title: Contribution of KCNQ1 to the regulatory volume decrease in the human mammary epithelial cell line MCF-7.
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.
authors.affiliation: Dept. of Physiology and Biophysics, Dalhousie Univ., Halifax, Nova Scotia B3H 1X5, Canada. elizabeth.cowley@dal.ca).
authors.forename: Brenna L
authors.initials: BL
authors.lastname: vanTol
authors.forename: Sergey
authors.initials: S
authors.lastname: Missan
authors.forename: Julie
authors.initials: J
authors.lastname: Crack
authors.forename: Shasta
authors.initials: S
authors.lastname: Moser
authors.forename: William H
authors.initials: WH
authors.lastname: Baldridge
authors.forename: Paul
authors.initials: P
authors.lastname: Linsdell
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Cowley
mesh_terms: D000230:Adenocarcinoma; D001943:Breast Neoplasms; D045744:Cell Line, Tumor; D016764:Cell Polarity / Q000502:physiology; D004847:Epithelial Cells / Q000166:cytology / Q000502:physiology*; D045604:Extracellular Fluid / Q000378:metabolism; D006801:Humans; D007038:Hypotonic Solutions / Q000494:pharmacology; D007552:Isotonic Solutions / Q000494:pharmacology; D051657:KCNQ1 Potassium Channel / Q000235:genetics / Q000378:metabolism*; D042361:Mammary Glands, Human / Q000166:cytology*; D008564:Membrane Potentials / Q000502:physiology; D016297:Mutagenesis, Site-Directed; D009997:Osmotic Pressure; D011188:Potassium / Q000378:metabolism; D024642:Potassium Channels, Voltage-Gated / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D014882:Water-Electrolyte Balance / Q000502:physiology*
chemical_list: D007038:Hypotonic Solutions; D007552:Isotonic Solutions; C418492:KCNE3 protein, human; D051657:KCNQ1 Potassium Channel; C496909:KCNQ1 protein, human; D024642:Potassium Channels, Voltage-Gated; D012333:RNA, Messenger; D011188:Potassium