INTERACTION OF A NOVEL SNAKE VENOM NEUROTOXIN DRYSDALIN AND ITS MUTANTS WITH NICOTINIC ACETYLCHOLINE RECEPTORS

Abstract

NICOTINIC ACETYLCHOLINE RECEPTORS (NACHRS) PLAY IMPORTANT ROLE IN SEVERAL NEURO-PATHOLOGIES. HIGHLY SELECTIVE LIGANDS HELP UNDERSTAND THEIR DISTRIBUTION AND PHYSIOLOGICAL ROLES, WHICH ARE NOT YET CLEAR. SNAKE VENOM IS A GOOD SOURCE OF SUCH NACHR ANTAGONISTS. IN THIS STUDY WE HAVE CHARACTERIZED A NOVEL ANTAGONIST DRYSDALIN FROM THE SNAKE DRYSDALIA CORONOIDES. THIS LONG-CHAIN THREE-FINGER TOXIN (3FTX) HAS AN UNUSUALLY LONG C-TERMINAL TAIL AND THREE KEY FUNCTIONAL RESIDUES ARE REPLACED. FUNCTIONALLY, DRYSDALIN SHOWS POTENT (IC50, 37 NM), IRREVERSIBLE POSTSYNAPTIC ACTIVITY ON CHICK BIVENTER CERVICIS MUSCLE PREPARATIONS. IN ELECTROPHYSIOLOGICAL EXPERIMENTS WITH NACHRS EXPRESSED IN XENOPUS OOCYTES, DRYSDALIN SHOWS NANOMOLAR POTENCY TO RAT MUSCLE AND HUMAN A7 NACHRS. CELL-BASED FLUORESCENCE ASSAY MEASURING INTRACELLULAR CALCIUM RELEASE ALSO SHOWS NANOMOLAR POTENCY TO HUMAN A7 NACHR. IN RADIOLIGAND BINDING ASSAYS, DRYSDALIN SHOWS 10-FOLD HIGHER AFFINITY TO APLYSIA CALIFORNICA ACETYLCHOLINE BIN