A New Negative Allosteric Modulator AP14145 for the Study of Small Conductance Calcium-Activated Potassium Channels

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Background and purpose: Small conductance Ca2+-activated K+ (KCa2) channels represent a promising atrial-selective target for treatment of atrial fibrillation (AF). Here, we establish the mechanism of KCa2 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 KCa2 channels. The biological efficacy of AP14145 was assessed by measuring atrial effective refractory period (AERP) prolongation in anaesthetised 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 KCa2.2 and KCa2.3 channels (IC50 = 1.1 ± 0.3 μM L-1). The presence of AP14145 (10 μM L-1) increased the EC50 of Ca2+ on KCa2.3 from 0.36 ± 0.02 μM L-1 to 1.2 ± 0.1 μM L-1. The inhibitory effect strongly depended on two amino acids, S508 and A533. AP14145 concentration-dependently prolonged AERP in rats. Moreover, AP14145 (10 mg kg-1) did not trigger any apparent CNS effects in mice.

Conclusion and implications: AP14145 is a negative allosteric modulator of KCa2.2 and KCa2.3 that shifts the calcium dependence of channel activation, an effect strongly dependent on two identified amino acids. AP14145 prolongs AERP in rats and does not trigger any acute CNS effects in mice. The understanding of how KCa2 inhibition is accomplished at the molecular level will help future development of drugs targeting KCa2 channels.
Original languageEnglish
JournalBritish Journal of Pharmacology
Issue number23
Pages (from-to)4396-4408
Number of pages13
Publication statusPublished - 5 Dec 2017

    Research areas

  • Faculty of Health and Medical Sciences - AP14145, Atrial fibrillation, small conductance calcium-activated potassium channels, Electrophysiology, SK channel, negative allosteric modulator

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