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The chitin synthase genes chsA and chsC are not required for cell wall stress responses in the human pathogen Aspergillus fumigatus.

ABSTRACT: Invasive aspergillosis is a leading cause of mortality in immunocompromised patients. The fungal cell wall is an attractive antifungal target, but it is dynamic and responsive to external stressors. The existence of multiple chitin synthases within Aspergilli is thought to reflect specialized functions in cell wall damage responses that facilitate continued growth and viability. We previously reported increased transcription of Aspergillus fumigatus chitin synthases chsA and chsC following echinocandin treatment, suggesting important roles for these chitin synthases in cell wall compensation. As only partial disruptions have been made of these genes, we generated deletion mutants of chsA and chsC singly (?chsA and ?chsC) and doubly (?chsA ?chsC). The ?chsA ?chsC strain displayed reduced total chitin synthase activity. Interestingly, deletion of these chitin synthase genes did not affect levels of chitin or ?-1,3-glucan.The ?chsA, ?chsC and ?chsA ?chsC strains produced wild-type echinocandin-mediated chitin increases, consistent with unaltered cell wall compensation. Furthermore, transcript levels of the remaining chitin synthase genes were unchanged in the mutant strains. Taken together, these results indicate that chsA and chsC do not play a direct role in the cell wall stress response. Our findings support the existence of complex post-transcriptional regulatory mechanisms controlling chitin biosynthetic machinery in response to cell wall damage.

SUBMITTER: Rogg LE

PROVIDER: S-EPMC3712863 | biostudies-literature | 2011 Aug

REPOSITORIES: biostudies-literature

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The chitin synthase genes chsA and chsC are not required for cell wall stress responses in the human pathogen Aspergillus fumigatus.

Rogg Luise E LE Fortwendel Jarrod R JR Juvvadi Praveen Rao PR Lilley Amanda A Steinbach William J WJ

Biochemical and biophysical research communications 20110705 3

Invasive aspergillosis is a leading cause of mortality in immunocompromised patients. The fungal cell wall is an attractive antifungal target, but it is dynamic and responsive to external stressors. The existence of multiple chitin synthases within Aspergilli is thought to reflect specialized functions in cell wall damage responses that facilitate continued growth and viability. We previously reported increased transcription of Aspergillus fumigatus chitin synthases chsA and chsC following echin ...[more]

PMID: 21763289

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Project description:Understanding the surface properties of the human opportunistic pathogen Aspergillus fumigatus conidia is essential given the important role they play during the fungal interactions with the human host. Although chitin synthases with myosin motor-like domain (CSM) play a major role in cell wall biosynthesis, the extent to which deletion of the CSM genes alter the surface structural and biophysical-biological properties of conidia is not fully characterized. We used three complementary atomic force microscopy techniques-i.e., structural imaging, chemical force microscopy with hydrophobic tips, and single-molecule force spectroscopy with lectin tips-to gain detailed insights into the nanoscale surface properties (ultrastructure, hydrophobicity) and polysaccharide composition of the wild-type and the chitin synthase mutant (ΔcsmA, ΔcsmB, and ΔcsmA/csmB) conidia of A. fumigatus. Wild-type conidia were covered with a highly hydrophobic layer of rodlet nanostructures. By contrast, the surface of the ΔcsmA mutant was almost completely devoid of rodlets, leading to loss of hydrophobicity and exposure of mannan and chitin polysaccharides. The ΔcsmB and ΔcsmA/csmB mutants showed a different behavior, i.e., the surfaces featured poorly organized rodlet layers, yet with a low hydrophobicity and substantial amounts of exposed mannan and chitin at the surface. As the rodlet layer is important for masking recognition of immunogenic fungal cell wall components by innate immune cells, disappearance of rodlet layers in all three chitin synthase mutant conidia was associated with an activation of human dendritic cells. These nanoscale analyses emphasize the important and distinct roles that the CSMA and CSMB genes play in modulating the surface properties and immune interactions of A. fumigatus and demonstrate the power of atomic force microscopy in fungal genetic studies for assessing the phenotypic characteristics of mutants altered in cell surface organization.

Dataset Information

The chitin synthase genes chsA and chsC are not required for cell wall stress responses in the human pathogen Aspergillus fumigatus.

Publications

The chitin synthase genes chsA and chsC are not required for cell wall stress responses in the human pathogen Aspergillus fumigatus.

Similar Datasets

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