Department of Cell Biology, Johns Hopkins University School of Medicine , Baltimore , MD , USA.
Departments of Neurology and Neuroscience, Johns Hopkins University School of Medicine , Baltimore , MD , USA.
Autophagy. 2019 Nov;15(11):2012-2018. doi: 10.1080/15548627.2019.1643185. Epub 2019 Jul 24.
The ubiquitination of mitochondrial proteins labels damaged mitochondria for degradation through mitophagy. We recently developed an system in which mitophagy is slowed by inhibiting mitochondrial division through knockout of , a dynamin related GTPase that mediates mitochondrial division. Using this system, we revealed that the ubiquitination of mitochondrial proteins required SQSTM1/p62, but not the ubiquitin E3 ligase PRKN/parkin, during mitophagy. Here, we tested the role of PINK1, a mitochondrial protein kinase that activates mitophagy by phosphorylating ubiquitin, in mitochondrial ubiquitination by knocking out in -knockout liver. We found mitochondrial ubiquitination did not decrease in the absence of PINK1; instead, PINK1 was required for the degradation of MFN1 (mitofusin 1) and MFN2, two homologous outer membrane proteins that mediate mitochondrial fusion in -knockout hepatocytes. These data suggest that mitochondrial ubiquitination is promoted by SQSTM1 independently of PINK1 and PRKN during mitophagy. PINK1 and PRKN appear to control the balance between mitochondrial division and fusion . DNM1L/DRP1: dynamin 1-like; KEAP1: kelch-like ECH-associated protein 1; KO: knockout; MAP1LC3/LC3: microtubule-associated protein 1 light chain 3; MFN1/2: mitofusin 1/2; OPA1: OPA1, mitochondrial dynamin like GTPase; PDH: pyruvate dehydrogenase E1; PINK1: PTEN induced putative kinase 1; PRKN/parkin: parkin RBR E3 ubiquitin protein ligase.
线粒体蛋白的泛素化将受损的线粒体标记为通过自噬进行降解。我们最近开发了一种系统，通过敲除 ，即一种介导线粒体分裂的与动力蛋白相关的 GTP 酶，来减缓线粒体的分裂，从而减缓自噬。使用该系统，我们揭示了在线粒体自噬过程中，线粒体蛋白的泛素化需要 SQSTM1/p62，但不需要泛素 E3 连接酶 PRKN/parkin。在这里，我们通过在 - 敲除的肝脏中敲除 ，测试了线粒体蛋白激酶 PINK1（通过磷酸化泛素激活自噬）在线粒体泛素化中的作用。我们发现，在没有 PINK1 的情况下，线粒体泛素化并没有减少；相反，PINK1 是 - 敲除肝细胞中两种同源的外膜蛋白 MFN1（线粒体融合蛋白 1）和 MFN2 降解所必需的，这两种蛋白介导线粒体融合。这些数据表明，在线粒体自噬过程中，PINK1 和 PRKN 独立于 SQSTM1 促进线粒体泛素化。PINK1 和 PRKN 似乎控制着线粒体分裂和融合之间的平衡。DNM1L/DRP1：dynamin 1 样；KEAP1：kelch 样 ECH 相关蛋白 1；KO：敲除；MAP1LC3/LC3：微管相关蛋白 1 轻链 3；MFN1/2：线粒体融合蛋白 1/2；OPA1：OPA1，线粒体动力蛋白样 GTP 酶；PDH：丙酮酸脱氢酶 E1；PINK1：PTEN 诱导的假定激酶 1；PRKN/parkin：parkin RBR E3 泛素蛋白连接酶。
