Neuroprotective Mechanisms of Parkin

parkin基因突变导致其正常功能丧失，导致常染色体隐性遗传的早发性帕金森病。帕金蛋白已被证明是参与泛素-蛋白酶体途径降解细胞蛋白的酶。帕金蛋白不仅具有与泛素-蛋白质连接酶活性相关的分子结构域，而且是含有与泛素肽同源的区域的少数大蛋白质之一。这种罕见的结构域已在结合分子伴侣和蛋白酶体的蛋白质中被鉴定。我们的初步工作表明，帕金可以逆转两种不同的有毒、易聚集蛋白质的有害影响，并加速它们的降解。帕金还能够结合分子伴侣HSP 70和蛋白酶体，并且特别适合于促进异常错误折叠蛋白的降解，所述异常错误折叠蛋白的积累导致聚集、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能力的分子：1）通过多聚泛素化将异常蛋白质靶向蛋白酶体。2)通过分子伴侣的募集来帮助解折叠异常蛋白质，和3）直接结合并将这些异常蛋白质以适于进入和降解的状态呈递给蛋白酶体。我们将评估该模型的有效性，并确定帕金的分子结构域的相互作用，负责其整体功能。为了快速实现这一目标，细胞系将与毒性异常蛋白质的基因沿着与帕金蛋白的正常或特定突变形式共转染。在这种情况下，将评估帕金突变形式1）逆转细胞毒性2）防止蛋白质聚集3）加速毒性蛋白质降解4）维持蛋白酶体功能5）结合HSP 70和蛋白酶体的能力。在确定帕金蛋白的重要分子结构域后，我们将确定它们在单个复合物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，其中对细胞蛋白质的氧化损伤水平增加与遗传性和偶发性帕金森病的发病机制有关。增强对帕金神经保护特性的分子基础的理解可能会导致开发新的治疗方法来呈现帕金森病中的细胞损伤和死亡。

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.