The effect of bone morphogenetic protein-7 on the expression of type I inositol 1,4,5-trisphosphate receptor in G-292 osteosarcoma cells and primary osteoblast cultures.

Abstract

Bone morphogenetic protein-7 (BMP-7) affects differentiation of preosteoblasts enabling the resultant cells to respond optimally to acutely acting regulators. As the phosphoinositide cascade and, particularly, the calcium-mobilizing inositol 1,4,5-trisphosphate (InsP3) receptor are integral to stimulus-secretion coupling in osteoblasts, the hypothesis that BMP-7 affects InsP3 receptor expression was examined in the G-292 human osteosarcoma cell line and in primary cultures of human osteoblasts. G-292 osteosarcoma cells were found to be a valid experimental model for primary human osteoblasts, expressing osteoblastic mRNAs encoding osteocalcin, bone sialoprotein, alkaline phosphatase, alpha1-collagen, epidermal growth-factor receptor, and BMP type II receptor. When cultured long term in the presence of ascorbic acid and beta-glycerophosphate, G-292 cells underwent further osteoblastic differentiation, forming nodules and exhibiting restricted mineralization. G-292 cells responded to BMP-7 with an increase in InsP3 receptor density. Ligand-binding studies established that BMP-7 (50 ng/ml) treatment of G-292 cells increased InsP3 receptor density 2.4-fold with no apparent change in affinity. Immunoblot analysis with antibodies specific for type I, type II, and type III InsP3 receptors revealed that BMP-7 (50 ng/ml) treatment resulted in a specific increase (206+/-8%) in the type I receptor. Reverse transcription-polymerase chain reaction and Northern blot analyses of G-292 and primary human osteoblasts confirmed an increase in type I InsP3 receptor mRNA upon BMP-7 treatment. These results demonstrate that G-292 cells respond to BMP-7 with an increase InsP3 receptor density, consistent with the enhanced capacity of these cells to respond to Ca2+-mobilizing secretory hormones during osteoblast differentiation.

• Authors: P G Bradford, J M Maglich, A S Ponticelli, K L Kirkwood
• Journal: Archives of oral biology (Arch Oral Biol) Vol. 45 Issue 2 Pg. 159-66 (Feb 2000) ISSN: 0003-9969 [Print] England
• PMID: 10716620 (Publication Type: Journal Article)

Chemical References

• BMP7 protein, human
• Bone Morphogenetic Protein 7
• Bone Morphogenetic Proteins
• Calcium Channels
• Glycerophosphates
• IBSP protein, human
• ITPR1 protein, human
• Inositol 1,4,5-Trisphosphate Receptors
• Integrin-Binding Sialoprotein
• Phosphatidylinositols
• RNA, Messenger
• Receptors, Cell Surface
• Receptors, Cytoplasmic and Nuclear
• Receptors, Growth Factor
• Sialoglycoproteins
• Transforming Growth Factor beta
• Osteocalcin
• Inositol 1,4,5-Trisphosphate
• Collagen
• ErbB Receptors
• Bone Morphogenetic Protein Receptors
• Alkaline Phosphatase
• Ascorbic Acid
• beta-glycerophosphoric acid

Topics

• Alkaline Phosphatase (genetics)
• Ascorbic Acid (pharmacology)
• Blotting, Northern
• Bone Morphogenetic Protein 7
• Bone Morphogenetic Protein Receptors
• Bone Morphogenetic Proteins (pharmacology)
• Calcification, Physiologic
• Calcium Channels (drug effects, genetics)
• Cell Differentiation
• Cells, Cultured
• Collagen (genetics)
• ErbB Receptors (genetics)
• Gene Expression Regulation
• Gene Expression Regulation, Neoplastic
• Glycerophosphates (pharmacology)
• Humans
• Immunoblotting
• Inositol 1,4,5-Trisphosphate (metabolism)
• Inositol 1,4,5-Trisphosphate Receptors
• Integrin-Binding Sialoprotein
• Osteoblasts (drug effects, metabolism)
• Osteocalcin (genetics)
• Osteosarcoma (genetics, pathology)
• Phosphatidylinositols (metabolism)
• Polymerase Chain Reaction
• RNA, Messenger (genetics)
• Receptors, Cell Surface (genetics)
• Receptors, Cytoplasmic and Nuclear (drug effects, genetics)
• Receptors, Growth Factor
• Sialoglycoproteins (genetics)
• Transforming Growth Factor beta (pharmacology)
• Tumor Cells, Cultured