粒線體是一種動態平衡的胞器，持續進行的分裂與融合對於調控ATP的產生、細胞內鈣離子平衡與細胞計畫性死亡有重大影響。在神經退化性疾病的病人中可以發現因融合與分裂平衡改變所導致與常規不同的粒線體型態，而且粒線體過度分裂的現象也被發現和神經細胞功能不正常甚至死亡有相關。粒線體的分裂過程中Drp1扮演一個重要的角色，但是目前為止調控Drp1功能的機制還未被釐清。Cdk5一直被認為與神經細胞的生存與死亡息息相關，我們發現，在細胞內可藉由過量表現Cdk5的活化因子p35造成Drp1的Ser-616位置磷酸化，本篇論文的研究目標將以釐清Cdk5在Drp1上的轉譯後修飾對於Drp1功能的影響，藉由觀察平衡狀態下的粒線體型態進一步分析Drp1分裂粒線體的能力。實驗結果顯示在細胞中過量表現模擬磷酸化的Drp1 S616D會造成粒線體型態改變，並且促使Drp1在細胞內分佈位置改變到粒線體上。根據我們的研究結果，我們認為當Drp1 S616被Cdk5所磷酸化之後，將會調控Drp1的功能與在細胞內的位置進而影響其分裂粒線體的能力。

Mitochondria are dynamic organelles that continually divide and fuse with one another. These processes facilitate the control of mitochondrial morphology and respond to cell metabolic demands, such as ATP production, Ca2+ homeostasis and cell apoptosis. The excessive mitochondrial division is associated with neuronal cell death and neuronal dysfunction. Moreover, abnormal mitochondrial morphology can be found in many neurological disorders. Drp1 (dynamin-related protein 1) is a critical protein that facilitates mitochondrial division. However, the regulatory mechanism remains largely unclear. Cdk5 (cyclin dependent kinase 5) is implicated in neuronal death and survival. Previously, we found that Drp1 phosphorylated by Cdk5 in vitro. The goal of this thesis is to characterize the effects of Cdk5 dependent post-translational modification on Drp1 function. Overexpression of Drp1 S616D phospho-mimetic mutant led mitochondrial dynamic balance toward fusion and promoted Drp1 translocation to mitochondria. Our results suggest that Cdk5 phosphorylation of Drp1 at Ser-616 affects Drp1 protein function and mediates translocation of Drp1 to mitochondria. We consider Cdk5 phosphorylation is one of the mitochondrial division regulatory machineries.

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