Ubiquitin Project, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan.
Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, The University of Tokyo, Chiba, Japan.
J Cell Biol. 2020 Sep 7;219(9). doi: 10.1083/jcb.201912144.
Damaged mitochondria are selectively eliminated in a process called mitophagy. Parkin and PINK1, proteins mutated in Parkinson's disease, amplify ubiquitin signals on damaged mitochondria with the subsequent activation of autophagic machinery. Autophagy adaptors are thought to link ubiquitinated mitochondria and autophagy through ATG8 protein binding. Here, we establish methods for inducing mitophagy by mitochondria-targeted ubiquitin chains and chemical-induced mitochondrial ubiquitination. Using these tools, we reveal that the ubiquitin signal is sufficient for mitophagy and that PINK1 and Parkin are unnecessary for autophagy activation per se. Furthermore, using phase-separated fluorescent foci, we show that the critical autophagy adaptor OPTN forms a complex with ATG9A vesicles. Disruption of OPTN-ATG9A interactions does not induce mitophagy. Therefore, in addition to binding ATG8 proteins, the critical autophagy adaptors also bind the autophagy core units that contribute to the formation of multivalent interactions in the de novo synthesis of autophagosomal membranes near ubiquitinated mitochondria.
受损的线粒体在称为自噬的过程中被选择性地消除。帕金森病中突变的蛋白质 Parkin 和 PINK1 放大受损线粒体上的泛素信号，随后激活自噬机制。自噬衔接蛋白被认为通过 ATG8 蛋白结合将泛素化的线粒体与自噬联系起来。在这里，我们建立了通过线粒体靶向泛素链和化学诱导的线粒体泛素化诱导自噬的方法。使用这些工具，我们揭示了泛素信号足以引发自噬，并且 PINK1 和 Parkin 本身对于自噬的激活并非必需。此外，我们使用相分离的荧光焦点显示，关键的自噬衔接蛋白 OPTN 与 ATG9A 小泡形成复合物。破坏 OPTN-ATG9A 相互作用不会诱导自噬。因此，除了与 ATG8 蛋白结合外，关键的自噬衔接蛋白还与自噬核心单元结合，有助于在靠近泛素化线粒体的新合成的自噬体膜上形成多价相互作用。
