Candida albicans Vrp1 is required for polarized morphogenesis and interacts with Wal1 and Myo5

Abstract

Recently, a link between endocytosis and hyphal morphogenesis has been identified inCandida albicansvia the Wiskott–Aldrich syndrome gene homologueWAL1. To get a more detailed mechanistic understanding of this link we have investigated a potentially conserved interaction between Wal1 and theC. albicansWASP-interacting protein (WIP) homologue encoded byVRP1. Deletion of both alleles ofVRP1results in strong hyphal growth defects under serum inducing conditions but filamentation can be observed on Spider medium. Mutantvrp1cells show a delay in endocytosis – measured as the uptake and delivery of the lipophilic dye FM4-64 into small endocytic vesicles – compared to the wild-type. Vacuolar morphology was found to be fragmented in a subset of cells and the cortical actin cytoskeleton was depolarized invrp1daughter cells. The morphology of thevrp1null mutant could be complemented by reintegration of the wild-typeVRP1gene at theBUD3locus. Using the yeast two-hybrid system we could demonstrate an interaction between the C-terminal part of Vrp1 and the N-terminal part of Wal1, which contains the WH1 domain. Furthermore, we found that Myo5 has several potential interaction sites on Vrp1. This suggests that a Wal1–Vrp1–Myo5 complex plays an important role in endocytosis and the polarized localization of the cortical actin cytoskeleton to promote polarized hyphal growth inC. albicans.