Promoter cloning and characterization of the rabbit BK channel β1 subunit gene

Zhang, Xiaoyong; Wang, Sha; Zhang, Yan; Zhang, Yingqi; Wan, Yi; Zhang, Bin; Wang, Lifeng; Chai, Yubo; Wei, Jing-Guo

doi:10.1016/j.gene.2009.03.001

Cited by 3 publications

(2 citation statements)

References 38 publications

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“…Despite the reporting of several MEF2 and E-box elements in the KCNMB1 promoter (22), there has been virtually no information as to how this SMCrestricted gene is regulated transcriptionally either in vitro or in vivo. In fact, the only published report of authentic KCNMB1 promoter activity is a recent one suggesting a role for Sp1 in the regulation of rabbit Kcnmb1 (63). Comparative sequence analysis, however, proves that the Sp1 binding site is not conserved in human and mouse orthologous promoters.…”

Section: Discussionmentioning

confidence: 95%

The Smooth Muscle Cell-restricted KCNMB1 Ion Channel Subunit Is a Direct Transcriptional Target of Serum Response Factor and Myocardin

Long

Tharp

Georger

et al. 2009

Journal of Biological Chemistry

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Large conductance calcium-activated potassium (MaxiK) channels play a pivotal role in maintaining normal arterial tone by regulating the excitation-contraction coupling process. MaxiK channels comprise ␣ and ␤ subunits encoded by Kcnma and the cell-restricted Kcnmb genes, respectively. Although the functionality of MaxiK channel subunits has been well studied, the molecular regulation of their transcription and modulation in smooth muscle cells (SMCs) is incomplete. Using several model systems, we demonstrate down-regulation of Kcnmb1 mRNA upon SMC phenotypic modulation in vitro and in vivo. As part of a broad effort to define all functional CArG elements in the genome (i.e. the CArGome), we discovered two conserved CArG boxes located in the proximal promoter and first intron of the human KCNMB1 gene. Gel shift and chromatin immunoprecipitation assays confirmed serum response factor (SRF) binding to both CArG elements. A luciferase assay showed myocardin (MYOCD)-mediated transactivation of the KCNMB1 promoter in a CArG element-dependent manner. In vivo analysis of the human KCNMB1 promoter disclosed activity in embryonic heart and aortic SMCs; mutation of both conserved CArG elements completely abolished in vivo promoter activity. Forced expression of MYOCD increased Kcnmb1 expression in a variety of rodent and human non-SMC lines with no effect on expression of the Kcnma1 subunit. Conversely, knockdown of Srf resulted in decreases of endogenous Kcnmb1. Functional studies demonstrated MYOCD-induced, iberiotoxin-sensitive potassium currents in porcine coronary SMCs. These results reveal the first ion channel subunit as a direct target of SRF-MYOCD transactivation, providing further insight into the role of MYOCD as a master regulator of the SMC contractile phenotype. Smooth muscle cells (SMCs)2 are of crucial importance in maintaining normal structural and contractile integrity of various organs and tissues throughout the vertebrate body. Unlike skeletal and cardiac muscle cells, which largely undergo irreversible terminal differentiation, SMCs have the inherent ability to alter their differentiated state in response to diverse stimulatory cues. This process of SMC phenotypic modulation is a hallmark of several human pathological conditions, including vascular occlusive disease, asthma, intestinal and bladder obstruction, and Alzheimer disease. SMC phenotypic modulation is often defined in terms of unique molecular signatures of gene expression involved with contraction and cytoskeletal architecture as well as extracellular matrix remodeling (1, 2). For example, vascular SMCs display reduced levels of contractile filaments following injury to the vessel wall, adopting the so-called synthetic phenotype characterized by an overabundance of rough endoplasmic reticulum (3). On the other hand, recent studies have shown an exaggerated SMC contractile phenotype thought to contribute to disease progression (4, 5).The majority of SMC-restricted genes contain one or more conserved CArG elements that bind the widely express...

