IL-1beta-specific up-regulation of neutrophil gelatinase-associated lipocalin is controlled by IkappaB-zeta.
Neutrophil gelatinase-associated lipocalin (NGAL) is a siderophore-binding protein that exerts a bacteriostatic effect by sequestering iron. Strong induction of NGAL synthesis has been observed in inflamed epithelium of the lungs and colon. Expression of NGAL is up-regulated in the lung epithelial cell line A549 by IL-1beta, but not by TNF-alpha, despite an induction of NF-kappaB binding to the NGAL promoter by both cytokines. In this study, we present evidence that the IL-1beta specificity is caused by a requirement of the NGAL promoter for the NF-kappaB-binding cofactor IkappaB-zeta for transcriptional activation. Up-regulation of NGAL expression in A549 cells following IL-1beta stimulation was dependent on de novo protein synthesis and was greatly diminished by a small interfering against IkappaB-zeta mRNA. Cotransfection of A549 cells with a plasmid expressing IkappaB-zeta made TNF-alpha capable of inducing NGAL transcription, indicating that IkappaB-zeta induction is the only factor discriminating between IL-1beta and TNF-alpha in their ability to induce NGAL expression. Coexpression of the cofactor Bcl-3, which is closely related to IkappaB-zeta, did not enable TNF-alpha to induce NGAL transcription. A functional NF-kappaB site of the NGAL promoter was required for IkappaB-zeta to exert its effect. The human beta defensin 2 gene also required IkappaB-zeta for its IL-1beta-specific induction in A549 cells. Our findings indicate that a common regulatory mechanism has evolved to control expression of a subset of antimicrobial proteins expressed in epithelial cells.
Cowland
Jack B
JB
Department of Hematology L-9322, Granulocyte Research Laboratory, Rigshospitalet, University of Copenhagen, 9 Blegdamsvej, DK-2100 Copenhagen, Denmark. jcowland@rh.dk
Muta
Tatsushi
T
Borregaard
Niels
N
D000209:Acute-Phase Proteins / Q000096:biosynthesis* / Q000235:genetics; D048868:Adaptor Proteins, Signal Transducing; D001665:Binding Sites; D045744:Cell Line, Tumor; D015536:Down-Regulation / Q000187:drug effects; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D020672:I-kappa B Proteins; D007375:Interleukin-1 / Q000494:pharmacology*; D016328:NF-kappa B / Q000378:metabolism; D009687:Nuclear Proteins; D011401:Promoter Regions, Genetic / Q000235:genetics; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis* / Q000235:genetics; D034622:RNA Interference; D013997:Time Factors; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D015854:Up-Regulation / Q000187:drug effects; D023083:beta-Defensins / Q000378:metabolism
D000209:Acute-Phase Proteins; D048868:Adaptor Proteins, Signal Transducing; D020672:I-kappa B Proteins; D007375:Interleukin-1; D016328:NF-kappa B; C417234:NFKBIZ protein, human; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; D014409:Tumor Necrosis Factor-alpha; D023083:beta-Defensins