Department of Neurology, Washington University School of Medicine, St. Louis, MO 63110, USA.
J Cell Biol. 2009 Dec 14;187(6):875-88. doi: 10.1083/jcb.200908115.
Mutations in valosin-containing protein (VCP) cause inclusion body myopathy (IBM), Paget's disease of the bone, and frontotemporal dementia (IBMPFD). Patient muscle has degenerating fibers, rimmed vacuoles (RVs), and sarcoplasmic inclusions containing ubiquitin and TDP-43 (TARDNA-binding protein 43). In this study, we find that IBMPFD muscle also accumulates autophagosome-associated proteins, Map1-LC3 (LC3), and p62/sequestosome, which localize to RVs. To test whether VCP participates in autophagy, we silenced VCP or expressed adenosine triphosphatase-inactive VCP. Under basal conditions, loss of VCP activity results in autophagosome accumulation. After autophagic induction, these autophagosomes fail to mature into autolysosomes and degrade LC3. Similarly, IBMPFD mutant VCP expression in cells and animals leads to the accumulation of nondegradative autophagosomes that coalesce at RVs and fail to degrade aggregated proteins. Interestingly, TDP-43 accumulates in the cytosol upon autophagic inhibition, similar to that seen after IBMPFD mutant expression. These data implicate VCP in autophagy and suggest that impaired autophagy explains the pathology seen in IBMPFD muscle, including TDP-43 accumulation.
包含缬氨酰（VAL）蛋白（VCP）的突变导致包涵体肌病（IBM）、Pagets 骨病和额颞叶痴呆（IBMPFD）。患者的肌肉有退行性纤维、边缘空泡（RV）和包含泛素和 TDP-43（TARDNA 结合蛋白 43）的肌浆内包涵体。在这项研究中，我们发现 IBMPFD 肌肉还会积累自噬体相关蛋白 Map1-LC3（LC3）和 p62/自噬体，它们定位于 RV 中。为了测试 VCP 是否参与自噬，我们沉默了 VCP 或表达了三磷酸腺苷酶无活性的 VCP。在基础条件下，VCP 活性的丧失会导致自噬体的积累。在自噬诱导后，这些自噬体不能成熟为自溶体并降解 LC3。同样，在细胞和动物中表达 IBMPFD 突变 VCP 会导致非降解性自噬体的积累，这些自噬体在 RV 处融合，并不能降解聚集的蛋白质。有趣的是，自噬抑制后 TDP-43 在细胞质中积累，类似于 IBMPFD 突变表达后观察到的情况。这些数据表明 VCP 参与自噬，并提示自噬受损解释了 IBMPFD 肌肉中的病理学变化，包括 TDP-43 的积累。
