Molecular basis and function of voltage-gated K+ channels in pulmonary arterial smooth muscle cells.
K(+)-channel activity-mediated alteration of the membrane potential and cytoplasmic free Ca2+ concentration ([Ca2+]cyt) is a pivotal mechanism in controlling pulmonary vasomotor tone. By using combined approaches of patch clamp, imaging fluorescent microscopy, and molecular biology, we examined the electrophysiological properties of K+ channels and the role of different K+ currents in regulating [Ca2+]cyt and explored the molecular identification of voltage-gated K+ (KV)- and Ca(2+)-activated K+ (KCa)-channel genes expressed in pulmonary arterial smooth muscle cells (PASMC). Two kinetically distinct KV currents [IK(V)], a rapidly inactivating (A-type) and a noninactivating delayed rectifier, as well as a slowly activated KCa current [IK(Ca)] were identified. IK(V) was reversibly inhibited by 4-aminopyridine (5 mM), whereas IK(Ca) was significantly inhibited by charybdotoxin (10-20 nM). K+ channels are composed of pore-forming alpha-subunits and auxiliary beta-subunits. Five KV-channel alpha-subunit genes from the Shaker subfamily (KV1.1, KV1.2, KV1.4, KV1.5, and KV1.6), a KV-channel alpha-subunit gene from the Shab subfamily (KV2.1), a KV-channel modulatory alpha-subunit (KV9.3), and a KCa-channel alpha-subunit gene (rSlo), as well as three KV-channel beta-subunit genes (KV beta 1.1, KV beta 2, and KV beta 3) are expressed in PASMC. The data suggest that 1) native K+ channels in PASMC are encoded by multiple genes; 2) the delayed rectifier IK(V) may be generated by the KV1.1, KV1.2, KV1.5, KV1.6, KV2.1, and/or KV2.1/KV9.3 channels; 3) the A-type IK(V) may be generated by the KV1.4 channel and/or the delayed rectifier KV channels (KV1 subfamily) associated with beta-subunits; and 4) the IK(Ca) may be generated by the rSlo gene product. The function of the KV channels plays an important role in the regulation of membrane potential and [Ca2+]cyt in PASMC.
Yuan
X J
XJ
Department of Medicine, University of Maryland School of Medicine, Baltimore 21201, USA.
Wang
J
J
Juhaszova
M
M
Golovina
V A
VA
Rubin
L J
LJ
D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000502:physiology; D002478:Cells, Cultured; D003593:Cytoplasm / Q000378:metabolism; D051668:Delayed Rectifier Potassium Channels; D004594:Electrophysiology; D015151:Immunoblotting; D015640:Ion Channel Gating / Q000502:physiology*; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism*; D009994:Osmolar Concentration; D015221:Potassium Channels / Q000235:genetics / Q000502:physiology*; D024642:Potassium Channels, Voltage-Gated; D011651:Pulmonary Artery / Q000166:cytology / Q000378:metabolism*; D051381:Rats; D051669:Shab Potassium Channels; D014158:Transcription, Genetic / Q000502:physiology
D051668:Delayed Rectifier Potassium Channels; C496991:Kcnb1 protein, rat; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D051669:Shab Potassium Channels; D002118:Calcium