The JAK2-Akt-glycogen synthase kinase-3β signaling pathway is involved in toll-like receptor 2-induced monocyte chemoattractant protein-1 regulation

Monocyte chemoattractant protein-1 (MCP-1) is an essential cytokine for the migration of monocytes into vessels, and is also involved in the pathogenesis of atherosclerosis. In this study, we investigated the importance of janus kinase 2 (JAK2) and the function of the Akt and glycogen synthase kinase-3β (GSK3β) pathway in toll-like receptor (TLR2)-mediated MCP-1 expression. The TLR2 agonist, Pam(3)CSK(4), induced MCP-1 expression in the Raw264.7 cell line. The induction of MCP-1 was seen in the bone marrow-derived macrophages of wild-type mice but not in TLR2 knockout mice. The TLR2-mediated MCP-1 induction was myeloid differentiation primary response gene 88 (MyD88)-independent. By contrast, the inactivation of JAK2 attenuated TLR2-mediated MCP-1 expression. The JAK inhibitor suppressed the phosphorylation of GSK3β as well as Akt by Pam(3)CSK(4) stimulation. While the inactivation of Akt by LY294002 suppressed TLR2-mediated MCP-1 induction, the inactivation of GSK3β by LiCl potentiated TLR2-mediated MCP-1 induction. Furthermore, Akt inhibitor suppressed TLR2-mediated phosphorylation of GSK3β. Taken together, these results suggest that a MyD88-independent pathway exists in TLR2 signaling; the JAK2-Akt-GSK3β pathway is a novel MyD88-independent pathway for MCP-1 induction.