The family of K channels is the largest, most diverse group in the Ion Channel Superfamily. The venomous cone snails (Conus) have evolved a correspondingly complex set of peptides targeted to various K channels. The Project has two major components: the first is to investigate mechanisms that underlie a translational application discovered for peptides previously characterized through this Program: cardioprotection during a myocardial infarction after ischemia. There are also a number of long-term discovery initiatives that will be pursued. Several of the Conus peptides that have been extensively characterized are channel blockers of the Kv1 subfamily. A completely unexpected, therapeutically significant translational application of two of these previously characterized peptides was established from work in several laboratories: they are cardioprotective in several animal models of myocardial infarction due to ischemia. It is now established that two structurally different peptides, Kappa-conotoxin PVIIA and KappaM-conotoxin RINK are both cardioprotective in the rat model of myocardial infarction. The fact that the two cardioprotective peptides are completely unrelated to each other structurally, but both target Kv1 channels is suggestive that these are likely to have a common physiologically-relevant target in the Kv1 subfamily of channels, as well as novel (and not presently understood) features in their interactions with their target K channel that lead to cardioprotection. The underlying biophysical mechanisms that lead to cardioprotection will be investigated. As a control, a third peptide closely related to KappaM-conotoxin RIIIK, KappaM-conotoxin RIIIJ, which is not cardioprotective will be characterized in parallel with the two cardioprotective peptides. We will specifically explore the hypothesis that these peptides have a high affinity target in the Kv1 subfamily, and that because K channel blockers would generally be expected to exacerbate cardiotoxicity rather than be cardioprotective, that the peptides have important state dependent interactions with their target. In particular, potential modulation of the progression to channel inactivation will be evaluated. In addition to the focused study on the three peptides relevant to cardioprotection which are already biochemically characterized, there is a significant discovery component in this project that will be carried out in conjunction with the Program Cores. A discovery pathway to develop highly subtype specific Conus peptides that target different members of the Kv1 subfamily has been initiated. We will also begin characterization of conopeptides that are high affinity, subtype selective ligands for other subfamilies of K channels.
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