TY - JOUR
T1 - Transforming growth factor-β up-regulates the β5 integrin subunit expression via Sp1 and Smad signaling
AU - Lai, C. F.
AU - Feng, X.
AU - Nishimura, R.
AU - Teitelbaum, S. L.
AU - Avioli, L. V.
AU - Ross, F. P.
AU - Cheng, S. L.
PY - 2000/11/17
Y1 - 2000/11/17
N2 - Integrin-mediated cell-matrix interactions play important roles in regulating cell function. Since transforming growth factor-β (TGF-β) modulates many osteoblast activities, we hypothesized that the growth factor acts in part by modulating integrin expression. TGF-β increased cell adhesion to vitronectin and up-regulated the surface level of α(v)β5 via increasing β5 protein synthesis by a transcriptional mechanism. Promoter activity analysis demonstrated that a TGF-β-responsive element resides between nucleotides -63 and -44. Electrophoretic mobility shift assay and immunoprecipitation/Western studies indicated that the nuclear complex formed using the -66/-42 oligonucleotide contained both Sp1/Sp3 and Smad proteins. Since nuclear Sp1/Sp3 levels were not altered, whereas Smad levels were increased by TGF-β, we investigated the roles of Smad proteins in the up-regulation of β5 gene activation. Co-transfection of cells with β5 promoter reporter construct and expression vectors for Smad3, Smad4, and Sp1 increased the stimulatory effect of TGF-β. Furthermore, expression of dominant negative Smad3 or Smad4 in cells decreased or abolished the stimulation of β5 promoter activity by TGF-β. Smad4 mutant also inhibited the up-regulation of surface β5 level by TGF-β. Thus, TGF-β increases expression of the integrin β5 gene by mechanisms involving Sp1/Sp3 and Smad transcription factors.
AB - Integrin-mediated cell-matrix interactions play important roles in regulating cell function. Since transforming growth factor-β (TGF-β) modulates many osteoblast activities, we hypothesized that the growth factor acts in part by modulating integrin expression. TGF-β increased cell adhesion to vitronectin and up-regulated the surface level of α(v)β5 via increasing β5 protein synthesis by a transcriptional mechanism. Promoter activity analysis demonstrated that a TGF-β-responsive element resides between nucleotides -63 and -44. Electrophoretic mobility shift assay and immunoprecipitation/Western studies indicated that the nuclear complex formed using the -66/-42 oligonucleotide contained both Sp1/Sp3 and Smad proteins. Since nuclear Sp1/Sp3 levels were not altered, whereas Smad levels were increased by TGF-β, we investigated the roles of Smad proteins in the up-regulation of β5 gene activation. Co-transfection of cells with β5 promoter reporter construct and expression vectors for Smad3, Smad4, and Sp1 increased the stimulatory effect of TGF-β. Furthermore, expression of dominant negative Smad3 or Smad4 in cells decreased or abolished the stimulation of β5 promoter activity by TGF-β. Smad4 mutant also inhibited the up-regulation of surface β5 level by TGF-β. Thus, TGF-β increases expression of the integrin β5 gene by mechanisms involving Sp1/Sp3 and Smad transcription factors.
UR - http://www.scopus.com/inward/record.url?scp=0034680856&partnerID=8YFLogxK
U2 - 10.1074/jbc.M002131200
DO - 10.1074/jbc.M002131200
M3 - Article
C2 - 10964912
AN - SCOPUS:0034680856
SN - 0021-9258
VL - 275
SP - 36400
EP - 36406
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 46
ER -