Park Hye-Min, Kim Goo-Young, Nam Min-Kyung, Seong Geun-Hye, Han Chul, Chung Kwang Chul, Kang Seongman, Rhim Hyangshuk
School of Life Sciences and Biotechnology, Korea University, Seoul, Republic of Korea.
Biochem Biophys Res Commun. 2009 Sep 25;387(3):537-42. doi: 10.1016/j.bbrc.2009.07.079. Epub 2009 Jul 23.
The serine protease HtrA2 is important in regulating not only apoptosis but also cellular homeostasis. Recently, several lines of evidence suggest that HtrA2 may be intimately associated with Parkin; however, little is known about the functional relationships between HtrA2 and Parkin. Here we have shown that HtrA2 is co-localized with Parkin in the cytosol through the release of HtrA2 from the mitochondria upon cellular stresses. Moreover, endogenous levels of Parkin were significantly decreased in wild-type (HtrA2(+/+)) mouse embryonic fibroblasts (MEF) compared with those in HtrA2-knockout (HtrA2(-/-)) MEF under the same stress conditions. Using cleavage and binding assays, we have demonstrated that HtrA2 specifically binds to and directly cleaves the E3 ubiquitin (Ub) ligase Parkin. Interestingly, the HtrA2-mediated Parkin cleavage irreversibly disrupts Parkin-mediated synphilin-1 ubiquitination and autoubiquitination, indicating that HtrA2 may play a critical role in the Parkin-related pathway involved in the ubiquitin proteasome system.
丝氨酸蛋白酶HtrA2不仅在调节细胞凋亡方面很重要，在调节细胞内稳态方面也很重要。最近，有几条证据表明HtrA2可能与帕金蛋白密切相关；然而，关于HtrA2与帕金蛋白之间的功能关系却知之甚少。在这里我们已经表明，在细胞应激时，HtrA2通过从线粒体释放而与帕金蛋白在细胞质中共定位。此外，在相同应激条件下，与HtrA2基因敲除（HtrA2(-/-)）的小鼠胚胎成纤维细胞（MEF）相比，野生型（HtrA2(+/+)）MEF中帕金蛋白的内源性水平显著降低。通过切割和结合试验，我们已经证明HtrA2特异性结合并直接切割E3泛素（Ub）连接酶帕金蛋白。有趣的是，HtrA2介导的帕金蛋白切割不可逆地破坏了帕金蛋白介导的突触核蛋白-1泛素化和自身泛素化，这表明HtrA2可能在参与泛素蛋白酶体系统的帕金蛋白相关途径中起关键作用。
