Department of Physiology, UT Southwestern Dallas, TX 75390, USA.
Cell. 2013 Feb 28;152(5):1051-64. doi: 10.1016/j.cell.2013.01.051.
Endosomal protein trafficking is an essential cellular process that is deregulated in several diseases and targeted by pathogens. Here, we describe a role for ubiquitination in this process. We find that the E3 RING ubiquitin ligase, MAGE-L2-TRIM27, localizes to endosomes through interactions with the retromer complex. Knockdown of MAGE-L2-TRIM27 or the Ube2O E2 ubiquitin-conjugating enzyme significantly impaired retromer-mediated transport. We further demonstrate that MAGE-L2-TRIM27 ubiquitin ligase activity is required for nucleation of endosomal F-actin by the WASH regulatory complex, a known regulator of retromer-mediated transport. Mechanistic studies showed that MAGE-L2-TRIM27 facilitates K63-linked ubiquitination of WASH K220. Significantly, disruption of WASH ubiquitination impaired endosomal F-actin nucleation and retromer-dependent transport. These findings provide a cellular and molecular function for MAGE-L2-TRIM27 in retrograde transport, including an unappreciated role of K63-linked ubiquitination and identification of an activating signal of the WASH regulatory complex.
内体蛋白运输是一种重要的细胞过程，在几种疾病中失调，并成为病原体的靶向目标。在这里，我们描述了泛素化在这个过程中的作用。我们发现 E3 RING 泛素连接酶 MAGE-L2-TRIM27 通过与逆行转运体复合物的相互作用定位于内体。MAGE-L2-TRIM27 或 Ube2O E2 泛素缀合酶的敲低显着损害了逆行转运体介导的运输。我们进一步证明，MAGE-L2-TRIM27 泛素连接酶活性对于 WASH 调节复合物介导的内体 F-肌动蛋白成核是必需的，WASH 是已知的逆行转运体介导的运输调节剂。机制研究表明，MAGE-L2-TRIM27 促进了 WASH K220 的 K63 连接泛素化。重要的是，破坏 WASH 泛素化会损害内体 F-肌动蛋白成核和逆行转运体依赖性运输。这些发现为 MAGE-L2-TRIM27 在逆行运输中的细胞和分子功能提供了依据，包括 K63 连接泛素化的未被认识的作用以及 WASH 调节复合物的激活信号的鉴定。
