title: Molecular basis for the cell type specific induction of SnoN expression by hepatocyte growth factor.
abstract: Hepatocyte growth factor (HGF) is a potent antifibrotic cytokine that antagonizes the TGF-beta1/Smad signaling in diverse types of kidney cells by different mechanisms. HGF is shown to induce Smad co-repressor Sloan-Kettering Institute proto-oncogene-related novel gene, non-Alu-containing (SnoN) expression in proximal tubular epithelial cells (HKC-8) but not in glomerular mesangial cells and interstitial fibroblasts. This study investigated the molecular mechanisms underlying the cell type-specific induction of SnoN by HGF. Treatment of HKC-8 cells with actinomycin D completely abolished HGF-mediated SnoN induction, suggesting its dependence on gene transcription. Although HGF activated several signal pathways in HKC-8 cells, blockade of extracellular signal-regulated kinase-1 and -2 (Erk-1/2) activation but not Akt and p38 mitogen-activated protein kinase abolished SnoN induction. HGF rapidly activated both upstream and downstream signaling of Erk-1/2, which led to the activation of the cAMP response element-binding protein (CREB). In the promoter region of human SnoN gene, two cAMP response elements were located in close proximity to Sp1 sites. Chromatin immunoprecipitation assay revealed that activated CREB and Sp1 bound to their cognate cis-acting elements in SnoN promoter in response to HGF stimulation. Ectopic expression of wild-type CREB promoted SnoN expression, whereas dominant negative mutant CREB abrogated SnoN induction by HGF. Likewise, chemical blockade of Sp1 binding abolished HGF-mediated SnoN induction. Furthermore, HGF selectively induced CREB phosphorylation in HKC-8 cells but not in mesangial cells and fibroblasts. In vivo, administration of HGF gene induced renal Erk-1/2 phosphorylation, CREB activation, and SnoN expression in obstructive nephropathy. Collectively, these results suggest that CREB activation, in concert with Sp1, constitutes a molecular switch that confers the cell type-specific induction of SnoN in response to HGF stimulation.
authors.affiliation: Department of Pathology, University of Pittsburgh, S-405 Biomedical Science Tower, 200 Lothrop Street, Pittsburgh, PA 15261, USA.
authors.forename: Ruoyun
authors.initials: R
authors.lastname: Tan
authors.forename: Xianghong
authors.initials: X
authors.lastname: Zhang
authors.forename: Junwei
authors.initials: J
authors.lastname: Yang
authors.forename: Yingjian
authors.initials: Y
authors.lastname: Li
authors.forename: Youhua
authors.initials: Y
authors.lastname: Liu
mesh_terms: D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D004847:Epithelial Cells / Q000201:enzymology; D015870:Gene Expression / Q000187:drug effects / Q000502:physiology; D017228:Hepatocyte Growth Factor / Q000378:metabolism* / Q000494:pharmacology; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics*; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000502:physiology*; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology*; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic / Q000235:genetics; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins / Q000235:genetics*; D016329:Sp1 Transcription Factor / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects / Q000502:physiology
chemical_list: D017362:Cyclic AMP Response Element-Binding Protein; D047908:Intracellular Signaling Peptides and Proteins; C000715470:MAS1 protein, human; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins; C060615:SKIL protein, human; D016329:Sp1 Transcription Factor; D017228:Hepatocyte Growth Factor; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3