Brefeldin A inhibits antigen- or calcium ionophore-mediated but not PMA-induced phospholipase D activation in rat basophilic leukemia (RBL-2H3) cells.
Recent reports have indicated that ADP-ribosylation factor (ARF) plays a role in the regulation of phospholipase D (PLD) activity in the in vitro assay system. Since a fungal metabolite brefeldin A (BFA) is known to interfere with ARF function, the effect of BFA on antigen-induced PLD activation was examined in rat basophilic leukemia (RBL-2H3) cells. BFA inhibited the antigen-induced formation of phosphatidylbutanol (PBut), a specific and stable metabolite produced by PLD activity in a concentration-dependent manner. The maximal inhibition obtained at 10 micrograms/ml of the drug was nearly 70% and further inhibition was not observed at higher concentrations. Ca(2+)-ionophore A23187-mediated PLD activation was also prevented by BFA. In contrast, BFA failed to inhibit PLD activation in response to 4 beta-phorbol 12-myristate 13-acetate (PMA), an activator of protein kinase C (PKC). This indicates that there are BFA-sensitive and BFA-insensitive pathways leading to PLD activation in RBL-2H3 cells and also that the PKC-mediated pathway may be insensitive to BFA treatment, suggesting the existence of PLD isozymes. BFA inhibited Ag-induced serotonin release at a concentration 20-fold lower than that needed for the inhibition of PLD. Moreover, PMA caused a marked production of PBut, but it failed to elicit secretory response. This implies that PLD may be not a crucial element for secretory responses.
Nakamura
Y
Y
Department of Otolaryngology, Gifu University School of Medicine, Japan.
Nakashima
S
S
Kumada
T
T
Ojio
K
K
Miyata
H
H
Nozawa
Y
Y
D000818:Animals; D000941:Antigens / Q000187:drug effects* / Q000276:immunology; D020126:Brefeldin A; D000001:Calcimycin / Q000494:pharmacology*; D003517:Cyclopentanes / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects; D007946:Leukemia, Mast-Cell / Q000201:enzymology*; D010739:Phospholipase D / Q000037:antagonists & inhibitors* / Q000187:drug effects*; D051381:Rats; D012701:Serotonin / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
D000941:Antigens; D003517:Cyclopentanes; D020126:Brefeldin A; D012701:Serotonin; D000001:Calcimycin; D010739:Phospholipase D; D013755:Tetradecanoylphorbol Acetate