Potential requirement of a functional double-stranded RNA-dependent protein kinase (PKR) for the tumoricidal activation of macrophages by lipopolysaccharide or IFN-alpha beta, but not IFN-gamma.
We analyzed the expression of the dsRNA-dependent protein kinase (PKR) during the activation of murine macrophages to the tumoricidal state by LPS and/or IFNs. LPS induced PKR expression in a dose-dependent manner at levels that were comparable with those observed in response to IFNs. By using the PKR inhibitor 2-aminopurine (2-AP), we have shown that the pathways of macrophage tumoricidal activation elicited by LPS and IFN-alpha beta, but not by IFN-gamma, included a 2-AP-sensitive step. In fact, LPS- and IFN-alpha beta-induced activation was inhibited by 2-AP, whereas the activation by IFN-gamma was not affected by the presence of the inhibitor. 2-AP did not affect the activation of protein kinase C or protein kinase A in intact cells. In the presence of 2-AP the up-regulation of IFN-beta mRNA by LPS was specifically inhibited, whereas the expression of glyceraldehyde-3-phosphate dehydrogenase mRNA or the induction of PKR remained unchanged, thereby demonstrating that 2-AP inhibited selective macrophage genes. The differential sensitivity to 2-AP suggested that the expression of a functional PKR may be required for the macrophage tumoricidal response triggered by LPS and IFN-alpha beta but not IFN-gamma.
Gusella
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Biological Carcinogenesis and Development Program, Program Resources, PRI/DynCorp, Frederick, MD 21702.
Musso
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Rottschafer
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Pulkki
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Varesio
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D015075:2-Aminopurine / Q000494:pharmacology; D000818:Animals; D002461:Cell Line, Transformed; D003602:Cytotoxicity, Immunologic / Q000502:physiology; D004789:Enzyme Activation / Q000187:drug effects; D005786:Gene Expression Regulation / Q000187:drug effects; D016898:Interferon-alpha / Q000494:pharmacology*; D007371:Interferon-gamma / Q000494:pharmacology*; D008070:Lipopolysaccharides / Q000494:pharmacology; D008262:Macrophage Activation / Q000187:drug effects*; D017737:Macrophages, Peritoneal / Q000187:drug effects; D012515:Mast-Cell Sarcoma; D051379:Mice; D008810:Mice, Inbred C57BL; D010766:Phosphorylation / Q000187:drug effects; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000502:physiology*; D011994:Recombinant Proteins; D014407:Tumor Cells, Cultured; D019892:eIF-2 Kinase
D016898:Interferon-alpha; D008070:Lipopolysaccharides; D011994:Recombinant Proteins; D015075:2-Aminopurine; D007371:Interferon-gamma; D017346:Protein Serine-Threonine Kinases; D019892:eIF-2 Kinase