Basic fibroblast growth factor stimulates fibronectin expression through phospholipase C gamma, protein kinase C alpha, c-Src, NF-kappaB, and p300 pathway in osteoblasts.
Fibronectin (Fn) is involved in early stages of bone formation and basic fibroblast growth factor (bFGF) is an important factor regulating osteogenesis. bFGF increased Fn expression, which was attenuated by phosphatidylinositol phospholipase inhibitor (U73122), protein kinase C inhibitor (GF109203X), Src inhibitor (PP2), NF-kappaB inhibitor (PDTC), IkappaBalpha phosphorylation inhibitor (Bay 117082), or IkappaB protease inhibitor (TPCK). bFGF-induced increase of Fn-luciferase activity was antagonized by cells transfected with Fn construct without NF-kappaB regulatory site. Stimulation of osteoblasts with bFGF activated IkappaB kinase alpha/beta (IKK alpha/beta) and increased IkappaBalpha phosphorylation, IkappaBalpha degradation, p65 and p50 translocation from the cytosol to the nucleus, the formation of an NF-kappaB-specific DNA-protein complex and kappaB-luciferase activity. bFGF-mediated an increase of IKKalpha/beta activity and DNA-binding activity was inhibited by U73122, GF109203X, or PP2. The binding of p65 to the NF-kappaB element, as well as the recruitment of p300 and the enhancement of p50 acetylation on the Fn promoter was enhanced by bFGF. Overexpression of constitutively active FGF receptor 2 (FGFR2) increased Fn-luciferase activity, which was inhibited by co-transfection with dominant negative (DN) mutants of PLCgamma2, PKCalpha, c-Src, IKKalpha, or IKKbeta. Our results suggest that bFGF increased Fn expression in rat osteoblasts via the FGFR2/PLCgamma2/PKCalpha/c-Src/NF-kappaB signaling pathway.
Tang
Chih-Hsin
CH
Department of Pharmacology, College of Medicine, National Taiwan University, Taipei, Taiwan.
Yang
Rong-Sen
RS
Chen
Yuh-Fung
YF
Fu
Wen-Mei
WM
D000818:Animals; D002118:Calcium / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D016222:Fibroblast Growth Factor 2 / Q000494:pharmacology*; D005353:Fibronectins / Q000235:genetics / Q000378:metabolism*; D005799:Genes, Dominant; D019833:Genistein / Q000494:pharmacology; D020672:I-kappa B Proteins / Q000378:metabolism; D008156:Luciferases / Q000378:metabolism; D008954:Models, Biological; D050505:Mutant Proteins / Q000378:metabolism; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000378:metabolism*; D010006:Osteoblasts / Q000187:drug effects* / Q000201:enzymology; D051966:Phospholipase C gamma / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D011401:Promoter Regions, Genetic / Q000187:drug effects; D051571:Protein Kinase C-alpha / Q000378:metabolism*; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000378:metabolism; D051381:Rats; D015854:Up-Regulation / Q000187:drug effects; D050880:p300-CBP Transcription Factors / Q000378:metabolism*
D004791:Enzyme Inhibitors; D005353:Fibronectins; C083487:I kappa B beta protein; D020672:I-kappa B Proteins; D050505:Mutant Proteins; D016328:NF-kappa B; C000606206:Nfkbia protein, rat; D016222:Fibroblast Growth Factor 2; D000072000:NF-KappaB Inhibitor alpha; D019833:Genistein; D008156:Luciferases; D050880:p300-CBP Transcription Factors; D016392:Proto-Oncogene Proteins pp60(c-src); D051571:Protein Kinase C-alpha; D051966:Phospholipase C gamma; D002118:Calcium