Honda Shinji, Aihara Takeshi, Hontani Masayasu, Okubo Katsuhiko, Hirose Shigehisa
Department of Biological Sciences, Tokyo Institute of Technology, 4259-B-19 Nagatsuta-cho, Midori-ku, Yokohama 226-8501, Japan.
J Cell Sci. 2005 Jul 15;118(Pt 14):3153-61. doi: 10.1242/jcs.02449. Epub 2005 Jun 28.
Mitofusin-2 (Mfn2) is an essential component of mitochondrial fusion machinery, but its molecular mechanism of action is not clear. We found that a Mfn2 deletion mutant lacking two transmembrane spans (Mfn(DeltaTM)) acts as a dominant-negative mutant and blocks mitochondrial fusion. Furthermore, detailed analysis of various mutants of Mfn(DeltaTM) revealed that GTPase activity and four regions highly conserved from nematodes to mammals are necessary for the dominant-negative effect. Immunoprecipitation studies of the N- and C-terminal cytosolic tails of Mfn2 showed that in addition to the coiled-coil domains previously identified, a highly conserved domain in the most N-terminal region and GTPase activity are necessary for the interaction between the N- and C-terminal tails, which is in turn required for the dominant-negative effect. In addition, we found unexpectedly that overexpression of the deletion mutant composed of one short region each in the N- and C-terminal tails of Mfn2 resulted in loss of mitochondrial membrane potential, suggesting that Mfn2 might also be connected to maintenance of mitochondrial membrane potential.
线粒体融合蛋白2（Mfn2）是线粒体融合机制的一个重要组成部分，但其分子作用机制尚不清楚。我们发现，缺少两个跨膜结构域的Mfn2缺失突变体（Mfn(DeltaTM)）作为显性负性突变体，可阻断线粒体融合。此外，对Mfn(DeltaTM)各种突变体的详细分析表明，GTP酶活性以及从线虫到哺乳动物高度保守的四个区域对于显性负性效应是必需的。对Mfn2的N端和C端胞质尾巴进行免疫沉淀研究表明，除了先前确定的卷曲螺旋结构域外，最N端区域的一个高度保守结构域和GTP酶活性对于N端和C端尾巴之间的相互作用是必需的，而这种相互作用反过来又是显性负性效应所必需的。此外，我们意外地发现，由Mfn2的N端和C端尾巴各一个短区域组成的缺失突变体的过表达导致线粒体膜电位丧失，这表明Mfn2可能也与线粒体膜电位的维持有关。
