Identification and characterization of Rvs162/Rvs167-3, a novel N-BAR heterodimer in the human fungal pathogen Candida albicans

Abstract

Membrane reshaping resides at the core of many important cellular processes and amongst its mediators are the BAR (Bin, Amphiphysin, Rvs) domain-containing proteins. We have explored the diversity and function of the Rvs BAR proteins in Candida albicans and identified a novel family member, Rvs167-3 (orf19.1861). We show that Rvs167-3 specifically interacts with Rvs162 to form a stable BAR heterodimer able to bind liposomes in vitro. A second, distinct, heterodimer is formed by the canonical BAR proteins Rvs161 and Rvs167. Purified Rvs161/Rvs167 complex also binds liposomes indicating that C. albicans expresses two functional BAR heterodimers. We used life cell imaging to localize GFP-tagged Rvs167-3 and Rvs167 and show that both proteins concentrate in small cortical spots. However, while Rvs167 strictly co-localizes with the endocytic marker protein Abp1, we do not observe any co-localization of Rvs167-3 with sites of endocytosis marked by Abp1. Furthermore, the rvs167-3Δ/Δ mutant is not defective in endocytosis and strains lacking Rvs167-3 or its partner Rvs162 do not display increased sensitivity to high salt or decreased cell wall integrity, phenotypes observed for rvs167Δ/Δ and rvs161Δ/Δ strains and which are linked to endocytosis defects. Taken together, our results indicate different roles for the two BAR heterodimers in C. albicans: the canonical Rvs161/Rvs167 heterodimer functions in endocytosis, whereas the novel Rvs162/Rvs167-3 heterodimer seems not to be involved in this process. Nevertheless, despite their different roles our phenotypic analysis revealed a genetic interaction between the two BAR heterodimers, suggesting that they may have a related but distinct membrane-associated function.