title: Hypoxia-inducible factor-1α regulates KCNMB1 expression in human pulmonary artery smooth muscle cells.
abstract: Previously, we observed that hypoxia increases the expression of the β1-subunit (KCNMB1) of the calcium-sensitive potassium channel (BK(Ca)). Herein, we elucidate the mechanism whereby hypoxia increases KCNMB1 expression in human pulmonary artery smooth muscle cells (hPASMC). In response to hypoxia, the expression of both the transcription factor hypoxia-inducible factor 1-α (HIF-1α) and KCNMB1 are increased. Knockdown of HIF-1α using a shRNA plasmid blocked the hypoxic induction of KCNMB1 expression. Chromatin immunoprecipitation (ChIP) demonstrated HIF-1α binding to three discrete regions of the human KCNMB1 promoter known to contain hypoxia response elements (HREs). A KCNMB1 promoter reporter assay combined with site-directed mutagenesis identified two adjacent HREs located between -3,540 bp and -3,311 bp that are essential for the hypoxic induction of KCNMB1 promoter activity. Furthermore, additional ChIP assays demonstrated recruitment of the HIF-1α transcriptional coactivator, p300, to this same promoter region. Treatment of hPASMC with the histone deacetylase inhibitor, trichostatin, prolonged the increase in KCNMB1 observed with hypoxia, suggesting that alterations in chromatin remodeling function to limit the hypoxic induction of KCNMB1. Finally, KCNMB1 knockdown potentiated the hypoxia-induced increase in cytosolic calcium in hPASMC, highlighting the contribution of the β1-subunit in modulating vascular SMC tone in response to acute hypoxia. In conclusion, HIF-1α increases KCNMB1 expression in response to hypoxia in hPASMC by binding to two HREs located at -3,540 to -3,311 of the KCNMB1 promoter. We speculate that selective modulation of KCNMB1 expression may serve as a novel therapeutic approach to address diseases characterized by an increase in vascular tone.
authors: Ctr. for Excellence in Pulmonary Biology, Division of Pediatric Pulmonary, Asthma and Critical Care Medicine, Stanford Univ. Medical School Medicine, Stanford, CA 94305, USA.
authors: Yong-Tae
authors: YT
authors: Ahn
authors: Yu-Mee
authors: YM
authors: Kim
authors: Eloa
authors: E
authors: Adams
authors: Shu-Chen
authors: SC
authors: Lyu
authors: Cristina M
authors: CM
authors: Alvira
authors: David N
authors: DN
authors: Cornfield
mesh_terms: D001483:Base Sequence; D002118:Calcium / Q000378:metabolism; D015687:Cell Hypoxia; D002478:Cells, Cultured; D005786:Gene Expression Regulation; D006655:Histone Deacetylases / Q000378:metabolism; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D007223:Infant; D051038:Large-Conductance Calcium-Activated Potassium Channel beta Subunits / Q000235:genetics / Q000378:metabolism*; D009131:Muscle, Smooth, Vascular / Q000166:cytology*; D032389:Myocytes, Smooth Muscle / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D011651:Pulmonary Artery / Q000166:cytology*; D020218:Response Elements; D014158:Transcription, Genetic
chemical_list: C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; C531905:KCNMB1 protein, human; D051038:Large-Conductance Calcium-Activated Potassium Channel beta Subunits; D006655:Histone Deacetylases; D002118:Calcium