Function of Kv1.5 channels and genetic variations of KCNA5 in patients with idiopathic pulmonary arterial hypertension.
The pore-forming alpha-subunit, Kv1.5, forms functional voltage-gated K(+) (Kv) channels in human pulmonary artery smooth muscle cells (PASMC) and plays an important role in regulating membrane potential, vascular tone, and PASMC proliferation and apoptosis. Inhibited Kv channel expression and function have been implicated in PASMC from patients with idiopathic pulmonary arterial hypertension (IPAH). Here, we report that overexpression of the Kv1.5 channel gene (KCNA5) in human PASMC and other cell lines produced a 15-pS single channel current and a large whole cell current that was sensitive to 4-aminopyridine. Extracellular application of nicotine, bepridil, correolide, and endothelin-1 (ET-1) all significantly and reversibly reduced the Kv1.5 currents, while nicotine and bepridil also accelerated the inactivation kinetics of the currents. Furthermore, we sequenced KCNA5 from IPAH patients and identified 17 single-nucleotide polymorphisms (SNPs); 7 are novel SNPs. There are 12 SNPs in the upstream 5' region, 2 of which may alter transcription factor binding sites in the promoter, 2 nonsynonymous SNPs in the coding region, 2 SNPs in the 3'-untranslated region, and 1 SNP in the 3'-flanking region. Two SNPs may correlate with the nitric oxide-mediated decrease in pulmonary arterial pressure. Allele frequency of two other SNPs in patients with a history of fenfluramine and phentermine use was significantly different from patients who have never taken the anorexigens. These results suggest that 1) Kv1.5 channels are modulated by various agonists (e.g., nicotine and ET-1); 2) novel SNPs in KCNA5 are present in IPAH patients; and 3) SNPs in the promoter and translated regions of KCNA5 may underlie the altered expression and/or function of Kv1.5 channels in PASMC from IPAH patients.
Remillard
Carmelle V
CV
Department of Medicine, University of California--San Diego, 9500 Gilman Dr., MC 0725, La Jolla, CA 92093-0725, USA.
Tigno
Donna D
DD
Platoshyn
Oleksandr
O
Burg
Elyssa D
ED
Brevnova
Elena E
EE
Conger
Diane
D
Nicholson
Ann
A
Rana
Brinda K
BK
Channick
Richard N
RN
Rubin
Lewis J
LJ
O'connor
Daniel T
DT
Yuan
Jason X-J
JX
D000280:Administration, Inhalation; D000595:Amino Acid Sequence; D000818:Animals; D000959:Antihypertensive Agents / Q000008:administration & dosage; D001483:Base Sequence; D019556:COS Cells; D002478:Cells, Cultured; D002522:Chlorocebus aethiops; D005260:Female; D005787:Gene Frequency; D005838:Genotype; D006801:Humans; D006976:Hypertension, Pulmonary / Q000188:drug therapy / Q000235:genetics* / Q000378:metabolism; D051666:Kv1.5 Potassium Channel / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism*; D008297:Male; D008564:Membrane Potentials; D008875:Middle Aged; D008969:Molecular Sequence Data; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000378:metabolism*; D009569:Nitric Oxide / Q000008:administration & dosage; D018408:Patch-Clamp Techniques; D010641:Phenotype; D020641:Polymorphism, Single Nucleotide; D011188:Potassium / Q000378:metabolism; D026902:Potassium Channel Blockers / Q000494:pharmacology; D011651:Pulmonary Artery / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D014162:Transfection; D016896:Treatment Outcome
D000959:Antihypertensive Agents; C496981:KCNA5 protein, human; D051666:Kv1.5 Potassium Channel; D026902:Potassium Channel Blockers; D009569:Nitric Oxide; D011188:Potassium