Differential role of Dok1 and Dok2 in TLR2-induced inflammatory signaling in glia.
Accumulating evidence continues to underpin the role of the innate immune system in pathologies associated with neuroinflammation. Innate immunity is regulated by pattern recognition receptors that detect pathogens, and in the case of Gram-positive bacteria, binding of bacterial lipopeptides to toll-like receptor (TLR)2 is emerging as an important mechanism controlling glial cell activation. In the present study, we employed the use of the synthetic bacterial lipoprotein and a selective TLR2 agonist, Pam3CSK4, to induce inflammatory signaling in microglia and astrocytes. The adaptor proteins, downstream of kinase (Dok)1 and Dok2, are known to have a role in negatively regulating the Ras-ERK signaling cascade, with downstream consequences on pro-inflammatory cytokine expression. Data presented herein demonstrate that TLR2 enhanced the tyrosine phosphorylation of Dok1 and Dok2 in astrocytes and microglia, and that knockdown of these adaptors using small interfering RNA robustly elevated TLR2-induced ERK activation. Importantly, TLR2-induced NF-κB activation, and IL-6 production was exacerbated in astrocytes transfected with Dok1 and Dok2 siRNA, indicating that both Dok proteins negatively regulate TLR2-induced inflammatory signaling in astrocytes. In contrast, Dok1 knockdown attenuated TLR2-induced NF-κB activation and IL-6 production in microglia, while Dok2 siRNA failed to affect TLR2-induced NF-κB activity and subsequent cytokine expression in this cell type. Overall, this indicates that Dok1 and Dok2 are novel adaptors for TLR2 in glial cells and importantly indicates that Dok1 and Dok2 differentially regulate TLR2-induced pro-inflammatory signaling in astrocytes and microglia.
['Downer|Eric J|EJ|', 'Johnston|Daniel G W|DG|', 'Lynch|Marina A|MA|']
D048868:Adaptor Proteins, Signal Transducing D000818:Animals D001253:Astrocytes D002478:Cells, Cultured D004268:DNA-Binding Proteins D007249:Inflammation D015850:Interleukin-6 D055666:Lipopeptides D020935:MAP Kinase Signaling System D051379:Mice D008810:Mice, Inbred C57BL D017628:Microglia D016328:NF-kappa B D010750:Phosphoproteins D016601:RNA-Binding Proteins D051195:Toll-Like Receptor 2
Glia Innate immunity pattern recognition receptors Toll-like receptor downstream of kinase small interfering RNA ERK NF-κB siRNA Dok AD Alzheimer's disease CNS DAMPs EMSA GM-CSF HBSS Hanks' balanced salt solution buffered IFN Inflammation M-CSF MAPK MS Mal MyD88 MyD88-adaptor like PAMPs PD PH PPRs PTK Parkinson's disease SH SLAM Src homology TIR TLR TRAM TRIF TRIF-related adaptor molecule Toll-interleukin-1 receptor Toll-interleukin-1 receptor (TIR)-domain-containing adaptor-inducing IFN-β central nervous system damage-associated molecular patterns electrophoretic mobility shift assay extracellular signal-regulated kinase granulocyte macrophage colony stimulating factor interferon macrophage colony stimulating factor mitogen-activated protein kinase multiple sclerosis myeloid differentiation factor 88 nuclear factor-κB pathogen-associated molecular patterns pleckstrin homology protein tyrosine kinase signaling lymphocyte activation molecule