Cholera toxin increases the rate of antigen-stimulated calcium influx in rat basophilic leukemia cells.
Cholera toxin pretreatment has been found to cause a 3-fold increase in the initial rate of antigen-stimulated secretion of serotonin from rat basophilic leukemia (RBL) cells. Under similar conditions, cholera toxin enhances the antigen-stimulated rise in cytoplasmic free ionized calcium levels and causes a 2-3-fold increase in the rate of antigen-stimulated influx of 45Ca. In intact RBL cells cholera toxin pretreatment potentiates the antigen-stimulated production of inositol phosphates, but in permeabilized cells, with strongly buffered free calcium levels, no effect of cholera toxin pretreatment on the antigen-stimulated activation of cellular phospholipase activities is observed. In addition, pretreatment of cells with tetradecanoylphorbol acetate inhibits antigen-stimulated production of inositol phosphates by greater than 95%, while the stimulated influx of 45Ca remains unaffected. These data indicate that the antigen-stimulated influx of calcium into RBL cells can be dissociated from the production of inositol phosphates in these cells. The observed effects of cholera toxin on exocytosis and Ca2+ influx in RBL cells are not due to the elevation of cellular cyclic AMP levels since a variety of agents capable of elevating cellular cyclic AMP levels do not mimic these effects. Together, these data suggest that a cholera toxin-sensitive guanine nucleotide-binding protein is involved in the pathway responsible for the antigen-stimulated influx of calcium into RBL cells.
Narasimhan
V
V
Section of Biochemistry, Cell and Molecular Biology, Cornell University, Ithaca, New York 14853.
Holowka
D
D
Fewtrell
C
C
Baird
B
B
D000818:Animals; D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D002772:Cholera Toxin / Q000494:pharmacology*; D000242:Cyclic AMP / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D004140:Dinitrophenols / Q000494:pharmacology*; D006241:Haptens; D007294:Inositol / Q000378:metabolism; D007295:Inositol Phosphates / Q000378:metabolism*; D007700:Kinetics; D015471:Leukemia, Basophilic, Acute / Q000378:metabolism*; D051381:Rats; D012701:Serotonin / Q000378:metabolism*; D012710:Serum Albumin, Bovine / Q000494:pharmacology*; D013403:Sugar Phosphates / Q000378:metabolism*
D001095:Arachidonic Acids; D004140:Dinitrophenols; D006241:Haptens; D007295:Inositol Phosphates; D013403:Sugar Phosphates; C034638:dinitrophenyl-bovine serum albumin; D012710:Serum Albumin, Bovine; D016718:Arachidonic Acid; D012701:Serotonin; D007294:Inositol; D002772:Cholera Toxin; D000242:Cyclic AMP; D002118:Calcium