Cellular Mechanisms of Aggregation of Abnormal Proteins

描述(由申请人提供)：泛素蛋白酶体机制和分子伴侣的故障可能导致突变或受损的多肽聚集，从而导致各种破坏性疾病。然而，特殊的分子机制已经进化成最后一道防线，通过将错误折叠的蛋白质聚集体/低聚物运输到中心体定位的侵袭体来减轻蛋白质毒性。这项提议的主要目的是揭示攻击性形成的机制。这项拟议的工作是基于我们的酵母模型，即具有扩展的聚谷氨酰胺(PolyQ)结构域的蛋白质聚集。在过去，这个模型被用来在HD小鼠模型中识别抑制多聚Q聚集、改善运动能力和减少神经元萎缩的小分子。通过这个模型，我们建立了：(A)酵母和哺乳动物细胞中的侵袭体的形成需要底物蛋白上可转移的侵袭体靶向信号，例如Huntingtin外显子1的富含Pro区域(P区)，(B)SH3结构域蛋白Boi2作为P区侵袭体靶向信号的识别元件，(C)酵母14-3-3蛋白Bmh1和CDC48/VCP-Ufd1-Nlp4复合体的组成部分在侵袭体形成中发挥重要作用。我们还建立了侵袭体形成的细胞培养模型，以研究酵母中鉴定的侵袭体成分与哺乳动物细胞的相关性。在目标1中，我们将阐明侵略性机制如何识别小的多聚Q聚集体/低聚物。我们将确定SH3结构域蛋白Boi2在酵母聚集体识别中的作用，并将阐明Boi2同源蛋白在哺乳动物细胞中是否具有识别亨廷顿蛋白和其他含多聚Q的病理蛋白的功能。在目标2中，我们将建立14-3-3蛋白Bmh1在酵母侵袭体形成早期阶段的功能，并将测试14-3-3蛋白是否在哺乳动物细胞侵袭体形成中发挥普遍作用。这些实验将有助于阐明攻击性机制如何区分异常多肽的小聚集体/低聚物和可溶性单体。在目标3中，使用生化和遗传方法，我们将确定与侵袭体形成有关的新成分。作为这项工作的结果，我们计划获得足够的信息来理解攻击性形成的机制。公共卫生相关性许多毁灭性的疾病，包括主要的神经退行性疾病，都是由异常蛋白质的积累引起的。这些异常物种倾向于聚集，在这里我们将建立蛋白质聚集的细胞机制。这项工作将揭示生物体如何试图保护自己免受洪廷顿氏症和某些其他疾病的影响。

DESCRIPTION (provided by applicant): Failure of the ubiquitin proteasome machinery and molecular chaperones may result in aggregation of mutant or damaged polypeptides leading to various devastating diseases. However, special molecular machinery has evolved as a last line of defense to relieve proteotoxicity by transporting misfolded protein aggregates/oligomers to the centrosome-localized aggresome. The main objective of this proposal is to uncover the mechanisms of aggresome formation. The proposed work is based on our yeast model of aggregation of proteins with expanded polyglutamine (polyQ) domains. In the past, this model was used to identify small molecules that suppress polyQ aggregation, improve motor performance and reduce neuronal atrophy in a mouse model of HD. With this model, we have established that (a) aggresome formation both in yeast and mammalian cells requires transferable aggresome-targeting signals on substrate proteins, e.g. the proline-rich region (P-region) of exon 1 of huntingtin, (b) an SH3-domain protein Boi2 serves as a recognition element for the P-region aggresome- targeting signal, (c) a yeast 14-3-3 protein Bmh1 and components of the Cdc48/VCP-Ufd1-Nlp4 complex play an essential role in aggresome formation. We also established a cell culture model of aggresome formation to investigate the relevance for mammalian cells of aggresome components identified in yeast. In Aim 1 we will clarify how the aggresome machinery recognizes small polyQ aggregates/oligomers. We will establish the role of the SH3-domain protein Boi2 in the recognition of the aggregates in yeast, and will clarify whether Boi2 homologs function in mammalian cells to recognize huntingtin and other polyQ-containing pathological proteins. In Aim 2 we will establish the function of the 14-3-3 protein Bmh1 in early stages of aggresome formation in yeast, and will test whether 14-3-3 proteins play a general role in aggresome formation in mammalian cells. These experiments will help to clarify how the aggresome machinery distinguishes small aggregates/oligomers of abnormal polypeptides from soluble monomers. In Aim 3 using both biochemical and genetic approaches we will identify novel components involved in aggresome formation. As a result of this work, we plan to obtain sufficient information for understanding the mechanism of aggresome formation. PUBLIC HEALTH RELEVANCE Many devastating diseases, including major neurodegenerative disorders, are caused by accumulation of abnormal proteins. These abnormal species tend to aggregate, and here we will establish cellular mechanisms of protein aggregation. This work will uncover how organisms try to protect themselves from development of Hungtington's and certain other diseases.