The eukaryotic plasma membrane is organized into distinct domains that contribute to its function. One new type of plasma membrane domain was identified by studies on the Sur7 protein, which was discovered in the yeast S. cerevisiae to localize into stable punctate patches known as MCC or eisosomes. Sur7 shares similarities with Claudin proteins that form tight junction domains in animal cells, suggesting common roles for these tetraspanning membrane proteins. Recent analysis of C. albicans revealed broad new roles for Sur7; a sur7Delta mutant mislocalized septins and actin and was defective in morphogenesis. Strikingly, cell wall synthesis was very abnormal, including long projections of chitin-rich cell wall into the cytoplasm. Some phenotypes of the sur7Delta mutant are similar to the effects of inhibiting cell wall beta-glucan synthesis. This suggests that the abnormal cell wall structures are related to the increased chitin synthesis commonly seen under cell wall stress conditions, which could be mediated in part by the altered septin localization. Altogether, these results identify new roles for Sur7 and MCC/eisosomes in plasma membrane organization and coordination of the different aspects of cell wall synthesis.
Keywords: Candida albicans; MCC; Saccharomyces cerevisiae; Sur7; cell wall synthesis; chitin; eisosome; hyphae; septin; yeast.