Miro1调控线粒体移动在肾小球足细胞损伤中的作用及机制

足细胞损伤与慢性肾脏病蛋白尿的发生关系密切。申请人前期工作证实线粒体分裂在足细胞损伤中作用重要。线粒体移动障碍可介导线粒体分裂。线粒体移动在足细胞中尚无报道。线粒体外膜的GTPase家族成员Miro1是介导线粒体移动的关键蛋白，当Miro1与马达分子Kinesin发生解离将导致线粒体移动障碍。我们预实验也证实，醛固酮可引起Miro1与Kinesin解离。Miro1主要受细胞内钙离子调控，而瞬时受体电位阳离子通道蛋白6（TRPC6）是介导足细胞钙内流主要途径。我们推测：醛固酮激活TRPC6-钙离子内流使Miro1与Kinesin解离，线粒体移动发生障碍，使线粒体分裂增加，最终导致线粒体功能损伤及足细胞损伤的发生。本研究将从体外培养肾小球足细胞系、动物实验、足细胞特异性Miro1转基因小鼠三方面阐述Miro1介导的线粒体移动及其调控机制在足细胞损伤中的作用，为解析足细胞损伤机制提供新的思路。

Podocytes are highly specialized glomerular visceral epithelial cells that cover the outside of the glomerular basement membrane. Podocyte injury plays a pivotal role in the onset of proteinuria and progression of glomerular diseases. The mechanisms that underlie podocyte injury are a focus of intense research. Mitochondria are cellular organelles that produce the energy required for cellular processes through synthesis of ATP. Mitochondrial morphology regulated by fission and fusion is important for normal mitochondrial function through maintenance of the metabolite and protein balance between internal compartments. Our previous study has showed that mitochondrial fission played a crucial role in podocyte injury. Recent studies showed that defective mitochondrial movement could induce mitochondrial fission..Mitochondria movement, which serves to distribute mitochondrial functions in a dynamic and non-uniform fashion, has attracted special interest in recent years. Mitochondrial movement is regulated by a series of molecular adaptors that mediate the attachment of mitochondria to molecular motors. Miro1 belongs to the mitochondrial Rho GTPase family and are critical for mitochondrial movement. Miro1 links mitochondria to kinesin motor proteins allowing mitochondria to move along microtubules. Miro1 is the key Ca2+ sensor for Ca2+-dependent mitochondrial stopping in axons and dendrites, which are dependent on its EF-hand domains. Increased cytoplasmic Ca2+ halts mitochondrial movement by binding to Miro1 EF-hand domains, thus leading to altered interactions between Miro1 and the kinesin motor. Furthermore, one of the key proteins responsible for calcium influx in the podocytes is transient receptor potential cation channel, subfamily C, member 6 (TRPC6). Both increased TRPC6 channel activity and expression lead to a pathologically high Ca2+ influx in podocytes, which eventually causes podocyte injury. The role of mitochondrial movement in podocyte injury is poorly investigated. Our preliminary studies found that aldosterone induced calcium influx and reduced the interaction of Miro1 with kinesin in podocytes..Therefore, we hypothesize here that TRPC6-Ca2+-Miro1 signaling may be involved in the process of aldosterone induced podocyte injury by targeting mitochondrial movement. To establish our main hypothesis, proposed studies are designed to investigate the effects of TRPC6-Ca2+-Miro1 signaling and mitochondrial movement in podocyte injury both in cultured podocytes and in animal experiments. These studies are expected to reveal the molecular mechanism of mitochondrial movement in podocyte injury, which may provide us with unprecedented opportunities for therapeutic interventions of glomerular diseases.