Syntrophin is a well-known adaptor protein that links intracellular proteins with the dystrophin-glycoprotein complex (DGC) at the sarcolemma. However, little is known about the underlying mechanism that regulates the intracellular localization of α-syntrophin and its interaction with dystrophin. In this study, we demonstrate that α-syntrophin phosphorylation determines its intracellular localization and interaction with dystrophin in muscle cells. α-Syntrophin, a predominant isoform in skeletal muscles, directly interacts with ion channels, enzymes, receptors, and DGC proteins. Despite α-syntrophin being a potential signaling molecule, most studies focus on its function as a dystrophin-associated protein. However, we previously reported that α-syntrophin has a variety of DGC-independent functions to modulate cell migration, differentiation, survival, and protein stability. According to the results of the in vitro phosphorylation assays using subcellular fractions, the phosphorylated α-syntrophin accumulated only at the plasma membrane, and this event occurred regardless of dystrophin expression. However, the α-syntrophin interacting with dystrophin at the membrane was not in a phosphorylated state. We also identified that protein kinase C (PKC) was involved in the phosphorylation of α-syntrophin, which restricted α-syntrophin to interact with dystrophin. In conclusion, we demonstrate that the phosphorylation of α-syntrophin by PKC regulates its intracellular localization and interaction with dystrophin.

中文翻译：

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α-syntrophin的磷酸化负责其亚细胞定位以及与肌细胞中的dystrophin相互作用

Syntrophin是一种众所周知的衔接蛋白，可将细胞内蛋白与肌膜上的肌营养不良蛋白-糖蛋白复合物（DGC）连接起来。然而，关于调节α-突触核蛋白的细胞内定位及其与肌营养不良蛋白相互作用的基本机制知之甚少。在这项研究中，我们证明了α-syntrophin的磷酸化决定了其在细胞内的定位以及与肌营养不良蛋白在肌肉细胞中的相互作用。α-Syntrophin是骨骼肌中的主要同工型，可直接与离子通道，酶，受体和DGC蛋白相互作用。尽管α-syntrophin是潜在的信号分子，但大多数研究仍集中在其作为与dystrophin相关的蛋白质的功能上。但是，我们先前曾报道，α-突触核蛋白具有多种DGC独立功能来调节细胞迁移，分化，存活率和蛋白质稳定性。根据结果在使用亚细胞级分的体外磷酸化测定中，磷酸化的α-syntrophin仅在质膜上积累，并且无论肌营养不良蛋白的表达如何都发生该事件。然而，在膜上与肌营养不良蛋白相互作用的α-syntrophin未处于磷酸化状态。我们还发现蛋白激酶C（PKC）参与了α-突触核蛋白的磷酸化，从而限制了α-突触核蛋白与肌营养不良蛋白的相互作用。总之，我们证明了PKC对α-syntrophin的磷酸化调节了其在细胞内的定位以及与dystrophin的相互作用。