STIMULATION OF PHOSPHOINOSITIDE HYDROLYSIS BY GLYCERALDEHYDE-3-PHOSPHATE IN ELECTROPORATED HIT-T15 CELLS

HIT-T15 cells labeled with myo-[H-3] inositol were permeabilized by el ectroporation and subsequently stimulated with various glycolytic inte rmediates in the presence of 20 mM LiCl in a buffer mimicking cytosoli c ionic composition. Of the various glycolytic intermediates tested. O nly D-glyceraldehyde-3-phosphate (G3-P) stimulated the formation of la beled inositol phosphates. The half-maximal response to G3-P occured a t a concentration of 0.75 mM. Formation of inositol phosphates in elec troporated cells was also observed in response to GTP. G3-P further po tentiated the formation of inositol phosphates in response to GTP, how ever, the interaction between G3-P and GTP was additive rather than sy nergistic. indicating that G3-P stimulates phosphoinositide hydrolysis in a manner different than the receptor mediated GTP-dependent activa tion of phospholipase C. The potentiation of the GTP response by G3-P did not appear to involve inhibition of the GTPase activity of a phosp hoinositide-specific G protein, since G3-P also potentiated the format ion of inositol phosphates in response to GTP-gamma-S or NaF in a near ly additive manner.