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The CspC pseudoprotease regulates germination of Clostridioides difficile spores in response to multiple environmental signals.

ABSTRACT: The gastrointestinal pathogen, Clostridioides difficile, initiates infection when its metabolically dormant spore form germinates in the mammalian gut. While most spore-forming bacteria use transmembrane germinant receptors to sense nutrient germinants, C. difficile is thought to use the soluble pseudoprotease, CspC, to detect bile acid germinants. To gain insight into CspC's unique mechanism of action, we solved its crystal structure. Guided by this structure, we identified CspC mutations that confer either hypo- or hyper-sensitivity to bile acid germinant. Surprisingly, hyper-sensitive CspC variants exhibited bile acid-independent germination as well as increased sensitivity to amino acid and/or calcium co-germinants. Since mutations in specific residues altered CspC's responsiveness to these different signals, CspC plays a critical role in regulating C. difficile spore germination in response to multiple environmental signals. Taken together, these studies implicate CspC as being intimately involved in the detection of distinct classes of co-germinants in addition to bile acids and thus raises the possibility that CspC functions as a signaling node rather than a ligand-binding receptor.

SUBMITTER: Rohlfing AE

PROVIDER: S-EPMC6636752 | biostudies-literature | 2019 Jul

REPOSITORIES: biostudies-literature

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The CspC pseudoprotease regulates germination of Clostridioides difficile spores in response to multiple environmental signals.

Rohlfing Amy E AE Eckenroth Brian E BE Forster Emily R ER Kevorkian Yuzo Y Donnelly M Lauren ML Benito de la Puebla Hector H Doublié Sylvie S Shen Aimee A

PLoS genetics 20190705 7

The gastrointestinal pathogen, Clostridioides difficile, initiates infection when its metabolically dormant spore form germinates in the mammalian gut. While most spore-forming bacteria use transmembrane germinant receptors to sense nutrient germinants, C. difficile is thought to use the soluble pseudoprotease, CspC, to detect bile acid germinants. To gain insight into CspC's unique mechanism of action, we solved its crystal structure. Guided by this structure, we identified CspC mutations that ...[more]

PMID: 31276487

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Project description:UnlabelledClostridium difficile spore germination is essential for colonization and disease. The signals that initiate C. difficile spore germination are a combination of taurocholic acid (a bile acid) and glycine. Interestingly, the chenodeoxycholic acid class (CDCA) bile acids competitively inhibit taurocholic acid-mediated germination, suggesting that compounds that inhibit spore germination could be developed into drugs that prophylactically prevent C. difficile infection or reduce recurring disease. However, a recent report called into question the utility of such a strategy to prevent infection by describing C. difficile strains that germinated in the apparent absence of bile acids or germinated in the presence of the CDCA inhibitor. Because the mechanisms of C. difficile spore germination are beginning to be elucidated, the mechanism of germination in these particular strains could yield important information on how C. difficile spores initiate germination. Therefore, we quantified the interaction of these strains with taurocholic acid and CDCA, the rates of spore germination, the release of DPA from the spore core, and the abundance of the germinant receptor complex (CspC, CspB, and SleC). We found that strains previously observed to germinate in the absence of taurocholic acid correspond to more potent 50% effective concentrations (EC50 values; the concentrations that achieve a half-maximum germination rate) of the germinant and are still inhibited by CDCA, possibly explaining the previous observations. By comparing the germination kinetics and the abundance of proteins in the germinant receptor complex, we revised our original model for CspC-mediated activation of spore germination and propose that CspC may activate spore germination and then inhibit downstream processes.ImportanceClostridium difficile forms metabolically dormant spores that persist in the health care environment. In susceptible hosts, C. difficile spores germinate in response to certain bile acids and glycine. Blocking germination by C. difficile spores is an attractive strategy to prevent the initiation of disease or to block recurring infection. However, certain C. difficile strains have been identified whose spores germinate in the absence of bile acids or are not blocked by known inhibitors of C. difficile spore germination (calling into question the utility of such strategies). Here, we further investigate these strains and reestablish that bile acid activators and inhibitors of germination affect these strains and use these data to suggest another role for the C. difficile bile acid germinant receptor.

Dataset Information

The CspC pseudoprotease regulates germination of Clostridioides difficile spores in response to multiple environmental signals.

Publications

The CspC pseudoprotease regulates germination of Clostridioides difficile spores in response to multiple environmental signals.

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