Kozjak-Pavlovic Vera, Ross Katharina, Benlasfer Nouhad, Kimmig Sonja, Karlas Alexander, Rudel Thomas
Department of Molecular Biology, Max-Planck-Institut für Infektionsbiologie, Charitéplatz 1, D-10117, Berlin, Germany.
EMBO Rep. 2007 Jun;8(6):576-82. doi: 10.1038/sj.embor.7400982. Epub 2007 May 18.
Voltage-dependent anion-selective channel (VDAC) is a beta-barrel protein in the outer mitochondrial membrane that is necessary for metabolite exchange with the cytosol and is proposed to be involved in certain forms of apoptosis. We studied the biogenesis of VDAC in human mitochondria by depleting the components of the mitochondrial import machinery by using RNA interference. Here, we show the importance of the translocase of the outer mitochondrial membrane (TOM) complex in the import of the VDAC precursor. The deletion of Sam50, the central component of the sorting and assembly machinery (SAM), led to both a strong defect in the assembly of VDAC and a reduction in the steady-state level of VDAC. Metaxin 2-depleted mitochondria had reduced levels of metaxin 1 and were deficient in import and assembly of VDAC and Tom40, but not of three matrix-targeted precursors. We also observed a reduction in the levels of metaxin 1 and metaxin 2 in Sam50-depleted mitochondria, implying a connection between these three proteins, although Sam50 and metaxins seemed to be in different complexes. We conclude that the pathway of VDAC biogenesis in human mitochondria involves the TOM complex, Sam50 and metaxins, and that it is evolutionarily conserved.
电压依赖性阴离子选择性通道（VDAC）是线粒体外膜中的一种β桶状蛋白，它对于与细胞质进行代谢物交换是必需的，并且被认为参与了某些形式的细胞凋亡。我们通过使用RNA干扰耗尽线粒体导入机制的组分，研究了人线粒体中VDAC的生物发生。在此，我们展示了线粒体外膜转位酶（TOM）复合物在VDAC前体导入中的重要性。分选与组装机制（SAM）的核心组分Sam50的缺失，导致VDAC组装出现严重缺陷以及VDAC稳态水平降低。Metaxin 2耗尽的线粒体中，metaxin 1水平降低，并且在VDAC和Tom40的导入与组装方面存在缺陷，但三种靶向基质的前体则没有。我们还观察到Sam50耗尽的线粒体中metaxin 1和metaxin 2水平降低，这意味着这三种蛋白质之间存在联系，尽管Sam50和metaxins似乎处于不同的复合物中。我们得出结论，人线粒体中VDAC的生物发生途径涉及TOM复合物、Sam50和metaxins，并且在进化上是保守的。
