title: Putative binding sites for arachidonic acid on the human cardiac Kv 1.5 channel.
abstract: OBJECTIVE
  In human heart, the Kv 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 Kv 1.5 (hKv 1.5) channel.
  
  
  METHODS
  Site-directed mutagenesis was conducted to mutate amino acids that reside within the pore domain of the hKv 1.5 channel. Whole-cell patch-clamp method was used to record membrane currents through wild type and mutant hKv 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 Kv 1.5 channel.
  
  
  RESULTS
  The hKv 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 Kv 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 hKv 1.5 channel. Docking simulation predicted that H463, T480, R487, I508, V512 and V516 are potentially accessible for interaction with AA.
  
  
  CONCLUSIONS
  AA itself interacts with multiple amino acids located in the pore domain of the hKv 1.5 channel. These findings may provide useful information for future development of selective blockers of hKv 1.5 channels.
authors: Department of Physiology, Shiga University of Medical Science, Otsu, Japan.
authors: Jia-Yu
authors: JY
authors: Bai
authors: Department of Physiology, Shiga University of Medical Science, Otsu, Japan.
authors: Wei-Guang
authors: WG
authors: Ding
authors: Department of Anesthesiology, Shiga University of Medical Science, Otsu, Japan.
authors: Akiko
authors: A
authors: Kojima
authors: Department of Anesthesiology, Shiga University of Medical Science, Otsu, Japan.
authors: Tomoyoshi
authors: T
authors: Seto
authors: Department of Physiology, Shiga University of Medical Science, Otsu, Japan.
authors: Hiroshi
authors: H
authors: Matsuura
mesh_terms: D000818:Animals; D016718:Arachidonic Acid / Q000494:pharmacology*; D001665:Binding Sites; D016466:CHO Cells; D003412:Cricetulus; D006801:Humans; D051666:Kv1.5 Potassium Channel / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D062105:Molecular Docking Simulation; D009154:Mutation
chemical_list: D051666:Kv1.5 Potassium Channel; D016718:Arachidonic Acid