探討人類類哺乳類Ste20激酵素3 (Mst3)在粒線體生物能量學與動態變化中之角色

Abstract

本計畫的主要目標為瞭解人類Ste20蛋白激酵素3 (Mst3)在正常及癌症細胞之粒線 體中對氧化磷酸化作用、生物能量學與代謝動態變化的生理角色。在前期的研究中， 我們發現Mst3可同時存在於細胞質及粒線體中。然而，許多個證據已顯示Mst3存在 於粒線體的内外膜的間隙，並與调亡促進因子(apoptosis-inducing factor; AIF)及核酸内 切酵素G (Endonuclease G; EndoG)結合成為一促调亡的蛋白複合體。而以RNAi選擇性 的降低Mst3表現，結果發現會造成粒線體中電子傳遞鏈中Complex I及III表現亮的 降低，進而促進粒線體内生物能量生合成的變異。這些前期研究的結果顯示Mst3在粒 線體中必然參與了生物能量的調控。因此，在這一個三年期的計晝中，我們希望延續 先前的研究方向，希望在正常及癌細胞中對Mst3影響粒線體的完整性、形態變動及生 物能量生合成等議題上作進一步研究。另外，我們亦希望研究在降低Mst3的生合成或 是大量表現失活的Mst3後，細胞内的生物能量產製的輪廓、代謝作用的輪廓及糖解作 用效率等議題。此外，對Mst3在粒線體型態變化中的角色亦是本計晝的研究重點，可 有助於我們對粒線體生理與生物能量的瞭解。我們希望藉由這些實驗所獲得的結果， 可讓我們更加瞭解Mst3在粒線體中的角色與分子作用機轉。

The main objective of this project is to elucidate the role of mammalian Ste20-like protein kinases 3 (Mst3) in the mitochondrial oxidative phosphorylation (OXPHOS), bioenergetics and the metabolic adaptation of normal and cancer cells. In a preliminary study endogenous Mst3 was shown to distribute in both mitochondria and cytoplasm at resting state. In mitochondria, it was found to locate in the intermembrane space and to associate with AIF and Endonuclease G Recently, we found that the selective knockdown of Mst3 in HeLa cells markedly reduced the activity of mitochondrial OXPHOS system by reducing the protein level of complexes I and III of electron transport chain. This result suggests that Mst3 may play roles in regulating the mitochondrial bioenergetics. Therefore, in this three-year proposal, we want to extend our previous studies to further investigate the role of Mst3 in the mitochondrial integrity and bioenergetics status of normal and tumorigenic cells. The bioenergetics profile, metabolic profile and glycolytic efficiency in cells either with selective knockdown of Mst3 or overexpression of mitochondria-targeted Mst3 mutants will be determined and analyzed. The role of Mst3 in the mitochondrial morphogenesis is also an important issue in understanding the mitochondrial physiology and bioenergetics. It is our hope that the results obtained from this proposal will allow us to understand more about the role of Mst3 in the mitochondria and serving as guiding principles for the ongoing researches.