title: Hydrogen peroxide regulates osteopontin expression through activation of transcriptional and translational pathways.
abstract: Recent in vivo studies establish that osteopontin (OPN) expression is hydrogen peroxide (H2O2)-dependent. However, the mechanisms by which H2O2 increases OPN expression remain poorly defined. OPN protein expression increased in an unusual biphasic pattern in response to H2O2. To investigate whether these increases were mediated through transcriptional and/or translational regulation of OPN, smooth muscle cells stimulated with 50 μM H2O2 were used as an in vitro cell system. Early protein increases at 6 h were not preceded by increased mRNA, whereas later increases (18 h) were, suggesting multiple mechanisms of regulation by H2O2. Polyribosomal fractionation assays established that early increases (6 h) in OPN expression were due to increased translation. This increase in translation occurred through phosphorylation of 4E-BP1 at the reactive oxygen species-sensitive Ser-65, which allowed for release and activation of eukaryotic initiation factor eIF4E and subsequent OPN translation. This early increase (6 h) in OPN was blunted in cells expressing a phospho-deficient 4E-BP1 mutant. H2O2 stimulation increased rat OPN promoter activity at 8 and 18 h, and promoter truncation studies established that promoter region -2284 to -795 is crucial for H2O2-dependent OPN transcription. ChIP studies determined that H2O2-dependent transcription is mediated by the reactive oxygen species-sensitive transcription factors NF-κB and AP-1. In conclusion, H2O2 stimulates OPN expression in a unique biphasic pattern, where early increases are translational and late increases are transcriptional.
authors.affiliation: From the Division of Cardiology and.
authors.forename: Alicia N
authors.initials: AN
authors.lastname: Lyle
authors.forename: Ebony W
authors.initials: EW
authors.lastname: Remus
authors.forename: Aaron E
authors.initials: AE
authors.lastname: Fan
authors.forename: Bernard
authors.initials: B
authors.lastname: Lassègue
authors.forename: Grant A
authors.initials: GA
authors.lastname: Walter
authors.forename: Arihiro
authors.initials: A
authors.lastname: Kiyosue
authors.forename: Kathy K
authors.initials: KK
authors.lastname: Griendling
authors.forename: W Robert
authors.initials: WR
authors.lastname: Taylor
mesh_terms: D000818:Animals; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D002478:Cells, Cultured; D039561:Eukaryotic Initiation Factor-4E / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects* / Q000502:physiology; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D047908:Intracellular Signaling Peptides and Proteins; D009154:Mutation; D032389:Myocytes, Smooth Muscle / Q000166:cytology / Q000378:metabolism*; D053495:Osteopontin / Q000096:biosynthesis* / Q000235:genetics; D016877:Oxidants / Q000494:pharmacology*; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects / Q000502:physiology; D011132:Polyribosomes / Q000235:genetics / Q000378:metabolism; D014176:Protein Biosynthesis / Q000187:drug effects* / Q000502:physiology; D051381:Rats; D014158:Transcription, Genetic / Q000187:drug effects* / Q000502:physiology
chemical_list: D002352:Carrier Proteins; C499526:Eif4ebp1 protein, rat; D039561:Eukaryotic Initiation Factor-4E; D047908:Intracellular Signaling Peptides and Proteins; D016877:Oxidants; D010750:Phosphoproteins; C506897:Spp1 protein, rat; D053495:Osteopontin; D006861:Hydrogen Peroxide
keywords: Hydrogen Peroxide; Osteopontin; Reactive Oxygen Species (ROS); Transcription; Translation