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Putative binding sites for arachidonic acid on the human cardiac K v 1.5 channel
Author(s) -
Bai JiaYu,
Ding WeiGuang,
Kojima Akiko,
Seto Tomoyoshi,
Matsuura Hiroshi
Publication year - 2015
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.13314
Subject(s) - depolarization , arachidonic acid , patch clamp , repolarization , cardiac action potential , biophysics , chemistry , membrane potential , extracellular , potassium channel , electrophysiology , binding site , amino acid , chinese hamster ovary cell , mutagenesis , docking (animal) , biochemistry , mutant , biology , receptor , enzyme , medicine , neuroscience , nursing , gene
Background and Purpose In human heart, the K v 1.5 channel contributes to repolarization of atrial action potentials. This study examined the electrophysiological and molecular mechanisms underlying arachidonic acid (AA)‐induced inhibition of the human K v 1.5 (hK v 1.5) channel. Experimental Approach Site‐directed mutagenesis was conducted to mutate amino acids that reside within the pore domain of the hK v 1.5 channel. Whole‐cell patch‐clamp method was used to record membrane currents through wild type and mutant hK v 1.5 channels heterologously expressed in CHO cells. Computer docking simulation was conducted to predict the putative binding site(s) of AA in an open‐state model of the K v 1.5 channel. Key Results The hK v 1.5 current was minimally affected at the onset of depolarization but was progressively reduced during depolarization by the presence of AA, suggesting that AA acts as an open‐channel blocker. AA itself affected the channel at extracellular sites independently of its metabolites and signalling pathways. The blocking effect of AA was attenuated at pH 8.0 but not at pH 6.4. The blocking action of AA developed rather rapidly by co‐expression of K v β1.3. The AA‐induced block was significantly attenuated in H463C, T480A, R487V, I502A, I508A, V512A and V516A, but not in T462C, A501V and L510A mutants of the hK v 1.5 channel. Docking simulation predicted that H463, T480, R487, I508, V512 and V516 are potentially accessible for interaction with AA. Conclusions and Implications AA itself interacts with multiple amino acids located in the pore domain of the hK v 1.5 channel. These findings may provide useful information for future development of selective blockers of hK v 1.5 channels.