The objective of this project is to isolate new peptide ligands for K+ channels for which there are none available, and to use them to investigate channel structure and function. Potassium channels are present in every cell in the human body and therefore are important for a vast array of physiological processes. These include the generation and processing of electrical signals in the nervous system, regulation of heart contraction, secretion of hormones which regulate blood sugar, and control of water and salt balance in kidney. A thorough understanding of these channels and their molecular pharmacology should dramatically increase our ability to treat human disease. New peptide inhibitors will be purified from a variety of natural sources (spider and scorpion venom) using a screening procedure that involves the expression of cloned K+ channels in Xenopus oocytes. Molecular biological and electrophysiological techniques will be combined to study how these agents interact with K+ channels. I have already isolated a completely new type of K+ channel inhibitor (hanatoxin) from spider venom using this strategy. Hanatoxin is the only known inhibitor of Kv2.1 (DRK1), a voltage-gated neuronal K+ channel. This proposal has four specific aims: (1) to determine the selectivity of hanatoxin; (2) to study the mechanism of hanatoxin-mediated inhibition; (3) to identify the hanatoxin receptor on the Kv2.1 channel and study the interaction surfaces; and (4) to isolate new ligands for inward rectifier K+ channels. Once isolated these ligands will be used to study this very interesting, but poorly understood, class of K+ channels.
