title: Activation of extracellular signal-regulated kinase by TGF-beta1 via TbetaRII and Smad7 dependent mechanisms in human bronchial epithelial BEP2D cells.
abstract: Transforming growth factor-beta1 (TGF-beta1) can activate mitogen-activated protein kinases (MAPKs) in many types of cells. The mechanism of this activation is not well elucidated. Here, we explore the role of TGF-beta/Smads signaling compounds in TGF-beta1-mediated activation of extracellular signal-regulated kinase (ERK) MAPK in human papillomavirus (HPV)-18 immortalized human bronchial epithelial cell line BEP2D and the role of TGF-beta1-induced phosphorylation of ERK in proliferation and apoptosis of BEP2D. The cell models of siRNA-mediated silencing of TGF-beta receptor type II (TbetaRII), Smad2, Smad3, Smad4, and Smad7 were employed in this study. Our results demonstrate that TGF-beta1 activates ERK in a time-dependent manner with a maximum effect at 60 min; overexpression of Smad7 increased this TGF-beta1-mediated phosphorylation of the ERK; and siRNA-mediated silencing of TbetaRII, Smad3, Smad4, and Smad7 abrogated this effect. Moreover, we observed that overexpression of Smad7 restored TGF-beta1-mediated ERK phosphorylation in Smad4 knockdown cells but not in TbetaRII knockdown cells. In BEP2D cells, TGF-beta1 treatment effectively inhibited cells' proliferation and induced their apoptosis. Pretreatment with U0126, an inhibitor of ERK1/2, significantly enhanced the TGF-beta1-mediated antiproliferative and apoptosis induction effects in BEP2D cells. These data revealed that TbetaRII and Smad7 play the critical roles in TGF-beta1-mediated activation of ERK; Smad3 and Smad4 can play an indirect role through up-regulating Smad7 expression; and TGF-beta1-induced phosphorylation of ERK may participate in BEP2D cell proliferation and apoptosis regulation.
authors.affiliation: Department of Radiation Toxicology and Oncology, Beijing Institute of Radiation Medicine, 27 Taiping Road, Haidian District, Beijing, 100850, PR China. yanying_huo@yahoo.com.cn
authors.forename: Y-Y
authors.initials: YY
authors.lastname: Huo
authors.forename: Y-C
authors.initials: YC
authors.lastname: Hu
authors.forename: X-R
authors.initials: XR
authors.lastname: He
authors.forename: Y
authors.initials: Y
authors.lastname: Wang
authors.forename: B-Q
authors.initials: BQ
authors.lastname: Song
authors.forename: P-K
authors.initials: PK
authors.lastname: Zhou
authors.forename: M-X
authors.initials: MX
authors.lastname: Zhu
authors.forename: G
authors.initials: G
authors.lastname: Li
authors.forename: D-C
authors.initials: DC
authors.lastname: Wu
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D001483:Base Sequence; D001980:Bronchi / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D020935:MAP Kinase Signaling System / Q000187:drug effects*; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D000077294:Receptor, Transforming Growth Factor-beta Type II; D018125:Receptors, Transforming Growth Factor beta / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D051899:Smad2 Protein / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D051900:Smad3 Protein / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D051901:Smad4 Protein / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D051906:Smad7 Protein / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D014162:Transfection; D053773:Transforming Growth Factor beta1 / Q000494:pharmacology*
chemical_list: D012333:RNA, Messenger; D034741:RNA, Small Interfering; D018125:Receptors, Transforming Growth Factor beta; C497782:SMAD2 protein, human; C497790:SMAD3 protein, human; C497796:SMAD4 protein, human; C497806:SMAD7 protein, human; D051899:Smad2 Protein; D051900:Smad3 Protein; D051901:Smad4 Protein; D051906:Smad7 Protein; D053773:Transforming Growth Factor beta1; D017346:Protein Serine-Threonine Kinases; D000077294:Receptor, Transforming Growth Factor-beta Type II