title: Structural basis of drugs that increase cardiac inward rectifier Kir2.1 currents.
abstract: OBJECTIVE
  We hypothesize that some drugs, besides flecainide, increase the inward rectifier current (IK1) generated by Kir2.1 homotetramers (IKir2.1) and thus, exhibit pro- and/or antiarrhythmic effects particularly at the ventricular level. To test this hypothesis, we analysed the effects of propafenone, atenolol, dronedarone, and timolol on Kir2.x channels.
  
  
  RESULTS
  Currents were recorded with the patch-clamp technique using whole-cell, inside-out, and cell-attached configurations. Propafenone (0.1 nM-1 µM) did not modify either IK1 recorded in human right atrial myocytes or the current generated by homo- or heterotetramers of Kir2.2 and 2.3 channels recorded in transiently transfected Chinese hamster ovary cells. On the other hand, propafenone increased IKir2.1 (EC50 = 12.0 ± 3.0 nM) as a consequence of its interaction with Cys311, an effect which decreased inward rectification of the current. Propafenone significantly increased mean open time and opening frequency at all the voltages tested, resulting in a significant increase of the mean open probability of the channel. Timolol, which interacted with Cys311, was also able to increase IKir2.1. On the contrary, neither atenolol nor dronedarone modified IKir2.1. Molecular modelling of the Kir2.1-drugs interaction allowed identification of the pharmacophore of drugs that increase IKir2.1.
  
  
  CONCLUSIONS
  Kir2.1 channels exhibit a binding site determined by Cys311 that is responsible for drug-induced IKir2.1 increase. Drug binding decreases channel affinity for polyamines and current rectification, and can be a mechanism of drug-induced pro- and antiarrhythmic effects not considered until now.
authors.affiliation: Department of Pharmacology, School of Medicine, Universidad Complutense, Madrid 28040, Spain.
authors.forename: Ricardo
authors.initials: R
authors.lastname: Gómez
authors.affiliation: Department of Pharmacology, School of Medicine, Universidad Complutense, Madrid 28040, Spain Instituto de Investigación Sanitaria Gregorio Marañón, School of Medicine, Universidad Complutense, Madrid 28040, Spain rcaballero@med.ucm.es.
authors.forename: Ricardo
authors.initials: R
authors.lastname: Caballero
authors.affiliation: Department of Pharmacology, School of Medicine, Universidad Complutense, Madrid 28040, Spain Instituto de Investigación Sanitaria Hospital Clínico San Carlos, School of Medicine, Universidad Complutense, Madrid, Spain.
authors.forename: Adriana
authors.initials: A
authors.lastname: Barana
authors.affiliation: Department of Pharmacology, School of Medicine, Universidad Complutense, Madrid 28040, Spain Instituto de Investigación Sanitaria Gregorio Marañón, School of Medicine, Universidad Complutense, Madrid 28040, Spain.
authors.forename: Irene
authors.initials: I
authors.lastname: Amorós
authors.affiliation: Department of Pharmacology, School of Medicine, Universidad Complutense, Madrid 28040, Spain.
authors.forename: Sue-Haida
authors.initials: SH
authors.lastname: De Palm
authors.affiliation: Department of Pharmacology, School of Medicine, Universidad Complutense, Madrid 28040, Spain Instituto de Investigación Sanitaria Gregorio Marañón, School of Medicine, Universidad Complutense, Madrid 28040, Spain.
authors.forename: Marcos
authors.initials: M
authors.lastname: Matamoros
authors.affiliation: Department of Pharmacology, School of Medicine, Universidad Complutense, Madrid 28040, Spain Instituto de Investigación Sanitaria Gregorio Marañón, School of Medicine, Universidad Complutense, Madrid 28040, Spain.
authors.forename: Mercedes
authors.initials: M
authors.lastname: Núñez
authors.affiliation: Department of Pharmacology, School of Medicine, Universidad Complutense, Madrid 28040, Spain Instituto de Investigación Sanitaria Hospital Clínico San Carlos, School of Medicine, Universidad Complutense, Madrid, Spain.
authors.forename: Marta
authors.initials: M
authors.lastname: Pérez-Hernández
authors.affiliation: Department of Organic Chemistry, School of Pharmacy, Universidad de Alcalá, Alcalá de Henares, Spain.
authors.forename: Isabel
authors.initials: I
authors.lastname: Iriepa
authors.affiliation: Department of Pharmacology, School of Medicine, Universidad Complutense, Madrid 28040, Spain Instituto de Investigación Sanitaria Hospital Clínico San Carlos, School of Medicine, Universidad Complutense, Madrid, Spain.
authors.forename: Juan
authors.initials: J
authors.lastname: Tamargo
authors.affiliation: Department of Pharmacology, School of Medicine, Universidad Complutense, Madrid 28040, Spain Instituto de Investigación Sanitaria Gregorio Marañón, School of Medicine, Universidad Complutense, Madrid 28040, Spain.
authors.forename: Eva
authors.initials: E
authors.lastname: Delpón
mesh_terms: D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology* / Q000633:toxicity; D001145:Arrhythmias, Cardiac / Q000139:chemically induced / Q000378:metabolism / Q000503:physiopathology; D001665:Binding Sites; D016466:CHO Cells; D003412:Cricetulus; D003545:Cysteine; D004305:Dose-Response Relationship, Drug; D006168:Guinea Pigs; D006339:Heart Rate / Q000187:drug effects*; D006801:Humans; D015640:Ion Channel Gating / Q000187:drug effects*; D008564:Membrane Potentials; D049990:Membrane Transport Modulators / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology* / Q000633:toxicity; D062105:Molecular Docking Simulation; D015394:Molecular Structure; D032383:Myocytes, Cardiac / Q000187:drug effects* / Q000378:metabolism; D024661:Potassium Channels, Inwardly Rectifying / Q000819:agonists* / Q000235:genetics / Q000378:metabolism; D011405:Propafenone / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology* / Q000633:toxicity; D011485:Protein Binding; D015398:Signal Transduction; D013329:Structure-Activity Relationship; D013997:Time Factors; D014162:Transfection
chemical_list: D000889:Anti-Arrhythmia Agents; C489457:KCNJ2 protein, human; D049990:Membrane Transport Modulators; D024661:Potassium Channels, Inwardly Rectifying; D011405:Propafenone; D003545:Cysteine
keywords: Atenolol; Dronedarone; IK1; Inward rectifier channels; Propafenone