Differential effects of inhibiting chitin and 1,3-{beta}-D-glucan synthesis in ras and calcineurin mutants of Aspergillus fumigatus.
Aspergillus fumigatus must be able to properly form hyphae and maintain cell wall integrity in order to establish invasive disease. Ras proteins and calcineurin each have been implicated as having roles in these processes. Here, we further delineate the roles of calcineurin and Ras activity in cell wall biosynthesis and hyphal morphology using genetic and pharmacologic tools. Strains deleted for three genes encoding proteins of these pathways, rasA (the Ras protein), cnaA (calcineurin), or crzA (the zinc finger transcription factor downstream of calcineurin), all displayed decreased cell wall 1,3-beta-d-glucan content. Echinocandin treatment further decreased the levels of 1,3-beta-d-glucan for all strains tested yet also partially corrected the hyphal growth defect of the DeltarasA strain. The inhibition of glucan synthesis caused an increase in chitin content for wild-type, dominant-active rasA, and DeltarasA strains. However, this important compensatory response was diminished in the calcineurin pathway mutants (DeltacnaA and DeltacrzA). Taken together, our data suggest that the Ras and calcineurin pathways act in parallel to regulate cell wall formation and hyphal growth. Additionally, the calcineurin pathway elements cnaA and crzA play a major role in proper chitin and glucan incorporation into the A. fumigatus cell wall.
Fortwendel
Jarrod R
JR
Department of Pediatrics, Duke University Medical Center, Durham, NC 27710, USA.
Juvvadi
Praveen Rao
PR
Pinchai
Nadthanan
N
Perfect
B Zachary
BZ
Alspaugh
J Andrew
JA
Perfect
John R
JR
Steinbach
William J
WJ
D000617:Aminoglycosides / Q000494:pharmacology; D000935:Antifungal Agents / Q000494:pharmacology; D001232:Aspergillus fumigatus / Q000187:drug effects / Q000235:genetics*; D019703:Calcineurin / Q000235:genetics*; D000077336:Caspofungin; D002473:Cell Wall / Q000187:drug effects / Q000378:metabolism; D002686:Chitin / Q000037:antagonists & inhibitors* / Q000096:biosynthesis*; D054714:Echinocandins / Q000494:pharmacology; D005456:Fluorescent Dyes; D005656:Fungal Proteins / Q000235:genetics; D005800:Genes, Fungal / Q000187:drug effects / Q000235:genetics*; D011905:Genes, ras / Q000235:genetics*; D055666:Lipopeptides; D008826:Microbial Sensitivity Tests; D008856:Microscopy, Fluorescence; D009154:Mutation / Q000235:genetics / Q000502:physiology; D015398:Signal Transduction / Q000187:drug effects; D047071:beta-Glucans / Q000037:antagonists & inhibitors* / Q000378:metabolism*
D000617:Aminoglycosides; D000935:Antifungal Agents; C530975:CrzA protein, Aspergillus fumigatus; D054714:Echinocandins; D005456:Fluorescent Dyes; D005656:Fungal Proteins; D055666:Lipopeptides; D047071:beta-Glucans; D002686:Chitin; C033363:beta-1,3-glucan; C011952:nikkomycin; D019703:Calcineurin; D000077336:Caspofungin