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

Rafel Simo Vicens, Jeppe Egedal Kirchhoff, Bernardo Dolce , Lea Abildgaard, Tobias Speerschneider, Ulrik Svane Sørensen, Morten Grunnet, Jonas Goldin Diness, Bo Hjorth Bentzen

13 Citations (Scopus)
46 Downloads (Pure)

Abstract

Background and Purpose: Small conductance calcium-activated potassium (KCa2) channels represent a promising atrial-selective target for treatment of atrial fibrillation. Here, we establish the mechanism of KCa2 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 KCa2 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 KCa2.2 and KCa2.3 channels (IC50 = 1.1 ± 0.3 μM). The presence of AP14145 (10 μM) increased the EC50 of Ca2+ on KCa2.3 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 KCa2.2 and KCa2.3 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 KCa2 channels are inhibited, at the molecular level, will help further development of drugs targeting KCa2 channels.

Original languageEnglish
JournalBritish Journal of Pharmacology
Volume174
Issue number23
Pages (from-to)4396-4408
Number of pages13
ISSN0007-1188
DOIs
Publication statusPublished - 5 Dec 2017

Keywords

  • 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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