Membrane damage during Candida albicans epithelial invasion is localized to distinct host subcellular niches

Candida albicans is an opportunistic fungal pathogen normally found as a commensal in human mucosa. In susceptible patients, its hyphal filamentous form can invade and damage host epithelium leading to local or systemic infection. The secreted fungal toxin candidalysin is required for epithelial damage, although both hyphal extension and candidalysin are required for inducing maximal infection damage, for reasons that are not well understood. Here we study the interplay between hyphal extension and epithelial damage in vitro using live cell imaging combined with damage-sensitive reporters and volume electron microscopy. We first quantify candidalysin-induced host membrane rupture and host cell death at the single cell level and determine the three-dimensional architecture of invasion in our experimental system. We then show that the spatial organization of host membrane rupture is regulated by candidalysin and is predictive of host cell death. Finally, we demonstrate that membrane rupture occurs at two distinct host subcellular niches: the juxtanuclear region and the cell-cell boundary, with the latter the main driver of subsequent host cell death. Based on these results, we propose that C. albicans invasion damages epithelial membranes in a sequential process in which candidalysin secretion first acts to weaken host membranes enveloping invading hyphae, followed by membrane rupture occurring as hyphae traverse two distinct host subcellular niches.