Involvement of the p97-Ufd1-Npl4 complex in the regulated endoplasmic reticulum-associated degradation of inositol 1,4,5-trisphosphate receptors
Involvement of the p97-Ufd1-Npl4 complex in the regulated endoplasmic reticulum-associated degradation of inositol 1,4,5-trisphosphate receptors
复制标题
DOI：
10.1074/jbc.m508890200
复制
发表时间：
2005-10-14
影响因子：
4.8
通讯作者：
Wojcikiewicz, RJH
中科院分区：
文献类型：
--
作者：
Alzayady, KJ;Panning, MM;Wojcikiewicz, RJH
肌醇1，4，5-三磷酸（IP 3）受体在内质网膜中形成四聚体IP 3门控通道，其控制Ca 2+从该细胞器的释放。响应于持续升高IP 3浓度的某些G蛋白偶联受体的激活，IP 3受体被泛素化并通过泛素-蛋白酶体途径降解。IP 3受体泛素化由泛素缀合酶（mam）Ubc 7介导，Ubc 7是内质网相关降解途径的组分。然而，泛素化的IP 3受体转移到蛋白酶体的机制尚不清楚。在这里，我们研究这一过程，并显示在几种哺乳动物细胞类型的ATP酶p97协会与IP 3受体在响应激素刺激，诱导IP 3受体泛素化。为了研究p97与IP 3受体相互作用的功能相关性，我们使用RNA干扰将Rat-1成纤维细胞中的p97蛋白水平稳定且特异性地降低了62 +/- 3%。在这些细胞中，内皮素-1诱导的IP 3受体降解显着延迟和泛素化的IP 3受体的积累显着增强。这些影响被逆转的外源性p97的表达。此外，与p97复合的Ufd 1和Np 14在激素刺激时也与IP 3受体相关。我们的结论是，p97-Ufd 1-Npl 4复合物偶联泛素化的IP 3受体蛋白酶体降解，因此，在IP 3受体处理中发挥了关键作用。这些数据还确定了p97-Ufd 1-Npl 4复合物介导哺乳动物细胞中的内质网相关降解。
Inositol 1,4,5-trisphosphate (IP3) receptors form tetrameric, IP3-gated channels in endoplasmic reticulum membranes that govern the release of Ca2+ from this organelle. In response to activation of certain G protein-coupled receptors that persistently elevate IP3 concentration, IP3 receptors are ubiquitinated and degraded by the ubiquitin-proteasome pathway. IP3 receptor ubiquitination is mediated by the ubiquitin-conjugating enzyme, (mam)Ubc7, a component of the endoplasmic reticulum-associated degradation pathway. However, the mechanism by which ubiquitinated IP3 receptors are transferred to the proteasome is not known. Here, we examine this process and show in several mammalian cell types that the ATPase p97 associates with IP3 receptors in response to hormonal stimuli that induce IP3 receptor ubiquitination. To examine the functional relevance of the p97 interaction with IP3 receptors, we stably and specifically reduced p97 protein levels by 62 +/- 3% in Rat-1 fibroblasts using RNA interference. In these cells, endothelin-1- induced IP3 receptor degradation was markedly retarded and the accumulation of ubiquitinated IP3 receptors was markedly enhanced. These effects were reversed by expression of exogenous p97. In addition, Ufd1 and Npl4, which complex with p97, also associated with IP3 receptors upon hormonal stimulation. We conclude that the p97-Ufd1-Npl4 complex couples ubiquitinated IP3 receptors to proteasomal degradation and, thus, plays a key role in IP3 receptor processing. These data also establish that the p97-Ufd1-Npl4 complex mediates endoplasmic reticulum-associated degradation in mammalian cells.