Regulation of Ca(2+)-activated K+ channels by protein kinase A and phosphatase inhibitors.
Regulation of Ca(2+)-activated K+ channels by protein kinase A and phosphatase inhibitors.
复制标题
蛋白激酶 A 和磷酸酶抑制剂对 Ca(2) 激活的 K 通道的调节。
DOI：
10.1152/ajpcell.1991.261.2.c387
复制
发表时间：
1991
期刊：
影响因子：
--
通讯作者：
Sanders,KM
中科院分区：
文献类型：
--
作者：
Carl,A;Kenyon,JL;Uemura,D;Fusetani,N;Sanders,KM
包括离子通道在内的许多蛋白质都受磷酸化的调节。本实验观察了10U/ml催化亚单位蛋白激酶A对犬近端结肠平滑肌细胞膜片上260-PS钙激活钾通道的影响。在+50 mV+10(-7)M和-50 mV+10(-6)M Ca~(2+)时，通道开放概率增加到对照组的270+/-48%(n=12)。这一增加是由于电压依赖性激活向更负的电位移动了13.9+/-3.2 mV(n=3)。无ATP时，蛋白激酶A对通道活动无影响(n=3)。磷酸化的调节必须伴随着去磷酸化。我们测试了两种有效的蛋白磷酸酶抑制剂--花盏花素A和冈田酸的效果。在蛋白激酶A存在的情况下，每种抑制剂10(-9)到10(-6)M的应用进一步增加了高达250%的开放概率。Calyculin A在增加开放概率方面似乎不如冈田酸有效，这表明涉及的磷酸酶既不是1，2A，也不是2B。在没有蛋白激酶A的情况下，Calyculin A无效。这些数据表明，内源性磷酸酶在切除的膜片中被发现，并且磷酸化和去磷酸化之间的平衡可能对结肠运动提供重要的控制。
Many proteins including ion channels are regulated by phosphorylation. We tested the effect of 10 U/ml catalytic subunit protein kinase A on 260-pS Ca(2+)-activated K+ channels in excised inside-out membrane patches from freshly dispersed smooth muscle cells of the canine proximal colon. At +50 mV with 10(-7) M Ca2+ and -50 mV with 10(-6) M Ca2+, open probability of the channels was increased to 270 +/- 48% of control (n = 12). This increase was due to a shift in voltage-dependent activation by 13.9 +/- 3.2 mV (n = 3) to more negative potentials. Protein kinase A in the absence of ATP had no effect on channel activity (n = 3). Regulation by phosphorylation must be accompanied by dephosphorylation. We tested the effect of two potent inhibitors of protein phosphatases, calyculin A and okadaic acid. Application of 10(-9) to 10(-6) M of each inhibitor in the presence of protein kinase A further increased open probability by up to 250%. Calyculin A appeared to be less effective in increasing open probability than okadaic acid, suggesting that the phosphatase involved is neither type 1, 2A, nor 2B. Calyculin A in the absence of protein kinase A was ineffective. These data suggest that endogenous phosphatases are found in excised membrane patches and that a balance between phosphorylation and dephosphorylation may provide an important control of colonic motility.