Neuroprotective Mechanisms of Parkin

Parkin基因的突变导致其正常功能的丧失，导致早发性帕金森病，并具有常染色体隐性遗传模式。Parkin已被证明是一种参与泛素-蛋白酶体途径的酶，用于降解细胞蛋白质。Parkin不仅有一个与泛素蛋白连接酶活性相关的分子结构域，而且是少数几个包含与泛素多肽同源的区域的大型蛋白质之一。这个罕见的结构域已经在结合分子伴侣和蛋白酶体的蛋白质中被发现。我们的初步工作表明，parkin可以逆转两种不同的有毒、易于聚集的蛋白质的有害影响，并加速它们的降解。Parkin还能够结合分子伴侣HSP70和蛋白酶体，特别适合于促进异常错误折叠蛋白的降解，这些蛋白的积累会导致聚集、蛋白酶体抑制和细胞毒性。我们认为Parkin似乎是唯一已知的具有以下功能的分子：1)通过多泛构化将异常蛋白靶向蛋白酶体。2)通过分子伴侣的招募帮助解开异常蛋白；3)将这些异常蛋白直接结合并以适合进入和降解的状态呈现给蛋白酶体。我们将评估这个模型的有效性，并确定Parkin的分子结构域之间的相互作用，这些分子结构域负责其整体功能。为了快速实现这一目标，将用有毒异常蛋白的基因与正常或特定突变形式的parkin共转染细胞系。在这种情况下，将评估突变形式的parkin的能力：1)逆转细胞毒性；2)防止蛋白质聚集；3)加速有毒蛋白质的降解；4)维持蛋白酶体功能；5)结合HSP70和蛋白酶体。在确定了parkin的重要分子结构域后，我们将确定它们在单个复合体中的连接是否对分子的整体功能至关重要。这种酶可能对多巴胺能神经元特别重要，在那里，细胞蛋白氧化损伤水平的增加与遗传性和散发性帕金森氏病的发病机制有关。对parkin神经保护特性的分子基础的深入了解可能会导致开发新的治疗方法来呈现帕金森病的细胞损伤和死亡。

Mutations in the parkin gene leading to a loss in its normal function result in early onset Parkinson's Disease with an autosomal recessive pattern of inheritance. Parkin has been shown to be an enzyme involved in the ubiquitin-proteasome pathway for degradation of cellular proteins. Parkin not only has a molecular domain associated with ubiquitin-protein ligase activity, but is one of few large proteins to contain a region with homology to the ubiquitin peptide. This rare domain has been identified in proteins that bind molecular chaperones and the proteasome. Our preliminary work has demonstrated that parkin can reverse the harmful effects of two different toxic, aggregation prone proteins and accelerates their degradation. Parkin is also capable of binding both the molecular chaperone HSP70 and the proteasome, and is particularly suited to facilitate the degradation of aberrant misfolded proteins whose accumulation whose accumulation leads to aggregation, proteasomal inhibition and cytotoxicity. We propose that parkin appears to be the only known molecular with capacity to: 1) target aberrant proteins to the proteasome through polyubiquination. 2) assist in unfolding aberrant proteins through recruitment of molecular chaperones and 3) directly bind and present these aberrant proteins to the proteasome in a state suitable for entry and degradation. We will assess the validity of this model and determine the interaction of the molecular domains of parkin responsible for its overall function. To rapidly accomplish this goal, cell lines will be co-transfected with genes for toxic aberrant proteins Along with normal or specific mutant forms of parkin. Mutant forms of parkin will be assessed in this setting for their capacity to 1) reverse cytotoxicity 2) prevent protein aggregation 3) accelerate toxic protein degradation 4) maintain proteasomal function 5) bind HSP70 and the proteasome. After identifying the important molecular domains of parkin we will determine if their linkage within a single complex is essential for the overall function of the molecule. This enzyme may be particular importance to dopaminergic neurons where increased levels of oxidative injury to cellular proteins have been implicated in the pathogenesis of both inherited and sporadically occurring Parkinson's Disease. An enhanced understanding of the molecular basis for the neuroprotective properties of parkin could lead to the development of new therapeutics to present cellular injury and death in Parkinson's Disease.