Structure-Activity Relationship Evaluation of Wasp Toxin β-PMTX Leads to Analogs with Superior Activity for Human Neuronal Sodium Channels.

Beta-pompilidotoxin (β-PMTX) is a 13-amino acid wasp venom peptide that activates human neuronal sodium channel Na1.1 with weak activity (40% activation at 3.3 μM of β-PMTX). Through rational design of β-PMTX analogs, we have identified peptides with significantly improved activity on human Na1.1 (1170% activation at 3.3 μM of peptide ). The underlying structure-activity relationship suggests importance of charge interactions (from residue Lys-3) and lipophilic interactions (from residue Phe-7 and Ser-11). Three top-ranked analogs showed parallel activity improvement for other neuronal sodium channels (human Na1.2/1.3/1.6/1.7) but not muscular subtypes (Na1.4/1.5). Finally, we found that analog could partially rescue the pharmacological block imposed by Na1.1/1.3 selective inhibitor ICA-121431 in cultured mouse cortical GABAergic neurons, demonstrating an activating effect of this peptide on native neuronal sodium channels and its potential utility as a neuropharmacological tool.