ROLE OF CHAIN LENGTH AND SEQUENCE CONTEXTS ON POLYGLUTAMINE OLIGOMERIZATION

链长度和序列背景对聚谷氨酰胺低聚的作用

• 批准号: 8208875
• 负责人: ROHIT V PAPPU
• 金额: $ 33.25万
• 依托单位: WASHINGTON UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-04-15 至 2016-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8208875
• 关键词: Age of Onset; C-terminal; CAG repeat; Calcium Channel; Codon Nucleotides; Complex; Conflict (Psychology); Coupling; Cysteine; DRPLA protein; Data; Dentatorubral-Pallidoluysian Atrophies; Dependency; Disease; Equilibrium; Exons; Gatekeeping; Genes; Goals; Huntington Disease; In Vitro; Individual; Kinetics; Lead; Length; Link; MJD1 protein; Machado-Joseph Disease; Measurement; Mediating; Methodology; Modeling; Mutation; N-terminal; Nature; Nerve Degeneration; Neurodegenerative Disorders; Neurons; Onset of illness; Peptides; Phase; Protein Fragment; Proteins; Proteolysis; Pyrenes; Role; Route; Scanning; Severities; Severity of illness; Staging; Stretching; System; Testing; Toxic effect; Type 6 Spinocerebellar Ataxia; base; design; dimer; driving force; drug development; gain of function; human Huntingtin protein; inhibitor/antagonist; interest; intermolecular interaction; monomer; novel; polyglutamine; polyproline; preference; protein aggregation; research study; simulation

DESCRIPTION (provided by applicant): Huntington's disease is a devastating neurodegenerative disease caused by CAG codon expansion in exon 1 of the huntingtin (htt) gene. Similar CAG repeat expansions in eight other proteins are associated with eight different neurodegenerative diseases. In all nine diseases, the CAG repeat expansions encode polyglutamine expansions in the protein products, and the onset and severity of disease are inversely correlated with the polyglutamine length although the quantitative nature of this correlation is different for each of the nine disorders. Polyglutamine expansions end up in insoluble neuronal inclusions and there is growing evidence that the mechanisms of aggregation and the soluble oligomeric species are directly linked to selective neurodegeneration in each of the nine diseases. Polyglutamine expansions destabilize their host proteins and increase the likelihood of proteolysis. Fragments of proteolysis consist of polyglutamine tracts and flanking N- and C-terminal segments. The N- and C-terminal segments that flank the polyglutamine stretch are unique to each disease-related protein. Driving forces for aggregation of homopolymeric polyglutamine becomes stronger with increasing chain length and naturally occurring N- and C-terminal flanking sequences modulate this driving force. Our goal is to understand how sequences that flank polyglutamine expansions in disease-related proteins modulate the intrinsic, length-dependent conformational preferences and aggregation mechanisms of polyglutamine. Our approaches are based on a combination of novel atomistic simulations and a panel of in vitro experiments. Our recent results are consistent with the hypothesis that naturally occurring flanking sequences can act as "gatekeepers" to suppress intrinsic aggregation propensities of aggregation-prone regions. Therefore, the current proposal is guided by the following hypothesis: Naturally occurring flanking sequences in disease-related proteins can act as gatekeepers to decrease the intrinsic aggregation tendencies of polyglutamine tracts. This effect can be overcome by expansion mutations that lead to increased polyglutamine lengths. Additionally, gatekeeping mechanisms likely vary with flanking sequence, giving rise to differences in gatekeeping efficiencies. We will use a combination of novel atomistic simulations and in vitro experiments to characterize 1) conformational changes within different naturally occurring terminal flanking sequences and the coupling between these changes and the degree of sequestration / exposure of aggregation-prone polyglutamine regions within intramolecular interfaces as a function of polyglutamine length and 2) if naturally occurring flanking sequences are bona fide gatekeepers and to quantify the degree to which these sequences modulate aggregation as a function of polyglutamine length. Precise understanding of the mechanisms of coupling between flanking sequences and polyglutamine expansions will allow us to identify targets for inhibition of routes to aggregation-mediated toxicity and neurodegeneration. PUBLIC HEALTH RELEVANCE: There is clear connection between aggregation and the onset of devastating polyglutamine expansion diseases such as Huntington's disease. The role of flanking sequences in modulating aggregation is of direct relevance to the progression of polyglutamine expansion diseases. Mechanistic studies proposed here have a direct bearing on the development of drugs that inhibit the gain of function associated with polyglutamine aggregation.

描述（由申请人提供）：亨廷顿氏病是由亨廷顿（HTT）基因外显子1中CAG密码子扩张引起的毁灭性神经退行性疾病。其他八种蛋白质中的类似CAG重复扩展与八种不同的神经退行性疾病有关。在所有九种疾病中，CAG重复膨胀编码蛋白质产物中的多谷氨酰胺扩展，尽管这种相关性的定量性质在九种疾病中的每种情况都不同，但疾病的发作和严重程度与聚谷氨酰胺长度呈负相关。聚谷氨酰胺的膨胀最终以不溶性神经元包裹体而最终出现，并且越来越多的证据表明，聚集机理和可溶性寡聚物种与九种疾病中的每种疾病中的选择性神经变性直接相关。聚谷氨酰胺扩展破坏了其宿主蛋白，并增加了蛋白水解的可能性。蛋白水解的片段由聚谷氨酰胺区和侧翼N-和C末端段组成。侧翼聚谷氨酰胺拉伸的N-和C末端片段是每种与疾病相关的蛋白质所独有的。均聚糖聚谷氨酰胺聚集的驱动力随着链长的增加而变得更强大，并且天然发生的N-和C末端侧翼序列调节了这种驱动力。我们的目标是了解与疾病相关蛋白质中聚谷氨酸扩张的序列如何调节多谷氨酰胺的固有，长度依赖性构象偏好和聚集机制。我们的方法基于新型原子模拟和一组体外实验的组合。我们最近的结果与以下假设一致：天然发生的侧翼序列可以充当抑制易于聚集区域的内在聚集倾向的“守门人”。因此，当前的提案以以下假设为指导：与疾病相关蛋白质中的天然发生的侧翼序列可以充当守门人，以减少多谷氨酰胺道的固有聚集趋势。通过膨胀突变，可以克服这种效果，从而导致多谷氨酰胺长度增加。此外，守门机制可能随侧翼序列而变化，从而导致守门效率的差异。我们将结合新的原子模拟和体外实验来表征1）在不同的天然发生的末端侧翼序列和这些变化之间的构象变化以及这些变化之间的耦合以及聚集 /暴露于聚集的隔离 /暴露于聚集的多谷氨酰胺的隔离 /暴露于多肠内和2）在多肠内的范围内的序列范围内的多谷氨酸界限，如果是多谷氨酸的范围，则是多谷氨酸的范围。量化这些序列将聚集作为多谷氨酰胺长度的函数的程度。对侧翼序列和多谷氨酰胺扩展之间耦合机制的精确理解将使我们能够识别抑制聚集介导的毒性和神经变性的途径的靶标。 公共卫生相关性：聚集与毁灭性聚谷氨酰胺扩张疾病（如亨廷顿氏病）之间存在明显的联系。侧翼序列在调节聚集中的作用与多谷氨酰胺扩张疾病的进展直接相关。这里提出的机械研究直接取决于抑制与多谷氨酰胺聚集有关的功能增长的药物的发展。