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

控制身体机能的电信号是由离子通量通过高离子选择性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是由罗德里克·麦金农获得诺贝尔奖的钾选择通道的x射线晶体结构所理解的。钾离子通道中的离子选择性涉及沙漏形离子选择孔的最窄点，那里存在临界离子选择性过滤器残留物。*** Spafford实验室的工作表明，钾离子通道的离子选择性模型并不同样适用于真核生物的钠离子或钙离子通道。Spafford实验室发现了自然界产生具有钠和钙选择性孔的离子通道的唯一机制，这些离子通道为钠和钙的选择性调节提供了独特的见解。我们提出了探索NALCN （NA Leak ChaNnel）和Cav3 t型通道的实验，它们分别具有可选择剪接的外显子，将NALCN和t型通道转变为钙或钠选择通道。这项工作是重要的，因为它证明了离子选择性可以产生与标准离子选择性过滤器。***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一个独特的视角。例如，我们将评估Nav1通道及其β亚基如何在缺乏脊椎动物锚蛋白和胶质依赖信号的发育中的神经系统中适应快速、有效的电通信和模式；钠选择性t型通道如何在无脊椎动物心脏中取代Nav1通道，以及t型通道如何受钙传感器钙调蛋白的普遍调节。我们的分析扩展到基础单细胞真核生物，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，因为迄今为止，钠和钙通道只在具有神经系统的动物中被考虑过。Spafford实验室的研究提供了一个非传统的视角来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。在离子通道领域，迄今为止的研究结果在很大程度上提供了反教条的见解，这些见解主要来自脊椎动物生理研究或细菌通道结构的狭窄窗口

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.**