Homodimerization of Ror2 Tyrosine Kinase Receptor Induces 14-3-3β Phosphorylation and Promotes Osteoblast Differentiation and Bone Formation

Ror2 receptor plays a key role in bone formation, but its signaling pathway is not completely understood. We demonstrate that Ror2 homodimerizes at the cell surface, and that dimerization can be induced by a bivalent antibody. Antibody-mediated dimerization causes receptor autophosphorylation and induces functional consequences of its signaling, including osteogenesis in mesenchymal stem cells and bone formation in organ culture. We further show that Ror2 associates with and phosphorylates 14-3-3β scaffold protein. Endogenous Ror2 binds 14-3-3β in U2OS osteosarcoma cells, and purified intracellular domain of Ror2 interacts with 14-3-3β in vitro. 14-3-3β Is tyrosine phosphorylated in U2OS cells, and this phosphorylation is inhibited by down-regulating Ror2 and enhanced by overexpressing the kinase. Purified Ror2 phosphorylates 14-3-3β in vitro, confirming 14-3-3β as the first identified Ror2 substrate. Down-regulating 14-3-3β potentiates osteoblastogenesis in mesenchymal stem cells and increases bone forma...