The yeast claudin Dcv1 is important for demarcating the front domain of pheromone-responding yeast cells
Cell polarization in response to chemical gradients is important in development and homeostasis across eukaryota. Chemosensing cells orient toward or away from gradient sources by polarizing along a front-rear axis. Using the chemotropic mating response of the budding yeast S. cerevisiae as a model of environmentally-induced cell polarization, we found that Dcv1, a claudin homolog, is a determinant of front-rear polarity. Although Dcv1 localized uniformly on the plasma membrane (PM){dagger} of vegetative cells, it was confined to the rear of cells responding to pheromone, away from the pheromone receptor and mating projection. Deletion of DCV1 conferred mislocalization of sensory, polarity, and trafficking proteins, as well as the PM lipids ergosterol, phosphatidylinositol-4,5-bisphosphate (PIP2), and phosphatidylserine (PS). These phenotypes correlated with defects in pheromone-gradient tracking and cell fusion. We propose that the novel claudin-like and rear-domain protein, Dcv1, demarcates the mating-specific front domain primarily by restricting PM lipid distribution. Consistent with this hypothesis, a mutation that blocks ergosterol biosynthesis partially phenocopies dcv1{Delta}. Summary statementThe yeast claudin Dcv1 facilitates the proper localization of plasma membrane lipids and proteins that are required for front-rear polarity, efficient chemotropism, and cell fusion.