Organization of a sterol-rich membrane domain by cdc15p during cytokinesis in fission yeast

Many membrane processes occur in discrete membrane domains containing lipid rafts(1), but little is known about how these domains are organized and positioned. In the fission yeast Schizosaccharomyces pombe, a sterol-rich membrane domain forms at the cell-division site(2). Here, we show that formation of this membrane domain is independent of the contractile actin ring, septation, mid1p and the septins, and also requires cdc15p(3), an essential contractile ring protein that associates with lipid rafts. cdc15 mutants have membrane domains in the shape of spirals. Overexpression of cdc15p in interphase cells induces abnormal membrane domain formation in an actin-independent manner. We propose that cdc15p functions to organize lipid rafts at the cleavage site for cytokinesis.