Origins, roles and mechanisms of ion selectivity for voltage-gated sodium and calcium channels

控制身体功能的电信号是由离子流量通过高度离子选择性的电压门控通道形成的。我们目前对离子通道如何具有离子选择性的理解被罗德里克·麦金农获得诺贝尔奖的钾选择性通道的X射线晶体结构所理解。钾通道中的离子选择性涉及沙漏状离子选择孔的最窄处，在那里有关键的离子选择性过滤残留物。*斯普夫德实验室的工作表明，为钾通道提出的离子选择性模型并不同样适用于真核细胞的钠或钙通道。斯普费尔德实验室发现了自然界产生具有选择性钠和钙选择性毛孔的离子通道的唯一机制，这些离子通道为钠和钙选择性的调节提供了独特的见解。我们提出了探索NALCN(NA泄漏通道)和Cav3T型通道的实验，它们分别具有交替剪接的外显子，将NALCN和T型通道转换为钙或钠选择性通道。这项工作意义重大，因为它证明了离子选择性可以在有和没有离子选择性过滤器的情况下产生。*非脊椎动物模型的简单性为理解离子信号如何适应不同的身体计划提供了独特的视角。例如，我们将评估NAV1通道及其β亚基如何适应发育中的神经系统中快速、高效的电子通信和模式，缺乏脊椎动物骨架蛋白和神经胶质依赖信号；钠选择性T-型通道如何在功能上取代无脊椎动物心脏中的NAV1通道；以及T-型通道如何普遍受到钙感受器和钙调蛋白的调节。我们的分析延伸到了基本的单细胞真核生物Salpingoeca Rosetta。单细胞真核生物的观点改变了我们对这些离子通道的解释，因为到目前为止，钠和钙通道只被认为是在有神经系统的动物的背景下。斯普费德实验室的研究为分析从基础的单细胞祖先到无脊椎动物的电压门控钠和钙通道提供了一种非传统的视角。迄今为止的结果在离子通道领域提供了很大程度上是反教条的见解，这些观点主要来自脊椎动物生理研究的狭窄窗口或细菌通道结构的观点。

The electrical signals which control bodily functions are shaped by ion flux through highly ion selective voltage-gated channels. Our current understanding of how ion channels are ion selective is understood by Roderick Mackinnon's Nobel Prize winning X-ray crystal structure of the potassium-selective channel. Ion selectivity in potassium channels involves the narrowest point of the hourglass shaped ion selective pore where there are critical ion selectivity filter residues.***The work of the Spafford lab shows that the ion selectivity model proposed for potassium channels, doesn't equally apply for eukaryotic sodium or calcium channels. The Spafford lab has discovered the only mechanism where nature generates ion channels with alternative sodium and calcium selective pores, and these ion channels provide unique insights into the regulation of sodium and calcium selectivity. We propose experiments to explore NALCN (NA Leak ChaNnel) and Cav3 T-type channel, respectively which possess alternatively spliced exons that transforms NALCN and T-type channels into calcium- or sodium-selective channels. This work is momentous as it demonstrates that ion selectivity can be generated with and without the canonical ion selectivity filter.***The simplicity of non-vertebrates models provides a unique perspective in understanding how ionic signalling is adapted for differing body plans. We will evaluate for example, how Nav1 channels and their beta subunits are adapted for rapid, efficient electrical communication and patterning within the developing nervous systems lacking vertebrate ankyrin and glial dependent signalling; how sodium-selective T-type channels can functionally replace Nav1 channels in the invertebrate heart, and how T-type channels are universally regulated by calcium sensor, calmodulin. Our analyses extends to basal single cell eukaryote, Salpingoeca rosetta. The single cell eukaryote perspective alters our interpretation of what these ion channels are for, as sodium and calcium channels have only been considered to date in the context of animals with nervous systems. The Spafford lab's research provide a non-traditional perspective in the analyses of voltage-gated sodium and calcium channels from basal, single cell ancestors to invertebrates. Results to date have provided insights that are largely anti-dogmatic, in an ion channel field dominated by perspectives derived from a narrow window of physiological studies in vertebrates or from bacterial channel structures.**