Amberg G C, Koh S D, Perrino B A, Hatton W J, Sanders K M
Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada 89557, USA.
Am J Physiol Cell Physiol. 2001 Dec;281(6):C2020-8. doi: 10.1152/ajpcell.2001.281.6.C2020.
A rapidly inactivating K(+) current (A-type current) participates in the regulation of colonic muscle excitability. We found 19-pS K(+) channels in cell-attached patches of murine colonic myocytes that activated and inactivated with kinetics similar to the A-type current. The A-type current in colonic myocytes is regulated by Ca(2+)/calmodulin-dependent protein kinase II. Therefore, we studied regulation of the 19-pS K(+) channels by Ca(2+)-dependent phosphorylation/dephosphorylation. The rates of inactivation of ensemble-averaged currents resulting from 19-pS K(+) channels were increased by the calmodulin antagonist W-7. Inhibitors of calcineurin, cyclosporin A and FK-506, slowed the inactivation of the 19-pS K(+) channels. Okadaic acid, an inhibitor of the calcineurin/inhibitor-1/protein phosphatase 1 cascade, also slowed inactivation of the 19-pS K(+) channels. Polymerase chain reaction detected transcripts encoding calcineurin A in isolated colonic smooth muscle cells, and immunohistochemical studies demonstrated specific expression of calcineurin A-like immunoreactivity in colonic muscle tissues and in colonic myocytes. These data, when considered with previous findings, suggest that Ca(2+)-dependent phosphorylation/dephosphorylation regulates the A-type current in murine colonic smooth muscle cells.
一种快速失活的钾离子电流（A 型电流）参与结肠肌肉兴奋性的调节。我们在小鼠结肠肌细胞的细胞贴附式膜片中发现了 19 皮安的钾离子通道，其激活和失活动力学与 A 型电流相似。结肠肌细胞中的 A 型电流受钙/钙调蛋白依赖性蛋白激酶 II 调节。因此，我们研究了钙依赖性磷酸化/去磷酸化对 19 皮安钾离子通道的调节作用。钙调蛋白拮抗剂 W-7 增加了由 19 皮安钾离子通道产生的总体平均电流的失活速率。钙调神经磷酸酶抑制剂环孢素 A 和 FK-506 减缓了 19 皮安钾离子通道的失活。冈田酸是钙调神经磷酸酶/抑制剂-1/蛋白磷酸酶 1 级联反应的抑制剂，它也减缓了 19 皮安钾离子通道的失活。聚合酶链反应在分离的结肠平滑肌细胞中检测到编码钙调神经磷酸酶 A 的转录本，免疫组织化学研究表明钙调神经磷酸酶 A 样免疫反应性在结肠肌肉组织和结肠肌细胞中特异性表达。这些数据与先前的研究结果相结合，表明钙依赖性磷酸化/去磷酸化调节小鼠结肠平滑肌细胞中的 A 型电流。
