p125 Is Localized in Endoplasmic Reticulum Exit Sites and Involved in Their Organization*
p125 Is Localized in Endoplasmic Reticulum Exit Sites and Involved in Their Organization*
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DOI：
10.1074/jbc.m409673200
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发表时间：
2005-03
影响因子：
4.8
通讯作者：
Wakako Shimoi;Ichiko Ezawa;K. Nakamoto;Shihoko Uesaki;Gavin Gabreski;M. Aridor;A. Yamamoto;M. Nagahama;M. Tagaya;K. Tani
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文献类型：
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作者：
Wakako Shimoi;Ichiko Ezawa;K. Nakamoto;Shihoko Uesaki;Gavin Gabreski;M. Aridor;A. Yamamoto;M. Nagahama;M. Tagaya;K. Tani
由Sar1p、Sec23p-Sec24p和Sec13p-Sec31p组装而成的COPII复合体包裹着运输小泡，参与内质网(ER)的蛋白质输出。我们以前发现并鉴定了一种新的Sec23P相互作用蛋白p125，它只在哺乳动物中表达，并与磷脂酸偏好磷脂酶A1(PA-PLA1)具有序列同源性。在本研究中，我们详细研究了p125的定位和功能。通过使用免疫荧光和电子显微镜，我们发现p125主要定位于内质网出口部位，在那里产生了COPII包被的囊泡。对p125和哺乳动物PA-PLA1家族另外两个成员(PA-PLA1和KIAA0725p)组成的嵌合蛋白的分析表明，对于定位到ER出口位点，p125特异的N末端区域是关键的，推测的脂肪酶结构域可以与KIAA0725p互换，但不能与PA-PLA1互换。RNA干扰介导的p125缺失影响内质网退出位点的组织。顺式高尔基体室的结构也受到了很大的干扰，而内侧高尔基体室则没有。在p125耗尽的细胞中，内质网的蛋白质输出没有明显的延迟。我们的研究表明，p125是内质网出口部位的哺乳动物特有的成分，并参与了这个间隔的组织。
Transport vesicles coated with the COPII complex, which is assembled from Sar1p, Sec23p-Sec24p, and Sec13p-Sec31p, are involved in protein export from the endoplasmic reticulum (ER). We previously identified and characterized a novel Sec23p-interacting protein, p125, that is only expressed in mammals and exhibits sequence homology with phosphatidic acid-preferring phospholipase A1 (PA-PLA1). In this study, we examined the localization and function of p125 in detail. By using immunofluorescence and electron microscopy, we found that p125 is principally localized in ER exit sites where COPII-coated vesicles are produced. Analyses of chimeric proteins comprising p125 and two other members of the mammalian PA-PLA1 family (PA-PLA1 and KIAA0725p) showed that, for localization to ER exit sites, the p125-specific N-terminal region is critical, and the putative lipase domain is interchangeable with KIAA0725p but not with PA-PLA1. RNA interference-mediated depletion of p125 affected the organization of ER exit sites. The structure of the cis-Golgi compartment was also substantially disturbed, whereas the medial-Golgi was not. Protein export from the ER occurred without a significant delay in p125-depleted cells. Our study suggests that p125 is a mammalian-specific component of ER exit sites and participates in the organization of this compartment.