Ko Jae Hong, Park Won Sun, Kim Sung Joon, Earm Yung E
Department of Physiology and National Research Laboratory for Cellular Signaling, Seoul National University College of Medicine, Seoul 110-799, South Korea.
Eur J Pharmacol. 2006 Mar 18;534(1-3):48-54. doi: 10.1016/j.ejphar.2006.01.018. Epub 2006 Feb 20.
In this study, the effect of staurosporine, a potent protein kinase C (PKC) inhibitor, on Na+ current (I(Na)) was examined by whole-cell patch recording in rabbit atrial myocytes. The most prominent staurosporine effect was a slowing of I(Na) inactivation and 1 microM staurosporine reduced amplitude of I(Na) about 33%. Staurosporine decreased I(Na) at all potentials and slowed the I(Na) inactivation in a dose-dependent manner, with a Kd value of 1.107+/-0.162 microM. Staurosporine did not change the recovery kinetics and show use dependence. However, the activation and the steady-state inactivation curves were shifted toward more negative potentials (-5.5 and -5.1 mV, respectively). Two other PKC inhibitors, GF 109203X (1 microM) and chelerythrine (3 microM), did not show a slowing effect on I(Na) inactivation. In conclusion, our results indicate that the slowing of I(Na) inactivation by staurosporine seems not to be through blockade of PKC rather to act directly on the Na+ channels, and the direct blocking effects of staurosporine on the Na+ channel should be taken into consideration when staurosporine is used in functional studies of ion channel modulation by protein phosphorylation.
在本研究中，通过全细胞膜片钳记录技术，检测了强效蛋白激酶C（PKC）抑制剂星形孢菌素对兔心房肌细胞钠电流（I(Na)）的影响。星形孢菌素最显著的作用是减缓I(Na)失活，1 μM星形孢菌素使I(Na)幅度降低约33%。星形孢菌素在所有电位下均降低I(Na)，并以剂量依赖性方式减缓I(Na)失活，解离常数（Kd）值为1.107±0.162 μM。星形孢菌素未改变恢复动力学，也未表现出使用依赖性。然而，激活曲线和稳态失活曲线分别向更负的电位移动（-5.5和-5.1 mV）。另外两种PKC抑制剂，GF 109203X（1 μM）和白屈菜红碱（3 μM），对I(Na)失活未表现出减缓作用。总之，我们的结果表明，星形孢菌素对I(Na)失活的减缓作用似乎不是通过阻断PKC，而是直接作用于钠通道，在将星形孢菌素用于蛋白质磷酸化对离子通道调节的功能研究时，应考虑其对钠通道的直接阻断作用。
