Herzog Raimund I, Liu Chuanju, Waxman Stephen G, Cummins Theodore R
Department of Neurology and Paralyzed Veterans of America/Eastern Paralyzed Veterans Association Neuroscience Research Center, Yale School of Medicine, New Haven, Connecticut 06510, USA.
J Neurosci. 2003 Sep 10;23(23):8261-70. doi: 10.1523/JNEUROSCI.23-23-08261.2003.
Modulation of voltage-gated sodium channels (VGSC) can have a major impact on cell excitability. Analysis of calmodulin (CaM) binding to GST-fusion proteins containing the C-terminal domains of Nav1.1-Nav1.9 indicates that some of the tetrodotoxin-sensitive VGSC isoforms, including NaV1.4 and NaV1.6, are able to bind CaM in a calcium-independent manner. Here we demonstrate that association with CaM is important for functional expression of NaV1.4 and NaV1.6 VGSCs. Disrupting the interaction between CaM and the C terminus of NaV1.4 and NaV1.6 channels reduced current amplitude by 99 and 62%, respectively. Overexpression of CaM increased the current generated by Nav1.4 and Nav1.6 C-terminal mutant constructs that exhibited intermediate current densities and intermediate binding affinities for CaM, demonstrating that this effect on current density was directly dependent on the ability of the C terminus to bind CaM. In addition to the effects on current density, calmodulin also was able to modulate the inactivation kinetics of Nav1.6, but not Nav1.4, currents in a calcium-dependent manner. Our data demonstrate that CaM can regulate the properties of VGSCs via calcium-dependent and calcium-independent mechanisms and suggest that modulation of neuronal sodium channels may play a role in calcium-dependent neuronal plasticity.
电压门控钠通道（VGSC）的调节可对细胞兴奋性产生重大影响。对钙调蛋白（CaM）与含有Nav1.1 - Nav1.9 C末端结构域的GST融合蛋白结合的分析表明，一些对河豚毒素敏感的VGSC亚型，包括NaV1.4和NaV1.6，能够以不依赖钙的方式结合CaM。在此我们证明，与CaM的结合对于NaV1.4和NaV1.6 VGSCs的功能表达很重要。破坏CaM与NaV1.4和NaV1.6通道C末端之间的相互作用分别使电流幅度降低了99%和62%。CaM的过表达增加了由Nav1.4和Nav1.6 C末端突变体构建体产生的电流，这些构建体表现出中等电流密度和对CaM的中等结合亲和力，表明这种对电流密度的影响直接取决于C末端结合CaM的能力。除了对电流密度的影响外，钙调蛋白还能够以钙依赖的方式调节Nav1.6的失活动力学，但不能调节Nav1.4的电流。我们的数据表明，CaM可通过钙依赖和钙非依赖机制调节VGSCs的特性，并表明神经元钠通道的调节可能在钙依赖的神经元可塑性中起作用。
