Effects of inhibitors of signal transduction pathways on transforming growth factor B1 and osteogenic protein-1-induced insulinlike growth factor binding protein-3 expression in human bone cells

✍ Scribed by Narasimhan Srinivasan; David J. Baylink; Kuber Sampath; Subburaman Mohan

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 202 KB
• Volume: 173
• Category: Article
• ISSN: 0021-9541
• DOI: 10.1002/(sici)1097-4652(199710)173:1<28::aid-jcp4>3.0.co;2-l

✦ Synopsis

Signal transduction initiated by TGFb1 and OP-1 was studied in MG63 human osteosarcoma cells and in normal human bone cells (HBCs) in the presence of inhibitors of signal transduction events, using insulinlike growth factor binding protein-3 (IGFBP-3) production as an end point. Treatment of serum-free MG63 cells and normal HBCs with TGFb1 increased IGFBP-3 protein level several fold in the conditioned medium. This effect of TGFb1 was mediated by increased de novo synthesis because mRNA level increased to the same extent as protein level and TGFb1 treatment had very little effect on IGFBP-3 protease activity. The stimulatory effect of TGFb1 on IGFBP-3 production was inhibited in a dosedependent manner by pretreatment with staurosporine, a protein kinase C inhibitor, or with vanadate, a phosphotyrosyl protein phosphatase inhibitor in both MG63 cells and normal HBCs. In addition, pretreatment with okadoic acid, an inhibitor of serine/threonine protein phosphatase, counteracted TGFb1 induction of IGFBP-3 production. Interestingly, pretreatment of MG63 cells or HBCs with staurosporine, vanadate, or okadoic acid augmented OP-1 stimulation of IGFBP-3 production. Staurosporine-or vanadate-induced changes in IGFBP-3 protein levels in the presence of TGFb1 and OP-1 were associated with corresponding changes in IGFBP-3 mRNA levels in MG63 cells. These findings are consistent with the hypothesis that TGFb1 and OP-1 increase IGFBP-3 expression via distinct intracellular signal transduction pathways.