IBMPFD MUTATIONS IMPAIR UPS FUNCTION

描述(由申请人提供)：包涵体肌病(IBM)是一种致残性骨骼肌疾病，被认为是典型的年龄相关性肌肉疾病。目前还没有有效的治疗方法。IBM肌肉有特征性的“有边框的空泡”和嗜酸性的包涵体。这些结构含有泛素化和未降解的不可溶蛋白，包括ss-淀粉样蛋白和磷酸化tau；这些蛋白在阿尔茨海默病患者的大脑中积累。这种重叠的病理表明IBM和神经退行性疾病之间有一个共同的致病机制。P97/VCP蛋白突变的鉴定进一步加强了这种联系，这些突变导致常染色体显性遗传综合征、IBMPFD、与Paget病相关的IBM和额颞部痴呆(FTD)。P97/VCP对胞浆来源的蛋白酶体底物的降解以及错误折叠的分泌或跨膜蛋白的内质网相关降解是必不可少的。它通过辅因子选择性地与泛素化的底物结合，并将它们转移到26S蛋白酶体机械中来发挥这一作用。目前还不清楚p97/VCP突变是如何导致疾病的。IBMPFD的大脑和肌肉中含有泛素化的蛋白质包涵体。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。在小鼠骨骼肌中表达IBMPFD突变体p97/VCP会导致在出生30天前泛素化蛋白的增加，并在6个月后发生肌病变化。我们建议(1)研究IBMPFD突变体p97/VCP的结构、酶活性和底物结合的生化性质。我们还将评估(2)IBMPFD突变体p97/VCP对细胞培养和转基因动物泛素-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功能的生物发光成像。最后(3)将上述结果与p97/VCP的两个互补损失函数模型进行比较。尽管IBMPFD是一种罕见的疾病，但研究IBMPFD对于了解UPS在正常衰老和衰老相关疾病(如sIBM和FTD)中的作用是必不可少的。公共卫生相关性：IBMPFD是一种与衰老有关的多系统疾病，既有肌肉无力又有痴呆症，原因是泛素蛋白酶体系统(UPS)基本蛋白p97/VCP突变。我们建议探索p97/VCP疾病突变对骨骼肌UPS介导的蛋白质降解的影响及其与衰老相关疾病(如包涵体肌炎和额颞痴呆)的相关性。

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.