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

电压门控钠通道和钙通道离子选择性的起源、作用和机制

• 批准号: RGPIN-2016-03690
• 负责人: Spafford, JDavid
• 金额: $ 2.4万
• 依托单位: University of Waterloo
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2016
• 资助国家: 加拿大
• 起止时间: 2016-01-01 至 2017-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=614555
• 关键词: Origins; roles; mechanisms; ion; selectivity

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.

控制身体功能的电信号由通过高离子选择性电压门控通道的离子流形成。我们目前对离子通道如何具有离子选择性的理解可以通过罗德里克·麦金农 (Roderick Mackinnon) 获得诺贝尔奖的钾选择性通道的 X 射线晶体结构来理解。钾通道中的离子选择性涉及沙漏形离子选择性孔的最窄点，其中存在关键的离子选择性过滤器残留物。 Spafford 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钠或钙通道。 Spafford 实验室发现了自然界产生具有替代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选择性的调节提供了独特的见解。我们提出实验来探索 NALCN（NA Leak ChaNnel）和 Cav3 T 型通道，它们分别具有可变剪接的外显子，可将 NALCN 和 T 型通道转化为钙或钠选择性通道。这项工作意义重大，因为它证明了使用或不使用规范离子选择性过滤器都可以产生离子选择性。 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 亚基如何适应缺乏锚蛋白和神经胶质依赖性信号传导的脊椎动物发育中的神经系统中快速、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功能性地取代 Nav1 通道，以及 T 型通道如何普遍受到钙传感器钙调蛋白的调节。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用途的解释，因为迄今为止钠和钙通道仅在具有神经系统的动物中被考虑。斯帕福德实验室的研究为分析从基础单细胞祖先到无脊椎动物的电压门控钠和钙通道提供了非传统的视角。迄今为止的结果提供了在很大程度上反教条的见解，在离子通道领域中，该领域的观点主要来自脊椎动物生理学研究的狭窄窗口或细菌通道结构。