The renin-angiotensin system (RAS) regulates blood pressure by converting circulating angiotensinogen (AGT) into angiotensin II (AII) which stimulates synthesis of its own precursor AGT. The investigators have discovered a transcriptional mechanism for RAS positive feedback loop where AII activates AGT gene transcription through a previously characterized cytokine-inducible enhancer APRE (Acute Phase Response Element). The APRE sequence binds the nuclear factor-KB (NF-KB) transcription factor family members including RelA which is normally sequestered in the cytoplasm of unstimulated hepatocytes by association with the inhibitory IkB proteins. In preliminary results, the investigators show that AII induces the DNA binding activity of RelA and hypothesize that the NF-KB family members mediate the RAS positive feedback loop. The goal, therefore, is to define how AII activates the NF-KB transcription factors in hepatocyte. The investigators propose to: (1) characterize the AII- inducible NF-KB subunits using gel mobility shift assay, (2) identify the mechanism for activation of the RelA trans-activator, (3) map in detail the AII-inducible domain of RelA, and (4) identify the effect of AII on IKB association with RelA. The expected results will identify the role of RelA as an AII-inducible signal transducing protein and can be applied in the designs of therapeutics to block the effect of AII by inhibiting transcription factor function.
