Loss of the novel Vcp (valosin containing protein) interactor Washc4 interferes with autophagy-mediated proteostasis in striated muscle and leads to myopathy <i>in vivo</i>

VCP/p97 (valosin containing protein) is a key regulator of cellular proteostasis. It orchestrates protein turnover and quality control <i>in vivo</i>, processes fundamental for proper cell function. In humans, mutations in VCP lead to severe myo- and neuro-degenerative disorders such as inclusion body myopathy with Paget disease of the bone and frontotemporal dementia (IBMPFD), amyotrophic lateral sclerosis (ALS) or and hereditary spastic paraplegia (HSP). We analyzed here the <i>in vivo</i> role of Vcp and its novel interactor Washc4/Swip (WASH complex subunit 4) in the vertebrate model zebrafish (<i>Danio rerio</i>). We found that targeted inactivation of either Vcp or Washc4, led to progressive impairment of cardiac and skeletal muscle function, structure and cytoarchitecture without interfering with the differentiation of both organ systems. Notably, loss of Vcp resulted in compromised protein degradation via the proteasome and the macroautophagy/autophagy machinery, whereas Washc4 deficiency did not affect the function of the ubiquitin-proteasome system (UPS) but caused ER stress and interfered with autophagy function <i>in vivo</i>. In summary, our findings provide novel insights into the <i>in vivo</i> functions of Vcp and its novel interactor Washc4 and their particular and distinct roles during proteostasis in striated muscle cells.VCP/p97（含缬酪肽蛋白，valosin-containing protein）是细胞蛋白质稳态的关键调控因子，可在体内（in vivo）调控蛋白质周转与质量控制，这一过程对细胞正常功能至关重要。在人类中，VCP突变会引发严重的肌肉与神经退行性疾病，例如伴骨Paget病和额颞叶痴呆的包涵体肌病（IBMPFD）、肌萎缩侧索硬化症（ALS）以及遗传性痉挛性截瘫（HSP）。本研究分析了Vcp及其新型互作蛋白Washc4/Swip（WASH复合物亚基4，WASH complex subunit 4）在脊椎动物模型斑马鱼（Danio rerio）中的体内（in vivo）功能。研究发现，靶向失活Vcp或Washc4，会导致心脏与骨骼肌的功能、结构及细胞构筑进行性受损，但不会干扰这两个器官系统的分化过程。值得注意的是，Vcp缺失会通过蛋白酶体与巨自噬/自噬通路削弱蛋白质降解能力；而Washc4缺陷则不会影响泛素-蛋白酶体系统（UPS）的功能，但会引发内质网应激，并在体内（in vivo）干扰自噬功能。综上，本研究结果为Vcp及其新型互作蛋白Washc4的体内（in vivo）功能，以及二者在横纹肌细胞蛋白质稳态过程中的独特且差异化作用提供了新的见解。