CCN2 (also known as connective tissue growth factor) interacts with several growth factors involved in endochondral ossification via its characteristic four modules and modifies the effect of such growth factors. Presently we investigated whether CCN2 interacts with fibroblast growth factor 2 (FGF2). Solid-phase binding assay, immunoprecipitation-Western blot analysis, and surface plasmon resonance (SPR) spectroscopy revealed that the C-terminal module of CCN2 (CT) directly bound to FGF2 with a dissociation constant of 5.5 nM. Next, we examined the combinational effects of CCN2 and FGF2 on the proliferation of and matrix metalloproteinase (MMP)-9 and -13 productions by cultured chondrocytes. FGF2 promoted not only the proliferation but also the production of MMP9 and -13, however, combined of FGF2 with CT module nullified the enhancement of both MMP productions and proliferation.To clarify the mechanism, we investigated the binding of CCN2 or its CT module to FGF receptor 1. As a result, we found that CCN2 bound to FGF receptor 1 with a dissociation constant of 362 nM, whereas the CT module did not. In addition, when we tested FGF signaling in chondrocytic HCS-2/8 cells stimulated by the combination of FGF2 with CT module, the level of ERK1/2, p38 MAPK, and c-Jun N-terminal kinase phosphorylation was decreased compared with that found with FGF2 alone. These findings suggest that CCN2 may regulate the proliferation and matrix degradation of chondrocytes by forming a complex with FGF2 as a novel modulator of FGF2 functions.
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