Matsumoto Gen, Shimogori Tomomi, Hattori Nobutaka, Nukina Nobuyuki
Department of Neuroscience for Neurodegenerative Disorders and Laboratory for Structural Neuropathology and Laboratory for Molecular Mechanisms of Thalamus Development, RIKEN Brain Science Institute, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan and Core Research for Evolutionary Science and Technology (CREST), JST, 7, Gobancho, Chiyoda-ku, Tokyo 102-0076, Japan
Laboratory for Molecular Mechanisms of Thalamus Development, RIKEN Brain Science Institute, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan and.
Hum Mol Genet. 2015 Aug 1;24(15):4429-42. doi: 10.1093/hmg/ddv179. Epub 2015 May 13.
Selective autophagy adaptor proteins, including p62/SQSTM1, play pivotal roles in the targeted degradation of ubiquitinated proteins or organelles through the autophagy-lysosome system. However, how autophagy adaptors promote the autophagosomal engulfment of selected substrates is poorly understood. Here, we show that p62 phosphorylation at S403 is required for the efficient autophagosomal engulfment of polyubiquitinated mitochondria during Parkin-dependent mitophagy. p62 is able to interact with Parkin-recruited mitochondria without S403 phosphorylation under mitophagy-inducing conditions, but those mitochondria are not enclosed by autophagosomes. Intriguingly, the S403 phosphorylation occurs only in the early period of mitochondrial depolarization. Optineurin and TANK-binding kinase 1 (TBK1) are transiently recruited to the polyubiquitinated mitochondria, and the activated TBK1 phosphorylates p62 at S403. TBK1 inhibitor, BX795, prevents the p62-mediated autophagosomal engulfment of Parkin-recruited mitochondria. Our results suggest that TBK1-mediated S403 phosphorylation regulates the efficient autophagosomal engulfment of ubiquitinated mitochondria as an immediate response to the mitochondrial depolarization.
包括p62/SQSTM1在内的选择性自噬衔接蛋白，在通过自噬-溶酶体系统对泛素化蛋白或细胞器进行靶向降解过程中发挥着关键作用。然而，自噬衔接蛋白如何促进自噬体对选定底物的吞噬作用，目前还知之甚少。在此，我们表明，在帕金蛋白依赖性线粒体自噬过程中，p62在S403位点的磷酸化是多聚泛素化线粒体高效被自噬体吞噬所必需的。在诱导线粒体自噬的条件下，未发生S403磷酸化的p62能够与帕金蛋白募集的线粒体相互作用，但这些线粒体并未被自噬体包裹。有趣的是，S403磷酸化仅发生在线粒体去极化的早期。含卷曲螺旋结构域的衔接蛋白optineurin和TANK结合激酶1（TBK1）会短暂募集到多聚泛素化的线粒体上，且被激活的TBK1会使p62在S403位点发生磷酸化。TBK1抑制剂BX795可阻止p62介导的对帕金蛋白募集的线粒体的自噬体吞噬作用。我们的结果表明，TBK1介导的S403磷酸化作为对线粒体去极化的即时反应，调节泛素化线粒体的高效自噬体吞噬作用。
