TY - JOUR
T1 - AP-1 mediates stretch-induced expression of HB-EGF in bladder smooth muscle cells
AU - Park, John M.
AU - Adam, Rosalyn M.
AU - Peters, Craig A
AU - Guthrie, Paul D.
AU - Sun, Zijie
AU - Klagsbrun, Michael
AU - Freeman, Michael R.
PY - 1999
Y1 - 1999
N2 - 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 was 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.
AB - 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 was 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.
KW - Activator protein
KW - Gene expression
KW - Heparin-binding epidermal growth factor
KW - Mechanical signaling
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U2 - 10.1152/ajpcell.1999.277.2.c294
DO - 10.1152/ajpcell.1999.277.2.c294
M3 - Article
C2 - 10444406
AN - SCOPUS:0032829051
SN - 0363-6143
VL - 277
SP - C294-C301
JO - American Journal of Physiology - Cell Physiology
JF - American Journal of Physiology - Cell Physiology
IS - 2 46-2
ER -