Functional characterization of the role of evolutionary conserved Rho GTPases at the interface between mitochondria and the endoplasmic reticulum

线粒体与内质网(ER)的一小部分形成紧密连接。这些接触部位是两个隔室之间钙离子和磷脂交换所必需的，这是细胞存活所必需的。调节和调节这两个细胞器之间相互作用的机制仍然知之甚少。最近，一种名为Ermes的蛋白质复合体被发现在酵母中介导线粒体和内质网的连接。系统的遗传分析显示，进化保守的Rho GTP酶Gem1突变导致与Ermes突变体相似的表型。此外，Gem1和Ermes组分在物理上相互作用，强烈表明Gem1在mito-ER接触部位发挥作用。在拟议的研究中，我将描述Gem1在这些界面上的功能，并将确定Gem1的EF手和GTPase结构域在这一过程中的作用。哺乳动物细胞缺乏ERMES同源物，因此我将利用哺乳动物的Gem1同源物Miro1和Miro2作为研究人类细胞中有丝分裂-ER接触位点的起点。最后，我将进行系统的大规模分析，全面定义影响线粒体和内质网相互作用的成分。总之，这些分析有望显著提高我们对有丝分裂-ER接触位点的形成和调节及其对不同细胞过程的重要性的理解。

Mitochondria form tight connections with a subfraction of the endoplasmic reticulum (ER). These contact sites are required for Ca2+ and phospholipid exchange between both compartments, which is essential for cell viability. The mechanisms mediating and regulating the interaction between both cellular organelles remain poorly understood. Most recently, a protein complex, named ERMES, has been identified to mediate tethering of mitochondria and the ER in yeast. Mutation of the evolutionary conserved rho GTPase Gem1 results in similar phenotypes compared to ERMES mutants as revealed by a systematic genetic analysis. Moreover, Gem1 and ERMES components physically interact with each other, strongly suggesting a role of Gem1 at mito-ER contact sites. In the proposed study, I will characterize the function of Gem1 at these interfaces and will determine the role of the EF hands and GTPase domains of Gem1 in this process. Mammalian cells lack ERMES counterparts, wherefore I will exploit the mammalian Gem1 homologs, Miro1 and Miro2, as starting points for the investigation of mito-ER contact sites in human cells. Finally, I will perform a systematic large scale analysis to comprehensively define the components impacting on the interaction of mitochondria and the ER. Altogether, these analyses hold the promise to significantly enhance our understanding of the formation and regulation of mito-ER contact sites and their importance for diverse cellular processes.