Guo W, Grant A, Novick P
Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut 06520-8002, USA.
J Biol Chem. 1999 Aug 13;274(33):23558-64. doi: 10.1074/jbc.274.33.23558.
The exocyst is a multiprotein complex that plays an important role in secretory vesicle targeting and docking at the plasma membrane. Here we report the identification and characterization of a new component of the exocyst, Exo84p, in the yeast Saccharomyces cerevisiae. Yeast cells depleted of Exo84p cannot survive. These cells are defective in invertase secretion and accumulate vesicles similar to those in the late sec mutants. Exo84p co-immunoprecipitates with the exocyst components, and a portion of the Exo84p co-sediments with the exocyst complex in velocity gradients. The assembly of Exo84p into the exocyst complex requires two other subunits, Sec5p and Sec10p. Exo84p interacts with both Sec5p and Sec10p in a two-hybrid assay. Overexpression of Exo84p selectively suppresses the temperature sensitivity of a sec5 mutant. Exo84p specifically localizes to the bud tip or mother/daughter connection, sites of polarized secretion in the yeast S. cerevisiae. Exo84p is mislocalized in a sec5 mutant. These studies suggest that Exo84p is an essential protein that plays an important role in polarized secretion.
外泌体是一种多蛋白复合物，在分泌小泡靶向和停靠于质膜过程中发挥重要作用。在此，我们报告了酿酒酵母中外泌体新组分Exo84p的鉴定和特性。缺失Exo84p的酵母细胞无法存活。这些细胞在转化酶分泌方面存在缺陷，并积累与晚期sec突变体中类似的小泡。Exo84p与外泌体组分共免疫沉淀，并且一部分Exo84p在速度梯度中与外泌体复合物一起沉降。Exo84p组装到外泌体复合物中需要另外两个亚基Sec5p和Sec10p。在双杂交试验中，Exo84p与Sec5p和Sec10p都相互作用。Exo84p的过表达选择性地抑制sec5突变体的温度敏感性。Exo84p特异性定位于芽尖或母/女连接部位，即酿酒酵母中极化分泌的位点。Exo84p在sec5突变体中定位错误。这些研究表明，Exo84p是一种必需蛋白，在极化分泌中发挥重要作用。
