Membrane trafficking factors are involved in the hypotonic activation of the taurine channel in the little skate (Raja erinacea) red blood cell
Abstract
In response to volume expansion, red blood cells of the little skate (Raja erinacea) initially swell and then release small organic compounds and osmotically obligated water in what is called a regulatory volume decrease (RVD) to restore cell volume. One of the major intracellular solutes lost during this process is the non-metabolized beta amino acid taurine. This hypoosmotic-induced increase in cell taurine permeability requires the anion exchanger, skAE1. The abundance of this transporter increases on the surface plasma membrane by a process of exocytosis. The second-messenger pathways involved in exocytosis of skAE1 were investigated with the use of inhibitors which affect membrane trafficking. Hypoosmotic-stimulated taurine uptake was significantly decreased by 42% with wortmannin, a phosphatidylinositol 3-kinase (PI3 kinase) inhibitor. Additional evidence for the involvement of PI3K was obtained with a second inhibitor, LY294002, which decreased the hypoosmotic-stimulated taurine uptake by 28%. The state of actin is also involved, as the actin filament depolymerizer latrunculin B decreased hypoosmotic-stimulated taurine uptake by approximately 40%. Although hypoosmotic conditions did not stimulate changes in the distribut...Continue Reading
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