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The ER protein translocation channel subunit Sbh1 controls virulence of Cryptococcus neoformans

ABSTRACT: C. neoformans is an opportunistic human pathogen whose polysaccharide capsule anchored to the cell wall is critical for virulence. Biogenesis of both cell wall and capsule relies on the secretory pathway. Protein secretion begins with protein translocation across the endoplasmic reticulum (ER) membrane through a highly conserved channel formed by three proteins, Sec61, Sbh1, and Sss1. Sbh1 is most divergent and contains multiple phosphorylation sites which may allow it to control entry into the secretory pathway in a regulated, species- and protein-specific manner. We show here that in contrast to S. cerevisiae, C. neoformans lacking SBH1 are barely temperature-sensitive, but that absence of SBH1 causes a cell-wall defect in both species. Comparison of the proteomes of wildtype and Δsbh1 C. neoformans revealed a small set of secretory and transmembrane proteins whose expression under infection-like conditions was upregulated in wildtype, but not in the Δsbh1 mutant. These proteins are mostly involved in cell-wall biogenesis. We found that adhesion to macrophages was compromised in the Δsbh1 strain and in mice, the C. neoformans Δsbh1 mutant was virtually avirulent. We conclude that upon contact with the host Sbh1 controls entry of virulencefactors into the secretory pathway of Cryptococcus neoformans.

INSTRUMENT(S): Q Exactive

ORGANISM(S): Cryptococcus Neoformans Var. Grubii Serotype A (strain H99 / Atcc 208821 / Cbs 10515 / Fgsc 9487) (filobasidiella Neoformans Var. Grubii)

TISSUE(S): Cell Culture

SUBMITTER: Jennifer Geddes-McAlister

LAB HEAD: Jennifer Geddes-McAlister

PROVIDER: PXD013894 | Pride | 2023-01-27

REPOSITORIES: Pride

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	JGM_Cell10.raw	Raw
	JGM_Cell11.raw	Raw
	JGM_Cell12.raw	Raw
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Usv101 is a key regulator of cryptococcal virulence and determinant of host response

Project description:Cryptococcus neoformans is a fungal pathogen responsible for hundreds of thousands of deaths per year. Its critical virulence factor is a polysacharride capsule which grows large upon entry into a mammalian host. We previously identified USV101 as a transcription factor whose deletion results in enlarged capsules. Here, we characterize strains lacking or overexpressing USV101 in terms of their virulence-related phenotypes, the altered course of infection by them and immune response to them in a mouse model, the relationship of Usv101 to other transcription factors involved in capsule regulation, and the changes in Usv101 activity during capsule induction. To study the function of Usv101, a key C. neoformans regulator of virulence, and its interactions with downstream capsule-regulating TFs GAT201 and SP1, expression profiles were generated by RNA-seq of a usv101 deletion mutant, a USV101 overexpression mutant, strains expressing GAT201 under various promoters, various double mutants, and wildtype cells grown in a capsule non-inducing condition, a capsule inducing condition for 90 minutes, or a capsule inducing condition for 24 hours.

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Cross talk between the cell wall integrity and cAMP/protein kinase A pathways in Cryptococcus neoformans

Project description:Cryptococcus neoformans is a fungal pathogen of immunocompromised people that causes fatal meningitis. The fungal cell wall is essential to viability and pathogenesis of C. neoformans, and biosynthesis and repair of the wall is primarily controlled by the cell wall integrity (CWI) signaling pathway. Previous work by us and others have shown that deletion of genes encoding the four major kinases in the CWI signaling pathway, namely PKC1, BCK1, MKK2 and MPK1 results in severe cell wall phenotypes, sensitivity to a variety of cell wall stressors and, for Mpk1, reduced virulence in a mouse model. Here, we examined the global transcriptional response of gene deletions of BCK1, MKK2 and MPK1 compared to wild-type cells. We found over 1000 genes were differentially expressed in one or more of the deletion strains, with 115 genes differentially expressed in all three strains, many of which have been identified as genes regulated by the cAMP/protein kinase A (PKA) pathway. Biochemical measurements of cAMP levels in the kinase deletion stains revealed significantly less cAMP in all of the deletion strains compared to wild-type cells. The deletion strains also produced significantly smaller capsules than wild type KN99 under capsule inducing conditions, although they shed similar levels of capsule as wild type. Finally, addition of exogenous cAMP led to reduced sensitivity to cell wall stress and restored surface capsule to near wild-type levels. Thus, we have direct evidence of cross talk between the CWI and cAMP/PKA pathways that may have important implications for regulation of cell wall and capsule homeostasis.

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Cross talk between the cell wall integrity and cAMP/protein kinase A pathways in Cryptococcus neoformans

2014-07-01 | E-GEOD-57217 | biostudies-arrayexpress

Expression Profiling of the Response to Short-Term Exposure to Fluconazole in Cryptococcus neoformans Serotype A

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