Compound 48/80 activates mast cell phospholipase D via heterotrimeric GTP-binding proteins.
Previous studies have indicated the presence of a cholera toxin-sensitive phospholipase D (PLD) in cultured RBL-2H3 mast cells that is synergistically activated via calcium, protein kinase C, and another unidentified signal. Here we identify a third potential signal for activation transduced by a pertussis toxin-sensitive trimeric GTP-binding protein, most likely via G(i2) or G(i3). Quercetin-treated RBL-2H3 cells in which expression of G(alphai2) and G(alphai3) is enhanced more than 7-fold respond to the G(i) stimulant compound 48/80 with the activation of PLD, a transient activation of phospholipase C, and enhanced membrane GTPase activity. The activation of PLD was blocked in pertussis toxin-treated cells and, as with other stimulants of PLD, was enhanced in cholera toxin-treated cells. The PLD response to compound 48/80 was only partially inhibited by calcium deprivation and inhibition of protein kinase C to indicate a component of the response that was independent of calcium, protein kinase C, and, presumably, phospholipase C. Based on these and other data, we hypothesized that betagamma-subunits, released from G(i2) or G(i3) by compound 48/80 or from G(s) by cholera toxin, provide an additional signal for the activation of PLD. Consistent with this hypothesis, recombinant G(beta2gamma2) subunits, but not G(alphai-3) subunits, at concentrations of 50 to 300 nM markedly synergized PLD activation by compound 48/80 in permeabilized RBL-2H3 cells.
Chahdi
A
A
Laboratory of Molecular Immunology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892-1760, USA.
Fraundorfer
P F
PF
Beaven
M A
MA
D015153:Blotting, Western; D002118:Calcium / Q000172:deficiency; D002462:Cell Membrane / Q000187:drug effects / Q000201:enzymology*; D002478:Cells, Cultured; D002772:Cholera Toxin; D004347:Drug Interactions; D004586:Electrophoresis; D020558:GTP Phosphohydrolases / Q000378:metabolism; D020962:Heterotrimeric GTP-Binding Proteins / Q000502:physiology*; D008407:Mast Cells / Q000187:drug effects* / Q000378:metabolism; D010539:Permeability; D037342:Pertussis Toxin; D010739:Phospholipase D / Q000378:metabolism*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D011794:Quercetin / Q000494:pharmacology; D015398:Signal Transduction; D013997:Time Factors; D010738:Type C Phospholipases / Q000378:metabolism; D010566:Virulence Factors, Bordetella; D003189:p-Methoxy-N-methylphenethylamine / Q000494:pharmacology*
D010566:Virulence Factors, Bordetella; D003189:p-Methoxy-N-methylphenethylamine; D002772:Cholera Toxin; D011794:Quercetin; D037342:Pertussis Toxin; D011493:Protein Kinase C; D010738:Type C Phospholipases; D010739:Phospholipase D; D020558:GTP Phosphohydrolases; D020962:Heterotrimeric GTP-Binding Proteins; D002118:Calcium