人類Ste20蛋白質激酵素，Mst3，在細胞凋亡與OXPHOS系統調控機轉之研究

Abstract

Mst3在細胞淍亡及正常生理調控上扮演舉足輕重的角色。在之前的研究中發現，雖然caspase參與了與Mst3相關之細胞淍亡，但caspase的inhibitor，z-DEVD-fmk，卻只能輕微地抑制staurosporine引起的細胞淍亡。由此可知，Mst3不只參與了caspase-dependent 的細胞淍亡途徑，也參與了caspase-independent的途徑。在我們的研究中發現，Mst3藉由調節粒腺體的Bax使得粒腺體的細胞淍亡前趨蛋白AIF及Endo G從粒腺體轉移到細胞核，之後，Endo G的nuclease活性使得DNA斷裂。也因此，Mst3被懷疑可能存在於與AIF與Endo G同樣的位置，即粒腺體的intermembrane space。隨後，我們也證明了Mst3的確在粒腺體的intermembrane space。而位於粒腺體的Mst3調節了電子傳遞鏈的complexes I及III，並影響了與葡萄糖有關之ATP生成。所以本研究的結論是Mst3不只在caspase- dependent及caspase-independent的細胞淍亡扮演了重要角色，也參與粒腺體OXPHOS系統之調控。

Mammalian sterile-20 protein kinase 3 (Mst3) plays an essential role in the apoptotic and non-apoptotic pathway. Caspases are shown to be involved in the Mst3-mediated apoptosis, but the staurosporine-induced apoptosis is slightly suppressed by the caspase inhibitor, z-DEVD-fmk. Mst3 is though that Mst3 is not only involves in caspase-dependent but also in caspase-independent apoptotic pathway. The study demonstrates that Mst3 controls the mitochondrial integrity through the regulation of Bax and subsequently promote the nuclear translocation of caspase-independent proapoptotic members, apoptosis-inducing factor and endonuclease G from mitochondria in HeLa cells. Following, the nuclease activity associated with endonuclease G is modulated. Thus, Mst3 is inferred that the participation in staurosporine-induced apoptosis mediated its cellular localization of the intermembrane space of mitochondria. The bold is confirmed by co-immunofluorescent staining, transmission electron microscopic imaging and immuno-blotting after subcellular fractionation. Similar results are also observed in human trophoblast cell line 3A-sub-E cells, suggesting that the mitochondrial localization of Mst3 is a general phenomenon. The mitochondrial targeting segment of Mst3 is between residues 314-431. The intermembrane space-Mst3 regulate the respiratory transport chain complexes I and III and the dependence of glucose for ATP synthesis. The results indicate that Mst3 plays an important role not only in caspase dependent and independent- apoptotic pathway but also in oxidative phosphorylation.