Mohamed A S, Swope S L
Department of Neurology, Division of Neuroscience, Georgetown Institute for Cognitive and Computational Sciences, Georgetown University Medical Center, Washington, D.C. 20007-2197, USA.
J Biol Chem. 1999 Jul 16;274(29):20529-39. doi: 10.1074/jbc.274.29.20529.
Src class protein-tyrosine kinases bind to and phosphorylate the nicotinic acetylcholine receptor of skeletal muscle. This study provided evidence for the functional importance of Src kinases in regulating the nicotinic acetylcholine receptor at the neuromuscular junction. Three Src class kinases, Fyn, Fyk, and Src, each formed a complex with the endplate-specific cytoskeletal protein rapsyn. In addition, cellular phosphorylation by each kinase was stimulated by rapsyn in heterologous transfected cells. Several lines of evidence supported rapsyn as a substrate for Src kinases. Most importantly, rapsyn regulation of Fyn, Fyk, and Src resulted in phosphorylation of the nicotinic acetylcholine receptor beta and delta subunits and anchoring of the receptor to the cytoskeleton. Both nicotinic acetylcholine receptor phosphorylation and cytoskeletal anchoring were blocked by the Src kinase-selective inhibitor herbimycin A. Rapsyn alone also induced a modest increase in nicotinic acetylcholine receptor phosphorylation and cytoskeletal translocation. However, inhibition by herbimycin A and a catalytically inactive dominant negative Src demonstrated that the effects of rapsyn were mediated by endogenous Src kinases. These data support the importance of Src class kinases for stabilization of the nicotinic acetylcholine receptor at the endplate during synaptic differentiation at the neuromuscular junction.
Src家族蛋白酪氨酸激酶可与骨骼肌的烟碱型乙酰胆碱受体结合并使其磷酸化。本研究为Src激酶在调节神经肌肉接头处烟碱型乙酰胆碱受体方面的功能重要性提供了证据。三种Src家族激酶，即Fyn、Fyk和Src，各自与终板特异性细胞骨架蛋白rapsyn形成复合物。此外，在异源转染细胞中，rapsyn可刺激每种激酶的细胞磷酸化作用。多条证据支持rapsyn是Src激酶的底物。最重要的是，rapsyn对Fyn、Fyk和Src的调节导致烟碱型乙酰胆碱受体β和δ亚基的磷酸化以及该受体与细胞骨架的锚定。烟碱型乙酰胆碱受体的磷酸化和细胞骨架锚定都被Src激酶选择性抑制剂赫伯霉素A所阻断。单独的rapsyn也可适度增加烟碱型乙酰胆碱受体的磷酸化和细胞骨架易位。然而，赫伯霉素A和催化无活性的显性负性Src的抑制作用表明，rapsyn的作用是由内源性Src激酶介导的。这些数据支持了Src家族激酶对于神经肌肉接头处突触分化过程中终板处烟碱型乙酰胆碱受体稳定性的重要性。
