Mitochondria fusion and fission regulatory pathways are not yet completely understood. Mitochondrial dynamics via fission (Dnm1) and fusion (Fzo1) pathways has been demonstrated in yeast Saccharomyces cerevisiae. Our lab have identified a novel protein Srv2 that interacts with Dnm1. Srv2 is a protein with multifunctional domains; the N-terminal Srv2 encodes the adenylate cyclase activation domain, which is involved in Ras signaling pathway, and the C-terminal Srv2 encodes an actin monomer binding domain which is involved in actin recycling. In this thesis, I aim to clarify the role of Srv2 in mitochondrial fusion and fission pathways. I used mtGFP to label mitochondria and analyzed the status of mitochondrial dynamics. Deletion of SRV2 causes mitochondrial fragmentation. The fragmented phenotype depends on the conventional fission protein Dnm1 and can be compensated by ectopic Srv2 expression. The genes deletion results indicated that Srv2 may not depend on the Ras signaling pathway to regulate mitochondrial dynamics. In addition, the disruption of Srv2 and actin interaction by mutagenesis had similar mitochondrial fragmentation as SRV2 deletion. Thus, it is highly possible that Srv2 affects mitochondrial fusion and fission through its interaction with actin. Although the detail mechanisms of how Srv2 affects mitochondrial dynamics remain to be clarify, my results indicate that Srv2 is a novel regulatory protein of mitochondrial fusion and fission.

粒線體透過分裂和融合的過程達到動態平衡而在細胞體內形成不同的形態，不同的平衡狀態也影響了粒線體的功能。我們以酵母菌(Saccharomyces cerevisiae)為模式生物，利用蛋白交互作用的實驗發現了一個與粒線體動態平衡有關的蛋白Srv2。Srv2是一個具有多個功能性區域(functional domain)的蛋白，其N端為具有活化adenylyl cyclase的區域，可以調控一個與酵母菌細胞凋亡(apoptosis)有關的途徑(Ras signaling pathway)。C端為具有與肌動蛋白結合能力的區域，與肌動蛋白的回收(actin recycling)有關。我們以能夠標定粒線體的螢光蛋白(mtGFP)來觀察粒線體動態平衡之後的的形態，並分別針對Ras signaling及actin recycling兩個途徑，利用調控基因表現、基因剔除的方式來釐清Srv2調控粒線體的動態平衡的方式。我們發現剔除SRV2會使細胞中片斷狀的粒線體增加，而此一影響必須透過粒線體分裂蛋白Dnm1來達成。我們的實驗結果初步排除了Srv2透過Ras signaling pathway調控下游之蛋白質進而調控粒線體的動態平衡的可能性；剔除SRV2所造成的碎片狀粒線體與此蛋白與肌動蛋白的交互做用有密切關係。我們針對SRV2基因對粒線體融合與分裂的影響所做的實驗證明粒線體的動態平衡的確受到嚴謹的調控，雖然Srv2在此一機制中的詳盡角色仍需更進一步的探討，但Srv2確為此一機制中新發現的一份子。

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