Re-engineering the μ-conotoxin SIIIA scaffold

• Published in: Biopolymers 2014-04, Vol.101 (4), p.347-354
• Main Authors: Akondi, K. B., Lewis, R. J., Alewood, P. F.
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Animals; Chromatography, High Pressure Liquid; Chromatography, Reverse-Phase; Conotoxins - chemistry; Magnetic Resonance Spectroscopy; Molecular Sequence Data; Mutant Proteins - chemistry; NAV1.2 Voltage-Gated Sodium Channel - metabolism; NMR spectroscopy; peptides; peptidomimetics; Protein Engineering; Protein Folding; Protein Structure, Secondary; Rats, Wistar; SPPS; structure activity relationships; Tissue Scaffolds - chemistry; voltage gated sodium channels; μ-conotoxin; μ-SIIIA
• ISSN: 0006-3525; 1097-0282
• DOI: 10.1002/bip.22368

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 Nav1.2 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 Nav1.2 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. © 2013 Wiley Periodicals, Inc. Biopolymers 101: 347–354, 2014.