title: Re-engineering the μ-conotoxin SIIIA scaffold.
abstract: Voltage-gated sodium (Nav) channels are responsible for generation and propagation of action potentials throughout the nervous system. Their malfunction causes several disorders and chronic conditions including neuropathic pain. Potent subtype specific ligands are essential for deciphering the molecular mechanisms of Nav channel function and development of effective therapeutics. µ-Conotoxin SIIIA is a potent mammalian Nav 1.2 channel blocker that exhibits analgesic activity in rodents. We undertook to reengineer loop 1 through a strategy involving charge alterations and truncations which led to the development of µ-SIIIA mimetics with novel selectivity profiles. A novel [N5K/D15A]SIIIA(3-20) mutant with enhanced net positive charge showed a dramatic increase in its Nav 1.2 potency (IC50 of 0.5 nM vs. 9.6 nM for native SIIIA) though further truncations led to loss of potency. Unexpectedly, it appears that SIIIA loop 1 significantly influences its Nav channel interactions despite loop 2 and 3 residues constituting the pharmacophore. This minimal functional conotoxin scaffold may allow further development of selective NaV blockers.
authors.affiliation: Institute for Molecular Bioscience (IMB), The University of Queensland, Brisbane, 4072, Queensland, Australia.
authors.forename: K B
authors.initials: KB
authors.lastname: Akondi
authors.forename: R J
authors.initials: RJ
authors.lastname: Lewis
authors.forename: P F
authors.initials: PF
authors.lastname: Alewood
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002851:Chromatography, High Pressure Liquid; D056148:Chromatography, Reverse-Phase; D020916:Conotoxins / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D050505:Mutant Proteins / Q000737:chemistry; D062551:NAV1.2 Voltage-Gated Sodium Channel / Q000378:metabolism; D015202:Protein Engineering; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017208:Rats, Wistar; D054457:Tissue Scaffolds / Q000737:chemistry*
chemical_list: D020916:Conotoxins; D050505:Mutant Proteins; D062551:NAV1.2 Voltage-Gated Sodium Channel
keywords: NMR spectroscopy; SPPS; peptides; peptidomimetics; structure activity relationships; voltage gated sodium channels; μ-SIIIA; μ-conotoxin