Cofilin线粒体转位通过影响线粒体分裂调控细胞凋亡的分子机制

It has been shown that many connections have been discovered between mitocondrial fission and apoptosis. However, the mechanistic link between mitochondrial fission and apoptosis remains unclear. Our recent findings indicate that during mitochondrial apoptosis, cofilin was activated/dephosphorylated and translocated from the cytosol to the mitochondria, leading to mitochondrial fragmentation. Downregulation of cofilin with siRNA markedly reduced mitochondrial fission and apoptosis. Based on our previous study, we hypothesize that cofilin has an important role in the regulation of excessive mitochondrial fission, cytochrome c release, as well as apoptosis through its translocation from the cytosol to mitochondria. To this end, we will study the effects of cofilin activation and mitochondrial translocation on mitochondrial fragmentation and apoptosis by using siRNA and genetic approaches. We will focus on understanding the molecular mechanism of cofilin mitochondrial translocation and the interaction between cofilin and Drp-1. We will also clarify the relationship between Cofilin and mitochondrial fission and cytochrome C release, and finally elucidate the possible mechanistic link between cofilin and apoptosis. Our study will reveal a novel role of cofilin in regulation of mitochondrial fission and apoptosis, and suggest cofilin as a potential target for the regulation of apoptosis.

线粒体分裂与细胞凋亡关系密切，但其发生的分子机制尚不清楚。我们前期发现,Cofilin在线粒体凋亡途径中被激活，发生线粒体转位，参与线粒体分裂与片段化。而阻断Cofilin的表达将抑制线粒体分裂和细胞凋亡的发生，提示Cofilin调控的线粒体分裂途径在细胞凋亡中发挥了重要作用。本项目拟以Cofilin 在线粒体分裂和细胞凋亡中的作用为重点和突破口，研究Cofilin的激活和线粒体转位对线粒体分裂及细胞凋亡发生的影响，着重了解Cofilin线粒体转位的分子机制，探索Cofilin如何通过与线粒体分裂其他重要分子如Drp-1等的相互作用，明确Cofilin与线粒体分裂及细胞色素C释放的关系，阐明Cofilin影响细胞凋亡的分子机制。本项目的开展将对线粒体分裂与凋亡的理论提供新的认识，并为以Cofilin为靶点的凋亡调控研究开拓新的思路。

线粒体分裂和线粒体自噬在细胞生命活动功能和肿瘤发生发展过程中发挥了十分重要的作用。探明线粒体分裂和线粒体自噬的分子机制将为癌症的预防和治疗提供新的策略。已有研究表明肌动蛋白Actin参与了线粒体分裂和线粒体自噬的调控。Cofilin是已知的Actin解聚因子。然而，Cofilin调控线粒体分裂和线粒体自噬的分子机制尚不清楚。我们研究发现敲低Cofilin可阻断STS/ETO/CCCP诱导的线粒体分裂和PINK1/PARK2依赖的线粒体自噬，而过表达Cofilin可增强STS/ETO/CCCP诱导的线粒体分裂和线粒体自噬。Cofilin主要通过影响线粒体膜电位，从而对线粒体蛋白酶MPPβ，PARL，AFG3L2进行调节，引起PINK1蓄积。我们还发现CCCP处理后，Cofilin可与G-actin/F-actin在线粒体分裂位点发生共定位。肌动蛋白聚合抑制剂LatB预处理能增加STS/ETO/CCCP诱导的Actin线粒体转位，而肌动蛋白解聚抑制剂Jas则减少STS/ETO/CCCP诱导的Actin线粒体转位，但LatB和Jas均能阻断CCCP诱导的线粒体分裂和线粒体自噬。我们研究结果表明表明，G-actin是Actin的线粒体转位形式，Cofilin是通过在线粒体分裂位点解聚Actin从而发挥调控线粒体分裂和线粒体自噬的作用。