Wang Yanzhuang, Satoh Ayano, Warren Graham, Meyer Hemmo H
Institute of Biochemistry, ETH Hoenggerberg, HPM G17.1, 8093 Zurich, Switzerland.
J Cell Biol. 2004 Mar 29;164(7):973-8. doi: 10.1083/jcb.200401010. Epub 2004 Mar 22.
The AAA-ATPase p97/Cdc48 functions in different cellular pathways using distinct sets of adapters and other cofactors. Together with its adaptor Ufd1-Npl4, it extracts ubiquitylated substrates from the membrane for subsequent delivery to the proteasome during ER-associated degradation. Together with its adaptor p47, on the other hand, it regulates several membrane fusion events, including reassembly of Golgi cisternae after mitosis. The finding of a ubiquitin-binding domain in p47 raises the question as to whether the ubiquitin-proteasome system is also involved in membrane fusion events. Here, we show that p97-p47-mediated reassembly of Golgi cisternae requires ubiquitin, but is not dependent on proteasome-mediated proteolysis. Instead, it requires the deubiquitinating activity of one of its cofactors, VCIP135, which reverses a ubiquitylation event that occurs during mitotic disassembly. Together, these data reveal a cycle of ubiquitylation and deubiquitination that regulates Golgi membrane dynamics during mitosis. Furthermore, they represent the first evidence for a proteasome-independent function of p97/Cdc48.
AAA-ATP酶p97/Cdc48通过不同的衔接蛋白和其他辅助因子组合在不同的细胞途径中发挥作用。它与其衔接蛋白Ufd1-Npl4一起，从膜上提取泛素化底物，以便在内质网相关降解过程中随后递送至蛋白酶体。另一方面，它与其衔接蛋白p47一起调节多种膜融合事件，包括有丝分裂后高尔基体潴泡的重新组装。在p47中发现泛素结合结构域引发了一个问题，即泛素-蛋白酶体系统是否也参与膜融合事件。在这里，我们表明p97-p47介导的高尔基体潴泡重新组装需要泛素，但不依赖于蛋白酶体介导的蛋白水解。相反，它需要其辅助因子之一VCIP135的去泛素化活性，该活性可逆转有丝分裂解体过程中发生的泛素化事件。总之，这些数据揭示了一个泛素化和去泛素化循环，该循环在有丝分裂期间调节高尔基体膜动力学。此外，它们代表了p97/Cdc48不依赖蛋白酶体功能的首个证据。
