Kitami Y, Fukuoka T, Hiwada K, Inagami T
Second Department of Internal Medicine, Ehime University School of Medicine, Onsen-gun, Ehime, Japan.
Circ Res. 1999;84(1):64-73. doi: 10.1161/01.res.84.1.64.
-Platelet-derived growth factor-alpha receptor (PDGF-alphaR) expression is markedly elevated in cultured vascular smooth muscle cells (VSMCs) from spontaneously hypertensive rats (SHR) when compared with normotensive rat strains, Sprague-Dawley, Wistar, and Wistar-Kyoto rats (WKY). This "almost-all-or-none" type of differential expression strongly suggests that PDGF-alphaR or its transcription-regulating mechanisms or factors are significantly related to genetic hypertension. To evaluate the role of PDGF-alphaR in vascular remodeling and hypertension, we have investigated the underlying molecular mechanism. We have recently shown that the regulatory domain responsible for this difference is localized to the PDGF-alphaR promoter region between -246 and -139, which contains an enhancer core sequence specific for CCAAT-enhancer binding proteins (C/EBPs). We defined the roles of this element for hypertensive strain-specific PDGF-alphaR gene transcription. DNA-protein binding studies by competition in electromobility shift and supershift assays revealed that 2 members, C/EBP-beta and C/EBP-delta, are mainly responsible for DNA-protein complex formation; the former acts as a transcriptional repressor and the latter as an activator of the PDGF-alphaR gene, respectively. Western or Northern blot analyses supported evidence for high expression of C/EBP-delta seen only in SHR-derived VSMCs. Furthermore, forced expression of C/EBP-delta transactivated the transcriptional efficiency of the PDGF-alphaR gene even in WKY-derived VSMCs, whereas that of C/EBP-beta had an opposite effect in SHR-derived VSMCs. These findings indicate that differential expression of members of the C/EBP family, mainly C/EBP-delta and possibly C/EBP-beta, are responsible for the strain-specific gene transcription of PDGF-alphaR in VSMCs.
与正常血压大鼠品系（斯普拉格 - 道利大鼠、Wistar大鼠和Wistar - Kyoto大鼠（WKY））相比，自发性高血压大鼠（SHR）培养的血管平滑肌细胞（VSMC）中血小板衍生生长因子α受体（PDGF - αR）的表达明显升高。这种“几乎全有或全无”类型的差异表达强烈表明，PDGF - αR或其转录调控机制或因子与遗传性高血压显著相关。为了评估PDGF - αR在血管重塑和高血压中的作用，我们研究了其潜在的分子机制。我们最近发现，负责这种差异的调控域定位于PDGF - αR启动子区域的 - 246至 - 139之间，该区域包含CCAAT增强子结合蛋白（C/EBP）特有的增强子核心序列。我们确定了该元件在高血压品系特异性PDGF - αR基因转录中的作用。通过电泳迁移率变动分析和超迁移分析中的竞争进行的DNA - 蛋白质结合研究表明，C/EBP - β和C/EBP - δ这两个成员主要负责DNA - 蛋白质复合物的形成；前者分别作为转录抑制因子，后者作为PDGF - αR基因的激活因子。蛋白质免疫印迹或Northern印迹分析支持了仅在SHR来源的VSMC中观察到C/EBP - δ高表达的证据。此外，即使在WKY来源的VSMC中，C/EBP - δ的强制表达也能激活PDGF - αR基因的转录效率，而C/EBP - β在SHR来源的VSMC中则有相反的作用。这些发现表明，C/EBP家族成员的差异表达，主要是C/EBP - δ，可能还有C/EBP - β，是VSMC中PDGF - αR品系特异性基因转录的原因。
