Characterization of nucleotide-dependent structural rearrangements in atlastin

描述(申请人提供)：遗传性痉挛截瘫(HSP)是一组遗传性神经疾病，导致肢体进行性痉挛和虚弱。Atlastin-1基因突变是该病的主要突变热点之一，约占常染色体显性遗传HSP病例(SPG3A亚型)的10%，大多数病例发生在婴儿或儿童中。这种蛋白质的缺陷会导致特殊神经元的轴突退化，在这种情况下，上运动神经元，但其分子机制却知之甚少。Atlastin-1属于大G蛋白的Dynamin超家族，其成员参与多种细胞功能，包括内吞作用、细胞器融合和分裂、胞质分裂和抗病毒活性。在细胞水平上，atlastin-1通过促进同型膜融合参与了管状内质网(ER)网络的形成。这些与动力蛋白相关的G蛋白催化生物膜的同型融合，在这个家族中只占一小部分，并且还没有广泛地描述它们的结构-功能关系。结构特征以及对伴侣蛋白相互作用的研究将为atlastin-1的缺陷如何以及为什么导致其致病效应提供关键的见解。第一个目标将是沿着核苷酸水解循环的阿特拉斯汀-1的结构特征。这一目标还将包括确定与HSP相关的蛋白质突变变体的结构，以揭示致病机制。第二个目标是利用生化和生物物理方法对atlastin-1突变体的功能进行表征。这些研究将补充结晶学分析。通过对野生型和突变型atlastin-1突变体进行深入的结构和功能分析，可以推导出疾病发病的分子机制，为疾病的预后和干预提供更好的手段。

DESCRIPTION (provided by applicant): Hereditary spastic paraplegia (HSP) is a group of inherited neurological disorders that cause progressive spasticity and weakness in the lower extremities. Mutations in the atlastin-1 gene, one of the major mutational hot spots in the disease, account for ~10% of autosomal dominant HSP cases (subtype SPG3A), and for the majority of cases in infants or children. Defects in this protein results in axonal degeneration in unique sets of neurons, in this case upper motor neurons, yet the molecular mechanism is poorly understood. Atlastin-1 belongs to the dynamin superfamily of large G-proteins, members of which participate in diverse cellular functions, including endocytosis, organelle fusion and fission, cytokinesis, and antiviral activity. On a cellular level, atlastin-1 is involved in generating the tubular endoplasmic reticulum (ER) network by facilitating homotypic membrane fusion. Those dynamin-related G proteins that catalyze homotypic fusion of biological membranes comprise a small minority of this family, and have not been characterized extensively in their structure-function relationship. Structural characterization as well as investigation of partner protein interactions will provide key insights into how and why defects in atlastin-1 result in its pathogenic effects. The first objective will be the structural characterization of atlastin-1 along the nucleotide hydrolysis cycle. This aim will also include the structure determination of HSP-associated mutant variants of the protein in order to reveal pathogenic mechanisms. The second aim focuses on a functional characterization of atlastin-1 mutants using biochemical and biophysical approaches. These studies will complement the crystallographic analyses. By conducting thorough structure-function analyses of wild-type and mutant atlastin-1 variants, a molecular mechanism for disease pathogenesis can be derived, which may provide better means with regard to disease prognosis and intervention.