Nitric oxide blocks hKv1.5 channels by S-nitrosylation and by a cyclic GMP-dependent mechanism.
OBJECTIVE
This study was undertaken to analyze whether nitric oxide (NO) modulates the human potassium channel hKv1.5, which generates the ultrarapid delayed rectifier current (IKur) that determines the height and duration of atrial action potentials.


METHODS
Currents were recorded using the whole-cell patch-clamp in Ltk- cells expressing hKv1.5 channels.


RESULTS
The NO donors (+/-)-S-Nitroso-N-acetylpenicillamine (SNAP) and sodium nitroprusside, a NO solution, and l-Arginine inhibited hKv1.5 currents in a concentration-dependent manner. The NO concentration in the cell chamber was monitored using a sensor, and the IC50 for NO-induced hKv1.5 block was 340+/-70 nM. SNAP also inhibited the IKur recorded in mouse ventricular myocytes. The NO effects were partially mediated by the activation of the soluble guanylate cyclase (sGC)/cGMP/cGMP-dependent protein kinase (PKG) pathway. The biotin-switch assay demonstrated the presence of S-nitrosylated cysteines (Cys) on the hKv1.5 protein in SNAP-treated cells. Molecular modeling of hKv1.5 channel structure suggests that S-nitrosylation of Cys331 (segment 2, S2) and Cys346 (S2) would be stabilized by hydrogen bridge bonds with Ile262 (S1) and Arg342 (S2), respectively.


CONCLUSIONS
NO inhibits the hKv1.5 current by a cGMP-dependent mechanism and by the S-nitrosylation of the hKv1.5 protein, an effect that contributes to shaping the human atrial action potentials.
Núñez
Lucía
L
Department of Pharmacology, School of Medicine, Universidad Complutense, 28040 Madrid, Spain.
Vaquero
Miguel
M
Gómez
Ricardo
R
Caballero
Ricardo
R
Mateos-Cáceres
Petra
P
Macaya
Carlos
C
Iriepa
Isabel
I
Gálvez
Enrique
E
López-Farré
Antonio
A
Tamargo
Juan
J
Delpón
Eva
E
D000704:Analysis of Variance; D000818:Animals; D016466:CHO Cells; D002478:Cells, Cultured; D006224:Cricetinae; D003412:Cricetulus; D006152:Cyclic GMP / Q000378:metabolism*; D017869:Cyclic GMP-Dependent Protein Kinases / Q000378:metabolism; D051668:Delayed Rectifier Potassium Channels / Q000378:metabolism; D005347:Fibroblasts / Q000378:metabolism; D006162:Guanylate Cyclase / Q000032:analysis / Q000378:metabolism; D006801:Humans; D015640:Ion Channel Gating / Q000187:drug effects*; D051666:Kv1.5 Potassium Channel / Q000737:chemistry / Q000187:drug effects* / Q000235:genetics; D051379:Mice; D008958:Models, Molecular; D009569:Nitric Oxide / Q000494:pharmacology*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000032:analysis / Q000378:metabolism; D009599:Nitroprusside / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D026423:S-Nitroso-N-Acetylpenicillamine / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects*
D051668:Delayed Rectifier Potassium Channels; D051666:Kv1.5 Potassium Channel; D020030:Nitric Oxide Donors; D009599:Nitroprusside; D009569:Nitric Oxide; D026423:S-Nitroso-N-Acetylpenicillamine; D019001:Nitric Oxide Synthase; D017869:Cyclic GMP-Dependent Protein Kinases; D006162:Guanylate Cyclase; D006152:Cyclic GMP