebGestalt) was used for gene ontology over-representation analysis of biological processes using the protein coding genome as the reference set. Differentially expressed genes identified by DESeq2 were analyzed with WebGestalt to identify biological processes implicated by the change in gene expression.
Metabolic analyses
Request a detailed protocolFor proton nuclear magnetic resonance spectroscopy (1H-NMRS) quantitation of metabolites in solution, plasma and lymph node interstitial fluids were collected and processed as previously reported (Haslene-Hox et al., 2011; Edwards et al., 2021). In brief, a total of 50 μL deuterated water (D2O) and 50 μL of 0.75% sodium 3-trimethylsilyl-2,2,3,3-tetradeuteropropionate (TSP) in D2O were added to 500 μL of diluted biological fluids and transferred to 5 mm NMR tubes (Wilmad- LabGlass, Kingsport, TN). 1H-NMRS spectra were acquired on an Avance III 600 MHz spectrometer equipped with a Triple Resonance CryoProbe (TCI) (Bruker) at 298 K with 7500 Hz spectral width, 32,768 time domain points, 32 scans, and a relaxation delay of 2.7 s. The water resonance was suppressed by a gated irradiation centered on the water frequency. The spectra were phased, baseline corrected, and referenced to TSP using Chenomx NMR Suite. Spectral assignments were based on literature values.
Oxygen consumption rate (OCR) and ECAR were measured using a Seahorse Bioscience XFe96 extracellular flux analyzer (Agilent Technologies, Santa Clara CA). B cells (2.5x105) activated for 2 days with anti-CD40, BAFF, IL-4, and IL-5 were seeded per well of a Cell-Tak (5 μg/mL; Corning) coated plate. Glycolytic and mitochondrial stress tests were performed as previously described (Brookens et al., 2024; Raybuck et al., 2018). Basal respiration, maximum respiration, and ATP production were calculated using formulas derived from the software accompanying the Agilent Seahorse platform. Steady-state ATP concentrations in activated B cells were measured using the Promega Mitochondrial ToxGlo Assay (Promega, Madison WI), following the manufacturer’s protocol. B cells activated and cultured 2 d in anti-CD40, BAFF, IL-4, and IL-5 after negative selection of splenocytes with anti-Thy1.2, in the presence or absence of metabolic inhibitors (CB839, UK5099, or both). Equal numbers of viable (Trypan Blueneg), washed twice with warm, sterile PBS, were resuspended in glucose-supplemented RPMI1640, with their designated drug treatment added, and cultured (105 B cells in 100 μL) 90 min at 37 °C. Cytotoxicity Reagent (20 µL 5 x) was added to each well followed (30 min) by quantifying fluorescence (520–520 nm Em; 485 nm Ex/). 100 μL of ATP Detection Reagent was then added to each well followed by orbital shaking (500 rpm for 5 min). Luminescence was then measured to quantify ATP present in the B cells.
For metabolomic analyses, frozen (–70 C) cell pellets were extracted in plastic vials with 40 µL of UPLC grade isopropanol, sonicated (3 cycles, 10 seconds each), and clarified by centrifugation (20 min). Total protein content was measured using Pierce BCA Protein Assay kit (Thermo Fisher Scientific). Supernatants were analyzed using the Biocrates MxP Quant 500 XL targeted metabolomic kit (Biocrates Life Sciences AG, Innsbruck, Austria), potentially quantitating 106 small molecules and free FAs in chromatography mode and 913 complex lipids in flow-injection mode (FIA-MS/MS).
