IBMPFD MUTATIONS IMPAIR UPS FUNCTION

描述（由申请方提供）：包涵体肌病（IBM）是一种致残性骨骼肌疾病，被认为是一种典型的年龄相关性肌肉疾病。没有有效的治疗方法。IBM肌肉有特征性的“镶边空泡”和嗜酸性包涵体。这些结构包含泛素化和未降解的不溶性蛋白质，包括β-淀粉样蛋白和磷酸化tau;在阿尔茨海默病大脑中积累的蛋白质。这种重叠的病理学表明IBM和神经退行性疾病之间存在共同的致病机制。这种联系通过鉴定引起常染色体显性遗传综合征、IBMPFD、与骨佩吉特病和额颞叶痴呆（FTD）相关的IBM的蛋白质p97/VCP中的突变而得到进一步加强。p97/VCP对于胞质衍生的蛋白酶体底物的降解以及对于错误折叠的分泌或跨膜蛋白的内质网相关降解是必需的。它通过辅因子选择性地与泛素化底物结合并将其转移到26 S蛋白酶体机制来发挥这一作用。目前尚不清楚p97/VCP突变如何导致疾病。IBMPFD脑和肌肉含有泛素化蛋白质内含物。我们的研究表明，IBMPFD突变体p97/VCP导致细胞中泛素化蛋白的增加。小鼠骨骼肌中IBMPFD突变体p97/VCP的表达导致早在出生后30天的泛素化蛋白的增加，之后在6个月龄后发生虚弱和肌病变化。本研究拟（1）从结构、酶活性和底物结合等方面研究IBMPFD突变体p97/VCP的生化特性。我们还将（2）在细胞培养和转基因动物中评估IBMPFD突变体p97/VCP对泛素-蛋白酶体系统（UPS）的影响。这些研究将使用活体动物骨骼肌中UPS功能的体内生物发光成像。最后（3）将上述结果与两个互补的p97/VCP功能缺失模型进行比较。虽然是一种罕见的疾病，但IBMPFD的研究对于了解UPS在正常衰老和衰老相关疾病（如sIBM和FTD）中的作用至关重要。 公共卫生相关性：IBMPFD是一种与衰老相关的多系统疾病，由于泛素蛋白酶体系统（UPS）必需蛋白p97/VCP的突变导致肌无力和痴呆。我们建议探讨疾病突变p97/VCP的UPS介导的蛋白质降解骨骼肌及其相关性的后果与衰老相关的疾病，如包涵体肌炎和额颞叶痴呆。

DESCRIPTION (provided by applicant): Inclusion body myopathies (IBM) are disabling skeletal muscle disorders and considered a prototypical age related muscle disease. There is no effective treatment. IBM muscle has characteristic "rimmed vacuoles" and eosinophilic inclusions. These structures contain ubiquitinated and undegraded insoluble proteins that include ss-amyloid and phosphorylated tau; proteins that accumulate in Alzheimer's Disease brains. This overlapping pathology suggests a common pathogenic mechanism between IBM and neurodegenerative disorders. This link is strengthened further by the identification of mutations in the protein p97/VCP that cause the autosomal dominant syndrome, IBMPFD, IBM associated with Paget's disease of the bone and frontotemporal dementia (FTD). p97/VCP is essential for the degradation of cytosolic derived proteasome substrates as well as for endoplasmic reticulum associated degradation of misfolded secreted or transmembrane proteins. It performs this role by selectively binding with ubiquitinated substrates via co-factors and transferring them to the 26S proteasome machinery. Currently it is unclear how mutations in p97/VCP cause disease. IBMPFD brain and muscle contains ubiquitinated protein inclusions. Our studies demonstrate that IBMPFD mutant p97/VCP leads to an increase in ubiquitinated proteins in cells. Skeletal muscle expression of IBMPFD mutant p97/VCP in mice causes an increase in ubiquitinated proteins as early as 30 days of life before weakness and myopathic changes which occur after 6 months of age. We propose to (1) study the biochemical properties of IBMPFD mutant p97/VCP with regard to structure, enzymatic activity and substrate binding. We will also (2) evaluate the effect of IBMPFD mutant p97/VCP on the ubiquitin-proteasome system (UPS) in cell culture and transgenic animals. These studies will use in vivo bioluminescent imaging of UPS function in skeletal muscle from living animals. Finally (3) we will compare the results obtained above with two complementary loss of p97/VCP function models. Although a rare disorder, the study of IBMPFD is essential to understand the role of the UPS in normal aging and aging related disorders such as sIBM and FTD. PUBLIC HEALTH RELEVANCE: IBMPFD is an aging related multi-system disorder with both muscle weakness and dementia, due to mutations in the ubiquitin proteasome system (UPS) essential protein p97/VCP. We propose to explore the consequence of disease mutations in p97/VCP on UPS-mediated protein degradation in skeletal muscle and its relevance to aging related disorders such as inclusion body myositis and fronto-temporal dementia.