Transduction of the IFN-gamma signal for HLA-DR expression in the promonocytic line THP-1 involves a late-acting PKC activity.
Interferon gamma (IFN-gamma) is the most potent known lymphokine for activating macrophages and has been shown to induce expression of HLA-DR in THP-1 cells, a monocytic tumor cell line which expresses many of the properties of monocytes, in a dose- and time-dependent manner. Experiments were designed to examine, by FACS analysis and by measurement of messenger RNA levels, the molecular mechanism regulating the expression of HLA-DR molecules. The expression of HLA-DR molecules induced by IFN-gamma was blocked by the protein kinase C (PKC) inhibitors sphingosine, staurosporine, and H7. H7 when added up to 20 hr after the initial stimulation with IFN-gamma prevented the further expression of HLA-DR. The general kinase inhibitors H8, H9, and HA1004, all less potent PKC inhibitors than H7, did not block the IFN-gamma-induced expression of HLA-DR at the concentrations employed. W7, a calmodulin antagonist, but not a PKC inhibitor, was also unable to prevent the IFN-gamma-induced expression of HLA-DR. Treatment of THP-1 with phorbol 12-myristate 13-acetate (PMA), a direct activator of PKC, alone or with Ca2+ ionophore A23187, was unable to induce HLA-DR expression. However, pretreatment with PMA for 24 hr prior to IFN-gamma stimulation decreased the IFN-gamma-induced expression of HLA-DR without decreasing IFN-gamma receptor levels. These results suggest that PKC plays a significant role in the IFN-gamma-induced signal transduction pathway leading to the expression of HLA-DR in cells of the mononuclear phagocytic lineage, and that PKC activity is required throughout the course of events leading to the actual expression of HLA-DR.
Department of Inflammation Biology and Immunology, Syntex Research, U.S.A., Inc., Palo Alto, California 94304.
R J
RJ
Gumina
J
J
Freire-Moar
L
L
DeYoung
D R
DR
Webb
B H
BH
Devens
D004789:Enzyme Activation / Q000187:drug effects; D006684:HLA-DR Antigens / Q000096:biosynthesis* / Q000235:genetics; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology*; D007948:Leukemia, Monocytic, Acute / Q000276:immunology; D009000:Monocytes / Q000276:immunology; D011493:Protein Kinase C / Q000502:physiology*; D015290:Second Messenger Systems / Q000502:physiology; D015398:Signal Transduction; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D006684:HLA-DR Antigens; D007371:Interferon-gamma; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate