title: Transforming growth factor-beta up-regulates the beta 5 integrin subunit expression via Sp1 and Smad signaling.
abstract: Integrin-mediated cell-matrix interactions play important roles in regulating cell function. Since transforming growth factor-beta (TGF-beta) modulates many osteoblast activities, we hypothesized that the growth factor acts in part by modulating integrin expression. TGF-beta increased cell adhesion to vitronectin and up-regulated the surface level of alpha(v)beta(5) via increasing beta(5) protein synthesis by a transcriptional mechanism. Promoter activity analysis demonstrated that a TGF-beta-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-beta, we investigated the roles of Smad proteins in the up-regulation of beta(5) gene activation. Co-transfection of cells with beta(5) promoter reporter construct and expression vectors for Smad3, Smad4, and Sp1 increased the stimulatory effect of TGF-beta. Furthermore, expression of dominant negative Smad3 or Smad4 in cells decreased or abolished the stimulation of beta(5) promoter activity by TGF-beta. Smad4 mutant also inhibited the up-regulation of surface beta(5) level by TGF-beta. Thus, TGF-beta increases expression of the integrin beta(5) gene by mechanisms involving Sp1/Sp3 and Smad transcription factors.
authors.affiliation: Division of Bone and Mineral Diseases, Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
authors.forename: C F
authors.initials: CF
authors.lastname: Lai
authors.forename: X
authors.initials: X
authors.lastname: Feng
authors.forename: R
authors.initials: R
authors.lastname: Nishimura
authors.forename: S L
authors.initials: SL
authors.lastname: Teitelbaum
authors.forename: L V
authors.initials: LV
authors.lastname: Avioli
authors.forename: F P
authors.initials: FP
authors.lastname: Ross
authors.forename: S L
authors.initials: SL
authors.lastname: Cheng
mesh_terms: D000818:Animals; D001483:Base Sequence; D002448:Cell Adhesion / Q000187:drug effects; D002460:Cell Line; D004247:DNA / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D016023:Integrins / Q000235:genetics* / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D009687:Nuclear Proteins / Q000032:analysis / Q000378:metabolism; D010006:Osteoblasts / Q000187:drug effects / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D019030:Receptors, Vitronectin; D020218:Response Elements / Q000235:genetics; D015398:Signal Transduction / Q000187:drug effects*; D051900:Smad3 Protein; D051901:Smad4 Protein; D016329:Sp1 Transcription Factor / Q000378:metabolism*; D051705:Sp3 Transcription Factor; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects; D016212:Transforming Growth Factor beta / Q000494:pharmacology*; D053781:Transforming Growth Factor beta2; D015854:Up-Regulation / Q000187:drug effects*; D019096:Vitronectin / Q000378:metabolism
chemical_list: D004268:DNA-Binding Proteins; D016023:Integrins; D009687:Nuclear Proteins; D012333:RNA, Messenger; D019030:Receptors, Vitronectin; D051900:Smad3 Protein; C497791:Smad3 protein, mouse; D051901:Smad4 Protein; C490810:Smad4 protein, mouse; D016329:Sp1 Transcription Factor; C497122:Sp3 protein, mouse; D015534:Trans-Activators; D014157:Transcription Factors; D016212:Transforming Growth Factor beta; D053781:Transforming Growth Factor beta2; D019096:Vitronectin; C064660:integrin alphaVbeta5; D051705:Sp3 Transcription Factor; D004247:DNA