Role of Huntingtin in Vesicle Transport

亨廷顿蛋白在囊泡运输中的作用

• 批准号: 6646477
• 负责人: Marian DiFiglia
• 金额: $ 59.36万
• 依托单位: MASSACHUSETTS GENERAL HOSPITAL
• 依托单位国家: 美国
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-08-15 至 2006-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6646477
• 关键词: Huntington's disease; autophagy; calpain; cell death; cell line; cellular pathology; chemical cleavage; genetically modified animals; glutamine; immunocytochemistry; immunofluorescence technique; immunoprecipitation; intracellular transport; laboratory mouse; molecular pathology; mutant; neurons; protein localization; protein protein interaction; proteins; tissue /cell culture; vesicle /vacuole; western blottings

DESCRIPTION (provided by applicant): A polygutamine expansion in the N-terminus of huntingtin (N-hn) causes Huntington's disease (HD). There is no effective treatment for HD. Although mutant N-Fin fragments are known to accumulate in HD neurons and cause cell dysfunction in vitro, a mechanism (or mechanisms) that explains the selective loss of striatal and cortical projection neurons remains elusive. Wild type and mutant htt associate with membranes in the endocytic and secretory pathway. Our overall hypothesis is that mutant N-htt 's association with neuronal membranes contributes to early cellular dysfunction in the cytoplasm in HD. One of these membrane compartments includes the autophagosome/lysosomal system, which accumulates full-length or large N-htt fragments of mutant htt. Although htt ostensibly lacks transmembrane domains, it associates tightly with membranes. We speculate that candidate domains in the N-terminus involved in protein-protein interactions promote membrane binding. Little is known about the degradative pathways that form N-htt fragments in vivo. Identifying the sites of protease cleavage in the N-terminus of htt is important for understanding how the protein is regulated. Calpain, a calcium dependent protease, which regulates the function of many proteins involved in membrane/cytoskeleton organization, cleaves htt near its N-terminus and produces long-lived N-htt fragments that are enriched in membrane fractions in brain. We speculate that mutant N-htt products of calpain cleavage undergo a different processing from the wt fragments in neurons that leads to cellular dysfunction in HD. HD mice also show abnormal function of striatal NMDA receptors. One way that mutant Fin might cause the dysfunction of NMDA receptors is by disrupting the assembly of NMDA receptor subtypes at the cell surface. The specific aims are: 1: To understand the role of mutant htt induced autophagy in cell dysfunction, 2: To determine whether htt proteolysis by calpain contributes to HD pathogenesis and 3: To determine the effects of mutant htt on protein transport within the secretory pathway. The results of these studies will provide new insights about the mechanisms of cellular dysfunction in HD and suggest novel therapeutic targets that can reduce the potentially harmful effects of mutant N-htt fragments.

描述（由申请人提供）：亨廷顿蛋白（N-hn）N末端的聚谷氨酰胺扩增导致亨廷顿病（HD）。 HD 没有有效的治疗方法。尽管已知突变型 N-Fin 片段会在 HD 神经元中积聚并在体外引起细胞功能障碍，但解释纹状体和皮质投射神经元选择性丧失的机制仍然难以捉摸。野生型和突变型 htt 与内吞和分泌途径中的膜相关。我们的总体假设是突变型 N-htt 与神经元膜的关联导致 HD 细胞质的早期细胞功能障碍。这些膜区室之一包括自噬体/溶酶体系统，该系统积累突变 htt 的全长或大 N-htt 片段。尽管 htt 表面上缺乏跨膜结构域，但它与膜紧密结合。我们推测参与蛋白质-蛋白质相互作用的 N 末端候选结构域促进膜结合。关于体内形成 N-htt 片段的降解途径知之甚少。识别 htt N 末端的蛋白酶切割位点对于了解蛋白质的调控方式非常重要。钙蛋白酶是一种钙依赖性蛋白酶，可调节参与膜/细胞骨架组织的许多蛋白质的功能，在其 N 末端附近裂解 htt，并产生富含大脑膜组分的长寿命 N-htt 片段。我们推测钙蛋白酶裂解的突变​​ N-htt 产物与神经元中的 wt 片段经历了不同的加工，从而导致 HD 中的细胞功能障碍。 HD 小鼠还表现出纹状体 NMDA 受体功能异常。突变型 Fin 可能导致 NMDA 受体功能障碍的一种方式是破坏细胞表面 NMDA 受体亚型的组装。具体目标是：1：了解突变体 htt 诱导的自噬在细胞功能障碍中的作用，2：确定钙蛋白酶的 htt 蛋白水解是否有助于 HD 发病机制，3：确定突变体 htt 对分泌途径内蛋白质转运的影响。这些研究的结果将为 HD 细胞功能障碍的机制提供新的见解，并提出可以减少突变 N-htt 片段潜在有害影响的新治疗靶点。