Maier Peter, Rathfelder Nicole, Finkbeiner Martin G, Taxis Christof, Mazza Massimiliano, Le Panse Sophie, Haguenauer-Tsapis Rosine, Knop Michael
EMBL, Cell Biology and Biophysics Unit, Meyerhofstrasse 1, 69117 Heidelberg, Germany.
EMBO J. 2007 Apr 4;26(7):1843-52. doi: 10.1038/sj.emboj.7601621. Epub 2007 Mar 8.
Intracellular budding is a developmentally regulated type of cell division common to many fungi and protists. In Saccaromyces cerevisiae, intracellular budding requires the de novo assembly of membranes, the prospore membranes (PSMs) and occurs during spore formation in meiosis. Ssp1p is a sporulation-specific protein that has previously been shown to localize to secretory vesicles and to recruit the leading edge protein coat (LEP coat) proteins to the opening of the PSM. Here, we show that Ssp1p is a multidomain protein with distinct domains important for PI(4,5)P(2) binding, binding to secretory vesicles and inhibition of vesicle fusion, interaction with LEP coat components and that it is subject to sumoylation and degradation. We found non-essential roles for Ssp1p on the level of vesicle transport and an essential function of Ssp1p to regulate the opening of the PSM. Together, our results indicate that Ssp1p has a domain architecture that resembles to some extent the septin class of proteins, and that the regulated removal of Ssp1p from the PSM is the major step underlying cytokinesis in yeast sporulation.
细胞内出芽是许多真菌和原生生物中常见的一种受发育调控的细胞分裂类型。在酿酒酵母中，细胞内出芽需要从头组装膜，即前孢子膜（PSM），并且发生在减数分裂过程中的孢子形成期间。Ssp1p是一种孢子形成特异性蛋白，先前已被证明定位于分泌囊泡，并将前缘蛋白衣被（LEP衣被）蛋白招募到PSM的开口处。在这里，我们表明Ssp1p是一种多结构域蛋白，具有对PI(4,5)P(2)结合、与分泌囊泡结合以及抑制囊泡融合、与LEP衣被成分相互作用很重要的不同结构域，并且它会发生SUMO化和降解。我们发现Ssp1p在囊泡运输水平上具有非必需作用，而Ssp1p在调节PSM开口方面具有必需功能。总之，我们的结果表明Ssp1p具有一种在一定程度上类似于septin类蛋白的结构域架构，并且从PSM中调控去除Ssp1p是酵母孢子形成中胞质分裂的主要步骤。