Metabolite identification was based on triple quadrupole ultra-high-performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) using a Shimadzu Nexera chromatography platform (Shimadzu Corporation, Kyoto, Japan) coupled to Sciex QTRAP 7500 mass spectrometer (AB Sciex LLC, Framingham, Massachusetts, USA). Metabolic indicators (474) were then calculated from sums or ratios of relevant metabolites according to Biocrates MetaboINDICATOR formulas (Limonciel, 2020). These indicators can be regarded as physiologically relevant measures and are statistically analyzed separately from metabolites. In addition, indicators denoted as ‘X synthesis’ were computed as a ratio of metabolite X and its main precursors as a reflection of the inferred conversion ratio. Using solvents of LC/UHPLC-MS grade, cleared extracts were transferred onto a kit plate with pre-injected internal standards, dried, derivatized with 5% phenylisothiocyanate in pyridine, ethanol, and water (1:1:1 v/v/v), and subsequent extraction with 5 mM ammonium acetate in methanol. UHPLC was performed with 0.2% formic acid in acetonitrile (organic mobile phase) and 0.2% formic acid in water (inorganic mobile phase). Flow-injection analysis was performed with methanol and Biocrates MxP Quant 500 XL additive. Sample handling, randomized with stratification prior to processing to avoid potential biases, was done on dry ice to avoid multiple freeze-thaw cycles. Plates included isopropanol blanks to calculate limits of detection, repeats of a kit quality control sample to calculate concentrations and monitor the coefficient of variation, and kit calibrators for seven-point calibrations of certain compounds. Analytes (metabolic indicators) were calculated according to Biocrates MetaboINDICATOR formulas (Limonciel, 2020). Ratios with zeros in the denominator were treated as missing values that were not considered in the analysis. As additional data transformations, Box-Cox transformation with R package car (Fox and Weisberg, 2018), and Tukey’s fencing (Tukey, 1977) were applied for metabolomic data. Furthermore, the values were standardized with respect to the DMSO group to facilitate comparison of regression coefficients in the statistical analysis.
Measurement of cytokine-induced STAT phosphorylation
Request a detailed protocolTo measure the levels of total and phosphorylated proteins, B cells were stimulated with anti-CD40 and BAFF, cultured in the presence or absence of inhibitors as detailed in Figure 6 and its Legend, and stimulated (25 min) with IFNβ, IFNγ, or IL-21. Total cell lysates were prepared with modified RIPA lysis buffer (50 mM Tris⋅Cl (pH 8.0), 150 mM NaCl, 1% NP-40, 0.1% SDS, 1 mM EGTA, 1 mM Na2VO4, 1 mM NaF, and protease inhibitor cocktail). Proteins resolved by SDS-PAGE were transferred onto Immobilon Nylon membranes (Millipore) that were then incubated with anti-phospho-STAT1-Y701 Ab, anti-phospho-STAT1-S727 Ab, anti-phospho-STAT3-Y705 Ab, anti-GLS1 Ab, or anti-cyclophilin Ab followed by fluorophore-conjugated, species-specific secondary anti-Ig Abs (Rockland Immunochemicals and LI-COR). Proteins were visualized and quantitated by Odyssey infrared imaging scanner (LI-COR).
Statistical analyses
Request a detailed protocolData are reported based on results replicated in at least three biologically independent performances. The primary analyses were conducted on pooled data points from independent samples and replicate experiments, t testing with post-test validation of its suitability. Tests used in particular settings are generally indicated in the Figure Legends. In experiments with individual analyses and comparisons of limited numbers of samples, t-tests or non-parametric formulae were applied as appropriate, based on modeling of the similarity of variances between data from the two conditions being compared, and of the estimated fit to Gaussian distributions; Mann-Whitney testing was used if statistical analysis indicated that the two sample sets probably had unequal variance. Data are displayed as mean (± SEM); conventionally, a difference is considered ‘statistically significant’ when the p value for the null hypothesis of a comparison was <0.05. In addition to the application of this method to individual features in the metabolomic analyses, a series of multivariable linear regression models were employed, each corresponding to a specific analyte, to analyze differences in metabolomic data. In these models, the values of the analytes served as the dependent variables, while individual non-DMSO treatment groups were included as key independent variables, that is considering the DMSO group as the reference.
