Fibroblast growth factor-2 represses platelet-derived growth factor receptor-α (PDGFR-α) transcription via ERK1/2-dependent Sp1 phosphorylation and an atypical cis-acting element in the proximal PDGFR-α promoter
Fibroblast growth factor-2 represses platelet-derived growth factor receptor-α (PDGFR-α) transcription via ERK1/2-dependent Sp1 phosphorylation and an atypical cis-acting element in the proximal PDGFR-α promoter
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DOI：
10.1074/jbc.m308254200
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发表时间：
2004-01-23
影响因子：
4.8
通讯作者：
Khachigian, LM
中科院分区：
文献类型：
--
作者：
Bonello, MR;Khachigian, LM
血小板衍生生长因子（PDGF）是一种有效的血管平滑肌细胞（SMCs）的有丝分裂原和化学引诱剂，其生物活性是通过与特定细胞表面受体的高亲和力相互作用介导的。调控PDGF受体α (pdgfr - α)表达的分子机制尚不清楚。我们发现pdgfr - α蛋白在SMCs中的转录调控受到锌指核蛋白Sp1的正向调控。电泳迁移位移、竞争和超位移分析显示，pdgfr - α启动子中存在一个非典型的富含g的sp1结合元件，位于转录起始位点上游61至- 52 bp处。该序列的突变破坏了内源性Sp1结合和pdgfr - α启动子的激活。pdgfr - α转录、mRNA和蛋白表达在暴露于成纤维细胞生长因子-2 （FGF-2）的SMCs中受到抑制。这种抑制是通过阻断细胞外信号调节激酶1/2 （ERK1/2）来恢复的。该sp1反应元件突变后，FGF-2对pdgfr - α转录的抑制作用被取消。FGF-2以erk1 /2而非p38依赖的方式刺激Sp1磷酸化，该生长因子增强Sp1与pdgfr - α启动子的相互作用。Sp1 （ERK磷酸化的氨基酸）中残基Thr（453）和Thr（739）的突变阻断了FGF-2对pdgfr - α转录的抑制。综上所述，这些发现表明FGF-2刺激erk1 /2依赖性Sp1磷酸化，从而通过pdgfr - α启动子中的- 61/ - 52元件抑制pdgfr - α转录。由FGF-2触发的磷酸化将Sp1从pdgfr - α转录的激活因子转换为抑制因子，这一发现在任何Sp1依赖基因中都没有报道过。
Platelet-derived growth factor ( PDGF) is a potent mitogen and chemoattractant for vascular smooth muscle cells (SMCs) whose biological activity is mediated via its high affinity interaction with specific cell surface receptors. The molecular mechanisms governing the expression of PDGF receptor-alpha (PDGFR-alpha) are poorly understood. Here we demonstrate that PDGFR-alpha protein and transcriptional regulation in SMCs is under the positive regulatory influence of the zinc finger nuclear protein, Sp1. Electrophoretic mobility shift, competition, and supershift analysis revealed the existence of an atypical G-rich Sp1-binding element located in the PDGFR-alpha promoter - 61 to - 52 bp upstream of the transcriptional start site. Mutation of this sequence ablated endogenous Sp1 binding and activation of the PDGFR-alpha promoter. PDGFR-alpha transcription, mRNA, and protein expression were repressed in SMCs exposed to fibroblast growth factor-2 (FGF-2). This inhibition was rescued by the blockade of extracellular signal-regulated kinase-1/2 (ERK1/2). FGF-2 repression of PDGFR-alpha transcription was abrogated upon mutation of this Sp1-response element. FGF-2 stimulated Sp1 phosphorylation in an ERK1/2-but not p38-dependent manner, the growth factor enhancing Sp1 interaction with the PDGFR-alpha promoter. Mutation of residues Thr(453) and Thr(739) in Sp1 ( amino acids phosphorylated by ERK) blocked FGF-2 repression of PDGFR-alpha transcription. These findings, taken together, demonstrate that FGF-2 stimulates ERK1/2-dependent Sp1 phosphorylation, thereby repressing PDGFR-alpha transcription via the - 61/ - 52 element in the PDGFR-alpha promoter. Phosphorylation triggered by FGF-2 switches Sp1 from an activator to a repressor of PDGFR-alpha transcription, a finding previously unreported in any Sp1-dependent gene.