Evolution of Tetrodotoxin Sensitivity

9410565安德森动物，如海葵、水母(蛇床纲)和扁虫(扁形蠕虫门)是我们所知的神经系统最初进化的生物体的现代代表。因此，它们为我们提供了一个了解早期神经系统和使神经系统发挥其功能的各种分子进化的窗口。神经生物学问题的进化论方法有一个额外的好处，因为它可以识别在神经生物学的某些方面存在细微差异的相对相近的动物群体。河豚毒素(TTX)的作用就是一个很好的例子。河豚毒素是一种高度特异性和高亲和力的阻断钠离子通道的毒素。河豚毒素阻断扁虫和高等动物的钠电流，但对水母完全无效。因此，人们可能会问，扁虫和水母钠通道之间的结构差异是什么导致了这种不同的敏感性。有了这些信息，确定哺乳动物钠通道上的同等位置应该相对容易，从而能够开发出新的高特异性、高效力的麻醉剂和通道阻滞剂，针对这一非常重要的蛋白质类上迄今为止尚未开发的位置。这项拟议工作的总体目标是利用扁虫和蛇毒钠通道对TTX敏感性的这种差异来确定TTX与钠通道结合的要求。除了使用分子克隆技术来确定海葵和扁平线虫的钠通道的一级结构外，PI还将使用传统的脂类分析和蛋白质生化技术来确定这些组中天然钠通道的脂环境，以及与这些蛋白质相连的糖部分的类型。PI将把这些数据与之前从水母中获得的同等数据进行比较。

9410565 Anderson Animals such as sea anemones, jellyfish (Phylum Cnidaria) and flatworms (Phylum Platyhelminthes) are modern-day representatives of organisms in which the nervous system, as we know it, first evolved. As such, they present us with a window into the evolution of the early nervous system and of the various molecules that enable nervous systems to function as they do. An evolutionary approach to neurobiological questions has an added benefit inasmuch as it is possible to identify groups of relatively closely related animals that differ subtly in some aspect of their neurobiology. A case in point concerns the action of tetrodotoxin (TTX) a toxin that blocks sodium channels extremely specifically and with high affinity. Tetrodotoxin blocks sodium currents in flatworms and higher animals, but is completely ineffective in jellyfish. Thus one might ask, what are the structural differences between the flatworm and jellyfish sodium channels that account for this differential sensitivity. Armed with this information, it should be relatively easy to identify the equivalent site on mammalian sodium channels thereby enabling the development of new classes of highly specific, and highly potent anesthetics and channel blockers that target this hitherto unexploited site on this very important class of proteins. The overall aim of the proposed work is to take advantage of this difference in the TTX sensitivity of flatworm and cnidarian sodium channels to identify the requirements for TTX binding to sodium channels. In addition to using molecular cloning techniques to determine the primary structure of sodium channels from a sea anemone, and a flatworm, the PI will use conventional lipid analysis and protein biochemical techniques to determine the lipid environment of the native sodium channels in these groups, and the types of sugar moieties linked to these proteins. The PI will compare these data with equivalent data previously obtained from a jell yfish.