Identification of SVIP as an endogenous inhibitor of endoplasmic reticulum-associated degradation
Identification of SVIP as an endogenous inhibitor of endoplasmic reticulum-associated degradation
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DOI：
10.1074/jbc.m704446200
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发表时间：
2007-11-23
影响因子：
4.8
通讯作者：
Fang, Shengyun
中科院分区：
文献类型：
--
作者：
Ballar, Petek;Zhong, Yongwang;Fang, Shengyun
内质网（ER）中错误折叠的蛋白质通过称为ER相关降解（ERAD）的过程消除，该过程以错误折叠的蛋白质识别开始，随后是泛素化、逆易位至细胞质溶胶、去糖基化和靶向蛋白酶体以进行降解。ER膜中的多亚基蛋白质机器的作用整合了这些步骤。我们假设，多亚基机械组装的调节是ERAD活性调节的机制。为了验证这一假设，我们研究了小p97/VCP相互作用蛋白（SVIP）对ERAD机制（包括泛素连接酶gp 78、AAA ATP酶p97/VCP和推定通道Derlin 1）形成的潜在调节作用。我们发现SVIP通过豆蔻酰化锚定在微粒体膜上，并与gp 78、Derlin 1、p97/VCP和钙连接蛋白共分馏到ER。与gp 78一样，SVIP也与p97/VCP和Derlin 1发生物理相互作用。SVIP的过表达阻断了未组装的CD 3 δ与gp 78和p97/VCP的结合，这伴随着CD 3 δ泛素化和降解的减少。沉默SVIP表达显著增强了gp 78-p97/VCP-Derlin 1复合物的形成，这与CD 3 δ和α-1-抗胰蛋白酶的错误折叠Z变体（gp 78的既定底物）的降解增加相关。这些结果表明，SVIP是ERAD的内源性抑制剂，通过调节gp 78-p97/VCP-Derlin 1复合物的组装发挥作用。
Misfolded proteins in the endoplasmic reticulum (ER) are eliminated by a process known as ER- associated degradation (ERAD), which starts with misfolded protein recognition, followed by ubiquitination, retrotranslocation to the cytosol, deglycosylation, and targeting to the proteasome for degradation. Actions of multisubunit protein machineries in the ER membrane integrate these steps. We hypothesized that regulation of the multisubunit machinery assembly is a mechanism by which ERAD activity is regulated. To test this hypothesis, we investigated the potential regulatory role of the small p97/VCP-interacting protein (SVIP) on the formation of the ERAD machinery that includes ubiquitin ligase gp78, AAA ATPase p97/VCP, and the putative channel Derlin1. We found that SVIP is anchored to microsomal membrane via myristoylation and co-fractionated with gp78, Derlin1, p97/VCP, and calnexin to the ER. Like gp78, SVIP also physically interacts with p97/VCP and Derlin1. Overexpression of SVIP blocks unassembled CD3 delta from association with gp78 and p97/VCP, which is accompanied by decreases in CD3 delta ubiquitination and degradation. Silencing SVIP expression markedly enhances the formation of gp78-p97/VCP-Derlin1 complex, which correlates with increased degradation of CD3 delta and misfolded Z variant of alpha-1-antitrypsin, established substrates of gp78. These results suggest that SVIP is an endogenous inhibitor of ERAD that acts through regulating the assembly of the gp78-p97/VCP-Derlin1 complex.