Effect of prenylcysteine analogues on chemoattractant receptor-mediated G protein activation.
The hypothesis that carboxylmethylation of gamma subunits plays a role in G protein activation was tested by examining the ability of N-acetyl-S-farnesyl-L-cysteine (AFC) and its methyl ester (AFC-ME) to inhibit G protein-mediated signalling in intact HL-60 granulocytes and isolated HL-60 plasma membranes. Incubation of HL-60 granulocytes with AFC or AFC-ME inhibited superoxide release stimulated by fMet-Leu-Phe, but not by opsonized bacteria. AFC-ME, but not AFC, inhibited NaF- and PMA-stimulated superoxide release. Addition of AFC to HL-60 membranes inhibited fMet-Leu-Phe-, leukotriene B4- (LTB4) and C5a-stimulated GTP gamma S binding and GTP hydrolysis more potently than it inhibited basal guanine nucleotide exchange. AFC-ME inhibited basal- and ligand-stimulated G protein activation with equal potency, but less potently than AFC. AFC also inhibited mastoparan-stimulated GTP gamma S binding. Binding of fMet-Leu-Phe and LTB4 to HL-60 membranes was completely inhibited by AFC, while AFC-ME inhibited ligand binding by less than 50%. Neither AFC nor AFC-ME inhibited pertussis toxin or cholera toxin-catalysed ADP-ribosylation of alpha i. It was concluded that AFC interrupts signal propagation in G protein-dependent pathways by multiple mechanisms, including inhibition of ligand-receptor interactions, of receptor-G protein coupling and of guanine nucleotide binding to G proteins. Carboxylmethylation alters the specificity of AFC interruption of signal propagation in intact cells and isolated membranes.
McLeish
K R
KR
Department of Medicine, University of Louisville, KY 40292.
Lederer
E D
ED
Klein
J B
JB
Hoffman
J L
JL
D000111:Acetylcysteine / Q000031:analogs & derivatives* / Q000494:pharmacology; D001426:Bacterial Proteins; D002460:Cell Line; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002478:Cells, Cultured; D002628:Chemoreceptor Cells / Q000378:metabolism*; D004952:Esters; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006098:Granulocytes / Q000187:drug effects / Q000378:metabolism*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000037:antagonists & inhibitors / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000037:antagonists & inhibitors / Q000378:metabolism; D006801:Humans; D007975:Leukotriene B4 / Q000037:antagonists & inhibitors / Q000378:metabolism; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000037:antagonists & inhibitors / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D013481:Superoxides / Q000378:metabolism
D001426:Bacterial Proteins; D004952:Esters; D013481:Superoxides; D007975:Leukotriene B4; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D009240:N-Formylmethionine Leucyl-Phenylalanine; D006160:Guanosine Triphosphate; D019204:GTP-Binding Proteins; C068268:N-acetyl-S-farnesylcysteine; D000111:Acetylcysteine