Angiotensin II induces nuclear factor (NF)-kappaB1 isoforms to bind the angiotensinogen gene acute-phase response element: a stimulus-specific pathway for NF-kappaB activation.
The vasopressor angiotensin II (AII) activates transcriptional expression of its precursor, angiotensinogen. This biological "positive feedback loop" occurs through an angiotensin receptor-coupled pathway that activates a multihormone-responsive enhancer of the angiotensinogen promoter, termed the acute-phase response element (APRE). Previously, we showed that the APRE is a cytokine [tumor necrosis factor-alpha (TNFalpha)]- inducible enhancer by binding the heterodimeric nuclear factor-kappaB (NF-kappaB) complex Rel A x NF-kappaB1. Here, we compare the mechanism for NF-kappaB activation by the AII agonist, Sar1 AII, with TNFalpha in HepG2 hepatocytes. Although Sar1 AII and TNFalpha both rapidly activate APRE-driven transcription within 3 h of treatment, the pattern of inducible NF-kappaB binding activity in electrophoretic mobility shift assay is distinct. In contrast to the TNFalpha mechanism, which strongly induces Rel A x NF-kappaB1 binding, Sar1 AII selectively activates a heterogenous pattern of NF-kappaB1 binding. Using a two-step microaffinity DNA binding assay, we observe that Sar1 AII recruits 50-, 56-, and 96-kDa NF-kappaB1 isoforms to bind the APRE. Binding of all three NF-kappaB1 isoforms occurs independently of changes in their nuclear abundance or proteolysis of cytoplasmic IkappaB inhibitors. Phorbol ester-sensitive protein kinase C (PKC) isoforms are required because PKC down-regulation completely blocks AII-inducible transcription and inducible NF-kappaB1 binding. We conclude that AII stimulates the NF-kappaB transcription factor pathway by activating latent DNA-binding activity of NF-kappaB subunits through a phorbol ester-sensitive (PKC-dependent) mechanism.
Jamaluddin
M
M
Department of Internal Medicine, University of Texas Medical Branch, Galveston 77555-1060, USA.
Meng
T
T
Sun
J
J
Boldogh
I
I
Han
Y
Y
Brasier
A R
AR
D000804:Angiotensin II / Q000031:analogs & derivatives / Q000494:pharmacology*; D000808:Angiotensinogen / Q000235:genetics* / Q000378:metabolism*; D001483:Base Sequence; D004305:Dose-Response Relationship, Drug; D005786:Gene Expression Regulation; D006801:Humans; D007700:Kinetics; D008025:Ligases / Q000378:metabolism; D008954:Models, Biological; D008969:Molecular Sequence Data; D016328:NF-kappa B / Q000378:metabolism*; D011485:Protein Binding; D020033:Protein Isoforms / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism; D020218:Response Elements; D015398:Signal Transduction; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013997:Time Factors; D014158:Transcription, Genetic; D014162:Transfection; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
D016328:NF-kappa B; D020033:Protein Isoforms; D014409:Tumor Necrosis Factor-alpha; D000808:Angiotensinogen; D000804:Angiotensin II; C074793:angiotensin II, Sar(1)-; D011493:Protein Kinase C; D008025:Ligases; C028812:guanosine 3',5'-polyphosphate synthetases; D013755:Tetradecanoylphorbol Acetate