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  • Title: Direct inhibition of phospholipid scrambling activity in erythrocytes by potassium ions.
    Author: Wolfs JL, Comfurius P, Bekers O, Zwaal RF, Balasubramanian K, Schroit AJ, Lindhout T, Bevers EM.
    Journal: Cell Mol Life Sci; 2009 Jan; 66(2):314-23. PubMed ID: 18989619.
    Abstract:
    The exposure of phosphatidylserine (PS) at the cell surface plays a critical role in blood coagulation and serves as a macrophage recognition moiety for the engulfment of apoptotic cells. Previous observations have shown that a high extracellular [K(+)] and selective K(+) channel blockers inhibit PS exposure in platelets and erythrocytes. Here we show that the rate of PS exposure in erythrocytes decreases by approximately 50% when the intracellular [K(+)] increases from 0 to physiological concentrations. Using resealed erythrocyte membranes, we further show that lipid scrambling is inducible by raising the intracellular [Ca(2+)] and that K(+) ions have a direct inhibitory effect on this process. Lipid scrambling in resealed ghosts occurs in the absence of cell shrinkage and microvesicle formation, processes that are generally attributed to Ca(2+)-induced lipid scrambling in intact erythrocytes. Thus, opening of Ca(2+)-sensitive K(+) channels causes loss of intracellular K(+) that results in reduced intrinsic inhibitory effect of these ions on scramblase activity.
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