Ent2 Governs Morphogenesis and Virulence in Part through Regulation of the Cdc42 Signaling Cascade in the Fungal Pathogen Candida albicans.

The ability to transition between yeast and filamentous growth states is critical for virulence of the leading human fungal pathogen Candida albicans. Large-scale genetic screens have identified hundreds of genes required for this morphological switch, but the mechanisms by which many of these genes orchestrate this developmental transition remain largely elusive. In this study, we characterized the role of Ent2 in governing morphogenesis in C. albicans. We showed that Ent2 is required for filamentous growth under a wide range of inducing conditions and is also required for virulence in a mouse model of systemic candidiasis. We found that the epsin N-terminal homology (ENTH) domain of Ent2 enables morphogenesis and virulence and does so via a physical interaction with the Cdc42 GTPase-activating protein (GAP) Rga2 and regulation of its localization. Further analyses revealed that overexpression of the Cdc42 effector protein Cla4 can overcome the requirement for the ENTH-Rga2 physical interaction, indicating that Ent2 functions, at least in part, to enable proper activation of the Cdc42-Cla4 signaling pathway in the presence of a filament-inducing cue. Overall, this work characterizes the mechanism by which Ent2 regulates hyphal morphogenesis in C. albicans, unveils the importance of this factor in enabling virulence in an in vivo model of systemic candidiasis and adds to the growing understanding of the genetic control of a key virulence trait. IMPORTANCE Candida albicans is a leading human fungal pathogen that can cause life-threatening infections in immunocompromised individuals, with mortality rates of ~40%. The ability of this organism to grow in both yeast and filamentous forms is critical for the establishment of systemic infection. Genomic screens have identified many genes required for this morphological transition, yet our understanding of the mechanisms that regulate this key virulence trait remains incomplete. In this study, we characterized Ent2 as a core regulator of C. albicans morphogenesis. We show that Ent2 regulates hyphal morphogenesis through an interaction between its ENTH domain and the Cdc42 GAP, Rga2, which signals through the Cdc42-Cla4 signaling pathway. Finally, we show that the Ent2 protein, and specifically its ENTH domain, is required for virulence in a mouse model of systemic candidiasis. Overall, this work identifies Ent2 as a key regulator of filamentation and virulence in C. albicans.