Departments of Pathology & Cell Biology.
Neurology.
J Neurosci. 2019 Sep 4;39(36):7074-7085. doi: 10.1523/JNEUROSCI.1691-18.2019. Epub 2019 Jul 12.
Maintaining a pool of functional mitochondria requires degradation of damaged ones within the cell. PINK1 is critical in this quality-control process: loss of mitochondrial membrane potential causes PINK1 to accumulate on the mitochondrial surface, triggering mitophagy. However, little is known about how PINK1 is regulated. Recently, we showed that PINK1 content is kept low in healthy mitochondria by continuous ubiquitination and proteasomal degradation of its mature form via a mechanism inconsistent with the proposed N-end rule process. Using both human female and monkey cell lines, we now demonstrate that once generated within the mitochondria, 52 kDa PINK1 adopts a mitochondrial topology most consistent with it being at the mitochondrial-endoplasmic reticulum (ER) interface. From this particular submitochondrial location, PINK1 interacts with components of the ER-associated degradation pathway, such as the E3 ligases gp78 and HRD1, which cooperate to catalyze PINK1 ubiquitination. The valosin-containing protein and its cofactor, UFD1, then target ubiquitinated PINK1 for proteasomal degradation. Our data show that PINK1 in healthy mitochondria is negatively regulated via an interplay between mitochondria and ER, and shed light on how this mitochondrial protein gains access to the proteasome. Regulation of mitochondrial content of PINK1, a contributor to mitophagy, is an important area of research. Recently, we found that PINK1 content is kept low in healthy mitochondria by continuous ubiquitination and proteasomal degradation. We now extend and refine this novel finding by showing that PINK1 localizes at the mitochondrial-endoplasmic reticulum (ER) interface, from where it interacts with the ER-associated degradation machinery, which catalyzes its ubiquitination and transfer to the proteasome. Thus, these data show that PINK1 in healthy mitochondria is negatively regulated via a mitochondria and ER interplay, and how this mitochondrial protein gains access to the proteasome.
维持功能正常的线粒体池需要细胞内降解受损的线粒体。PINK1 在这个质量控制过程中至关重要：线粒体膜电位丧失会导致 PINK1 在其表面积聚，从而引发线粒体自噬。然而，关于 PINK1 如何被调节的知之甚少。最近，我们发现健康线粒体中 PINK1 的含量保持在较低水平，这是通过一种与所提出的 N 端规则过程不一致的机制，对其成熟形式进行连续泛素化和蛋白酶体降解来实现的。我们使用人源女性和猴细胞系，现在证明一旦在线粒体中生成，52kDa 的 PINK1 采用一种最符合其位于线粒体-内质网 (ER) 界面的线粒体拓扑结构。从这个特定的亚线粒体位置，PINK1 与 ER 相关降解途径的成分相互作用，例如 E3 连接酶 gp78 和 HRD1，它们共同催化 PINK1 泛素化。然后，泛素结合蛋白和其辅助因子 UFD1 将泛素化的 PINK1 靶向蛋白酶体降解。我们的数据表明，健康线粒体中的 PINK1 通过线粒体和 ER 之间的相互作用受到负调控，并揭示了这种线粒体蛋白如何获得蛋白酶体。调节 PINK1 的线粒体含量，这是线粒体自噬的一个贡献因素，是一个重要的研究领域。最近，我们发现健康线粒体中 PINK1 的含量通过持续的泛素化和蛋白酶体降解来保持在较低水平。现在，我们通过显示 PINK1 定位于线粒体-内质网 (ER) 界面，从那里它与 ER 相关降解机制相互作用，从而催化其泛素化并将其转移到蛋白酶体，进一步扩展和完善了这一新颖的发现。因此，这些数据表明，健康线粒体中的 PINK1 通过线粒体和 ER 的相互作用受到负调控，以及这种线粒体蛋白如何获得蛋白酶体。
