Center for Biomedical Engineering and Technology, University of Maryland, Baltimore, MD 21201, USA.
Mol Biol Cell. 2011 Feb 1;22(3):291-300. doi: 10.1091/mbc.E10-09-0748. Epub 2010 Nov 30.
Recent studies have revealed a role for the ubiquitin/proteasome system in the regulation and turnover of outer mitochondrial membrane (OMM)-associated proteins. Although several molecular components required for this process have been identified, the mechanism of proteasome-dependent degradation of OMM-associated proteins is currently unclear. We show that an AAA-ATPase, p97, is required for the proteasomal degradation of Mcl1 and Mfn1, two unrelated OMM proteins with short half-lives. A number of biochemical assays, as well as imaging of changes in localization of photoactivable GFP-fused Mcl1, revealed that p97 regulates the retrotranslocation of Mcl1 from mitochondria to the cytosol, prior to, or concurrent with, proteasomal degradation. Mcl1 retrotranslocation from the OMM depends on the activity of the ATPase domain of p97. Furthermore, p97-mediated retrotranslocation of Mcl1 can be recapitulated in vitro, confirming a direct mitochondrial role for p97. Our results establish p97 as a novel and essential component of the OMM-associated protein degradation pathway.
最近的研究揭示了泛素/蛋白酶体系统在外膜（OMM）相关蛋白的调节和周转中的作用。尽管已经确定了这个过程所需的几个分子成分，但蛋白酶体依赖性 OMM 相关蛋白降解的机制目前尚不清楚。我们表明，一种 AAA-ATP 酶，p97，是 Mcl1 和 Mfn1 两种半衰期短的非相关 OMM 蛋白的蛋白酶体降解所必需的。许多生化测定以及光活化 GFP 融合的 Mcl1 定位变化的成像显示，p97 在蛋白酶体降解之前或同时，调节 Mcl1 从线粒体到细胞质的逆行转运。从 OMM 中 Mcl1 的逆行转运依赖于 p97 的 ATP 酶结构域的活性。此外，Mcl1 在体外可以被 p97 介导的逆行转运所再现，证实了 p97 在粒体中的直接作用。我们的结果确立了 p97 作为 OMM 相关蛋白降解途径的一个新的和必需的组成部分。
