Inhibition of phosphatidylserine synthesis by glutamate, acetylcholine, thapsigargin and ionophore A23187 in glioma C6 cells.

Phosphatidylserine synthesis was studied in glioma C6 cells with 14C]serine and in the presence or absence of agents which increase the level of Ca2+]i. It was found that glutamate and acetylcholine inhibited this synthesis by up to 40%, whereas thapsigargin and the ionophore A23187 inhibited by up to 70%. The inhibitory effect of thapsigargin and the A23187 was observed in Ca(2+)-free medium. The data show that the inhibition of this synthesis is caused by the Ca(2+)-depletion from endoplasmic reticulum, suggesting that the synthesis of phosphatidylserine occurs on the luminal side of these structures and can be regulated by transmembrane signaling systems.