IBMPFD MUTATIONS IMPAIR UPS FUNCTION

包涵体肌病（IBM）是一种致残性骨骼肌疾病， 一种典型的与年龄有关的肌肉疾病没有有效的治疗方法。IBM肌肉 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; 阿尔茨海默病患者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的共同致病机制。这个环节 进一步加强了蛋白质p97/VCP突变的鉴定，导致 常染色体显性遗传综合征，IBMPFD，与骨佩吉特病相关的IBM， 额颞叶痴呆（FTD）。p97/VCP是降解细胞质衍生的 蛋白酶体底物以及内质网相关降解 错误折叠的分泌或跨膜蛋白。它通过选择性地与 泛素化底物通过辅因子和转移到26 S蛋白酶体机器。 目前尚不清楚p97/VCP突变如何导致疾病。IBMPFD大脑和 肌肉含有泛素化的蛋白质内含物。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。骨骼肌表达 小鼠中IBMPFD突变体p97/VCP导致早在30岁时泛素化蛋白的增加 在6个月大后发生的虚弱和肌病变化之前的生命天数。我们 建议（1）研究IBMPFD突变体p97/VCP的生化特性， 结构、酶活性和底物结合。我们还将（2）评估 IBMPFD突变体p97/VCP对细胞培养物中泛素-蛋白酶体系统（UPS）的影响， 转基因动物这些研究将使用UPS功能的体内生物发光成像， 活体动物的骨骼肌。最后（3）我们将上述结果与 两种互补的p97/VCP功能缺失模型。虽然是一种罕见的疾病， IBMPFD对于了解UPS在正常老化和老化相关过程中的作用至关重要 例如sIBM和FTD。

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.