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MEMBRANE TRANSPORTERS, ION CHANNELS, AND PUMPS

Stimulation by caveolin-1 of the hypotonicity-induced release of taurine and ATP at basolateral, but not apical, membrane of Caco-2 cells

Laboratory of Physiology, K.U. Leuven, Campus Gasthuisberg, Leuven, Belgium

Submitted 27 October 2005 ; accepted in final form 27 November 2005

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.

caveolae; osmolyte; epithelial cell; chloride channel

This article has been cited by other articles:

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				S. Martin Caveolae and cell swelling. Focus on "Stimulation by caveolin-1 of the hypotonicity-induced release of taurine and ATP at basolateral, but not apical, membrane of Caco-2 cells" Am J Physiol Cell Physiol, May 1, 2006; 290(5): C1273 - C1274. [Full Text] [PDF]