Wang Z, Pavalko F M, Gunst S J
Department of Physiology and Biophysics, Indiana University School of Medicine, Indianapolis 46202, USA.
Am J Physiol. 1996 Nov;271(5 Pt 1):C1594-602. doi: 10.1152/ajpcell.1996.271.5.C1594.
Regulation of the attachment of actin filaments to the cell membrane at membrane-associated dense plaque (MADP) sites could allow smooth muscle cells to modulate their cytostructure in response to changes in external stress. In this study, changes in the tyrosine phosphorylation of the MADP protein paxillin were measured by Western blot during the contraction and relaxation of tracheal smooth muscle strips. Tyrosine phosphorylation of paxillin increased by three- to fourfold with a time course similar to force development during contractile stimulation with acetylcholine (ACh), 5-hydroxytryptamine, and KCl and decreased during washout of contractile stimuli and during relaxation induced by forskolin. Immunoprecipitation of muscle extracts with multiple rounds of anti-phosphotyrosine antibody removed approximately 20% of the total paxillin in resting muscles and approximately 60% of paxillin in muscles maximally stimulated with ACh. These results provide the first evidence associating the tyrosine phosphorylation of paxillin with the active contraction of smooth muscle or with any functional response of a fully differentiated tissue in vivo. The results are consistent with a role for MADP proteins in the regulation of force development in smooth muscle.
肌动蛋白丝在膜相关致密斑（MADP）位点与细胞膜的附着调节，可使平滑肌细胞根据外部应力变化调节其细胞结构。在本研究中，通过蛋白质印迹法测量气管平滑肌条收缩和舒张过程中MADP蛋白桩蛋白酪氨酸磷酸化的变化。在乙酰胆碱（ACh）、5-羟色胺和氯化钾收缩刺激期间，桩蛋白的酪氨酸磷酸化增加了三到四倍，其时间进程与力的发展相似；在收缩刺激洗脱期间和福斯高林诱导的舒张期间，酪氨酸磷酸化减少。用多轮抗磷酸酪氨酸抗体对肌肉提取物进行免疫沉淀，去除了静息肌肉中约20%的总桩蛋白和ACh最大刺激肌肉中约60%的桩蛋白。这些结果首次提供了证据，将桩蛋白的酪氨酸磷酸化与平滑肌的主动收缩或体内完全分化组织的任何功能反应联系起来。结果与MADP蛋白在平滑肌力发展调节中的作用一致。
