Potentiation of Gi-mediated phospholipase C activation by retinoic acid in HL-60 cells. Possible role of G gamma 2.
Differentiated HL-60 cells acquire responsiveness to fMet-Leu-Phe (fMLP), which activates phospholipase C and O2- generation in a pertussis toxin-sensitive manner. Addition of retinoic acid (RA) for the last 24 h during dimethyl sulfoxide (Me2SO)-induced differentiation enhanced fMLP-dependent signals and interaction between fMLP receptor and G(i). RA modifies both the function and subunit composition of G(i)2, the predominant G(i) of HL-60 membranes, as shown by comparing purified G(i)2 from membranes of Me2SO-treated cells (D-G(i)2) to G(i)2 from membranes of cells treated with both Me2SO and RA (DR-G(i)2). As compared to D-G(i)2, DR-G(i)2 induced more fMLP binding when added to membranes of pertussis toxin-treated HL-60 cells and, in the presence of GTP gamma S, stimulated beta gamma-sensitive phospholipase C in extracts of HL-60 cells to a much greater extent at a lower concentrations. Immunoblasts revealed that RA induced expression of the gamma 2 subunit, which was otherwise undetectable in G(i)2 purified from HL-60 cells or in HL-60 membranes. Possibly by inducing expression of gamma 2, RA alters two functions of the G(i) beta gamma subunit, modulation of fMLP receptor-G(i)2 coupling and activation of the effector, Phospholipase C.
Iiri
T
T
Department of Pharmacology, University of California, San Francisco 94143.
Homma
Y
Y
Ohoka
Y
Y
Robishaw
J D
JD
Katada
T
T
Bourne
H R
HR
D002454:Cell Differentiation; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D002846:Chromatography, Affinity; D004121:Dimethyl Sulfoxide / Q000494:pharmacology; D004357:Drug Synergism; D004789:Enzyme Activation; D019204:GTP-Binding Proteins / Q000302:isolation & purification / Q000378:metabolism*; D015870:Gene Expression; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D006160:Guanosine Triphosphate / Q000378:metabolism; D006801:Humans; D015151:Immunoblotting; D007700:Kinetics; D015473:Leukemia, Promyelocytic, Acute; D046911:Macromolecular Substances; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000378:metabolism / Q000494:pharmacology; D014212:Tretinoin / Q000494:pharmacology*; D014407:Tumor Cells, Cultured; D010738:Type C Phospholipases / Q000302:isolation & purification / Q000378:metabolism*
D046911:Macromolecular Substances; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D014212:Tretinoin; D009240:N-Formylmethionine Leucyl-Phenylalanine; D006160:Guanosine Triphosphate; D010738:Type C Phospholipases; D019204:GTP-Binding Proteins; D004121:Dimethyl Sulfoxide