Referenced in: none

Automatically associated channels: Kv7.1

Title: Contribution of KCNQ1 to the regulatory volume decrease in the human mammary epithelial cell line MCF-7.

Authors: Brenna L vanTol, Sergey Missan, Julie Crack, Shasta Moser, William H Baldridge, Paul Linsdell, Elizabeth A Cowley

Journal, date & volume: Am. J. Physiol., Cell Physiol., 2007 Sep , 293, C1010-9

PubMed link: http://www.ncbi.nlm.nih.gov/pubmed/17596298

Abstract
Using the human mammary epithelial cell line MCF-7, we have investigated volume-activated changes in response to hyposmotic stress. Switching MCF-7 cells from an isosmotic to a hyposmotic solution resulted in an initial cell swelling response, followed by a regulatory volume decrease (RVD). This RVD response was inhibited by the nonselective K(+) channel inhibitors Ba(2+), quinine, and tetraethylammonium chloride, implicating K(+) channel activity in this volume-regulatory mechanism. Additional studies using chromonol 293B and XE991 as inhibitors of the KCNQ1 K(+) channel, and also a dominant-negative NH(2)-terminal truncated KCNQ1 isoform, showed complete abolition of the RVD response, suggesting that KCNQ1 plays an important role in regulation of cell volume in MCF-7 cells. We additionally confirmed that KCNQ1 mRNA and protein is expressed in MCF-7 cells, and that, when these cells are cultured as a polarized monolayer, KCNQ1 is located exclusively at the apical membrane. Whole cell patch-clamp recordings from MCF-7 cells revealed a small 293B-sensitive current under hyposmotic, but not isosmotic conditions, while recordings from mammalian cells heterologously expressing KCNQ1 alone or KCNQ1 with the accessory subunit KCNE3 reveal a volume-sensitive K(+) current, inhibited by 293B. These data suggest that KCNQ1 may play important physiological roles in the mammary epithelium, regulating cell volume and potentially mediating transepithelial K(+) secretion.