title: C-type natriuretic peptide enhances osteogenic protein-1-induced osteoblastic cell differentiation via Smad5 phosphorylation.
abstract: In the present study, we examined the hypothesis that the C-type natriuretic peptide (CNP) enhances osteogenic protein-1 (OP-1) action in stimulating osteoblastic cell differentiation in primary cultures of fetal rat calvaria cell (FRC). CNP enhanced synergistically the OP-1-induced Alkaline Phosphatase (AP) activity and mineralized bone nodule formation in a dose- and time-dependent manner. To examine possible mechanism of the synergy between OP-1 and CNP, the expression levels of key BMP receptors and signaling molecules were examined. Western blot analysis showed that BMPR-IB and -II receptor protein expression was not affected by CNP alone, but was stimulated by OP-1 alone. The combination of OP-1 and CNP did not further increase their protein levels. The Runx2 protein expression level was not altered by CNP alone, but was elevated by OP-1 alone, and was slightly reduced by the combination. The Smad5 protein expression level was slightly decreased by CNP alone, but was stimulated by OP-1 alone, and was not further stimulated by the combination. Smad5 phosphorylation was not stimulated by CNP alone, but was stimulated significantly by OP-1 alone. The combination of OP-1 and CNP further stimulated the OP-1-induced Smad5 phosphorylation. Thus, one mechanism of the observed synergy between OP-1 and CNP involves enhancement of the Smad5 phosphorylation.
authors.affiliation: Department of Biochemistry, The University of Texas Health Science Center, 7703 Floyd Curl Drive, San Antonio, TX 78229-3900, USA. carolyeh@biochem.uthscsa.edu
authors.forename: Lee-Chuan C
authors.initials: LC
authors.lastname: Yeh
authors.forename: Michelle C
authors.initials: MC
authors.lastname: Zavala
authors.forename: John C
authors.initials: JC
authors.lastname: Lee
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D015153:Blotting, Western; D055419:Bone Morphogenetic Protein 7; D052005:Bone Morphogenetic Protein Receptors, Type I / Q000378:metabolism; D052006:Bone Morphogenetic Protein Receptors, Type II / Q000378:metabolism; D019485:Bone Morphogenetic Proteins / Q000494:pharmacology*; D002454:Cell Differentiation / Q000187:drug effects; D050659:Core Binding Factor Alpha 1 Subunit / Q000378:metabolism; D004357:Drug Synergism; D005333:Fetus / Q000166:cytology / Q000378:metabolism; D020098:Natriuretic Peptide, C-Type / Q000494:pharmacology*; D010006:Osteoblasts / Q000166:cytology* / Q000378:metabolism; D010012:Osteogenesis; D010766:Phosphorylation; D051381:Rats; D012886:Skull / Q000166:cytology / Q000378:metabolism; D051898:Smad1 Protein / Q000378:metabolism; D051902:Smad5 Protein / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000494:pharmacology*
chemical_list: C525821:Bmp7 protein, rat; D055419:Bone Morphogenetic Protein 7; D019485:Bone Morphogenetic Proteins; D050659:Core Binding Factor Alpha 1 Subunit; D051898:Smad1 Protein; D051902:Smad5 Protein; D016212:Transforming Growth Factor beta; D020098:Natriuretic Peptide, C-Type; D052005:Bone Morphogenetic Protein Receptors, Type I; D052006:Bone Morphogenetic Protein Receptors, Type II; D000469:Alkaline Phosphatase