Yang N, Eckhart A D, Xin X, Faber J E
Department of Physiology, University of North Carolina, Chapel Hill 27599-7545, USA.
Am J Physiol. 1997 Jul;273(1 Pt 2):H85-95. doi: 10.1152/ajpheart.1997.273.1.H85.
Contractile and binding studies indicate that alpha 2-adrenergic receptors (ARs) are differentially expressed by vascular smooth muscle cells (SMCs) according to vascular segment (artery, arteriole, vein). In the present study, alpha 2D-AR mRNA was two- to threefold higher in vena cava than in aorta. To understand vascular regulation of alpha 2D-AR expression in these cells, we sequenced 2.8 kb of the 5' flanking region of the alpha 2D-AR gene. Notable features include two potential TATA boxes, an adenosine 3',5'-cyclic monophosphate response element (CRE)-like binding element, and an Sp1 element. Comparison of the rat and human genes revealed an overall homology of 74% over the 1.87-kb sequence 5' to the translation initiator methionine, including complete homology at the distal TATA, CRE-like, and Sp1 sites, alpha 2D-AR transcription starts from the guanine nucleotide 18 base pair downstream from the distal TATA box. Reporter gene constructs demonstrated strong alpha 2D-AR promoter activity, but with several differences in construct activity, in both rat aorta and vena cava SMCs. Analysis of an essential promoter fragment revealed two regions protected by aorta and vena cava SMC nuclear proteins. The core sequences of these protected regions are TGACGCTA and TATAA. The former CRE-like element conferred specific binding of both aorta and vena cava nuclear proteins. In addition, promoter activity was increased 300% by forskolin or 8-bromoadenosine 3',5'-cyclic monophosphate, indicating that the CRE-like element may regulate alpha 2D-AR expression in vascular tissue.
收缩和结合研究表明，α2 - 肾上腺素能受体（ARs）在血管平滑肌细胞（SMCs）中的表达因血管段（动脉、小动脉、静脉）而异。在本研究中，腔静脉中α2D - AR mRNA的含量比主动脉中高两到三倍。为了解这些细胞中α2D - AR表达的血管调节机制，我们对α2D - AR基因5'侧翼区的2.8 kb序列进行了测序。显著特征包括两个潜在的TATA盒、一个腺苷3',5'-环磷酸反应元件（CRE）样结合元件和一个Sp1元件。大鼠和人类基因的比较显示，在翻译起始甲硫氨酸上游1.87 kb序列上，总体同源性为74%，包括远端TATA、CRE样和Sp1位点的完全同源性。α2D - AR转录从远端TATA盒下游18个碱基对的鸟嘌呤核苷酸开始。报告基因构建体在大鼠主动脉和腔静脉SMC中均显示出强大的α2D - AR启动子活性，但构建体活性存在一些差异。对一个必需启动子片段的分析揭示了两个受主动脉和腔静脉SMC核蛋白保护的区域。这些受保护区域的核心序列是TGACGCTA和TATAA。前一个CRE样元件赋予了主动脉和腔静脉核蛋白的特异性结合。此外，福司可林或8 - 溴腺苷3',5'-环磷酸可使启动子活性增加300%，表明CRE样元件可能调节血管组织中α2D - AR的表达。
