title: BK channels in rat and human pulmonary smooth muscle cells are BKα-β1functional complexes lacking the oxygen-sensitive stress axis regulated exon insert.
abstract: A loss of K+efflux in pulmonary arterial smooth muscle cells (PASMCs) contributes to abnormal vasoconstriction and PASMC proliferation during pulmonary hypertension (PH). Activation of high-conductance Ca2+-activated (BK) channels represents a therapeutic strategy to restore K+efflux to the affected PASMCs. However, the properties of BK channels in PASMCs-including sensitivity to BK channel openers (BKCOs)-are poorly defined. The goal of this study was to compare the properties of BK channels between PASMCs of normoxic (N) and chronic hypoxic (CH) rats and then explore key findings in human PASMCs. Polymerase chain reaction results revealed that 94.3% of transcripts encoding BKα pore proteins in PASMCs from N rats represent splice variants lacking the stress axis regulated exon insert, which confers oxygen sensitivity. Subsequent patch-clamp recordings from inside-out (I-O) patches confirmed a dense population of BK channels insensitive to hypoxia. The BK channels were highly activated by intracellular Ca2+and the BKCO lithocholate; these responses require BKα-β1subunit coupling. PASMCs of CH rats with established PH exhibited a profound overabundance of the dominant oxygen-insensitive BKα variant. Importantly, human BK (hBK) channels in PASMCs from human donor lungs also represented the oxygen-insensitive BKα variant activated by BKCOs. The hBK channels showed significantly enhanced Ca2+sensitivity compared with rat BK channels. We conclude that rat BK and hBK channels in PASMCs are oxygen-insensitive BKα-β1complexes highly sensitive to Ca2+and the BKCO lithocholate. BK channels are overexpressed in PASMCs of a rat model of PH and may provide an abundant target for BKCOs designed to restore K+efflux.
authors.affiliation: Department of Pharmacology and Toxicology, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA.
authors.forename: Neil D
authors.initials: ND
authors.lastname: Detweiler
authors.affiliation: Department of Pharmacology and Toxicology, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA.
authors.forename: Li
authors.initials: L
authors.lastname: Song
authors.affiliation: Department of Pharmacology and Toxicology, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA.
authors.forename: Samantha J
authors.initials: SJ
authors.lastname: McClenahan
authors.affiliation: Department of Pharmacology and Toxicology, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA.
authors.forename: Rachel J
authors.initials: RJ
authors.lastname: Versluis
authors.affiliation: Department of Anesthesiology, School of Medicine, Vanderbilt University, Nashville, Tennessee, USA.
authors.forename: Sujay V
authors.initials: SV
authors.lastname: Kharade
authors.affiliation: Department of Physiology and Biophysics and Department of Pediatrics, College of Medicine, University of Arkansas for Medical Sciences, Arkansas Children's Hospital Research Institute, Little Rock, Arkansas, USA.
authors.forename: Richard C
authors.initials: RC
authors.lastname: Kurten
authors.affiliation: Department of Pharmacology and Toxicology, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA.
authors.forename: Sung W
authors.initials: SW
authors.lastname: Rhee
authors.affiliation: Department of Pharmacology and Toxicology, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA.
authors.forename: Nancy J
authors.initials: NJ
authors.lastname: Rusch
keywords: lithocholate; oxygen sensitivity; pulmonary hypertension; stress axis regulated exon