Candida albicans cell wall glycosidases DFG5 and DCW1 are required for biofilm formation and Hog-1 signaling

Background: Candida albicans is a commensal fungus that inhabits the oral mucosal surface and causes oral and systemic candidiasis. Oral candidiasis most commonly occurs in patients with AIDS, denture wearers and newborn children. Systemic candidiasis occurs mainly in immunocompromised patients and patients admitted to hospitals for prolonged periods. The C. albicans homologous genes, DFG5 and DCW1 , encode for two closely related cell wall proteins with putative glycosyltransferase enzyme activity and C-terminal GPI-anchors. Past studies have shown that individual DFG5 and DCW1 mutations are viable but simultaneous deletion of DFG5 and DCW1 in C. albicans results in lethality. However, the exact functions of these cell wall based enzymes, which represent ideal drug targets, are not understood. Methods: . C. albicans DFG5/DCW1 heterologous and conditional double mutant strains, ES1 and ES195 respectively, were assessed for growth and biofilm formation in comparison to wild type and parental strains. Cell wall, osmotic and heat stress susceptibility of the mutant and control strains was assessed using agar spotting assays. Western Blot analysis of mutant strains and control strains was performed to assess Hog-1 phosphorylation status. Results: . Growth in planktonic cultures and biofilm formation was found to be affected in the DFG5/DCW1 double mutants as compared to control strains. The mutant strains were also less resistant to cell wall, osmotic and heat stresses as compared to control strains. Hog-1 phosphorylation was affected in the mutant strains. Conclusions: . These data indicate that Candida albicans DFG5 and DCW1 play critical roles in biofilm formation and Hog-1 signaling pathway.