ACTIVATION OF A CYCLIC-NUCLEOTIDE PHOSPHODIESTERASE 4 (PDE4) FROM RATTHYMOCYTES BY PHOSPHATIDIC-ACID

The cytosolic cyclic nucleotide phosphodiesterase (PDE) activity from rat thymocytes was resolved into five peaks by HPLC. Only two forms of the cAMP-specific PDE4 were found to be sensitive to physiologically relevant phosphatidic acid (PA) concentrations. PA activated the PDE4- peak 3 form, the fatty acid composition and unsaturation degree determ ining the efficiency of PA. The PDE4-peak 2 form was inhibited only by PA with saturated fatty acyl groups. PDE4 activation was specific of anionic phospholipids, a free phosphate group in the phospholipid mole cule being required for maximum activation. These results suggest that PA may contribute to the lowering of cAMP Level required in the early steps of a lympho-proliferative response, thus regulating immune func tions through PDE4 activation. Copyright (C) 1996 Elsevier Science Inc .