The enteric pathogen Cryptosporidium parvum exports proteins into the cytosol of the infected host cell
- University of Pennsylvania, United States
- The Francis Crick Institute, United Kingdom
- University of Georgia, United States
Abstract
The parasite Cryptosporidium is responsible for diarrheal disease in young children causing death, malnutrition, and growth delay. Cryptosporidium invades enterocytes where it develops in a unique intracellular niche. Infected cells exhibit profound changes in morphology, physiology and transcriptional activity. How the parasite effects these changes is poorly understood. We explored the localization of highly polymorphic proteins and found members of the C. parvum MEDLE protein family to be translocated into the cytosol of infected cells. All intracellular life stages engage in this export, which occurs after completion of invasion. Mutational studies defined an N-terminal host-targeting motif and demonstrated proteolytic processing at a specific leucine residue. Direct expression of MEDLE2 in mammalian cells triggered an ER stress response, which was also observed during infection. Taken together, our studies reveal the presence of a Cryptosporidium secretion system capable of delivering parasite proteins into the infected enterocyte.
Data availability
The RNA sequencing dataset generated from the MEDLE2 transfection experiment has been deposited in GEO under accession number GSE174117. Source code and data files for this dataset were provided. Furthermore, numerical source data used for imaging quantification experiments in Figures 2 and 3 were provided.
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The enteric pathogen Cryptosporidium parvum exports proteins into the cytoplasm of the infected host cellNCBI Gene Expression Omnibus, GSE174117.
Article and author information
Author details
Funding
National Institute of Allergy and Infectious Diseases (R01AI127798)
- Boris Striepen
National Institute of Allergy and Infectious Diseases (R01AI112427)
- Boris Striepen
National Institute of Allergy and Infectious Diseases (T32AI007532)
- Jennifer E Dumaine
National Institute of Allergy and Infectious Diseases (K99AI137442)
- Adam Sateriale
National Institute of Allergy and Infectious Diseases (T32A1055400)
- Jodi A Gullicksrud
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Ethics
Animal experimentation: All animals used in this study were handled and cared for in accordance with approved Institutional Animal Care and Use Committee protocols at the University of Georgia (protocol A2016 01-028-Y1-A4) and the University of Pennsylvania (protocol #806292).
Copyright
© 2021, Dumaine 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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The enteric pathogen Cryptosporidium parvum exports proteins into the cytosol of the infected host cell
eLife 10:e70451.
https://doi.org/10.7554/eLife.70451
Further reading
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- Immunology and Inflammation
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Type III secretion system (T3SS) is a virulence apparatus existing in many bacterial pathogens. Structurally, T3SS consists of the base, needle, tip, and translocon. The NLRC4 inflammasome is the major receptor for T3SS needle and basal rod proteins. Whether other T3SS components are recognized by NLRC4 is unclear. In this study, using Edwardsiella tarda as a model intracellular pathogen, we examined T3SS−inflammasome interaction and its effect on cell death. E. tarda induced pyroptosis in a manner that required the bacterial translocon and the host inflammasome proteins of NLRC4, NLRP3, ASC, and caspase 1/4. The translocon protein EseB triggered NLRC4/NAIP-mediated pyroptosis by binding NAIP via its C-terminal region, particularly the terminal 6 residues (T6R). EseB homologs exist widely in T3SS-positive bacteria and share high identities in T6R. Like E. tarda EseB, all of the representatives of the EseB homologs exhibited T6R-dependent NLRC4 activation ability. Together these results revealed the function and molecular mechanism of EseB to induce host cell pyroptosis and suggested a highly conserved inflammasome-activation mechanism of T3SS translocon in bacterial pathogens.
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