Center of Medical Biotechnology, Faculty of Biology, University of Duisburg-Essen, Essen, Germany.
Munich Cluster for Systems Neurology (SyNergy), Medical Faculty, Ludwig-Maximilians-Universität München, Feodor-Lynen-Str. 17, 81377 Munich, Germany.
Mol Cell. 2022 Jul 21;82(14):2633-2649.e7. doi: 10.1016/j.molcel.2022.06.012. Epub 2022 Jul 5.
Lysosomal membrane permeabilization (LMP) is an underlying feature of diverse conditions including neurodegeneration. Cells respond by extensive ubiquitylation of membrane-associated proteins for clearance of the organelle through lysophagy that is facilitated by the ubiquitin-directed AAA-ATPase VCP/p97. Here, we assessed the ubiquitylated proteome upon acute LMP and uncovered a large diversity of targets and lysophagy regulators. They include calponin-2 (CNN2) that, along with the Arp2/3 complex, translocates to damaged lysosomes and regulates actin filaments to drive phagophore formation. Importantly, CNN2 needs to be ubiquitylated during the process and removed by VCP/p97 for efficient lysophagy. Moreover, we identified the small heat shock protein HSPB1 that assists VCP/p97 in the extraction of CNN2 and show that other membrane regulators including SNAREs, PICALM, AGFG1, and ARL8B are ubiquitylated during lysophagy. Our data reveal a framework of how ubiquitylation and two effectors, VCP/p97 and HSPB1, cooperate to protect cells from the deleterious effects of LMP.
溶酶体膜通透性（LMP）是多种情况的一个基本特征，包括神经退行性变。细胞通过广泛的膜相关蛋白泛素化来应对，以通过溶酶体吞噬作用清除细胞器，该作用由泛素导向的 AAA-ATPase VCP/p97 促进。在这里，我们在急性 LMP 时评估了泛素化蛋白质组，发现了大量的靶标和溶酶体吞噬作用调节剂。它们包括钙调蛋白 2（CNN2），它与 Arp2/3 复合物一起转移到受损的溶酶体，并调节肌动蛋白丝以驱动吞噬体形成。重要的是，CNN2 在该过程中需要被泛素化，并被 VCP/p97 去除，以实现有效的溶酶体吞噬作用。此外，我们鉴定了小分子热休克蛋白 HSPB1，它协助 VCP/p97 提取 CNN2，并表明其他膜调节剂，包括 SNAREs、PICALM、AGFG1 和 ARL8B，在溶酶体吞噬作用期间被泛素化。我们的数据揭示了泛素化和两个效应因子 VCP/p97 和 HSPB1 如何合作，以保护细胞免受 LMP 的有害影响的框架。
