Regulations of energy metabolism and cellular fate via mitochondrial porin

线粒体孔蛋白一直被认为只是线粒体外膜上的一个“孔”。然而，最近的研究表明，线粒体！孔蛋白还调节细胞能量代谢和细胞命运。在这项研究中，我们对线粒体孔蛋白进行了表征，得到了以下结果：1)在肿瘤细胞中，大量己糖激酶附着在线粒体上。然而，当线粒体结合己糖激酶加入肝脏线粒体时，只有一小部分能附着在线粒体上。这一事实表明肝脏线粒体和肿瘤线粒体之间己糖激酶结合位点（即孔蛋白）可能存在差异。在这项研究中，我们对恶性肿瘤细胞中表达的编码孔蛋白的信息进行了表征。因此，肝脏线粒体的己糖激酶结合能力低于肿瘤线粒体的原因很清楚地解释了肝细胞和肿瘤细胞之间孔蛋白表达水平的差异。2)通过退化引物PCR鉴定出与1型孔蛋白结构相似的信息。这一结果提示可能存在线粒体孔蛋白的第四个成员。我们目前正在描述这条信息。3)孔蛋白的信息已经被很好地表征，但存在于线粒体外膜的孔蛋白尚未被研究。我们提出了针对孔蛋白的抗体，并分析了线粒体片段中存在的孔蛋白。结果发现，2型异构体是存在于线粒体外膜的主要孔蛋白异构体。

Mitochondrial porin has been regarded just a "pore" in the outer mitbchohdrial membrane. However, recent studies indicated that mitochondria! porin also regulates cellular energy metabolism and fate. In this study, we characterized mitochondrial porin and obtained following results.1) In tumor cells, a large amount of hexokinase is attached to the mitochondria. However, when mitochondria-bindable hexokinase was added to liver mitochondria, only a small portion can be attached to the mitochondria. This fact indicates the possible differences in the hexokinase binding sites (i.e. porin) between liver mitochondria and tumor mitochondria. In, this study, we characterized messages encoding porin(s) expressed in malignant tumor cells. As a result, the reason why liver mitochondria show lower hexokinase binding capacity than tumor mitochondria was clearly explained by the differences in the expression levels of porin between liver and tumor cells.2) A message showing structural similarity to type 1 porin was identified by degenerated primer based PCR. This result indicates possible existence of fourth member of mitochondrial porin. We are currently characterizing this message.3) Messages of porin have been well characterized but porin protein present in the mitochondrial outer membrane has not yet investigated. We raised antibody against porin protein and analyzed porin protein present in the mitochondrial fraction. As a result, type 2 isoform was found to be major porin isoform present in the outer mitochondrial membrane.