Guanidinium Toxins as Tools for Sodium Ion Channel Study

描述（由申请人提供）：该项目的总体目标是开发小分子工具，用于理解与神经细胞中高度复杂的离子传输机制相关的离子通道蛋白功能。天然存在的胍毒素——河豚毒素、蛤蚌毒素、gonyautoxin 2/3和zetekitoxin AB——构成了这些研究的基础。尽管分子大小和拓扑结构存在明显差异，但这四种分子都是电压门控钠离子通道（NaV）的非常有效的阻滞剂，其作用是通过阻塞离子电导孔的细胞外口（Site I）。随着天然来源的河豚毒素、蛤蚌毒素和少量结构相关形式的可用性，对NaV的结构和功能的研究取得了进展。NaV在哺乳动物中存在十种亚型。在缺乏晶体学数据的情况下，gonyautoxin 2/3、zetekitoxin AB和设计的蛤蚌毒素模拟物等分子结合蛋白质诱变实验，将使目前的通道孔同源性模型受到挑战并得到改进。从这些类型的研究中积累的知识可能导致以胍毒素为模板的新的化学制剂，这些化学制剂显示出NaV亚型特异性活性。这种工具对于绘制发育或损伤神经元中特定通道同种异构体的时空分布是理想的。由于NaV通道被认为是炎症和神经性疼痛反应机制的主要参与者，作用于特定通道亚型的药物可能代表治疗此类疾病的新一代疗法。公共卫生相关性：我们感兴趣的是在分子水平上理解神经细胞是如何传导电流的，以及神经损伤时电信号的过程是如何受到影响的。化学合成是驱动我们计划的引擎，并将使可用于研究这些复杂生物现象的选择性试剂的制备成为可能。这些研究的结果可以帮助指导急性和/或慢性疼痛治疗的新疗法的发展。

DESCRIPTION (provided by applicant): The overarching aim of this program is to develop small molecule tools for understanding ion channel protein function associated with the highly complex ionic mechanisms of electrical transmission in neuronal cells. Naturally occurring guanidinium poisons - tetrodotoxin, saxitoxin, gonyautoxin 2/3, and zetekitoxin AB - form the bedrock of these investigations. Despite evident differences in molecular size and topology, all four molecules are exquisitely potent blockers of voltage-gated sodium ion channels (NaV) that operate by occluding the extracellular mouth of the ion conductance pore (Site I). Studies of NaV structure, of which there exist ten mammalian isoforms, and function have been advanced with the availability from natural sources of tetrodotoxin, saxitoxin, and small number of structurally related forms. In the absence of crystallographic data, molecules such as gonyautoxin 2/3, zetekitoxin AB, and designed saxitoxin mimics in combination with protein mutagenesis experiments would enable current homology models of the channel pore to be challenged and refined. Knowledge accrued from these types of studies could lead to new chemical agents patterned after the guanidinium toxins that demonstrate NaV subtype specific activity. Such tools are desirable for mapping the spatial and temporal distribution of specific channel isoforms in developing or injured neurons. As NaV channels are considered lead actors in mechanisms for inflammation and neuropathic pain response, drugs that act on specific channel subtypes could represent next-generation therapies for the treatment of such ailments. PUBLIC HEALTH RELEVANCE: We are interested in understanding at a molecular level how nerve cells conduct electricity and how the process of electrical signaling is affected when a nerve is injured. Chemical synthesis is the engine that drives our program and will make possible the preparation of selective reagents that can be used to investigate these complex biological phenomena. Results from these studies could help guide the development of new therapies for the treatment of acute and/or chronic pain.