From the Department of Pediatrics, Cincinnati Children's Hospital Medical Center, University of Cincinnati, Cincinnati, Ohio 45229-3039.
the Department of Biomedical Sciences, Grand Valley State University, Allendale, Michigan 49401, and.
J Biol Chem. 2019 May 31;294(22):8918-8929. doi: 10.1074/jbc.RA119.007585. Epub 2019 Apr 21.
Valosin-containing protein (VCP), also known as p97, is an ATPase with diverse cellular functions, although the most highly characterized is targeting of misfolded or aggregated proteins to degradation pathways, including the endoplasmic reticulum-associated degradation (ERAD) pathway. However, how VCP functions in the heart has not been carefully examined despite the fact that human mutations in VCP cause Paget disease of bone and frontotemporal dementia, an autosomal dominant multisystem proteinopathy that includes disease in the heart, skeletal muscle, brain, and bone. Here we generated heart-specific transgenic mice overexpressing WT VCP or a VCP mutant with deficient ATPase activity. Transgenic mice overexpressing WT VCP exhibit normal cardiac structure and function, whereas mutant VCP-overexpressing mice develop cardiomyopathy. Mechanistically, mutant VCP-overexpressing hearts up-regulate ERAD complex components and have elevated levels of ubiquitinated proteins prior to manifestation of cardiomyopathy, suggesting dysregulation of ERAD and inefficient clearance of proteins targeted for proteasomal degradation. The hearts of mutant VCP transgenic mice also exhibit profound defects in cardiomyocyte nuclear morphology with increased nuclear envelope proteins and nuclear lamins. Proteomics revealed overwhelming interactions of endogenous VCP with ribosomal, ribosome-associated, and RNA-binding proteins in the heart, and impairment of cardiac VCP activity resulted in aggregation of large ribosomal subunit proteins. These data identify multifactorial functions and diverse mechanisms whereby VCP regulates cardiomyocyte protein and RNA quality control that are critical for cardiac homeostasis, suggesting how human mutations negatively affect the heart.
包含缬氨酸的蛋白（VCP），也称为 p97，是一种具有多种细胞功能的 ATP 酶，尽管其最具特征性的功能是将错误折叠或聚集的蛋白质靶向降解途径，包括内质网相关降解（ERAD）途径。然而，尽管 VCP 中的人类突变会导致 Pagets 骨病和额颞叶痴呆症，但 VCP 在心脏中的功能尚未被仔细研究，这是一种常染色体显性多系统蛋白病，包括心脏、骨骼肌、大脑和骨骼的疾病。在这里，我们生成了心脏特异性过表达 WT VCP 或缺乏 ATP 酶活性的 VCP 突变体的转基因小鼠。过表达 WT VCP 的转基因小鼠表现出正常的心脏结构和功能，而突变 VCP 过表达的小鼠则会发生心肌病。从机制上讲，突变 VCP 过表达的心脏上调 ERAD 复合物成分，并在发生心肌病之前具有升高的泛素化蛋白水平，这表明 ERAD 失调和靶向蛋白酶体降解的蛋白质清除效率低下。突变 VCP 转基因小鼠的心脏还表现出心肌细胞核形态的深刻缺陷，核膜蛋白和核纤层增加。蛋白质组学显示，内源性 VCP 与心脏中的核糖体、核糖体相关和 RNA 结合蛋白有压倒性的相互作用，并且心脏 VCP 活性的损害导致大亚基核糖体蛋白的聚集。这些数据确定了 VCP 调节心肌细胞蛋白质和 RNA 质量控制的多因素功能和多种机制，这对于心脏内稳态至关重要，表明人类突变如何对心脏产生负面影响。
