Kwak Y G, Navarro-Polanco R A, Grobaski T, Gallagher D J, Tamkun M M
Departments of Physiology and Biochemistry and Molecular Biology, Colorado State University, Ft. Collins, Colorado 80523, USA.
J Biol Chem. 1999 Sep 3;274(36):25355-61. doi: 10.1074/jbc.274.36.25355.
The Kv1.5 K(+) channel is functionally altered by coassembly with the Kvbeta1.3 subunit, which induces fast inactivation and a hyperpolarizing shift in the activation curve. Here we examine kinase regulation of Kv1.5/Kvbeta1.3 interaction after coexpression in human embryonic kidney 293 cells. The protein kinase C inhibitor calphostin C (3 microM) removed the fast inactivation (66 +/- 1.9 versus 11 +/- 0.25%, steady state/peak current) and the beta-induced hyperpolarizing voltage shift in the activation midpoint (V(1/2)) (-21.9 +/- 1.4 versus -4.3 +/- 2.0 mV). Calphostin C had no effect on Kv1.5 alone with respect to inactivation kinetics and V(1/2). Okadaic acid, but not the inactive derivative, blunted both calphostin C effects (V(1/2) = -17.6 +/- 2.2 mV, 38 +/- 1.8% inactivation), consistent with dephosphorylation being required for calphostin C action. Calphostin C also removed the fast inactivation (57 +/- 2.6 versus 16 +/- 0.6%) and the shift in V(1/2) (-22.1 +/- 1.4 versus -2.1 +/- 2.0 mV) conferred onto Kv1.5 by the Kvbeta1.2 subunit, which shares only C terminus sequence identity with Kvbeta1. 3. In contrast, modulation of Kv1.5 by the Kvbeta2.1 subunit was unaffected by calphostin C. These data suggest that Kvbeta1.2 and Kvbeta1.3 subunit modification of Kv1.5 inactivation and voltage sensitivity require phosphorylation by protein kinase C or a related kinase.
Kv1.5钾离子通道与Kvbeta1.3亚基共同组装后功能会发生改变，后者可诱导快速失活以及激活曲线的超极化偏移。在此，我们研究了在人胚肾293细胞中共表达后Kv1.5/Kvbeta1.3相互作用的激酶调节。蛋白激酶C抑制剂钙泊三醇C（3微摩尔）消除了快速失活（稳态/峰值电流分别为66±1.9%和11±0.25%）以及β诱导的激活中点（V(1/2)）的超极化电压偏移（-21.9±1.4毫伏和-4.3±2.0毫伏）。钙泊三醇C对单独的Kv1.5的失活动力学和V(1/2)没有影响。冈田酸而非其无活性衍生物减弱了钙泊三醇C的两种效应（V(1/2)=-17.6±2.2毫伏，失活率38±1.8%），这与钙泊三醇C发挥作用需要去磷酸化一致。钙泊三醇C还消除了由Kvbeta1.2亚基赋予Kv1.5的快速失活（57±2.6%和16±0.6%）以及V(1/2)的偏移（-22.1±1.4毫伏和-2.1±2.0毫伏），Kvbeta1.2亚基仅在C末端序列上与Kvbeta1.3具有同一性。相比之下，Kvbeta2.1亚基对Kv1.5的调节不受钙泊三醇C的影响。这些数据表明，Kvbeta1.2和Kvbeta1.3亚基对Kv1.5失活和电压敏感性的修饰需要蛋白激酶C或相关激酶的磷酸化作用。
