Arv1 interacts with and regulates the first step of GPI biosynthesis in Candida albicans

The ubiquitous ARV1 gene shows significant functional conservation across eukaryotes. In humans, it is implicated in early onset epileptic encephalopathy. Evidence suggests that the phenotypes manifested in affected patients are probably due to the deficiency in expression of cell surface GPI anchored proteins. S. cerevisiae Arv1 is proposed to be the elusive GPI flippase that delivers the GPI intermediate from the cytoplasmic face to the luminal side of the ER for further elaboration by the first mannosyltransferase of the pathway. Human and fungal ARV1 complement S. cerevisiae ARV1. Overexpressing some of the GPI-N-acetylglucosamine transferase (GPI-GnT) subunits rescues the null strain of S. cerevisiae ARV1. In mammals and in T. brucei Arv1 co-immunoprecipitates with one or more subunits of the GPI-GnT. Based on these reports we hypothesized a cross-talk for ARV1 with the GPI biosynthetic pathway in the human pathogenic fungus, C. albicans. Using super resolution radial fluctuation (SRRF) analysis for co-localization, co-immunoprecipitation assays, and acceptor-photobleaching Forster resonance energy transfer (FRET) studies, we show that C. albicans Arv1 physically interacts with the GPI-GnT. It also transcriptionally regulates the expression of the GPI-GnT genes to control the GPI biosynthetic pathway via its very first step. Overexpression of one of the GPI-GnT subunits, CaGpi19, in C. albicans ARV1 null strain rescues its cold-sensitive growth, azole sensitivity, cell wall phenotype and GPI-GnT activity. Thus, our results suggest extensive interactions between Arv1 and GPI biosynthesis in C. albicans.