TREM2 regulates purinergic receptor-mediated calcium signaling and motility in human iPSC-derived microglia
- University of California, United States
- University of California, Irvine, United States
- University of North Carolina, United States
- University G d'Annunzio of Chieti-Pescara, Italy
Abstract
The membrane protein TREM2 (Triggering Receptor Expressed on Myeloid cells 2) regulates key microglial functions including phagocytosis and chemotaxis. Loss-of-function variants of TREM2 are associated with increased risk of Alzheimer's disease (AD). Because abnormalities in Ca2+ signaling have been observed in several AD models, we investigated TREM2 regulation of Ca2+ signaling in human induced pluripotent stem cell-derived microglia (iPSC-microglia) with genetic deletion of TREM2. We found that iPSC-microglia lacking TREM2 (TREM2 KO) show exaggerated Ca2+ signals in response to purinergic agonists, such as ADP, that shape microglial injury responses. This ADP hypersensitivity, driven by increased expression of P2Y12 and P2Y13 receptors, results in greater release of Ca2+ from the endoplasmic reticulum (ER) stores, which triggers sustained Ca2+ influx through Orai channels and alters cell motility in TREM2 KO microglia. Using iPSC-microglia expressing the genetically encoded Ca2+ probe, Salsa6f, we found that cytosolic Ca2+ tunes motility to a greater extent in TREM2 KO microglia. Despite showing greater overall displacement, TREM2 KO microglia exhibit reduced directional chemotaxis along ADP gradients. Accordingly, the chemotactic defect in TREM2 KO microglia was rescued by reducing cytosolic Ca2+ using a P2Y12 receptor antagonist. Our results show that loss of TREM2 confers a defect in microglial Ca2+ response to purinergic signals, suggesting a window of Ca2+ signaling for optimal microglial motility.
Data availability
RNA sequencing data referenced in Figure 1- figure supplement 2 is available through Gene Expression Omnibus: GSE157652.
Article and author information
Author details
Funding
National Institutes of Health (R01 NS14609)
- Michael D Cahalan
National Institutes of Health (R01 AI121945)
- Michael D Cahalan
National Institutes of Health (R01 AG048099)
- Mathew Blurton-Jones
National Institutes of Health (R01 AG056303)
- Mathew Blurton-Jones
National Institutes of Health (R01 AG055524)
- Mathew Blurton-Jones
National Institutes of Health (core AG066519)
- Mathew Blurton-Jones
National Institutes of Health (U01 AI160397)
- Shivashankar Othy
National Institutes of Health (T32 NS082174)
- Amanda McQuade
National Institutes of Health (RF1DA048813)
- Sunil Gandhi
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Ethics
Human subjects: Human iPSC lines were generated by the University of California Alzheimer's Disease Research Center (UCI ADRC) stem cell core. Subject fibroblasts were collected under approved Institutional Review Boards (IRB) and human Stem Cell Research Oversight (hSCRO) committee protocols. Informed consent was received for all participants.
Copyright
© 2022, Jairaman et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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