De3p/Hrd1p is required for endoplasmic reticulum-associated degradation of misfolded lumenal and integral membrane proteins
De3p/Hrd1p is required for endoplasmic reticulum-associated degradation of misfolded lumenal and integral membrane proteins
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DOI：
10.1091/mbc.9.1.209
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发表时间：
1998-01-01
影响因子：
3.3
通讯作者：
Wolf, DH
中科院分区：
文献类型：
--
作者：
Bordallo, J;Plemper, RK;Wolf, DH
研究了酿酒酵母内质网（ER）校正和降解系统的组成。使用一个der 3 -1突变体缺陷的降解突变的内腔蛋白，羧肽酶yscY（CPY*），基因被克隆，编码64 kDa的蛋白质的ER膜。Der 3 p被发现与Hrd 1 p相同，Hrd 1 p是一种被鉴定为降解HMG-CoA还原酶所必需的蛋白质。Der 3 p含有5个假定的跨膜结构域和一个长的亲水性C-末端尾，该尾含有一个面向ER腔的RING-H2指状结构域。Der 3的缺失会导致CPY* 在ER内积聚，因为它的降解被完全阻止。此外，DER 3无效突变体等位基因抑制携带sec 61 -2等位基因的突变体的温度依赖性生长表型。这伴随着Sec 61 -2突变蛋白的稳定。相比之下，Der 3 p的过量生产在25 ℃的允许温度下在sec 61 -2菌株中是致命的。缺少包括RING-H2指结构域在内的内腔尾部的114个氨基酸的突变体Der 3 p不能介导CPY* 和Sec 61 - 2 p的降解。我们建议Der 3 p的行为之前，ER膜和内腔蛋白质的逆行运输到细胞质中，他们受到降解通过泛素-蛋白酶体系统。有趣的是，在ubc 6-ubc 7双突变体中，CPY* 在ER中积累，表明CPY* 逆行转运需要完整的细胞质蛋白水解机制。Der 3 p可能作为一个组件编程的转位ER蛋白的逆行运输，或它可能参与识别通过其内腔RING-H2基序的蛋白质的ER是注定要降解。
We have studied components of the endoplasmic reticulum (ER) proofreading and degradation system in the yeast Saccharomyces cerevisiae. Using a der3-1 mutant defective in the degradation of a mutated lumenal protein, carboxypeptidase yscY (CPY*), a gene was cloned which encodes a 64-kDa protein of the ER membrane. Der3p was found to be identical with Hrd1p, a protein identified to be necessary for degradation of HMG-CoA reductase. Der3p contains five putative transmembrane domains and a long hydrophilic C-terminal tail containing a RING-H2 finger domain which is oriented to the ER lumen. Deletion of DER3 leads to an accumulation of CPY* inside the ER due to a complete block of its degradation. In addition, a DER3 null mutant allele suppresses the temperature-dependent growth phenotype of a mutant carrying the sec61-2 allele. This is accompanied by the stabilization of the Sec61-2 mutant protein. In contrast, overproduction of Der3p is lethal in a sec61-2 strain at the permissive temperature of 25 degrees C. A mutant Der3p lacking 114 amino acids of the lumenal tail including the RING-H2 finger domain is unable to mediate degradation of CPY* and Sec61-2p. We propose that Der3p acts prior to retrograde transport of ER membrane and lumenal proteins to the cytoplasm where they are subject to degradation via the ubiquitin-proteasome system. Interestingly, in ubc6-ubc7 double mutants, CPY* accumulates in the ER, indicating the necessity of an intact cytoplasmic proteolysis machinery for retrograde transport of CPY*. Der3p might serve as a component programming the translocon for retrograde transport of ER proteins, or it might be involved in recognition through its lumenal RING-H2 motif of proteins of the ER that are destined for degradation.