Appendix 1
Reagent type (species) or resource | Designation | Source or reference | Identifiers | Additional information |
|---|---|---|---|---|
| Genetic reagent (Mus musculus) | C57/Bl6 (B6) – Gls1 f/f | Rathmell (VUMC, now U of Chicago); Johnson et al., 2018 | none | conditional loss-of-function allele encoding GLS |
| Genetic reagent (Mus musculus) | C57/Bl6 (B6) – Slc2a1 f/f | Rathmell (VUMC, now U of Chicago); Jackson Lab; Young et al., 2011 | none | conditional loss-of-function allele encoding GLUT1 |
| Genetic reagent (Mus musculus) | C56/Bl6(B6) – Mpc2 f/f | Bhattacharya (U of AZ); Lam et al., 2016 | none | conditional loss-of-function allele encoding MPC2 |
| Genetic reagent (Mus musculus) | B6 - Rosa26-CreERT2 | Ludwig (Ohio State Univ.); Shapiro-Shelef et al., 2005 | none | conditionally active recombinase |
| Genetic reagent (Mus musculus) | B6 - huCD20-CreERT2 | Shlomchik (Yale Univ; now @ UPMC); Khalil et al., 2012 | none | B cell-specific conditionally active recombinase |
| Peptide, recombinant protein | NP-ovalbumin | Biosearch Tech - now Fina Bio; Victora and Nussenzweig, 2022 | Catalog # N5051-100 | |
| Peptide, recombinant protein | NP(~20)-BSA | Biosearch Tech → Fina Bio | Catalog # N5050H | |
| Peptide, recombinant protein | NP2-PSA | Biosearch Tech → Fina Bio | Catalog # N5050L | |
| Antibody | Anti-GLS1 Ab (rabbit monoclonal) | Invitrogen | Catalog # 701965 | WB (1:1000) |
| Antibody | Anti-pSTAT1-Y701 Ab (rabbit monoclonal) | Cell Signaling Technologies | Catalog # 9167 | WB (1:1000) |
| Antibody | Anti-pSTAT1-S727 Ab (rabbit monoclonal) | Cell Signaling Technologies | Catalog # 8826 | WB (1:1000) |
| Antibody | Anti-pSTAT3-Y705 Ab (rabbit monoclonal) | Cell Signaling Technologies | Catalog # 9145 | WB (1:1000) |
| Antibody | Anti-pJak1-Y1034/1035 Ab (rabbit monoclonal) | Cell Signaling Technologies | Catalog # 74129 | WB (1:1000) |
| Antibody | Anti-mouse β-Actin Ab (mouse monoclonal) | Santa Cruz Biotech | Catalog # sc-517582 | WB (1:2000) |
| Antibody | Anti- Cyclophilin B Ab (rabbit polyclonal) | Millipore Sigma | Catalog # SAB4200201 | WB (1:5000) |
| Antibody | Anti-mouse GL7-FITC (rat monoclonal) | BD Biosciences | Catalog # 562080; RRID:AB_10894953 | FACS (1:250) IHC (1:100) |
| Antibody | Anti-mouse IgM-FITC (rat monoclonal) | BD Biosciences | Catalog # 553437; RRID:AB_394857 | FACS (1:500) |
| Antibody | Anti-mouse GL7-PE (rat monoclonal) | BD Biosciences | Catalog # 561530; RRID:AB_10715834 | FACS (1:250) |
| Antibody | Anti-mouse IgD-PE (rat monoclonal) | eBioscience | Catalog # 12-5993-83 | FACS (1:500) IHC (1:200) |
| Antibody | Anti-mouse PD1-PE (rat monoclonal) | BD Biosciences | Catalog # 568260 RRID:AB_2916860 | FACS (1:500) |
| Antibody | Anti-mouse CD21-BV510 (rat monoclonal) | BioLegends | Catalog # 123437; RRID:AB_2876441 | FACS (1:500) |
| Antibody | Anti-mouse TCRb-PE-cy5 (hamster monoclonal) | Invitrogen | Catalog # 15-5961-82 | FACS (1:500) |
| Chemical compound | Ghost Dye- Violet 450 | Tonbo Bioscience | Catalog # 13–0868 T500 | FACS (1:500) |
| Chemical compound | Ghost Dye- Violet 510 | Tonbo Bioscience | Catalog # 13–0870 T100 | FACS (1:500) |
| Antibody | Anti-mouse CD11b-PerCP (rat monoclonal) | Tonbo Bioscience | Catalog # 65–0112 U025 | FACS (1:500) |
