Department of Pathology and Applied Neurobiology, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kyoto 602-8566, Japan.
Department of Biomedical Sciences, College of Life Sciences, Ritsumeikan University, Kusatsu, Shiga 525-8577, Japan.
Hum Mol Genet. 2020 Nov 25;29(19):3312-3326. doi: 10.1093/hmg/ddaa217.
Dystrophin-dystroglycan complex (DGC) plays important roles for structural integrity and cell signaling, and its defects cause progressive muscular degeneration and intellectual disability. Dystrophin short product, Dp71, is abundantly expressed in multiple tissues other than muscle and is suspected of contributing to cognitive functions; however, its molecular characteristics and relation to dystroglycan (DG) remain unknown. Here, we report that DG physically interacts with Dp71 in cultured cells. Intriguingly, DG expression positively and DG knockdown negatively affected the steady-state expression, submembranous localization and subsequent phosphorylation of Dp71. Mechanistically, two EF-hand regions along with a ZZ motif of Dp71 mediate its association with the transmembrane proximal region, amino acid residues 788-806, of DG cytoplasmic domain. Most importantly, the pathogenic point mutations of Dp71, C272Y in the ZZ motif or L170del in the second EF-hand region, impaired its binding to DG, submembranous localization and phosphorylation of Dp71, indicating the relevance of DG-dependent Dp71 regulatory mechanism to pathophysiological conditions. Since Dp140, another dystrophin product, was also regulated by DG in the same manner as Dp71, our results uncovered a tight molecular relation between DG and dystrophin, which has broad implications for understanding the DGC-related cellular physiology and pathophysiology.
肌营养不良蛋白-糖胺聚糖复合物（DGC）在结构完整性和细胞信号转导中发挥重要作用，其缺陷导致进行性肌肉退化和智力障碍。肌营养不良蛋白短产物 Dp71 在肌肉以外的多种组织中大量表达，疑似对认知功能有贡献；然而，其分子特征及其与糖胺聚糖（DG）的关系仍不清楚。在这里，我们报告在培养细胞中 DG 与 Dp71 物理相互作用。有趣的是，DG 的表达正向影响和 DG 的敲低负向影响 Dp71 的稳态表达、亚膜定位和随后的磷酸化。从机制上讲，Dp71 的两个 EF 手区域以及一个 ZZ 基序介导其与 DG 细胞质域的跨膜近侧区域（氨基酸残基 788-806）结合。最重要的是，Dp71 的致病点突变，即 ZZ 基序中的 C272Y 或第二个 EF 手区域中的 L170del，损害了它与 DG 的结合、亚膜定位和 Dp71 的磷酸化，表明 DG 依赖的 Dp71 调节机制与病理生理条件相关。由于另一种肌营养不良蛋白产物 Dp140 也以与 Dp71 相同的方式受 DG 调节，我们的结果揭示了 DG 和肌营养不良蛋白之间的紧密分子关系，这对理解 DGC 相关的细胞生理学和病理学具有广泛的意义。
