PLASMA-MEMBRANE REDOX AND REGULATION OF CELL-GROWTH

Gene expression can be activated by external oxidants which are reduce d at the cell surface by plasma membrane electron transport. The signa ls generated in response to the plasma membrane electron transport inc lude activation of proton release, internal calcium changes, and chang e in reductant/oxidant ratio in the cytosol. H2O2 generated in respons e to ligands which bind to plasma membrane receptors can also activate protein tyrosine kinases and gene expression. Inhibition of oxygen ra dical generation at the cell surface in response to the mitogen, phorb ol myristate acetate by retinoic acid is consistent with a role for th e plasma membrane electron transport as the source for H2O2 in Balb 3T 3 cells. Agents which affect the binding of coenzyme Q to redox sites in the plasma membrane electron transport may increase formation of se miquinone radicals in the membrane which can be a source of oxygen rad icals and H2O2. The generation of H2O2 by transformed cells indicates that oncogene product expression in the plasma membrane may also incre ase quinone-based oxygen radical generation.