Typhoid toxin sorting and exocytic transport from Salmonella Typhi infected cells

  1. Shu-Jung Chang
  2. Yu-Ting Hsu
  3. Yun Chen
  4. Yen-Yi Lin
  5. Maria Lara-Tejero
  6. Jorge E Galan  Is a corresponding author
  1. Yale University School of Medicine, United States
  2. National Taiwan University, Taiwan

Abstract

Typhoid toxin is an essential virulence factor for Salmonella Typhi, the cause of typhoid fever in humans. This toxin has an unusual biology in that it is produced by Salmonella Typhi only when located within host cells. Once synthesized, the toxin is secreted to the lumen of the Salmonella-containing vacuole from where it is transported to the extracellular space by vesicle carrier intermediates. Here we report the identification of the typhoid toxin sorting receptor and components of the cellular machinery that packages the toxin into vesicle carriers, and exports it to the extracellular space. We found that the cation-independent mannose-6-phosphate receptor serves as typhoid toxin sorting receptor and that the coat protein COPII and the GTPase Sar1 mediate its packaging into vesicle carriers. Formation of the typhoid toxin carriers requires the specific environment of the Salmonella Typhi-containing vacuole, which is determined by the activities of specific effectors of its type III protein secretion systems. We also found that Rab11B and its interacting protein Rip11 control the intracellular transport of the typhoid toxin carriers, and the SNARE proteins VAMP7, SNAP23, and Syntaxin 4 their fusion to the plasma membrane. Typhoid toxin's cooption of specific cellular machinery for its transport to the extracellular space illustrates the remarkable adaptation of an exotoxin to exert its function in the context of an intracellular pathogen.

Data availability

All data generated or analysed during this study are included in the manuscript and supporting files; source data files for all figures have been provided

Article and author information

Author details

  1. Shu-Jung Chang

    1Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, United States
    Competing interests
    The authors declare that no competing interests exist.
  2. Yu-Ting Hsu

    Graduate Institute of Microbiology, National Taiwan University, Taipei, Taiwan
    Competing interests
    The authors declare that no competing interests exist.
  3. Yun Chen

    Graduate Institute of Microbiology, National Taiwan University, Taipei, Taiwan
    Competing interests
    The authors declare that no competing interests exist.
  4. Yen-Yi Lin

    Graduate Institute of Microbiology, National Taiwan University, Taipei, Taiwan
    Competing interests
    The authors declare that no competing interests exist.
  5. Maria Lara-Tejero

    Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, United States
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0002-1339-0859
  6. Jorge E Galan

    Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, United States
    For correspondence
    jorge.galan@yale.edu
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0002-6531-0355

Funding

National Institute of Allergy and Infectious Diseases (AI079022)

  • Jorge E Galan

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

Reviewing Editor

  1. Dominique Soldati-Favre, University of Geneva, Switzerland

Version history

  1. Preprint posted: August 10, 2021 (view preprint)
  2. Received: March 11, 2022
  3. Accepted: May 15, 2022
  4. Accepted Manuscript published: May 17, 2022 (version 1)
  5. Version of Record published: May 27, 2022 (version 2)

Copyright

© 2022, Chang 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.

Metrics

  • 3,149
    views
  • 335
    downloads
  • 8
    citations

Views, downloads and citations are aggregated across all versions of this paper published by eLife.

Download links

A two-part list of links to download the article, or parts of the article, in various formats.

Downloads (link to download the article as PDF)

Open citations (links to open the citations from this article in various online reference manager services)

Cite this article (links to download the citations from this article in formats compatible with various reference manager tools)

  1. Shu-Jung Chang
  2. Yu-Ting Hsu
  3. Yun Chen
  4. Yen-Yi Lin
  5. Maria Lara-Tejero
  6. Jorge E Galan
(2022)
Typhoid toxin sorting and exocytic transport from Salmonella Typhi infected cells
eLife 11:e78561.
https://doi.org/10.7554/eLife.78561

Share this article

https://doi.org/10.7554/eLife.78561

Further reading

    1. Immunology and Inflammation
    2. Microbiology and Infectious Disease
    Ffion R Hammond, Amy Lewis ... Philip M Elks
    Research Article

    Tuberculosis is a major global health problem and is one of the top 10 causes of death worldwide. There is a pressing need for new treatments that circumvent emerging antibiotic resistance. Mycobacterium tuberculosis parasitises macrophages, reprogramming them to establish a niche in which to proliferate, therefore macrophage manipulation is a potential host-directed therapy if druggable molecular targets could be identified. The pseudokinase Tribbles1 (Trib1) regulates multiple innate immune processes and inflammatory profiles making it a potential drug target in infections. Trib1 controls macrophage function, cytokine production, and macrophage polarisation. Despite wide-ranging effects on leukocyte biology, data exploring the roles of Tribbles in infection in vivo are limited. Here, we identify that human Tribbles1 is expressed in monocytes and is upregulated at the transcript level after stimulation with mycobacterial antigen. To investigate the mechanistic roles of Tribbles in the host response to mycobacteria in vivo, we used a zebrafish Mycobacterium marinum (Mm) infection tuberculosis model. Zebrafish Tribbles family members were characterised and shown to have substantial mRNA and protein sequence homology to their human orthologues. trib1 overexpression was host-protective against Mm infection, reducing burden by approximately 50%. Conversely, trib1 knockdown/knockout exhibited increased infection. Mechanistically, trib1 overexpression significantly increased the levels of proinflammatory factors il-1β and nitric oxide. The host-protective effect of trib1 was found to be dependent on the E3 ubiquitin kinase Cop1. These findings highlight the importance of Trib1 and Cop1 as immune regulators during infection in vivo and suggest that enhancing macrophage TRIB1 levels may provide a tractable therapeutic intervention to improve bacterial infection outcomes in tuberculosis.

    1. Microbiology and Infectious Disease
    2. Physics of Living Systems
    Chi Zhang, Rongjing Zhang, Junhua Yuan
    Research Article

    Bacteria in biofilms secrete potassium ions to attract free swimming cells. However, the basis of chemotaxis to potassium remains poorly understood. Here, using a microfluidic device, we found that Escherichia coli can rapidly accumulate in regions of high potassium concentration on the order of millimoles. Using a bead assay, we measured the dynamic response of individual flagellar motors to stepwise changes in potassium concentration, finding that the response resulted from the chemotaxis signaling pathway. To characterize the chemotactic response to potassium, we measured the dose–response curve and adaptation kinetics via an Förster resonance energy transfer (FRET) assay, finding that the chemotaxis pathway exhibited a sensitive response and fast adaptation to potassium. We further found that the two major chemoreceptors Tar and Tsr respond differently to potassium. Tar receptors exhibit a biphasic response, whereas Tsr receptors respond to potassium as an attractant. These different responses were consistent with the responses of the two receptors to intracellular pH changes. The sensitive response and fast adaptation allow bacteria to sense and localize small changes in potassium concentration. The differential responses of Tar and Tsr receptors to potassium suggest that cells at different growth stages respond differently to potassium and may have different requirements for potassium.