Regulation of phosphatidylserine synthesis in Jurkat T cell clones: caffeine bypasses CD3/TCR-induced protein tyrosine kinases and calcium signals.
Phosphatidylserine synthesis as measured by the incorporation of [(3)H]serine into phosphatidylserine (PtdSer) through the serine-base exchange enzyme system (serine-BEES) is markedly inhibited in Jurkat cells treated with caffeine. The caffeine-induced inhibition was compared to that observed in cells treated with either CD3 mAb or thapsigargin. While CD3- and thapsigargin-induced inhibition was related to the release of Ca(2+) from the endoplasmic reticulum (ER), a process that deprives the serine-BEES of its major cofactor, caffeine modified PtdSer synthesis in the absence of decreased Ca(2+) content of ER. Using Jurkat clones differing by the expression of cell surface markers or protein tyrosine kinases implicated in the CD3/TCR signal transmission pathway, we have shown that CD3 mAb-induced inhibition of PtdSer synthesis necessitates the expression of both the CD3/TCR and the protein tyrosine phosphatase CD45 at the cell surface as well as the presence of p56(lck) and ZAP-70 protein tyrosine kinases. By contrast, thapsigargin, a blocker of the Ca(2+)-ATPase of the ER, known for its Ca(2+) releasing properties, inhibited PtdSer synthesis in all the Jurkat clones tested, indicating that this compound bypasses the CD3/TCR-induced signals. Despite its lack of effect on Ca(2+) release from ER and on protein tyrosine phosphorylations, caffeine inhibited PtdSer synthesis in all the Jurkat clones. The use of several cAMP-inducing drugs and of others xanthine derivatives indicated that caffeine modify PtdSer synthesis either by a direct action on the serine-BEES or by a modification of the structure of the phospholipids used as substrate by the enzyme.
Pelassy
C
C
INSERM U343, Hôpital de l'Archet, Nice cedex 03, 06202, France.
Breittmayer
J P
JP
Aussel
C
C
D000911:Antibodies, Monoclonal / Q000276:immunology / Q000494:pharmacology; D017252:CD3 Complex / Q000276:immunology*; D002110:Caffeine / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D015759:Ionomycin / Q000494:pharmacology; D019169:Jurkat Cells; D010718:Phosphatidylserines / Q000096:biosynthesis*; D010766:Phosphorylation / Q000187:drug effects; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D015398:Signal Transduction; D019284:Thapsigargin / Q000494:pharmacology
D000911:Antibodies, Monoclonal; D017252:CD3 Complex; D004791:Enzyme Inhibitors; D010718:Phosphatidylserines; D002110:Caffeine; D015759:Ionomycin; D019284:Thapsigargin; D011505:Protein-Tyrosine Kinases; D000252:Calcium-Transporting ATPases; D002118:Calcium