FGF‐2 suppresses expression of nephronectin via JNK and PI3K pathways

Nephronectin (Npnt), an extracellular matrix protein, is a ligand for integrin α8β1 and is involved in the development of various organs, such as the kidneys, bones, liver, and muscles. Previously, we found that Npnt expression was inhibited by various cytokines including transforming growth factor‐β (Tgf‐β) and oncostatin M (Osm). Fibroblast growth factor (Fgf)‐2, otherwise known as basic Fgf, also plays important roles in skeletal development and postnatal osteogenesis. In this study, Npnt expression was found to be suppressed by Fgf‐2 in MC3T3‐E1 cells, an osteoblast‐like cell line, in a dose‐ and time‐dependent manners. Furthermore, Fgf‐2‐mediated Npnt mRNA suppression was shown to involve the Jun N‐terminal kinase (JNK) and phosphoinositide‐3 kinase (PI3K) pathways. Together, our results suggest that FGF‐2 suppresses Npnt gene expression via JNK and PI3K pathways.