title: Cross-talk between Wnt and bone morphogenetic protein 2 (BMP-2) signaling in differentiation pathway of C2C12 myoblasts.
abstract: Loss of function of the Wnt co-receptor, lipoprotein receptor-related protein 5, decreases bone formation, and a point mutation in this gene results in high bone mass, indicating the importance of this signaling pathway in bone formation. However, the exact mechanism is currently unknown. We examined a potential role for Wnt signaling and functional cross-talk of bone morphogenetic protein 2 (BMP-2) in osteoblast differentiation. To assess the contribution of Wnt, we generated C2C12 cells over-expressing Wnt3a or Wnt5a and treated these with BMP-2. We showed that expression of matrix extracellular phosphoglycoprotein was induced by BMP-2 in Wnt3a over-expressing C2C12 cells but not in Wnt5a over-expressing C2C12 cells. Over-expression of Wnt3a blocked BMP-2-induced inhibition of myotube formation in C2C12 cells when switched to low mitogen medium. In these cultures, expression of inhibitor of DNA binding/differentiation (Id) 1, a helix-loop-helix protein induced by BMP-2, decreased in stable Wnt3a- but not in Wnt5a-expressing cells. This suppression is mediated by a GC-rich region of the BMP-2-responsive element of the Id1 gene promoter, and interaction between Smad1/4 and beta-catenin is crucial for Wnt-mediated suppression of the BMP-2 response in C2C12 cells. Over-expression of the inhibitor of canonical Wnt signaling, Dickkopf, inhibits this suppression. In contrast, BMP-2 or Smad1/4 up-regulated Wnt3a or activated beta-catenin-induced lymphoid-enhancing factor 1/T cell factor-dependent transcriptional activity. These findings identify functional cross-talk of Id1 expression between Wnt and BMP signaling and demonstrate a novel mechanism for Wnt regulation of the BMP-2 response, linking Id1 expression to Wnt/beta-catenin signaling.
authors.affiliation: Department of Biochemistry and Molecular Biology, Graduate School of Dental Medicine, Hokkaido University, Sapporo, Japan.
authors.forename: Aiko
authors.initials: A
authors.lastname: Nakashima
authors.forename: Takenobu
authors.initials: T
authors.lastname: Katagiri
authors.forename: Masato
authors.initials: M
authors.lastname: Tamura
mesh_terms: D000818:Animals; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology*; D002460:Cell Line; D005786:Gene Expression Regulation; D006801:Humans; D051798:Inhibitor of Differentiation Protein 1 / Q000235:genetics; D051379:Mice; D032446:Myoblasts / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D015675:Osteocalcin / Q000235:genetics; D010750:Phosphoproteins / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D051785:Smad Proteins / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D051153:Wnt Proteins / Q000235:genetics / Q000378:metabolism*; D000071818:Wnt-5a Protein; D060508:Wnt3 Protein; D060509:Wnt3A Protein; D051176:beta Catenin / Q000378:metabolism
chemical_list: C525718:BMP2 protein, human; C525719:Bmp2 protein, mouse; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins; C497455:Idb1 protein, mouse; D051798:Inhibitor of Differentiation Protein 1; D010750:Phosphoproteins; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D051785:Smad Proteins; D016212:Transforming Growth Factor beta; C555510:WNT3A protein, human; D051153:Wnt Proteins; D000071818:Wnt-5a Protein; D060508:Wnt3 Protein; D060509:Wnt3A Protein; C555511:Wnt3a protein, mouse; C438615:Wnt5a protein, mouse; D051176:beta Catenin; D015675:Osteocalcin