| Antibody | Anti-mouse CD11c-PerCP (rat monoclonal) | Tonbo Bioscience | Catalog # 65–0114 U025 | FACS (1:500) |
| Antibody | Anti-mouse F4/80-PerCP (rat monoclonal) | Tonbo Bioscience | Catalog # 65–4801 U025 | FACS (1:500) |
| Antibody | Anti-mouse Gr1-PerCP (rat monoclonal) | Tonbo Bioscience | Catalog # 67–5931 U025 | FACS (1:500) |
| Antibody | Anti-mouse CD19-APC (rat monoclonal) | Tonbo Bioscience | Catalog # 20–0193 U025 | FACS (1:500) |
| Antibody | Anti-mouse CD19-PE-Cy7 (rat monoclonal) | Tonbo Bioscience | Catalog # 60–0193 U025 | FACS (1:500) |
| Antibody | Anti-mouse B220-APC-Cy7 (rat monoclonal) | Tonbo Bioscience | Catalog # 25–0452 U025 | FACS (1:500) |
| Antibody | Anti-mouse CD43-APC (rat monoclonal) | BD Biosciences | Catalog # 560663; RRID:AB_1727479 | FACS (1:500) |
| Antibody | Anti-mouse CXCR4-APC (rat monoclonal) | BD Biosciences | Catalog # 558644; RRID:AB_1645219 | FACS (1:250) |
| Antibody | Anti-mouse CD38-eFlour 450 (rat monoclonal) | eBioscience | Catalog # 48-0388-42 | FACS (1:500) |
| Antibody | Anti-mouse CD95-Biotin (hamster monoclonal) | BD Bioscience | Catalog # 554256; RRID:AB_395328 | FACS (1:500) |
| Antibody | Anti-mouse CD35-Biotin (rat monoclonal) | BD Bioscience | Catalog # 553816; RRID:AB_395068 | IHC (1:200) |
| Antibody | Anti-mouse CD138-PE (rat monoclonal) | BD Bioscience | Catalog # 561070; RRID:AB_2033998 | FACS (1:500) |
| Antibody | Anti-mouse cleaved (active) caspase 3-FITC (rabbit monoclonal) | BD Bioscience | Catalog # 559341; RRID:AB_397234 | FACS (10 µL / sample) |
| Commercial Assay, Kit | BrdU-APC | BD Bioscience | Catalog # 552598; RRID:AB_2861367 | Cell proliferation kit |
| Peptide, recombinant protein | Streptavidin-APC | BD Bioscience | Catalog # 554067; RRID:AB_10050396 | FACS (1:1000) IF (1:200) |
| Peptide, recombinant protein | Streptavidin-PE-Cy7 | BD Bioscience | Catalog # 557598 | FACS (1:1000) |
| Peptide, recombinant protein | Streptavidin-APC-Cy7 | BD Bioscience | Catalog # 554063; RRID:AB_10050396 | FACS (1:1000) |
| Peptide, recombinant protein | Annexin V-PE | BD Bioscience | Catalog # 560930 | FACS (1:100) |
| Chemical compound | 7-AAD | BD Bioscience | Catalog # 559925; RRID:AB_2869266 | FACS (1:1000) |
| Chemical compound | CellTrace Violet | Invitrogen | Catalog # C34557 | FACS |
| Chemical compound | H2DCFDA | Invitrogen | Catalog # D399 | FACS |
| Chemical compound | TMRE | Invitrogen | Catalog # T669 | FACS |
| Chemical compound | CB839 | Cayman | Catalog # 22038 | Cell culture |
| Chemical compound | UK5099 | Cayman | Catalog # 16980 | Cell culture |
| Chemical compound | Hydroxy-chloroquine | Cayman | Catalog # 17911 | Cell culture |
| Chemical compound | Menadione | Sigma Aldrich | Catalog # 58-27-5 | Cell culture |
| Antibody | Anti-mouse IgM-HRP Ab (Goat polyclonal) | SouthernBiotech | Catalog # 1021–05 | ELISA (1:1000) |
| Antibody | Anti-mouse IgG1-HRP Ab (Goat polyclonal) | SouthernBiotech | Catalog # 1071–05 | ELISA (1:1000) |
| Antibody | Anti-mouse IgM-Biotin Ab (Goat polyclonal) | SouthernBiotech | Catalog # 1021–08 | ELISpot (1:1000) |
| Antibody | Anti-mouse IgG1-Biotin Ab (Goat polyclonal) | SouthernBiotech | Catalog # 1070–08 | ELISpot (1:1000) |
