Desumoylation of the Endoplasmic Reticulum Membrane VAP Family Protein Scs2 by Ulp1 and SUMO Regulation of the Inositol Synthesis Pathway
Desumoylation of the Endoplasmic Reticulum Membrane VAP Family Protein Scs2 by Ulp1 and SUMO Regulation of the Inositol Synthesis Pathway
复制标题
DOI：
10.1128/mcb.05878-11
复制
发表时间：
2012-01-01
影响因子：
5.3
通讯作者：
Hochstrasser, Mark
中科院分区：
文献类型：
--
作者：
Felberbaum, Rachael;Wilson, Nicole R.;Hochstrasser, Mark
泛素样SUMO蛋白的翻译后蛋白修饰对真核细胞调控至关重要，但其操作和底物尚不清楚。在这里，我们报道了酿酒酵母Ulp1 SUMO蛋白酶的特定突变，包括其螺旋（CC）结构域，导致体内不同的sumoylated蛋白的积累。在Ulp1 CC突变体中积累了一个突出的类似于50 kda的同化蛋白。该蛋白被鉴定为Scs2，一种调节磷脂酰肌醇合成和脂质运输的内质网（ER）膜蛋白。Scs2的赖氨酸180突变使其同化作用消失。值得注意的是，在缺乏肌醇的情况下，细胞summoylation或细胞去summoylation机制的损害都会抑制细胞生长，并加剧由SCS2缺失引起的肌醇萎缩。缺乏Ulp2 SUMO蛋白酶的突变体受影响最严重，这种缺陷可以追溯到突变体诱导INO1转录的能力受损，INO1编码肌醇生物合成的限速酶。相反，肌醇饥饿会引起细胞SUMO偶联物的显著变化。这些结果为SUMO和肌醇通路之间的交叉调节提供了第一个证据，包括对磷脂合成和磷酸肌醇信号传导至关重要的内质网膜蛋白的聚合化。
Posttranslational protein modification by the ubiquitin-like SUMO protein is critical to eukaryotic cell regulation, but much remains unknown regarding its operation and substrates. Here we report that specific mutations in the Saccharomyces cerevisiae Ulp1 SUMO protease, including its coiled-coil (CC) domain, lead to the accumulation of distinct sumoylated proteins in vivo. A prominent similar to 50-kDa sumoylated protein accumulates in a Ulp1 CC mutant. The protein was identified as Scs2, an endoplasmic reticulum (ER) membrane protein that regulates phosphatidylinositol synthesis and lipid trafficking. Mutation of lysine 180 of Scs2 abolishes its sumoylation. Notably, impairment of either cellular sumoylation or cellular desumoylation mechanisms inhibits cell growth in the absence of inositol and exacerbates the inositol auxotrophy caused by deletion of SCS2. Mutants lacking the Ulp2 SUMO protease are the most severely affected, and this defect was traced to the mutants' impaired ability to induce transcription of INO1, which encodes the rate-limiting enzyme of inositol biosynthesis. Conversely, inositol starvation induces a striking change in the profiles of total cellular SUMO conjugates. These results provide the first evidence of cross-regulation between the SUMO and inositol pathways, including the sumoylation of an ER membrane protein central to phospholipid synthesis and phosphoinositide signaling.