Mechanism of Mitochondrial Fusion

描述（由申请人提供）：线粒体是动态的，必不可少的，双膜细胞器，在细胞内执行无数任务。与它们的细菌祖先不同，它们不是独立的实体。分离的线粒体是短暂的，并通过融合在细胞内形成局部和广泛的线粒体合胞体进行交流。线粒体分裂对抗融合，这些事件共同作用，创造了一个连接的隔室，可以访问mtDNA，因此具有功能，但能够通过肌动蛋白或微管网络的运输分布到遥远的细胞目的地。我们专注于了解线粒体融合的分子机制，以深入了解融合在细胞和疾病中的作用和调节。除了其基本的细胞作用外，线粒体融合还调节细胞内固有的凋亡，相反，促凋亡的Bcl-2蛋白调节健康细胞中的线粒体融合。胚胎发育需要线粒体融合，融合蛋白的突变导致神经退行性疾病和中风，这一事实强调了融合的重要细胞作用。线粒体融合的独特之处在于它是由高度保守的动力蛋白相关蛋白（DRPs）的作用介导的。DRPs是大型GTP酶，通过其自组装和水解GTP的能力，控制膜重塑事件。我们强大的酵母体外实验揭示了关于融合机制的丰富信息。我们已经证明，DRPs介导了线粒体内外膜融合过程中的膜系结和脂质混合步骤。我们最近的工作也表明，在内外膜融合的脂质混合步骤中，需要一种非drp外膜融合蛋白。在我们成功的基础上，我们现在已经在体外重建了类似的哺乳动物线粒体融合反应。利用我们的酵母和哺乳动物系统，我们将确定线粒体融合的基本机制，探索哺乳动物线粒体融合机器独特特征的机制意义，并确定Bcl-2蛋白调控线粒体融合的机制基础。所提出的实验数据将为理解线粒体融合在细胞中的生理作用提供基础。此外，它们将直接提供信息，阐明与突变融合成分相关的疾病的基础。最后，通过探索线粒体融合与细胞凋亡之间的机制联系，我们的实验将为Bcl-2蛋白家族的功能和调控提供基础信息，这将影响科学家对细胞凋亡调控的看法。

DESCRIPTION (provided by applicant): Mitochondria are dynamic, essential, double-membraned organelles that perform a myriad of tasks within cells. Unlike their bacterial ancestors, they are not discrete entities. Isolated mitochondria are transient and in communication via fusion to form both localized and widespread mitochondrial syncytia within cells. Mitochondrial division antagonizes fusion and together these events function to create a compartment that is connected, with access to mtDNA, and thus functional, yet able to be distributed to distant cellular destinations via transport on actin or microtubule networks. We are focused on understanding the molecular mechanism of mitochondrial fusion to gain insight into the roles and regulation of fusion in cells and disease. In addition to its fundamental cellular role, mitochondrial fusion also regulates intrinsic apoptosis in cells and conversely, the pro-apoptotic Bcl-2 proteins regulate mitochondrial fusion in healthy cells. The important cellular roles of fusion are underscored by the fact that mitochondrial fusion is required for embryonic development and mutations in fusion proteins cause neurodegenerative diseases and stroke. Mitochondrial fusion is unique in that it is mediated by the action of highly conserved dynamin-related proteins (DRPs). DRPs are large GTPases that, through their ability to self-assemble and hydrolyze GTP, control membrane remodeling events. Our powerful yeast in vitro assay has revealed a wealth of information regarding the fusion mechanism. We have demonstrated that DRPs mediate both membrane tethering and lipid-mixing steps in fusion at the mitochondrial outer and inner membranes. Our recent work also indicates that a non-DRP outer membrane fusion protein is required post-membrane tethering, at the lipid-mixing step of outer and inner membrane fusion. Building on our success, we have now reconstituted the analogous mammalian mitochondrial fusion reaction in vitro. Using our yeast and mammalian systems, we will determine the fundamental mechanism of mitochondrial fusion, explore the mechanistic significance of the unique features of the mammalian mitochondrial fusion machines, and determine the mechanistic basis of the regulation of mitochondrial fusion by Bcl-2 proteins. Data from the proposed experiments will provide a foundation to understand the physiological roles mitochondrial fusion plays in cells. In addition, they will directly provide information that illuminates the basis of the diseases linked to mutations fusion components. Finally, by probing the mechanistic link between mitochondrial fusion and apoptosis, our experiments will provide fundamental information regarding the function and regulation of the Bcl-2 family of proteins, which will impact how scientists view the regulation of apoptosis.