- 學位論文
探討ECM如何參與粒線體自噬作用與細胞凋亡之關聯性
ECM modulates the link between mitophagy regulation and apoptosis
摘要
果蠅CG1458基因是個老化基因,它具有鐵硫簇結合結構(CDGSH)的蛋白,是個高度保留性且分布於原核和真核生物中。在人類與老鼠中具有三個CDGSH iron-sulfur domain的蛋白，分別為CISD1、CISD2和CISD3。經過CDGSH domain的序列比對，發現在果蠅中具有兩個CISD蛋白，分別為CG1458和CG3420。其中CG1458具有單一CDGSH domain,而且CG1458序列與CISD2相似度較高。目前研究者發現此CISD2位於人類長壽基因的第四號染色體的長臂上。之前實驗室同仁研究發現隨著年齡增長，伴隨著累積CG1458；此外，當過量表現CG1458將會導致果蠅早衰,爬行能力減弱以及粒線體嚴重缺陷;反之，剔除CG1458之後, 明顯地觀察到延緩果蠅老化，並且改善其爬行能力。由於CG1458過度表現會導致粒線體型態變大且聚集現象,因此取名為ECM (Enlargement Clustering Mitochondria)。本實驗主要研究ECM的粒線體之外,還會利用細胞凋亡和粒線體自噬作用方式修復細胞內受損或衰老的粒線體。目前研究表明,Bcl-2家族蛋白參與粒線體自噬調節及粒線體分裂、融合的調控,在果蠅身上與Bcl-2的同源基因主要是Buffy和Debcl,因此本實驗將會探討這兩個基因對粒線體的影響。研究結果中發現當過度表現Buffy時,確實可以抑制ECM基因所造成的粒線體膨大和聚集現象;反之,當Debcl過度表現卻對ECM沒造成任何影響。從過去的研究發現，Bcl-2除了會抑制apoptosis以外，在autophagy中同時也扮演著抑制者的角色。而果蠅的自噬基因ATG6是Beclin 1的同源基因,因此我們同時表現Buffy與ATG6在ECM果蠅身上,與預期結果一樣,粒線體型態有明顯改善和變小。意料之外也發現下調ATG1基因也可以抑制ECM粒線體聚集。另外, 我們也進行一連串和細胞凋亡之關聯性基因進行研究，探討Reaper, Hid和Grim在果蠅肌肉組織裡對粒線體的影響,之後發現表現這三個基因於肌肉組織時,會導致果蠅致死,反之Reaper, Hid和Grim經過RNA干擾後,意外地發現竟可以抑制ECM所造成粒線體的膨大和融合現象,尤其以Reaper是最強效果可以抑制ECM。
並列摘要
Mitochondria play roles in the regulation of energy production and apoptosis. Mitochondrial fusion and fission are crucial processes in mitochondria homeostasis. During apoptosis and mitophagy, mitochondria undergo morphological changes, which include fission and clustering, but the link between mitophagy regulation and cellular apoptosis is unclear. The Enlargement and Clustering Mitochondria (ECM) gene encodes a protein that localizes to the mitochondria. In Drosophila cells, the overexpression of ECM increases the size and aggregation of mitochondria. To investigate the signaling pathways by which ECM induces changes in mitochondrial morphology, we identified the Buffy and ATG6 genes as extragenic suppressors of ECM gene function. Buffy functions as a pro-survival Bcl-2-like protein, and beclin1, the mammalian orthologue of ATG6, are required for autophagosome formation. The co-overexpression of Buffy and ATG6 ameliorated the effects of ECM overexpression on mitochondrial morphology. The effects of ECM overexpression were also reversed by the knockdown of Reaper, Grim, and Hid expression using gene-specific siRNA. Our results suggest that pro-survival signaling pathways involved in mitophagy regulation may suppress ECM gene function. Our findings provide important insight into the dynamic processes involved in mitochondria homeostasis, and may be useful for identifying molecular targets in the development of novel therapies for mitochondrial dysfunction-related conditions, including metabolism disorders and aging.