AAA ATPases linking mitochondria with microtubule processing in flies and yeast

描述(申请人提供)：线粒体是食物能量被利用成可用的三磷酸腺苷形式的细胞器，在特殊细胞内被移动和塑造以满足不同的能量需求。许多人类遗传性神经退行性疾病与线粒体动力学缺陷有关。果蝇精子发生是对线粒体形态发生保守机制进行遗传解剖的理想模型系统，因为线粒体在精子发育过程中经历了戏剧性的成形。减数分裂后，果蝇精子细胞中的所有线粒体通常会融合成两个巨大的线粒体衍生物，它们精确而复杂地相互缠绕，形成一个被称为Nebenkern的球形结构，然后它会沿着不断增长的精子尾巴展开和拉长。主要的焦点是阐明线粒体形成的分子机制，以此来表征其人类同源物可能导致线粒体功能障碍的基因。我们以前发现果蝇NMD基因(没有线粒体衍生物)是精子发生过程中线粒体聚集所必需的。NMD基因产物是一种与微管切断蛋白spastin和katanin相关的AAA ATPase，尽管与这些近亲不同，NMD在线粒体和中心体/基底上的定位是独一无二的。NMD的类似基因CG4701是精子发生后期线粒体成形所必需的。这两个副线似乎也是雄性减数分裂细胞质分裂所必需的，可能是通过对减数分裂纺锤体的影响。酵母菌同源基因是存在的，但还没有得到很好的描述。由于各种观察最初表明NMD家族成员在线粒体形成和微管加工中都扮演着保守的角色，因此本研究的主要重点是从遗传和生物化学的角度确定这些线粒体AAA ATPase(在果蝇和酵母中)与微管和其他结构之间的相互作用。这些基因产物与人类蛋白ATAD1同源，ATAD1在神经元中对受体内化很重要，但对其他方面知之甚少。ATAD1可能是另一种痉挛截瘫的很好候选，这种截瘫映射在基因组的同一区域。我们的工作将使我们能够深入了解这种人类基因在健康和疾病中的分子作用。作为最终目标，将在两个与NMD和CG4701表型相关的雄性不育果蝇品系中鉴定出缺陷基因，从而能够鉴定更多可能最终与 人类线粒体神经病、肌病和不孕综合征。 公共卫生相关性：线粒体形状和运动缺陷是许多神经退行性疾病的基础，可能与过早衰老和不孕不育有关。阐明线粒体形成的分子机制是由苍蝇和酵母线粒体蛋白介导的，这些线粒体蛋白与遗传性痉挛截瘫有关，这将使人类相关功能的表征成为可能。这些努力可能会加深对线粒体相关疾病的理解，并为治疗方案的设计奠定基础。

DESCRIPTION (provided by applicant): Mitochondria, the organelles in which food energy is harnessed into usable ATP form, are moved and shaped to fulfill different energy needs within specialized cells. Many human genetic neurodegenerative disorders are associated with defects of mitochondrial dynamics. Drosophila melanogaster spermatogenesis is an ideal model system for genetic dissection of conserved mechanisms of mitochondrial morphogenesis, since mitochondria undergo dramatic shaping during sperm development. After meiosis, all mitochondria in a Drosophila spermatid normally fuse into two giant mitochondrial derivatives that interwrap precisely and intricately to form a spherical structure called the Nebenkern, which then unfurls and elongates along the growing sperm tail. The main focus is to elucidate molecular mechanisms underlying mitochondrial shaping, as a way to characterize genes whose human homologs might underlie mitochondrial dysfunction. We previously identified the Drosophila nmd gene (no mitochondrial derivative) as required for aggregation of mitochondria during spermatogenesis. The Nmd gene product is an AAA ATPase related to microtubule-severing proteins spastin and katanin, though unlike those relatives, Nmd is unique in its localization to both mitochondria and centrosomes/basal bodies. A paralog of Nmd, CG4701, is required for mitochondrial shaping later in spermatogenesis. Both paralogs seem to be required also for male meiotic cytokinesis, perhaps through effects on the meiotic spindle. A yeast ortholog exists but has not been well characterized. Since various observations initially suggest a conserved role for Nmd family members in both mitochondrial shaping and microtubule processing, the primary emphasis in the proposed research is to determine genetically and biochemically the interactions between these mitochondrial AAA ATPases (in both flies and yeast) and microtubules and other structures. These gene products are homologous to human protein ATAD1 which is important in neurons for internalization of receptors but about which little else is known. ATAD1 may be a good candidate for another version of spastic paraplegia that maps in the same region of the genome. Our work will allow for important insight into the molecular roles of this human gene in health and disease. As a final aim, the genes defective in two male sterile Drosophila strains with related phenotypes to nmd and CG4701 will be identified, allowing identification of further gene families that may ultimately be associated with human mitochondrial neuropathies, myopathies, and infertility syndromes. PUBLIC HEALTH RELEVANCE: Defects of mitochondrial shaping and movement underlie many neurodegenerative diseases and may be associated with premature aging as well as infertility. Elucidation of molecular mechanisms by which mitochondrial shaping is mediated by fly and yeast mitochondrial proteins related to those implicated in hereditary spastic paraplegia will enable characterization of related functions in humans. These efforts may provide a deeper understanding of mitochondria-related disorders and set the stage for the design of treatments.