CD2+ REGULATION OF THE HYPERPOLARIZATION-ACTIVATED CURRENT I-AB IN CRAYFISH MUSCLE
CD2+ REGULATION OF THE HYPERPOLARIZATION-ACTIVATED CURRENT I-AB IN CRAYFISH MUSCLE
复制标题
DOI：
10.1085/jgp.105.6.725
复制
发表时间：
1995-06-01
影响因子：
3.8
通讯作者：
BUNO, W
中科院分区：
文献类型：
--
作者：
ARAQUE, A;CATTAERT, D;BUNO, W
Cd 2+对超极化激活的K+介导的电流（称为I-AB）的影响（Araque，A.，和W.布诺1994. Journal of Neuroscience. 14：399-408.）对克氏原螯虾开肌肌纤维进行了双电极电压痉挛的研究。细胞外Cd 2+以浓度依赖性方式可逆地还原I-AB，符合Hill方程，IC 50 = 0.452 +/- 0.045 mM，Hill系数为1（由I-AB的最大弦电导确定）Cd ~（2+）使I-AB电导（G（AB））降低，并使其电压依赖性向超极化电位方向移动，而不影响电压依赖性的斜率。I-AB活化时间常数增加，而I-AB失活时间常数没有被Cd ~（2+）改变。I-AB平衡电位（E（AB））未被Cd ~（2+）改变，表明I-AB通道的选择性渗透性未被改变。I-AB不受细胞内Cd ~（2+）的影响。Cd ~（2+）对I-AB的调节不依赖于[K ~+]（0），Cd ~（2+）不影响[K ~+]（0）对I-AB的调节，说明Cd ~（2+）不与K ~+竞争。因此，Cd 2+可能结合到不同的网站，参与K+渗透途径。我们的结论是，Cd 2（+）影响门控的I-AB通道，干扰其开放，但不与他们的关闭机制。这一结果可以用动力学模型来解释，在该模型中，Cd 2+与I-AB通道的结合将使门控装置稳定在其静止位置，增加了从关闭通道状态向开放通道状态过渡的能垒。
The effects of Cd2+ on the hyperpolarization-activated K+-mediated current called I-AB (Araque, A., and W. Buno. 1994. Journal of Neuroscience. 14:399-408.) were studied under two-electrode voltage-cramp in opener muscle fibers of the crayfish Procambarus clarkii. I-AB was reversibly reduced by extracellular Cd2+ in a concentration-dependent manner, obeying the Hill equation with IC50 = 0.452 +/- 0.045 mM and a Hill coefficient of 1 (determined from the maximal chord conductance of I-AB) Cd2+ decreased the I-AB conductance (G(AB)) and shifted its voltage dependence towards hyperpolarized potentials in a similar degree, without affecting the slope of the voltage dependence. The I-AB activation time constant increased, whereas the I-AB deactivation time constant was not modified by Cd2+. The I-AB equilibrium potential (E(AB)) was unmodified by Cd2+, indicating that the selective permeability of I-AB channels was not altered. I-AB was unaffected by intracellular Cd2+. The Cd2+-regulation of I-AB did not depend on [K+](0), and the effects of [K+](0) on I-AB were unchanged by Cd2+, indicating that Cd2+ did not compete with K+. Therefore, Cd2+ probably bound to a different site to that involved in the K+ permeability pathway. We conclude that Cd2(+) affected the gating of I-AB channels, interfering with their opening but not with their closing mechanism. The results can be explained by a kinetic model in which the binding of Cd2+ to the I-AB channels would stabilize the gating apparatus at its resting position, increasing the energy barrier for the transition from the closed to the open channel states.