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A new negative allosteric modulator, AP14145, for the study of small conductance calcium‐activated potassium (K Ca 2) channels
Author(s) -
SimóVicens Rafel,
Kirchhoff Jeppe E,
Dolce Bernardo,
Abildgaard Lea,
Speerschneider Tobias,
Sørensen Ulrik S,
Grunnet Morten,
Diness Jonas G,
Bentzen Bo H
Publication year - 2017
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/bph.14043
Subject(s) - allosteric regulation , chemistry , potassium channel , conductance , calcium , biophysics , calcium activated potassium channel , patch clamp , potassium , voltage dependent calcium channel , effective refractory period , allosteric modulator , pharmacology , refractory period , medicine , biochemistry , receptor , biology , mathematics , organic chemistry , combinatorics
Background and Purpose Small conductance calcium‐activated potassium (K Ca 2) channels represent a promising atrial‐selective target for treatment of atrial fibrillation. Here, we establish the mechanism of K Ca 2 channel inhibition by the new compound AP14145. Experimental Approach Using site‐directed mutagenesis, binding determinants for AP14145 inhibition were explored. AP14145 selectivity and mechanism of action were investigated by patch‐clamp recordings of heterologously expressed K Ca 2 channels. The biological efficacy of AP14145 was assessed by measuring atrial effective refractory period (AERP) prolongation in anaesthetized rats, and a beam walk test was performed in mice to determine acute CNS‐related effects of the drug. Key Results AP14145 was found to be an equipotent negative allosteric modulator of K Ca 2.2 and K Ca 2.3 channels (IC 50 = 1.1 ± 0.3 μM). The presence of AP14145 (10 μM) increased the EC 50 of Ca 2+ on K Ca 2.3 channels from 0.36 ± 0.02 to 1.2 ± 0.1 μM. The inhibitory effect strongly depended on two amino acids, S508 and A533 in the channel. AP14145 concentration‐dependently prolonged AERP in rats. Moreover, AP14145 (10 mg·kg −1 ) did not trigger any apparent CNS effects in mice. Conclusions and Implications AP14145 is a negative allosteric modulator of K Ca 2.2 and K Ca 2.3 channels that shifted the calcium dependence of channel activation, an effect strongly dependent on two identified amino acids. AP14145 prolonged AERP in rats and did not trigger any acute CNS effects in mice. The understanding of how K Ca 2 channels are inhibited, at the molecular level, will help further development of drugs targeting K Ca 2 channels.