title: Transcriptional induction of FosB/DeltaFosB gene by mechanical stress in osteoblasts.
abstract: Mechanical stress to bone plays a critical role in maintaining bone mass and strength. However, the molecular mechanism of mechanical stress-induced bone formation is not fully understood. In the present study, we demonstrate that FosB and its spliced variant DeltaFosB, which is known to increase bone mass by stimulating bone formation in vivo, is rapidly induced by mechanical loading in mouse hind limb bone in vivo and by fluid shear stress (FSS) in mouse calvarial osteoblasts in vitro both at the mRNA and protein levels. FSS induction of FosB/DeltaFosB gene expression was dependent on gadlinium-sensitive Ca(2+) influx and subsequent activation of ERK1/2. Analysis of the mouse FosB/DeltaFosB gene upstream regulatory region with luciferase reporter gene assays revealed that the FosB/DeltaFosB induction by FSS occurred at the transcriptional level and was conferred by a short fragment from -603 to -327. DNA precipitation assays and DNA decoy experiments indicated that ERK-dependent activation of CREB binding to a CRE/AP-1 like element (designated "CRE2") at the position of -413 largely contributed to the transcriptional effects of FSS. These results suggest that DeltaFosB participates in mechanical stress-induced intracellular signaling cascades that activate the osteogenic program in osteoblasts.
authors.affiliation: Department of Medicine and Bioregulatory Sciences, University of Tokushima Graduate School of Medicine, 3-18-15 Kuramoto-cho, Tokushima 770-8503, Japan. inoued@clin.med.tokushima-u.ac.jp
authors.forename: Daisuke
authors.initials: D
authors.lastname: Inoue
authors.forename: Shinsuke
authors.initials: S
authors.lastname: Kido
authors.forename: Toshio
authors.initials: T
authors.lastname: Matsumoto
mesh_terms: D017398:Alternative Splicing; D000818:Animals; D001483:Base Sequence; D002118:Calcium / Q000378:metabolism; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005682:Gadolinium / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D010006:Osteoblasts / Q000378:metabolism*; D011453:Prostaglandins / Q000378:metabolism; D016760:Proto-Oncogene Proteins c-fos / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger; D013314:Stress, Mechanical
chemical_list: D017362:Cyclic AMP Response Element-Binding Protein; C483819:Fosb protein, mouse; D011453:Prostaglandins; D016760:Proto-Oncogene Proteins c-fos; D012333:RNA, Messenger; D005682:Gadolinium; D048049:Extracellular Signal-Regulated MAP Kinases; D002118:Calcium