PHOSPHOENOLPYRUVATE AND CREATINE-PHOSPHATE AUGMENT ATP AND MAGNESIUM-DEPENDENT, FC-EPSILON-RI-MEDIATED ACTIVATION OF PHOSPHOLIPASE-C IN RBLCELL GHOSTS

We have previously reported that FCepsilonRI-mediated activation of PL C occurs in plasma membrane vesicles derived from RBL cells. This acti vity is dependent on ATP and magnesium, and is greatly enhanced by the addition of either PEP or CP. We undertook these studies to determine whether these compounds augment FCepsilonRI-mediated activation of PL C because of their ability to form ATP. The specific findings were 1) the addition of increasing amounts of ATP to the ghost vesicles cannot substitute for the combination of ATP and either PEP or CP; 2) the ad dition of increasing amounts of ATP or a combination of ATP and either PEP or CP results in similar levels of intravesicular ATP; 3) many me tabolically related compounds have some activity to support receptor-m ediated PI hydrolysis, but only PEP, CP, and 3-PG give a maximal signa l; and 4) the inability of ATP alone to support optimal receptor-media ted PI hydrolysis does not appear to be due to the accumulation of ADP because ADP is only modestly inhibitory. Taken together, these data a re evidence that augmentation of FcepsilonRI-mediated PI hydrolysis by PEP and CP is not explained simply by the ability of these compounds to generate intravesicular ATP.