Unknown,Transcriptomics,Genomics,Proteomics

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

ABSTRACT: 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. Comparison of three gene deletion strains to wild-type, with 3 biological replicates for each sample.

ORGANISM(S): Cryptococcus neoformans

SUBMITTER: Maureen Donlin

PROVIDER: E-GEOD-57217 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:WD40 motif-containing Msi1-like (MSIL) proteins play pleiotropic cellular functions as a negative regulator of the Ras/cAMP-pathways and a component of chromatin assembly factor-I (CAF-I), and yet have not been studied in fungal pathogens. Here we identified and characterized an MSIL protein, Msl1, in Cryptococcus neoformans, which can cause fatal meningoencephalitis in humans. Notably, Msl1 was not a functional ortholog for the yeast Msi1 but played pleiotropic roles in C. neoformans in both cAMP-dependent and -independent manners but mainly Ras-independently. Msl1 negatively controlled antioxidant melanin production and sexual differentiation, which can be repressed by inhibiting the cAMP-signaling pathways. In contrast, Msl1 controlled thermotolerance, diverse stress responses, and antifungal drugs resistance in Ras/cAMP-independent manners. Cac2, which is the second CAF-I component, appeared to play both redundant and distinct function with Msl1. Msl1 is required for full virulence of C. neoformans. Transcriptome and proteomic analysis identified a group of Msl1-regulated genes or -interacting proteins, respectively, which mostly include stress-related genes, including HSP12, HSP78, SSA1, SSA4, and STM1. Furthermore, we identified the third putative component of CAF-1, Rlf2, in C. neoformans. In conclusion, this study demonstrated the pleiotropic roles of Msl1 in human fungal pathogen C. neoformans, providing a novel antifungal therapeutic target. There is more than 95% genome homology between JEC21 and H99. Therefore, 6 slides of JEC21 (Cryptococcus neoformans var. neoformans serotype D) 70-mer oligos are used in this analysis. Total RNAs are extracted from 2 strains from H99 (H99 wild-type strain (Cryptococcus neoformans var. grubii serotype A), msl1M-NM-^T). 3 biological replicate experiments are performed for each strain. We use the mix of all total RNAs from this experiment as the control RNA. We use Cy3 as the test sample dye and Cy5 as the control dye.

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

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