AP-1 mediates stretch-induced expression of HB-EGF in bladder smooth muscle cells
AP-1 mediates stretch-induced expression of HB-EGF in bladder smooth muscle cells
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DOI：
10.1152/ajpcell.1999.277.2.c294
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发表时间：
1999-08-01
影响因子：
5.5
通讯作者：
Freeman, MR
中科院分区：
文献类型：
--
作者：
Park, JM;Adam, RM;Freeman, MR
生长因子合成的机械诱导可以介导平滑肌细胞（SMC）对物理负荷增加的适应性反应。我们以前证明，周期性机械拉伸诱导表达的SMC，成纤维细胞，上皮细胞有丝分裂原肝素结合表皮生长因子样生长因子（HB-EGF）在膀胱SMC，观察表明，这种生长因子可能参与代偿性膀胱肥大。在本研究中，我们提供的证据表明，激活蛋白-1（AP-1）转录因子在这一机械诱导过程中起着至关重要的作用。用一系列5 ′端缺失突变体瞬时转染大鼠膀胱平滑肌细胞，该突变体含有1.7kb的小鼠HB-EGF启动子，Tvas先前显示该启动子是牵张反应性的。随着核苷酸位置-1301至-881的缺失，延伸介导的启动子活性的增加被完全消除。通过电泳迁移率变动分析评估，AP-1与含有AP-1结合位点的合成寡核苷酸的结合在对拉伸的反应中增加，并且结合被对应于来自HB-EGF启动子的核苷酸-993至-973的过量未标记DNA抑制，所述HB-EGF启动子是含有先前识别的复合AP-1/Ets位点的区域。拉伸诱导的启动子活性显着抑制AP-1或Ets组件的这个网站的定点突变。与启动子和凝胶位移研究一致，姜黄素，AP-1激活的抑制剂，抑制拉伸后的HB-EGF mRNA诱导。拉伸还特异性地增加基质金属蛋白酶（MMP）-1的mRNA水平，其启动子含有功能性AP-1元件，但不增加MMP-2的mRNA水平，其启动子不含有AP-1元件。MMP-1基因的拉伸反应也被姜黄素完全抑制。总的来说，这些研究结果表明，AP-1介导的转录起着重要的作用，在膀胱肌肉中的基因表达的调节响应机械力。
Mechanical induction of growth factor synthesis may mediate adaptive responses of smooth muscle cells (SMC) to increases in physical load. We previously demonstrated that cyclic mechanical stretch induces expression of the SMC, fibroblast, and epithelial cell mitogen heparin-binding epidermal growth factor-like growth factor (HB-EGF) in bladder SMC, an observation that suggests that this growth factor may be involved in compensatory bladder hypertrophy. In the present study we provide evidence that the activator protein-1 (AP-1) transcription factor plays a critical role in this mechanoinduction process. Rat bladder SMC were transiently transfected with a series of 5' deletion mutants of a promoter-reporter construct containing 1.7 kb of the mouse HB-EGF promoter that Tvas previously shown to be stretch responsive. The stretch-mediated increase in promoter activity was completely ablated with deletion of nucleotide positions -1301 to -881. Binding of AP-1, as evaluated by electrophoretic mobility shift assay, to a synthetic oligonucleotide containing an AP-1 binding site increased in response to stretch, and binding was inhibited by excess unlabeled DNA corresponding to nucleotides -993 to -973 from the HB-EGF promoter, a region that contains a previously recognized composite AP-1/Ets site. Stretch-induced promoter activity was significantly inhibited by site-directed mutagenesis of the AP-1 or Ets components of this site. Consistent with the promoter and gel-shift studies, curcumin, an inhibitor of AP-1 activation, suppressed the HB-EGF mRNA induction after stretch. Stretch also specifically increased mRNA levels for matrix metalloproteinase (MMP)-1, the promoter of which contains a functional AP-1 element, but not for MMP-2, the promoter of which does not contain an AP-1 element. The stretch response of the MMP-1 gene was also completely inhibited by curcumin. Collectively, these findings indicate that AP-1-mediated transcription plays an important role in the regulation of gene expression in bladder muscle in response to mechanical forces.