Fibronectins containing extradomain A or B enhance osteoblast differentiation via distinct integrins

• Published in: The Journal of biological chemistry 2017-05, Vol.292 (19), p.7745-7760
• Main Authors: Sens, Carla, Huck, Katrin, Pettera, Stefan, Uebel, Stephan, Wabnitz, Guido, Moser, Markus, Nakchbandi, Inaam A.
• Format: Article
• Language: English
• Subjects: 3T3 Cells; Animals; Animals, Newborn; Cell Adhesion; Cell Biology; Cell Differentiation; differentiation; DNA, Complementary - metabolism; Enzyme-Linked Immunosorbent Assay; Extracellular Matrix - metabolism; fibronectin; Fibronectins - metabolism; Green Fluorescent Proteins - metabolism; Humans; integrin; Integrin alpha4beta1 - metabolism; Integrin alphaVbeta3 - metabolism; Mice; Oligopeptides - metabolism; osteoblast; Osteoblasts - cytology; Osteoblasts - metabolism; Osteogenesis; Protein Binding; Protein Domains; Protein Isoforms; RNA, Small Interfering - metabolism; Signal Transduction; signaling
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M116.739987

Fibronectin is a multidomain protein secreted by various cell types. It forms a network of fibers within the extracellular matrix and impacts intracellular processes by binding to various molecules, primarily integrin receptors on the cells. Both the presence of several isoforms and the ability of the various domains and isoforms to bind to a variety of integrins result in a wide range of effects. In vivo findings suggest that fibronectin isoforms produced by the osteoblasts enhance their differentiation. Here we report that the isoform characterized by the presence of extradomain A activates α4β1 integrin and augments osteoblast differentiation. In addition, the isoform containing extradomain B enhances the binding of fibronectin through the RGD sequence to β3-containing integrin, resulting in increased mineralization by and differentiation of osteoblasts. Our study thus reveals novel functions for two fibronectin isoforms and the mediating receptors in osteoblast differentiation.