Department of Molecular Cell Biology, Faculty of Medical Sciences, Kyushu University, Fukuoka, Japan.
EMBO J. 2011 Aug 2;30(17):3581-93. doi: 10.1038/emboj.2011.260.
Two distinct p97 membrane fusion pathways are required for Golgi biogenesis: the p97/p47 and p97/p37 pathways. VCIP135 is necessary for both pathways, while its deubiquitinating activity is required only for the p97/p47 pathway. We have now identified a novel VCIP135-binding protein, WAC. WAC localizes to the Golgi as well as the nucleus. In Golgi membranes, WAC is involved in a complex containing VCIP135 and p97. WAC directly binds to VCIP135 and increases its deubiquitinating activity. siRNA experiments revealed that WAC is required for Golgi biogenesis. In an in vitro Golgi reformation assay, WAC was necessary only for p97/p47-mediated Golgi reassembly, but not for p97/p37-mediated reassembly. WAC is hence thought to function in p97/p47-mediated Golgi membrane fusion by activating the deubiquitinating function of VCIP135. We also showed that the two p97 pathways function in ER membrane fusion as well. An in vitro ER reformation assay revealed that both pathways required VCIP135 but not its deubiquitinating activity for their ER membrane fusion. This was consistent with the finding that WAC is unnecessary for p97-mediated ER membrane fusion.
两种不同的 p97 膜融合途径对于高尔基体生物发生是必需的：p97/p47 和 p97/p37 途径。VCIP135 对于这两种途径都是必需的，而其去泛素化活性仅对于 p97/p47 途径是必需的。我们现在已经鉴定出一种新型的 VCIP135 结合蛋白，WAC。WAC 定位于高尔基体和细胞核。在高尔基体膜中，WAC 参与包含 VCIP135 和 p97 的复合物。WAC 直接结合 VCIP135 并增加其去泛素化活性。siRNA 实验表明 WAC 对于高尔基体生物发生是必需的。在体外高尔基体重建测定中，WAC 仅对于 p97/p47 介导的高尔基体重组装是必需的，但对于 p97/p37 介导的重组装不是必需的。因此，WAC 被认为通过激活 VCIP135 的去泛素化功能在 p97/p47 介导的高尔基体膜融合中发挥作用。我们还表明两种 p97 途径也在 ER 膜融合中起作用。体外 ER 重建测定表明，这两种途径都需要 VCIP135，但不需要其去泛素化活性来进行 ER 膜融合。这与 WAC 对于 p97 介导的 ER 膜融合是不必要的发现是一致的。
