Mammalian Sec16/p250 plays a role in membrane traffic from the endoplasmic reticulum
Mammalian Sec16/p250 plays a role in membrane traffic from the endoplasmic reticulum
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DOI：
10.1074/jbc.m611237200
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发表时间：
2007-06-15
影响因子：
4.8
通讯作者：
Tani, Katsuko
中科院分区：
文献类型：
--
作者：
Iinuma, Takayuki;Shiga, Akiko;Tani, Katsuko
在哺乳动物中，介导蛋白质从内质网（ER）输出的外壳蛋白复合物II（COPII）包被的囊泡/载体形成于特殊的ER亚结构域，称为ER出口位点或过渡性ER。COPII外壳由一个小的GTPase（Sar 1）和两个蛋白质复合物（Sec 23-Sec 24和Sec 13-Sec 31）组成。Sec 23-Sec 24和Sec 13-Sec 31似乎分别构成COPII涂层的内层和最外层。我们先前分离出两种与Sec 23结合的哺乳动物蛋白（p125和p250）。p125被发现是一种磷脂酶A（1）样的蛋白质，参与ER出口位点的组织化。在这里，我们表明，p250是由KIAA 0310克隆编码，并与酵母Sec 16蛋白序列相似。虽然KIAA 0310 p被发现是本地化的ER出口网站，亚细胞分馏显示其主要存在于胞质溶胶。胞质KIAA 0310 p以依赖于Sar 1的方式被募集到ER膜。KIAA 0310 p的耗竭轻度引起ER出口位点的紊乱和延迟的蛋白质从ER的转运，表明其在ER的膜运输中的意义。KIAA 0310 p过表达影响ER出口网站的方式不同于p125。结合实验表明，KIAA 0310 p与内层和最外层的涂层复合物相互作用，而p125主要结合到内层复合物。我们的研究结果表明，KIAA 0310 p，酵母Sec 16的哺乳动物同源物，建立了ER出口网站与p125合作，并发挥作用，从ER的膜交通。
Coat protein complex II ( COPII)-coated vesicles/carriers, which mediate export of proteins from the endoplasmic reticulum ( ER), are formed at special ER subdomains in mammals, termed ER exit sites or transitional ER. The COPII coat consists of a small GTPase, Sar1, and two protein complexes, Sec23-Sec24 and Sec13-Sec31. Sec23-Sec24 and Sec13-Sec31 appear to constitute the inner and the outermost layers of the COPII coat, respectively. We previously isolated two mammalian proteins ( p125 and p250) that bind to Sec23. p125 was found to be a mammalian-specific, phospholipase A(1)-like protein that participates in the organization of ER exit sites. Here we show that p250 is encoded by the KIAA0310 clone and has sequence similarity to yeast Sec16 protein. Although KIAA0310p was found to be localized at ER exit sites, subcellular fractionation revealed its predominant presence in the cytosol. Cytosolic KIAA0310p was recruited to ER membranes in a manner dependent on Sar1. Depletion of KIAA0310p mildly caused disorganization of ER exit sites and delayed protein transport from the ER, suggesting its implication in membrane traffic out of the ER. Overexpression of KIAA0310p affected ER exit sites in a manner different from that of p125. Binding experiments suggested that KIAA0310p interacts with both the inner and the outermost layer coat complexes, whereas p125 binds principally to the inner layer complex. Our results suggest that KIAA0310p, a mammalian homologue of yeast Sec16, builds up ER exit sites in cooperation with p125 and plays a role in membrane traffic from the ER.