Mechanism of spastin-mediated microtubule severing

描述(申请人提供)：Spastin是一种AAA ATPase，在遗传性痉挛性截瘫(HSP)中发生突变。HSP的特点是脊髓长轴突的神经变性，最终导致轮椅使用和膀胱控制困难。最近的研究表明，spastin可以切断微管。细胞骨架似乎在维持神经健康方面发挥着重要作用，因为微管电机的突变，如KIF5a和dynein，也会导致神经退行性疾病。与关于微管末端动力学的丰富信息相比，关于spastin使微管内部断裂的机制知之甚少。到目前为止，已经确定spastin组装成一个六聚体环，并且突出到环孔中的环识别微管蛋白的C-端氨基酸。关键的孔环氨基酸是切断所必需的，包括一种被疾病相关突变改变的氨基酸。Spastin还含有第二个微管结合域，它与微管发生明显的相互作用，是切断微管所必需的。这项研究将探索这些先前发现提出的问题，例如spastin是否通过将微管蛋白通过中央毛孔移位来展开微管蛋白，毛孔环如何促进切断，以及微管spastin结合在哪里。展开将通过使用GroEL陷阱和天然凝胶电泳或凝胶过滤层析进行评估。具有孔环突变的低聚物和ATPase缺失的突变体将被用来检测孔环在切断中的作用。化学交联将被用来绘制微管上与spastin结合的位置。这项工作对于更多地了解HSP中的神经变性和轴突维护具有重要意义。遗传性痉挛截瘫(HSP)是一种遗传性疾病，脊髓中最长的神经随着时间的推移而退化，导致无法行走。这个项目将使用生物化学来了解spastin的工作方式，spastin是导致HSP的基因之一。了解痉挛蛋白是如何工作的，可能会导致HSP的治疗，并增加对所有身体如何维持健康神经的理解。

DESCRIPTION (provided by applicant): Spastin, a AAA ATPase, is mutated in Hereditary Spastic Paraplegia (HSP). HSP is characterized by neurodegeneration of the long axons of the spinal cord, leading eventually to wheelchair use and difficulty with bladder control. Recently it has been shown that spastin severs microtubules. The cytoskeleton appears to play an important role in maintaining neural health, as mutations in microtubule motors, such as KIF5a and dynein, also cause neurodegenerative disorders. In contrast to the wealth of information regarding microtubule end dynamics, nothing is known about the mechanism by which spastin makes internal breaks in microtubules. So far, it has been determined that spastin assembles into a hexameric ring and that loops projecting into the pore of the ring recognize the C-terminal amino acids of tubulin. Key pore loop amino acids are required for severing, including one altered by a disease-associated mutation. Spastin also contains a second microtubule binding domain which makes a distinct interaction with microtubules and is required for severing. This study will explore questions raised by these previous findings, such as whether spastin unfolds tubulin by translocating it through the central pore, how the pore loops promote severing and where on the microtubule spastin binds. Unfolding will be assessed by use of a GroEL trap and native gel electrophoresis or gel filtration chromatography. Mixed oligomers with pore loop mutations and ATPase deficient mutants will be made to examine the role of the pore loops in severing. Chemical crosslinking will be used to map the location on the microtubule where spastin binds. This work will be important in learning more about neurodegeneration in HSP and axonal maintenance in general. Hereditary Spastic Paraplegia (HSP) is an inherited disease in which the longest nerves in the spinal cord degenerate over time, leading to an inability to walk. This project will use biochemistry to understand the way in which spastin, one of the genes that causes HSP, works. Understanding how spastin works may lead to treatments for HSP and an increased understanding of how all bodies maintain healthy nerves.