Molecular Biological Analysis of function and signal transduction of renin-binding protein

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Renin binding protein (RnBP) is a protein that binds to renin to form a protein complex called high molecular weight (HMW) renin. This protein inhibits renin activity. In search of its physiological function gene expression of RnBP in rat aorta were examined by Northern blot hybridization. RnBP gene expression was observed in rat aorta, in addition to kidney, adrenal gland, brain, and ovary.Using In situ RT-PCR analysis to determine RnBP mRNA localization in rat kidney, it was suggested that RnBP mRNA was expressed in juxtamedullary glomerulus and vascular endothelial cells in glomerulus. The artcrial endothelial cells derived from porcine aorta exhibited high level of RnBP gene expression, detected by Northern blot hybridization analysis. In order to study renin gene expression in relation to that of RnBP, porcine renin cDNA fragment was isolated by RT-PCR analysis of preine kidney mRNA, followed by determination of the nucleotide sequence for porcine renin. Finally, RT- PCR analysis of porcine renin mRNA in endothelial cells has shown that renin gene is also expressed in the same endothelium. RnBP gene expression was shown to be up-regulated by Angiotensin II and TGF-beta, hut not by TNF-alfa in cultured endothelial cells.Therefore, RnBP regulation by angiotensn II suggests that RnBP participate in blood pressure regulation at vascular endothelum as a member of vascular renin-angiotensin system.