Role of Retrograde Trafficking in Stress Response, Host Cell Interactions, and Virulence of Candida albicans

Abstract

In Saccharomyces cerevisiae, the vacuolar protein sorting complexes Vps51/52/53/54 and Vps15/30/34/38 are essential for efficient endosome-to-Golgi complex retrograde transport. Here we investigated the function of Vps15 and Vps51, representative members of these complexes, in the stress resistance, host cell interactions, and virulence of Candida albicans. We found that C. albicans vps15⌬/⌬ and vps51⌬/⌬ mutants had abnormal vacuolar morphology, impaired retrograde protein trafficking, and dramatically increased susceptibility to a variety of stressors. These mutants also had reduced capacity to invade and damage oral epithelial cells in vitro and attenuated virulence in the mouse model of oropharyngeal candidiasis. Proteomic analysis of the cell wall of the vps51⌬/⌬ mutant revealed increased levels of the Crh11 and Utr2 transglycosylases, which are targets of the calcineurin signaling pathway. The transcript levels of the calcineurin pathway members CHR11, UTR2, CRZ1, CNA1, and CNA2 were elevated in the vps15⌬/⌬ and vps51⌬/⌬ mutants. Furthermore, these strains were highly sensitive to the calcineurin-specific inhibitor FK506. Also, deletion of CHR11 and UTR2 further increased the stress susceptibility of these mutants. In contrast, overexpression of CRH11 and UTR2 partially rescued their defects in stress resistance, but not host cell interactions. Therefore, intact retrograde trafficking in C. albicans is essential for stress resistance, host cell interactions, and virulence. Aberrant retrograde trafficking stimulates the calcineurin signaling pathway, leading to the increased expression of Chr11 and Utr2, which enables C. albicans to withstand environmental stress.

An essential role for phosphatidylinositol 3-kinase in the inhibition of phagosomal maturation, intracellular survival and virulence inCandida glabrata

“…Susceptibility of the Cgvps15 Δ mutant to FK506 (Fig. B) is particularly intriguing as the C. albicans vps15 Δ/ vps15 Δ mutant but not the S. cerevisiae vps15 Δ mutant has recently been shown to be sensitive to FK506 (Parsons et al ., ; Liu et al ., ). These findings are suggestive of requirement for constitutive calcineurin activation in vps15 Δ mutants to be a unique feature of pathogenic yeasts.…”

“…A). Notably, the hyperadherence phenotype of Cgvps15 Δ and Cgvps34 Δ mutants is contrary to the reported diminished adherence capabilities of C. albicans vps15 Δ and vps34 Δ null mutants (Bruckmann et al ., ; Liu et al ., ). Fluorescence‐activated cell sorting (FACS) analysis using anti‐Epa1 antibody showed two‐ to six‐fold higher Epa1 cell surface expression in Cgvps15 Δ and Cgvps34 Δ mutants (Fig.…”

Trafficking through the Late Endosome Significantly Impacts Candida albicans Tolerance of the Azole Antifungals

“…Others have reported that a C. albicans vps15⌬/⌬ mutant defective in retrograde trafficking from the PVC back to the Golgi compartment is highly sensitive to fluconazole (48). Furthermore, two mutants lacking components of the endosomal sorting complex required for transport (ESCRT) that facilitates the formation of intralumenal multivesicular bodies from the PVC's surface membrane are also sensitive to fluconazole (49).…”

Endosomal Trafficking Defects Can Induce Calcium-Dependent Azole Tolerance in Candida albicans

“…Despite also exhibiting elevated expression levels of calcineurin-dependent genes, this mutant is highly sensitive to fluconazole (37). The reasons for this are unclear; however, it is apparent that the specific PVC trafficking step affected is a crucial determinant of the physiological impact of the azoles on the fungal cell.…”