| Commercial Assay, Kit | Seahorse XF Glycolysis stress test | Agilent | Catalog # 103020–100 | Metabolic flux analysis kit |
| Commercial Assay, Kit | Seahorse XF Mito stress test | Agilent | Catalog # 103016–100 | Metabolic flux analysis kit |
| Software | FlowJo | TreeStar → BD Biosciences | Flow cytometry data analysis |
Data availability
RNA-seq data are publicly available through the Gene Expression Omnibus (GEO) resource of the US National Center for Bio-InformaticsBioinformatics (NCBI), using accession numbers GSE341991 (in vitro cultured B cells during differentiation to Ab-secreting cells) and GSE338789 (flow purified naive and GC B cells). Quantitative data in support of the graphical figure panels have been included as source data files.
-
NCBI Gene Expression OmnibusID GSE341991. The role of glutaminolysis and mitochondrial pyruvate import on plasma cell differentiation.
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NCBI Gene Expression OmnibusID GSE338789. The role of GLS1 and MPC2 in germinal center B cell regulation.
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Article and author information
Author details
Funding
National Institutes of Health (AI1149722)
- Shawna K Brookens
- Ariel L Raybuck
- Kaylor Meyer
- Yeeun Paik
- Mark R Boothby
National Institutes of Health (AA113292)
- Shawna K Brookens
- Ariel L Raybuck
- Jennie Hamilton
- Jingxin Li
- Juyeon Lim
- Mark R Boothby
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Acknowledgements
Experimental work was supported by NIH grant R01 AI113292 followed by AI149722 (MRB). and Pathology-Microbiology-Immunology (PM&I) departmental funds. SK Brookens was supported by a supplement to AI113292. We thank D Bhattacharya (U of AZ) for generously shipping Mpc2 f/f breeding stock essential for this work, X Ye for helpful advice in RNA-seq analyses, MA Jones (Biocrates, Inc) for facilitating the metabolomic analysis, the Emory Integrated Genomics Core Facility (RRID:SCR_023529) for added support of the efforts, and Vanderbilt institutional cores (High-Throughput Screening; Flow Cytometry Shared Resource; Small Molecule NMR; Cell Imaging Shared Resource; VANTAGE) for equipment, expertise, and assistance. NIH Institutional Equipment (S10) grant 1S10OD018015 was instrumental in the acquisition of equipment for metabolic flux analyses and flow cytometry, and scholarships via the Cancer Center Support Grant (CA068485) and Diabetes Research Center (DK0205930) helped defray costs of Vanderbilt Cores.
Ethics
This study was conducted in accordance with strict permissions regulated by and requiring prior authorization of the Vanderbilt Institutional Animal Care and Use Committee (IACUC) and strict post-approval daily oversight by the veterinary staff and the Office of Animal Welfare Assurance (OAWA). No surgeries or procedures involving sustained pain or discomfort, or risks of morbidity or mortality, were part of the study.
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© 2025, Cho, Brookens, Raybuck et al.
This article is distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use and redistribution provided that the original author and source are credited.
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