The Ca2+-binding protein ALG-2 is recruited to endoplasmic reticulum exit sites by Sec31A and stabilizes the localization of Sec31A
The Ca2+-binding protein ALG-2 is recruited to endoplasmic reticulum exit sites by Sec31A and stabilizes the localization of Sec31A
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DOI：
10.1091/mbc.e06-05-0444
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发表时间：
2006-11-01
影响因子：
3.3
通讯作者：
Komada, Masayuki
中科院分区：
文献类型：
--
作者：
Yamasaki, Akinori;Tani, Katsuko;Komada, Masayuki
从内质网(ER)出口部位萌发的运输小泡的形成依赖于由三个组分组成的COPII外壳：小GTPase Sar1、Sec23/24复合体和Sec13/31复合体。在这里，我们提供了一种未知功能的呼叫结合蛋白--凋亡相关基因2(ALG-2)，它调节哺乳动物细胞内ER出口处的COPII功能。Alg-2以Ca21依赖的方式与酵母Sec31的富含Pro区的Sec31a结合，并与Sec31a在内质网出口处共存。一个钙离子结合缺陷的ALG-2突变体，不能结合Sec31a，失去了定位到内质网出口位点的能力。Sec31a富含Pro区的过表达或RNA干扰介导的Sec31a缺失也取消了ALG-2在这些位点的定位。相反，ALG-2的耗尽显著降低了内质网出口部位与膜相关的Sec31a的水平。最后，用细胞透性的钙离子螯合剂处理导致ALG-2的错误定位，并伴随着内质网出口部位Sec31a水平的降低。我们的结论是，ALG-2通过钙依赖的与Sec31a的相互作用被招募到ER退出部位，进而稳定Sec31a在这些部位的定位。
The formation of transport vesicles that bud from endoplasmic reticulum (ER) exit sites is dependent on the COPII coat made up of three components: the small GTPase Sar1, the Sec23/24 complex, and the Sec13/31 complex. Here, we provide evidence that apoptosis-linked gene 2 (ALG-2), a Call-binding protein of unknown function, regulates the COPII function at ER exit sites in mammalian cells. ALG-2 bound to the Pro-rich region of Sec31A, a ubiquitously expressed mammalian orthologue of yeast Sec31, in a Ca21-dependent manner and colocalized with Sec31A at ER exit sites. A Ca2+ binding-deficient ALG-2 mutant, which did not bind Sec31A, lost the ability to localize to ER exit sites. Overexpression of the Pro-rich region of Sec31A or RNA interference-mediated Sec31A depletion also abolished the ALG-2 localization at these sites. In contrast, depletion of ALG-2 substantially reduced the level of Sec31A associated with the membrane at ER exit sites. Finally, treatment with a cell-permeable Ca2+ chelator caused the mislocalization of ALG-2, which was accompanied by a reduced level of Sec31A at ER exit sites. We conclude that ALG-2 is recruited to ER exit sites via Ca2+-dependent interaction with Sec31A and in turn stabilizes the localization of Sec31A at these sites.