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Current Topics in Biochemical Research   Volumes    Volume 10  Issue 2
Abstract
The large-conductance Ca2+-activated K+ channel: A target for the modulators of estrogen receptors
Sheng-Nan Wu, Bing-Shuo Chen, Chih-Li Hsu, Tai-I Hsu
Pages: 93 - 101
Number of pages: 9
Current Topics in Biochemical Research
Volume 10  Issue 2

Copyright © 2008 Research Trends. All rights reserved

ABSTRACT
 
The large-conductance Ca2+-activated K+ (BKCa) channels, which are formed by α-subunit tetramers, are encoded by a nearly ubiquitous, alternatively spliced gene, Slo1 (KCa1.1 or KCNMA1). They are distinguished from other K+ channels in that their activation is under dual control, i.e., allosterically switched on either by membrane depolarization or by increased intracellular Ca2+. Recent studies suggested that in addition to their binding to estrogen receptors (ERs), these modulators may have direct effects on the activity of these channels in a non-genomic pathway. Disgenin (3-β-hydroxy-5-spirostene), extracted from the root of wild yam, can antagonize the binding of 17β-estradiol to ERs. It can elevate intracellular Ca2+, thereby stimulating BKCa channels in human cortical (HCN-1A) neurons. Quercetin, known to affect ER-β receptors, can increase BKCa-channel activity via the increase of L-type Ca2+ current. Rottlerin, an activator of protein kinase C-δ, can directly stimulate BKCa-channel activity in a time- and concentration-dependent fashion. PPT (4,4’,4”-(4-propyl)-[1H]-pyrazole-1,3,5-triyl)tirs-phenol) and DPN (2,3-bis(4-hydroxyphenyl)-propionitril) are ER agonists selective for ER-α and ER-β, respectively. In human cardiac fibroblasts, PPT or DPN applied to the intracellular face of the membrane enhanced the activity of BKCa channels with no change in single-channel conductance. PPT can potenitate membrane stretch-induced activation of BKCa channels in alveolar epithelial A549 cells. Taken together, the regulation by these ERs modulators of BKCa-channel activity can be due to the mechanisms unlinked to their binding to ERs. The increase by these compounds of BKCa-activity channel may unravel novel pharmacological properties contribute to cellular function.
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