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

肾素结合蛋白(RnBP)是一种与肾素结合形成高分子量(HMW)肾素的蛋白质复合体。这种蛋白质会抑制肾素活性。为探讨RnBP的生理功能，采用Northern杂交技术检测了RnBP在大鼠主动脉中的基因表达。RnBP基因在大鼠主动脉、肾脏、肾上腺、脑和卵巢中均有表达。用原位RT-PCR方法检测RnBP基因在大鼠肾脏中的定位，结果表明RnBP基因在延髓旁肾小球和肾小球血管内皮细胞中均有表达。Northern印迹杂交分析显示，猪主动脉来源的血管内皮细胞表达高水平的RnBP基因。为了研究猪肾素基因表达与RnBP基因表达的关系，通过RT-PCR分析Preine肾脏mRNA，获得了猪肾素基因片段，并测定了猪肾素基因的核苷酸序列。最后，对猪血管内皮细胞肾素基因的RT-PCR分析表明，肾素基因在同一内皮细胞中也有表达。血管紧张素Ⅱ和转化生长因子-β可上调血管内皮细胞RnBP基因的表达，但不受肿瘤坏死因子-α的影响。因此，血管紧张素Ⅱ对RnBP基因表达的调节表明，RnBP作为血管肾素-血管紧张素系统的一员参与了血管内皮细胞的血压调节。

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.