title: Molecular composition of 4-aminopyridine-sensitive voltage-gated K(+) channels of vascular smooth muscle.
abstract: Voltage-gated K(+) channels (Kv) play a critical role in regulating arterial tone by modulating the membrane potential of vascular smooth muscle cells. Our previous work demonstrated that the dominant 4-aminopyridine (4-AP)-sensitive, delayed rectifier Kv current of rabbit portal vein (RPV) myocytes demonstrates similar 4-AP sensitivity and biophysical properties to Kv1alpha-containing channels. To identify the molecular constituents underlying the 4-AP-sensitive Kv current of vascular myocytes, we characterized the expression pattern of Kv1alpha subunits and their modulatory Kvbeta subunits in RPV. The mRNAs encoding pore-forming subunits Kv1.2, Kv1.4, and Kv1.5 were detected by reverse transcriptase-polymerase chain reaction (RT-PCR), whereas Kv1.1, Kv1.3, and Kv1.6 transcripts were undetectable. Kvbeta1.1, beta1.2, beta1.3, beta2.1, and beta2.2 messages were expressed, whereas Kvbeta3.1 and beta4 mRNAs were undetected by RT-PCR. Kv1.2, Kv1.4, Kv1.5, Kvbeta1.2, beta1.3, and beta2.1 proteins were detected in RPV by Western blotting and/or immunocytochemistry of freshly isolated myocytes. We provide the first evidence, from coimmunoprecipitation studies, for the formation of heteromultimeric Kv channel complexes composed of Kv1.2, Kv1.5, and Kvbeta1.2 subunits in vascular smooth muscle.
authors.affiliation: Smooth Muscle Research Group, Canadian Institutes of Health Research (CIHR) Group in Regulation of Vascular Contractility, University of Calgary, Alberta, Canada.
authors.forename: K S
authors.initials: KS
authors.lastname: Thorneloe
authors.forename: T T
authors.initials: TT
authors.lastname: Chen
authors.forename: P M
authors.initials: PM
authors.lastname: Kerr
authors.forename: E F
authors.initials: EF
authors.lastname: Grier
authors.forename: B
authors.initials: B
authors.lastname: Horowitz
authors.forename: W C
authors.initials: WC
authors.lastname: Cole
authors.forename: M P
authors.initials: MP
authors.lastname: Walsh
mesh_terms: D015761:4-Aminopyridine / Q000494:pharmacology*; D000818:Animals; D015153:Blotting, Western; D007150:Immunohistochemistry; D051663:Kv1.2 Potassium Channel; D051665:Kv1.4 Potassium Channel; D051666:Kv1.5 Potassium Channel; D009131:Muscle, Smooth, Vascular / Q000378:metabolism*; D011169:Portal Vein / Q000378:metabolism; D026902:Potassium Channel Blockers / Q000494:pharmacology*; D015221:Potassium Channels / Q000737:chemistry* / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D024642:Potassium Channels, Voltage-Gated / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011233:Precipitin Tests; D021122:Protein Subunits; D012333:RNA, Messenger / Q000096:biosynthesis; D011817:Rabbits
chemical_list: D051663:Kv1.2 Potassium Channel; D051665:Kv1.4 Potassium Channel; D051666:Kv1.5 Potassium Channel; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D021122:Protein Subunits; D012333:RNA, Messenger; D015761:4-Aminopyridine