Free Radicals Induce Reversible Membrane-Cytoplasm Translocation of Glyceraldehyde-3-Phosphate Dehydrogenase in Human Erythrocytes

We investigated the role of oxygen free radicals in the modulation of glyceraldehyde-3-phosphate dehydrogenase binding to the erythrocyte membrane. Previous studies have demonstrated that in vitro tyrosine phosphorylation of Band 3 prevents the binding of various glycolytic enzymes to its cytoplasmic domain. Since these enzymes are inhibited in their bound state, the functional consequence of Band 3 tyrosine phosphorylation in red blood cells should be to increase glycolysis. To generate free radicals, we used an azocompound, the hydrophilic 2,2′-azobis(2-amidinopropane) hydrochloride, which, at 37°C and in the presence of oxygen, decomposes and produces peroxyl radicals at at constant rate. The reaction of peroxyl radicals with intact red cells induced a time-dependent loss of the membrane-bound glycolytic enzyme, glyceraldehyde-3-phosphate dehydrogenase, associated with a concomitant decrease in enzyme activity. At the same time, Band 3 was phosphorylated in tyrosine. These results were completely reversible in plasma after removal of the oxidative stress. The peroxyl radicals also enhanced the production of lactate in intact cells. Our data reveal a powerful mechanism of erythrocyte metabolic regulation that can boost or reduce energy production in times of special need such as during a free radical attack.