Effect of ionophore A23187 and thapsigargin on serine incorporation into phosphatidylserine in intact and permeabilized glioma C6 cells at high and low Ca2+ concentrations.
Intact and permeabilized glioma C6 cells were incubated with [14C]serine in media containing low (100 nM) or high (2 mM) [Ca2+] and serine incorporation into phosphatidylserine was examined. In all cases thapsigargin, a blocker of the endoplasmic reticulum Ca(2+)-ATPase, diminished this process, whereas the action of the ionophore A23187 was dependent on the external calcium concentration and time of incubation. In permeabilized cells incubated at 100 nM Ca2+, serine incorporation into phosphatidylserine was diminished when the endoplasmic reticulum Ca2+ levels were lowered by the ionophore. In intact cells incubated at 2 mM CaCl2, addition of A23187 had no effect for the first 30 min and later decreased [14C]serine incorporation. This result seems to be not connected with the degradation of already formed phosphatidylserine, or with an enhanced metabolic conversion of this phospholipid, but with the decrease of its synthesis. The mechanism of this last process appears to be involved in the ionophore-induced perturbation of cellular Ca2+ homeostasis. Our results indicate that phosphatidylserine synthesis is a Ca(2+)-regulated process.
Czarny
M
M
Department of Cellular Biochemistry, Nencki Institute of Experimental Biology, Warsaw, Poland.
Barańska
J
J
D000818:Animals; D000001:Calcimycin / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors*; D002463:Cell Membrane Permeability; D005910:Glioma; D010718:Phosphatidylserines / Q000096:biosynthesis / Q000378:metabolism*; D012694:Serine / Q000378:metabolism*; D013729:Terpenes / Q000494:pharmacology*; D019284:Thapsigargin; D014407:Tumor Cells, Cultured
D010718:Phosphatidylserines; D013729:Terpenes; D000001:Calcimycin; D012694:Serine; D019284:Thapsigargin; D000252:Calcium-Transporting ATPases; D002118:Calcium