Figure 7.

Model of Syk recruitment by SCIMP to TLRs. The transmembrane adapter SCIMP constitutively binds Lyn via a PRD-SH3 interaction. Upon ligand activation of TLR4, activated Lyn kinase phosphorylates SCIMP at three tyrosine sites. The Y96 and Y120 residues then function as two docking sites for the tandem SH2 domains of Syk, which triggers a conformational change of Syk to expose its kinase domain for amplifying SCIMP and TLR4 phosphorylation and enhancing their interaction. SCIMP-scaffolded Syk helps to propagate TLR4 signal transduction to drive proinflammatory cytokine secretion. Syk, Spleen tyrosine kinase; TLRs, Toll-like receptors; SH2, Src homology 2.