title: Notch 1 overexpression inhibits osteoblastogenesis by suppressing Wnt/beta-catenin but not bone morphogenetic protein signaling.
abstract: Notch proteins are transmembrane receptors that control cell-fate decisions. Upon ligand binding, Notch receptors undergo proteolytic cleavage leading to the release of their intracellular domain (NICD). Overexpression of NICD impairs osteoblastogenesis, but the mechanisms are not understood. We examined consequences of the constitutive activation of Notch 1 in ST-2 cells. Notch opposed the effects of bone morphogenetic protein (BMP)-2 and Wnt 3a on alkaline phosphatase activity (APA). BMP-2 induced the phosphorylation of Smad 1/5/8 and the transactivation of a BMP/Smad-responsive construct (12xSBE-Oc-pGL3), but the effect was not modified by Notch. BMP-2 had minimal effects on the phosphorylation of the mitogen-activated protein kinases ERK, p38, and JNK, in the absence or presence of NICD. Notch overexpression decreased the transactivating effect of Wnt 3a, cytoplasmic beta-catenin levels, and Wnt-dependent gene expression. Transfection of a mutant beta-catenin expression construct, or the use of a glycogen synthase kinase 3beta inhibitor to stabilize beta-catenin, partially blocked the inhibitory effect of NICD on Wnt signaling and on APA. HES-1 or Groucho1/TLE1 RNA interference enhanced basal and induced Wnt/beta-catenin signaling opposing NICD effects, but only HES-1 silencing enhanced Wnt 3a effects on APA. In conclusion, NICD overexpression prevents BMP-2 and Wnt biological effects by suppressing Wnt but not BMP signaling. HES-1 appears to mediate effects of Notch on osteoblastogenesis.
authors.affiliation: Department of Research, Saint Francis Hospital and Medical Center, Hartford, Connecticut 06105-1299, USA.
authors.forename: Valerie
authors.initials: V
authors.lastname: Deregowski
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Gazzerro
authors.forename: Leah
authors.initials: L
authors.lastname: Priest
authors.forename: Sheila
authors.initials: S
authors.lastname: Rydziel
authors.forename: Ernesto
authors.initials: E
authors.lastname: Canalis
mesh_terms: D000818:Animals; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins / Q000037:antagonists & inhibitors / Q000502:physiology*; D002454:Cell Differentiation / Q000235:genetics*; D002460:Cell Line; D019070:Cell Lineage / Q000235:genetics; D051379:Mice; D010006:Osteoblasts / Q000166:cytology* / Q000378:metabolism; D051881:Receptor, Notch1 / Q000096:biosynthesis / Q000235:genetics* / Q000502:physiology; D015398:Signal Transduction / Q000235:genetics*; D016212:Transforming Growth Factor beta / Q000037:antagonists & inhibitors / Q000502:physiology*; D051153:Wnt Proteins / Q000037:antagonists & inhibitors* / Q000502:physiology; D060508:Wnt3 Protein; D060509:Wnt3A Protein; D051176:beta Catenin / Q000037:antagonists & inhibitors* / Q000502:physiology
chemical_list: C525719:Bmp2 protein, mouse; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins; C497762:Notch1 protein, mouse; D051881:Receptor, Notch1; D016212:Transforming Growth Factor beta; D051153:Wnt Proteins; D060508:Wnt3 Protein; D060509:Wnt3A Protein; C555511:Wnt3a protein, mouse; D051176:beta Catenin