Figure 5

Model of the role of spleen tyrosine kinase (Syk) in osteoclastogenesis. Osteoclast differentiation and function are stimulated by signals from ITAM-bearing adapter chains. DAP12 associates with TREM2, and similarly OSCAR associates with FcγR chain. After ligation of the extracellular domain of the receptor, DAP12 or FcRγ is tyrosine-phosphorylated by Syk. Activation of Syk initiates a number of signaling events. DAP12, DNAX-activating protein of molecular mass 12 kDa; FcRγ, Fc receptor γ-chain; ITAM, immunoreceptor tyrosine-based activation motif; OSCAR, osteoclast-specific activating receptor; PLCγ2, phospholipase Cγ2; SH2, Src homology 2; TREM2, triggering receptor expressed on myeloid cells.