title: Selective expression in carotid body type I cells of a single splice variant of the large conductance calcium- and voltage-activated potassium channel confers regulation by AMP-activated protein kinase.
abstract: Inhibition of large conductance calcium-activated potassium (BKCa) channels mediates, in part, oxygen sensing by carotid body type I cells. However, BKCa channels remain active in cells that do not serve to monitor oxygen supply. Using a novel, bacterially derived AMP-activated protein kinase (AMPK), we show that AMPK phosphorylates and inhibits BKCa channels in a splice variant-specific manner. Inclusion of the stress-regulated exon within BKCa channel α subunits increased the stoichiometry of phosphorylation by AMPK when compared with channels lacking this exon. Surprisingly, however, the increased phosphorylation conferred by the stress-regulated exon abolished BKCa channel inhibition by AMPK. Point mutation of a single serine (Ser-657) within this exon reduced channel phosphorylation and restored channel inhibition by AMPK. Significantly, RT-PCR showed that rat carotid body type I cells express only the variant of BKCa that lacks the stress-regulated exon, and intracellular dialysis of bacterially expressed AMPK markedly attenuated BKCa currents in these cells. Conditional regulation of BKCa channel splice variants by AMPK may therefore determine the response of carotid body type I cells to hypoxia.
authors.affiliation: College of Life Sciences, University of Dundee, Dow Street, Dundee DD1 5EH, United Kingdom.
authors.forename: Fiona A
authors.initials: FA
authors.lastname: Ross
authors.forename: J Nicole
authors.initials: JN
authors.lastname: Rafferty
authors.forename: Mark L
authors.initials: ML
authors.lastname: Dallas
authors.forename: Oluseye
authors.initials: O
authors.lastname: Ogunbayo
authors.forename: Naoko
authors.initials: N
authors.lastname: Ikematsu
authors.forename: Heather
authors.initials: H
authors.lastname: McClafferty
authors.forename: Lijun
authors.initials: L
authors.lastname: Tian
authors.forename: Helene
authors.initials: H
authors.lastname: Widmer
authors.forename: Iain C M
authors.initials: IC
authors.lastname: Rowe
authors.forename: Christopher N
authors.initials: CN
authors.lastname: Wyatt
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Shipston
authors.forename: Chris
authors.initials: C
authors.lastname: Peers
authors.forename: D Grahame
authors.initials: DG
authors.lastname: Hardie
authors.forename: A Mark
authors.initials: AM
authors.lastname: Evans
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D000831:Animals, Newborn; D002344:Carotid Body / Q000378:metabolism*; D004594:Electrophysiology; D057809:HEK293 Cells; D006801:Humans; D051036:Large-Conductance Calcium-Activated Potassium Channels / Q000235:genetics / Q000378:metabolism*; D008099:Liver / Q000378:metabolism; D051379:Mice; D010766:Phosphorylation; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D051036:Large-Conductance Calcium-Activated Potassium Channels; D020033:Protein Isoforms; D055372:AMP-Activated Protein Kinases