Flecainide increases Kir2.1 currents by interacting with cysteine 311, decreasing the polyamine-induced rectification.
Both increase and decrease of cardiac inward rectifier current (I(K1)) are associated with severe cardiac arrhythmias. Flecainide, a widely used antiarrhythmic drug, exhibits ventricular proarrhythmic effects while effectively controlling ventricular arrhythmias associated with mutations in the gene encoding Kir2.1 channels that decrease I(K1) (Andersen syndrome). Here we characterize the electrophysiological and molecular basis of the flecainide-induced increase of the current generated by Kir2.1 channels (I(Kir2.1)) and I(K1) recorded in ventricular myocytes. Flecainide increases outward I(Kir2.1) generated by homotetrameric Kir2.1 channels by decreasing their affinity for intracellular polyamines, which reduces the inward rectification of the current. Flecainide interacts with the HI loop of the cytoplasmic domain of the channel, Cys311 being critical for the effect. This explains why flecainide does not increase I(Kir2.2) and I(Kir2.3), because Kir2.2 and Kir2.3 channels do not exhibit a Cys residue at the equivalent position. We further show that incubation with flecainide increases expression of functional Kir2.1 channels in the membrane, an effect also determined by Cys311. Indeed, flecainide pharmacologically rescues R67W, but not R218W, channel mutations found in Andersen syndrome patients. Moreover, our findings provide noteworthy clues about the structural determinants of the C terminus cytoplasmic domain of Kir2.1 channels involved in the control of gating and rectification.
Caballero
Ricardo
R
Department of Pharmacology, School of Medicine, Universidad Complutense, 28040 Madrid, Spain.
Dolz-Gaitón
Pablo
P
Gómez
Ricardo
R
Amorós
Irene
I
Barana
Adriana
A
González de la Fuente
Marta
M
Osuna
Lourdes
L
Duarte
Juan
J
López-Izquierdo
Angelica
A
Moraleda
Ignacio
I
Gálvez
Enrique
E
Sánchez-Chapula
José Antonio
JA
Tamargo
Juan
J
Delpón
Eva
E
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000378:metabolism / Q000494:pharmacology; D001667:Binding, Competitive; D002478:Cells, Cultured; D003545:Cysteine / Q000235:genetics / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D005424:Flecainide / Q000378:metabolism / Q000494:pharmacology*; D006168:Guinea Pigs; D006801:Humans; D015640:Ion Channel Gating / Q000187:drug effects* / Q000502:physiology; D008564:Membrane Potentials / Q000187:drug effects; D008958:Models, Molecular; D008969:Molecular Sequence Data; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D018408:Patch-Clamp Techniques; D011073:Polyamines / Q000378:metabolism / Q000494:pharmacology; D024661:Potassium Channels, Inwardly Rectifying / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D055503:Protein Multimerization; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D014162:Transfection
D000889:Anti-Arrhythmia Agents; C489461:Kir2.1 channel; D011073:Polyamines; D024661:Potassium Channels, Inwardly Rectifying; D003545:Cysteine; D005424:Flecainide