title: Understanding the molecular basis of toxin promiscuity: the analgesic sea anemone peptide APETx2 interacts with acid-sensing ion channel 3 and hERG channels via overlapping pharmacophores.
abstract: The sea anemone peptide APETx2 is a potent and selective blocker of acid-sensing ion channel 3 (ASIC3). APETx2 is analgesic in a variety of rodent pain models, but the lack of knowledge of its pharmacophore and binding site on ASIC3 has impeded development of improved analogues. Here we present a detailed structure-activity relationship study of APETx2. Determination of a high-resolution structure of APETx2 combined with scanning mutagenesis revealed a cluster of aromatic and basic residues that mediate its interaction with ASIC3. We show that APETx2 also inhibits the off-target hERG channel by reducing the maximal current amplitude and shifting the voltage dependence of activation to more positive potentials. Electrophysiological screening of selected APETx2 mutants revealed partial overlap between the surfaces on APETx2 that mediate its interaction with ASIC3 and hERG. Characterization of the molecular basis of these interactions is an important first step toward the rational design of more selective APETx2 analogues.
authors.affiliation: Institute for Molecular Bioscience, ‡School of Biomedical Sciences, and §Centre for Advanced Imaging, The University of Queensland , St Lucia, QLD 4072, Australia.
authors.forename: Jonas E
authors.initials: JE
authors.lastname: Jensen
authors.forename: Ben
authors.initials: B
authors.lastname: Cristofori-Armstrong
authors.forename: Raveendra
authors.initials: R
authors.lastname: Anangi
authors.forename: K Johan
authors.initials: KJ
authors.lastname: Rosengren
authors.forename: Carus H Y
authors.initials: CH
authors.lastname: Lau
authors.forename: Mehdi
authors.initials: M
authors.lastname: Mobli
authors.forename: Andreas
authors.initials: A
authors.lastname: Brust
authors.forename: Paul F
authors.initials: PF
authors.lastname: Alewood
authors.forename: Glenn F
authors.initials: GF
authors.lastname: King
authors.forename: Lachlan D
authors.initials: LD
authors.lastname: Rash
mesh_terms: D062565:Acid Sensing Ion Channels / Q000378:metabolism*; D000818:Animals; D003064:Cnidarian Venoms / Q000235:genetics / Q000494:pharmacology*; D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels / Q000037:antagonists & inhibitors* / Q000378:metabolism; D006801:Humans; D008958:Models, Molecular; D009154:Mutation; D012615:Sea Anemones; D013329:Structure-Activity Relationship
chemical_list: C501880:APETx2 protein, Anthopleura elegantissima; C112231:ASIC3 protein, human; D062565:Acid Sensing Ion Channels; D003064:Cnidarian Venoms; D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels; C000606913:KCNH2 protein, human