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Section: Discussionmentioning

confidence: 95%

The Smooth Muscle Cell-restricted KCNMB1 Ion Channel Subunit Is a Direct Transcriptional Target of Serum Response Factor and Myocardin

Long

Tharp

Georger

et al. 2009

Journal of Biological Chemistry

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“…The importance of Sp1 in the regulation of expression of KCNMB1 is also demonstrated in nonvascular smooth muscle. Overexpression of Sp1 in smooth muscle cells of rabbit sphincter of Oddi enhances KCNMB1 promoter activity [ 254 ].…”

Section: K Ca Channels and The Uteroplacental Circ...mentioning

confidence: 99%

Ca2+-Activated K+ Channels and the Regulation of the Uteroplacental Circulation

Zhang

2023

IJMS

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Adequate uteroplacental blood supply is essential for the development and growth of the placenta and fetus during pregnancy. Aberrant uteroplacental perfusion is associated with pregnancy complications such as preeclampsia, fetal growth restriction (FGR), and gestational diabetes. The regulation of uteroplacental blood flow is thus vital to the well-being of the mother and fetus. Ca2+-activated K+ (KCa) channels of small, intermediate, and large conductance participate in setting and regulating the resting membrane potential of vascular smooth muscle cells (VSMCs) and endothelial cells (ECs) and play a critical role in controlling vascular tone and blood pressure. KCa channels are important mediators of estrogen/pregnancy-induced adaptive changes in the uteroplacental circulation. Activation of the channels hyperpolarizes uteroplacental VSMCs/ECs, leading to attenuated vascular tone, blunted vasopressor responses, and increased uteroplacental blood flow. However, the regulation of uteroplacental vascular function by KCa channels is compromised in pregnancy complications. This review intends to provide a comprehensive overview of roles of KCa channels in the regulation of the uteroplacental circulation under physiological and pathophysiological conditions.

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Large T-antigen up-regulates Kv4.3 K+ channels through Sp1, and Kv4.3 K+ channels contribute to cell apoptosis and necrosis through activation of calcium/calmodulin-dependent protein kinase II

Zhang

Sheng

et al. 2012

Biochemical Journal

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Down-regulation of Kv4.3 K⁺ channels commonly occurs in multiple diseases, but the understanding of the regulation of Kv4.3 K⁺ channels and the role of Kv4.3 K⁺ channels in pathological conditions are limited. HEK (human embryonic kidney)-293T cells are derived from HEK-293 cells which are transformed by expression of the large T-antigen. In the present study, by comparing HEK-293 and HEK-293T cells, we find that HEK-293T cells express more Kv4.3 K⁺ channels and more transcription factor Sp1 (specificity protein 1) than HEK-293 cells. Inhibition of Sp1 with Sp1 decoy oligonucleotide reduces Kv4.3 K⁺ channel expression in HEK-293T cells. Transfection of pN3-Sp1FL vector increases Sp1 protein expression and results in increased Kv4.3 K⁺ expression in HEK-293 cells. Since the ultimate determinant of the phenotype difference between HEK-293 and HEK-293T cells is the large T-antigen, we conclude that the large T-antigen up-regulates Kv4.3 K⁺ channel expression through an increase in Sp1. In both HEK-293 and HEK-293T cells, inhibition of Kv4.3 K⁺ channels with 4-AP (4-aminopyridine) or Kv4.3 small interfering RNA induces cell apoptosis and necrosis, which are completely rescued by the specific CaMKII (calcium/calmodulin-dependent protein kinase II) inhibitor KN-93, suggesting that Kv4.3 K⁺ channels contribute to cell apoptosis and necrosis through CaMKII activation. In summary, we establish: (i) the HEK-293 and HEK-293T cell model for Kv4.3 K⁺ channel study; (ii) that large T-antigen up-regulates Kv4.3 K⁺ channels through increasing Sp1 levels; and (iii) that Kv4.3 K⁺ channels contribute to cell apoptosis and necrosis through activating CaMKII. The present study provides deep insights into the mechanism of the regulation of Kv4.3 K⁺ channels and the role of Kv4.3 K⁺ channels in cell death.

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Promoter cloning and characterization of the rabbit BK channel β1 subunit gene

Cited by 3 publications

References 38 publications

The Smooth Muscle Cell-restricted KCNMB1 Ion Channel Subunit Is a Direct Transcriptional Target of Serum Response Factor and Myocardin

The Smooth Muscle Cell-restricted KCNMB1 Ion Channel Subunit Is a Direct Transcriptional Target of Serum Response Factor and Myocardin

Ca2+-Activated K+ Channels and the Regulation of the Uteroplacental Circulation

Large T-antigen up-regulates Kv4.3 K+ channels through Sp1, and Kv4.3 K+ channels contribute to cell apoptosis and necrosis through activation of calcium/calmodulin-dependent protein kinase II

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