IFN-gamma-induced upregulation of Fcgamma-receptor-I during activation of monocytic cells requires the PKR and NFkappaB pathways.
Interferon (IFN)-gamma is a potent activator of macrophages, increasing the cells capacity to perform specific functions during inflammation and immune response. In this report we use IFN-gamma-induced upregulation of the high affinity receptor for IgG (FcgammaRI/CD64) in the human monocytic cell line U-937 as a model for monocytic activation. We show that upregulation of FcgammaRI is dependent on signals mediated by the dsRNA-dependent kinase PKR, and the transcription factor NFkappaB. Silencing of PKR expression by siRNA or inhibition of PKR by 2-aminopurine (2-AP) potently blocks the IFN-gamma-induced transcriptional activation of the FcgammaRI promoter. We find that the serine 727 phosphorylation of Stat1, required for full IFN-gamma-induced FcgammaRI promoter activity, is dependent on PKR. We further show that IFN-gamma induction of FcgammaRI upregulation is dependent on the NFkappaB pathway, as evidenced by inhibition of NFkappaB using a phosphorylation defective IkappaBalpha (S32A/S36A) mutant, or inhibiting the IkappaB-kinase (IKK) by treatment with BMS345541. Our results suggest that IFN-gamma-induced increase of FcgammaRI expression requires the integration of two signalling events: PKR-dependent Stat1 serine 727 phosphorylation, and activation of NFkappaB.
Kårehed
Karin
K
Department of Genetics and Pathology, Rudbeck Laboratory, Uppsala University, SE-751 85 Uppsala, Sweden.
Dimberg
Anna
A
Dahl
Staffan
S
Nilsson
Kenneth
K
Oberg
Fredrik
F
D002460:Cell Line; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D051550:I-kappa B Kinase / Q000037:antagonists & inhibitors / Q000502:physiology; D007093:Imidazoles / Q000494:pharmacology; D007371:Interferon-gamma / Q000494:pharmacology*; D008262:Macrophage Activation / Q000187:drug effects*; D009000:Monocytes / Q000187:drug effects / Q000502:physiology; D016328:NF-kappa B / Q000502:physiology; D010766:Phosphorylation; D011810:Quinoxalines / Q000494:pharmacology; D017452:Receptors, IgG / Q000096:biosynthesis*; D011994:Recombinant Proteins; D050794:STAT1 Transcription Factor / Q000502:physiology; D015398:Signal Transduction / Q000187:drug effects; D015854:Up-Regulation / Q000187:drug effects; D019892:eIF-2 Kinase / Q000502:physiology
C471109:4(2'-aminoethyl)amino-1,8-dimethylimidazo(1,2-a)quinoxaline; C489017:FCGR1A protein, human; D007093:Imidazoles; D016328:NF-kappa B; D011810:Quinoxalines; D017452:Receptors, IgG; D011994:Recombinant Proteins; D050794:STAT1 Transcription Factor; D007371:Interferon-gamma; D019892:eIF-2 Kinase; D051550:I-kappa B Kinase