Regulation of KCNMA1 transcription by Nrf2 in coronary arterial smooth muscle cells. (March 2020)

• Record Type: Journal Article
• Authors: Sun, Xiaojing; Qian, Ling-Ling; Li, Yong; Pfiefer, Teresa M.; Wang, Xiao-Li; Lee, Hon-Chi; Lu, Tong
• Is Part Of: Journal of molecular and cellular cardiology. Volume 140(2020)
• Page Start: 68
• Page End: 76
• Publication Date: 2020-03
• Subjects: Nrf2 -- KCNMA1 -- KCNMB1 -- Transcriptional regulation -- Vascular smooth muscle cell -- Dimethyl fumarate; Ad adenovirus -- ARE antioxidant response element -- BK channel the large conductance Ca2+-activated K+ channel -- BK-α the pore-forming subunit of BK channel -- BK-β1 the regulatory β1 subunit of BK channel -- DMF dimethyl fumarate -- DMSO dimethyl sulfoxide -- EGFP enhanced green fluorescent protein -- EF ejection fraction -- GFP green fluorescent protein -- IBTX iberiotoxin -- IVS interventricular septum -- KCNMA1 the gene encoding BK-α -- KCNMB1 the gene encoding BK-β1 -- Keap1 the Kelch-like ECH-associated protein 1 -- KO knockout -- LV left ventricle -- NFAT the nuclear factor of activated T-cells -- nPo single channel open probability -- Nrf2 the nuclear factor erythroid 2-related factor 2 -- RV right ventricle -- SFN sulforaphane -- shRNA short hairpin RNA -- SMC smooth muscle cell -- TEA tetraethylammonium -- UPS the ubiquitin-proteasome system -- WT wild type; Cardiology -- Periodicals; Heart Diseases -- Periodicals; Molecular Biology -- Periodicals; Cardiologie -- Périodiques; Cardiology; Electronic journals; Periodicals; 616.12
• DOI: 10.1016/j.yjmcc.2020.03.001
• Languages: English
• ISSNs: 0022-2828

Abstract

Abstract: The large conductance Ca 2+ -activated K + (BK) channels, composed of the pore-forming α subunits (BK-α, encoded by KCNMA1 gene) and the regulatory β1 subunits (BK-β1, encoded by KCNMB1 gene), play a unique role in the regulation of coronary vascular tone and myocardial perfusion by linking intracellular Ca 2+ homeostasis with excitation-contraction coupling in coronary arterial smooth muscle cells (SMCs). The nuclear factor erythroid 2-related factor 2 (Nrf2) belongs to a member of basic leucine zipper transcription factor family that regulates the expression of antioxidant and detoxification enzymes by binding to the antioxidant response elements (AREs) of these target genes. We have previously reported that vascular BK-β1 protein expression was tightly regulated by Nrf2. However, the molecular mechanism underlying the regulation of BK channel expression by Nrf2, particularly at transcription level, is unknown. In this study, we hypothesized that KCNMA1 and KCNMB1 are the target genes of Nrf2 transcriptional regulation. We found that BK channel protein expression and current density were diminished in freshly isolated coronary arterial SMCs of Nrf2 knockout (KO) mice. However, BK-α mRNA expression was reduced, but not that of BK-β1 mRNA expression, in the arteries of Nrf2 KO mice. Promoter-Nrf2 luciferase reporter assay confirmed that Nrf2 binds to the ARE of KCNMA1 promoter, but not that of KCNMB1 . Adenoviral expression and pharmacological activation of Nrf2 increased BK-α and BK-β1 protein levels and enhanced BK channel activity in coronary arterial SMCs. Hence, our results indicate that Nrf2 is a key determinant of BK channel expression and function in vascular SMCs. Nrf2 facilitates BK-α expression through a direct increase in gene transcription, whereas that on BK-β1 is through a different mechanism. Highlights: The goal of the present study was to investigate the role of Nrf2 in the regulation of coronary arterial BK channel expression and function using Nrf2 KO mice. Genetic ablation of Nrf2 diminished BK channel activity in freshly isolated coronary arterial smooth muscle cells (SMCs) of Nrf2 KO mice. Both RNA and protein expression of BK-α subunits (encoded by KCNMA1 gene) was downregulated in the arteries of Nrf2 KO mice; while only a decrease in the protein but not in the RNA levels of BK-β1 subunits (encoded by KCNMB1 gene) was found. Nrf2 upregulated BK-α expression by direct binding to the ARE motif of KCNMA1 promoter, whereas the effects of Nrf2 on BK-β1 expression was via a different mechanism. Treatment with FDA-approved Nrf2 activators promoted Nrf2 nuclear translocation and enhanced BK channel activity in the coronary arterial SMCs.