Ambivero Camilla T, Cilenti Lucia, Main Stacey, Zervos Antonis S
Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, 12722 Research Parkway, Orlando, FL 32826, USA.
Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, 12722 Research Parkway, Orlando, FL 32826, USA.
Cell Signal. 2014 Dec;26(12):2921-9. doi: 10.1016/j.cellsig.2014.09.004. Epub 2014 Sep 16.
Mulan is an E3 ubiquitin ligase embedded in the outer mitochondrial membrane (OMM) with its RING finger facing the cytoplasm and a large domain located in the intermembrane space (IMS). Mulan is known to have an important role in cell growth, cell death, and more recently in mitophagy. The mechanism of its function is poorly understood; but as an E3 ligase it is expected to interact with specific E2 ubiquitin conjugating enzymes and these complexes will bind and ubiquitinate specific substrates. The unique topology of Mulan can provide a direct link of communicating mitochondrial signals to the cytoplasm. Our studies identified four different E2 conjugating enzymes (Ube2E2, Ube2E3, Ube2G2 and Ube2L3) as specific interactors of Mulan. Each of these E2 conjugating enzymes was fused to the RING finger domain of Mulan and used in a modified yeast two-hybrid screen. Several unique interactors for each Mulan-E2 complex were isolated. One such specific interactor of Mulan-Ube2E3 was the GABARAP (GABAA receptor-associated protein). GABARAP is a member of the Atg8 family of proteins that plays a major role in autophagy/mitophagy. The interaction of GABARAP with Mulan-Ube2E3 required an LC3-interacting region (LIR) located in the RING finger domain of Mulan as well as the presence of Ube2E3. The isolation of four different E2 conjugating enzymes, as specific partners of Mulan E3 ligase, suggests that Mulan is involved in multiple biological pathways. In addition, the interaction of GABARAP with Mulan-Ube2E3 supports the role of Mulan as an important regulator of mitophagy and provides a plausible mechanism for its function in this process.
木兰是一种嵌入线粒体外膜（OMM）的E3泛素连接酶，其环指结构域面向细胞质，一个大结构域位于膜间隙（IMS）。已知木兰在细胞生长、细胞死亡以及最近发现的线粒体自噬中发挥重要作用。其功能机制尚不清楚；但作为一种E3连接酶，预计它会与特定的E2泛素结合酶相互作用，这些复合物将结合并泛素化特定底物。木兰独特的拓扑结构可以提供将线粒体信号传递到细胞质的直接联系。我们的研究确定了四种不同的E2结合酶（Ube2E2、Ube2E3、Ube2G2和Ube2L3）作为木兰的特异性相互作用蛋白。这些E2结合酶中的每一种都与木兰的环指结构域融合，并用于改良的酵母双杂交筛选。分离出了每种木兰-E2复合物的几种独特相互作用蛋白。木兰-Ube2E3的一种这样的特异性相互作用蛋白是GABARAP（GABAA受体相关蛋白）。GABARAP是Atg8家族蛋白的成员，在自噬/线粒体自噬中起主要作用。GABARAP与木兰-Ube2E3的相互作用需要位于木兰环指结构域中的LC3相互作用区域（LIR）以及Ube2E3的存在。分离出四种不同的E2结合酶作为木兰E3连接酶的特异性伙伴，这表明木兰参与多种生物学途径。此外，GABARAP与木兰-Ube2E3的相互作用支持了木兰作为线粒体自噬重要调节因子的作用，并为其在此过程中的功能提供了一种合理的机制。
