Evolution of Tetrodotoxin Sensitivity

海葵、水母（刺胞门）和扁形虫（扁形蠕虫门）等动物是我们所知的最早进化出神经系统的生物体的现代代表。因此，它们为我们提供了一扇窗口，让我们了解早期神经系统的进化，以及使神经系统正常运作的各种分子。用进化的方法来解决神经生物学问题还有一个额外的好处，因为它有可能识别出在神经生物学的某些方面有细微差别的相对密切的动物群体。一个恰当的例子涉及河豚毒素（TTX）的作用，这种毒素非常特异性地和高亲和力地阻断钠通道。河豚毒素在扁虫和高等动物中阻断钠电流，但在水母中完全无效。因此，有人可能会问，扁形虫和水母之间的钠通道结构差异是什么，导致了这种不同的灵敏度。有了这些信息，在哺乳动物钠通道上识别等效位点就相对容易了，从而能够开发出新的高特异性、强效麻醉剂和通道阻滞剂，靶向这类非常重要的蛋白质上迄今尚未开发的位点。这项工作的总体目标是利用扁虫和刺胞体钠通道对TTX敏感性的差异来确定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虫钠通道的主要结构外，PI还将使用传统的脂质分析和蛋白质生化技术来确定这些群体中天然钠通道的脂质环境，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那里获得的等效数据进行比较。

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.