Phosphatidylcholine-specific phospholipase C regulates thapsigargin-induced calcium influx in human lymphocytes.
The involvement of phosphatidylcholine-specific phospholipase C (PC-PLC) and D (PC-PLD) in the regulation of the thapsigargin-induced Ca2+ increase was investigated. Pretreatment of human lymphocytes with the PC-PLC inhibitors D609 or U73122 enhanced the thapsigargin-induced Ca2+ influx. By contrast, no effect was observed in the presence of phospholipase D inhibitor butanol. Addition of exogenous PC-PLC but not PC-PLD to lymphocytes prestimulated with thapsigargin led to a decrease of intracellular Ca2+. In addition, thapsigargin was shown to release diacylglycerol (DAG) from cellular phosphatidylcholine pools. The thapsigargin-induced DAG formation was inhibited by U73122 and D609 but not by butanol. Moreover, no formation of the PC-PLD activity marker phosphatidylbutanol was detected. Thapsigargin-induced DAG formation was dependent on the Ca2+ entry, as it was abolished in the absence of extracellular Ca2+ or in the presence of Ni2+. Further investigations demonstrated that the inhibition of the cellular DAG target, protein kinase C (PKC), enhanced thapsigargin-induced Ca2+ increase, whereas direct PKC activation had an inhibitory effect. Taken together, our results reveal the involvement of PC-PLC in the regulation of the thapsigargin-induced Ca2+ increase and point to the existence of a physiologic feedback mechanism activated by Ca2+ influx and acting via consecutive activation of PC-PLC and PKC to limit the rise of intracellular Ca2+.
Nofer
J R
JR
Institut für Klinische Chemie und Laboratoriumsmedizin, Zentrallaboratorium, Westfälische Wilhelms-Universität, Münster,, Federal Republic of Germany.
Tepel
M
M
Walter
M
M
Seedorf
U
U
Assmann
G
G
Zidek
W
W
D001952:Bridged-Ring Compounds / Q000494:pharmacology; D000440:Butanols / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D004963:Estrenes / Q000494:pharmacology; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D008214:Lymphocytes / Q000187:drug effects* / Q000378:metabolism; D009532:Nickel / Q000378:metabolism; D009636:Norbornanes; D010713:Phosphatidylcholines / Q000378:metabolism*; D010716:Phosphatidylinositols / Q000378:metabolism; D011433:Propranolol / Q000494:pharmacology; D011760:Pyrrolidinones / Q000494:pharmacology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D019284:Thapsigargin / Q000494:pharmacology*; D013859:Thiocarbamates; D013871:Thiones / Q000494:pharmacology; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors / Q000378:metabolism*
D001952:Bridged-Ring Compounds; D000440:Butanols; D004791:Enzyme Inhibitors; D004963:Estrenes; D007211:Indoles; D009636:Norbornanes; D010713:Phosphatidylcholines; D010716:Phosphatidylinositols; D011760:Pyrrolidinones; D013859:Thiocarbamates; D013871:Thiones; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; C046498:tricyclodecane-9-yl-xanthogenate; D019284:Thapsigargin; D009532:Nickel; D011433:Propranolol; D010738:Type C Phospholipases; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium; C064758:Ro 31-8220