Wang Cheng, Tan Jeanne M M, Ho Michelle W L, Zaiden Norazean, Wong Siew Heng, Chew Constance L C, Eng Pei Woon, Lim Tit Meng, Dawson Ted M, Lim Kah Leong
Neurodegeneration Research Laboratory, National Neuroscience Institute, Singapore.
J Neurochem. 2005 Apr;93(2):422-31. doi: 10.1111/j.1471-4159.2005.03023.x.
Mutations in the parkin gene, which encodes a ubiquitin ligase, are currently recognized as the main contributor to familial forms of Parkinson's disease (PD). A simple assumption about the effects of PD-linked mutations in parkin is that they impair or ablate the enzyme activity. However, a number of recent studies, including ours, have indicated that many disease-linked point mutants of parkin retain substantial catalytic activity. To understand how the plethora of mutations on parkin contribute to its dysfunction, we have conducted a systematic analysis of a significant number of parkin point mutants (22 in total), which represent the majority of parkin missense/nonsense mutations reported to date. We found that more than half of these mutations, including many located outside of the parkin RING fingers, produce alteration in the solubility of parkin which influences its detergent extraction property. This mutation-mediated alteration in parkin solubility is also associated with its propensity to form intracellular, aggresome-like, protein aggregates. However, they do not represent sites where parkin substrates become sequestered. As protein aggregation sequesters the functional forms away from their normal sites of action, our results suggest that alterations in parkin solubility and intracellular localization may underlie the molecular basis of the loss of function caused by several of its mutations.
编码泛素连接酶的帕金基因发生突变，目前被认为是家族性帕金森病（PD）的主要病因。关于帕金基因中与PD相关的突变的一个简单假设是，它们会损害或消除酶的活性。然而，包括我们的研究在内，最近的一些研究表明，帕金基因的许多与疾病相关的点突变体仍保留大量催化活性。为了了解帕金基因上过多的突变如何导致其功能障碍，我们对大量的帕金基因点突变体（总共22个）进行了系统分析，这些突变体代表了迄今为止报道的大多数帕金基因错义/无义突变。我们发现，这些突变中超过一半，包括许多位于帕金基因RING结构域外的突变，会导致帕金蛋白溶解度发生改变，从而影响其去污剂提取特性。这种由突变介导的帕金蛋白溶解度改变也与其形成细胞内、聚集体样蛋白聚集体的倾向有关。然而，它们并不代表帕金蛋白底物被隔离的位点。由于蛋白质聚集会使功能形式与其正常作用位点分离，我们的结果表明，帕金蛋白溶解度和细胞内定位的改变可能是其一些突变导致功能丧失的分子基础。
