title: Stimulation by caveolin-1 of the hypotonicity-induced release of taurine and ATP at basolateral, but not apical, membrane of Caco-2 cells.
abstract: Regulatory volume decrease (RVD) is a protective mechanism that allows mammalian cells to restore their volume when exposed to a hypotonic environment. A key component of RVD is the release of K(+), Cl(-), and organic osmolytes, such as taurine, which then drives osmotic water efflux. Previous experiments have indicated that caveolin-1, a coat protein of caveolae microdomains in the plasma membrane, promotes the swelling-induced Cl(-) current (I(Cl,swell)) through volume-regulated anion channels. However, it is not known whether the stimulation by caveolin-1 is restricted to the release of Cl(-) or whether it also affects the swelling-induced release of other components, such as organic osmolytes. To address this problem, we have studied I(Cl,swell) and the hypotonicity-induced release of taurine and ATP in wild-type Caco-2 cells that are caveolin-1 deficient and in stably transfected Caco-2 cells that express caveolin-1. Electrophysiological characterization of wild-type and stably transfected Caco-2 showed that caveolin-1 promoted I(Cl,swell), but not cystic fibrosis transmembrane conductance regulator currents. Furthermore, caveolin-1 expression stimulated the hypotonicity-induced release of taurine and ATP in stably transfected Caco-2 cells grown as a monolayer. Interestingly, the effect of caveolin-1 was polarized because only the release at the basolateral membrane, but not at the apical membrane, was increased. It is therefore concluded that caveolin-1 facilitates the hypotonicity-induced release of Cl(-), taurine, and ATP, and that in polarized epithelial cells, the effect of caveolin-1 is compartmentalized to the basolateral membrane.
authors.affiliation: Laboratory of Physiology, Campus Gasthuisberg, O&N, Herestraat 49, PO Box 802, B-3000 Leuven, Belgium.
authors.forename: Nina
authors.initials: N
authors.lastname: Ullrich
authors.forename: Adrian
authors.initials: A
authors.lastname: Caplanusi
authors.forename: Bert
authors.initials: B
authors.lastname: Brône
authors.forename: Diane
authors.initials: D
authors.lastname: Hermans
authors.forename: Els
authors.initials: E
authors.lastname: Larivière
authors.forename: Bernd
authors.initials: B
authors.lastname: Nilius
authors.forename: Willy
authors.initials: W
authors.lastname: Van Driessche
authors.forename: Jan
authors.initials: J
authors.lastname: Eggermont
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D018938:Caco-2 Cells; D051242:Caveolin 1 / Q000502:physiology*; D002462:Cell Membrane / Q000502:physiology*; D048429:Cell Size; D006801:Humans; D007038:Hypotonic Solutions; D007473:Ion Channels / Q000502:physiology*; D008564:Membrane Potentials / Q000502:physiology*; D008840:Microfilament Proteins; D009997:Osmotic Pressure; D013654:Taurine / Q000378:metabolism*; D014882:Water-Electrolyte Balance / Q000502:physiology*
chemical_list: D051242:Caveolin 1; D007038:Hypotonic Solutions; D007473:Ion Channels; D008840:Microfilament Proteins; C480498:osmosensing scaffold for MEKK3 protein, mouse; D013654:Taurine; D000255:Adenosine Triphosphate