The Sur7 protein resides in punctate membrane subdomains and mediates spatial regulation of cell wall synthesis in Candida albicans

Abstract

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 sur7Δ 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 sur7Δ mutant are similar to the effects of inhibiting cell wall β-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.

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Acknowledgements

This work was supported by research grant RO1 AI47837 from the National Institutes of Health that was awarded to James B. Konopka.

Figures and Tables

Figure 1 Localization of Sur7-GFP to punctate patches in the plasma membrane. C. albicans strain YJA15 carrying a SUR7-GFP fusion gene was analyzed by fluorescence microscopy. An image of the medial focal plane is on the left, the top of the cell is in the middle, and a light microscope image of the same cell is shown on the right.

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