Toll-like Receptor Signaling

Toll-like receptors (TLRs) belong to the family of pathogen-associated pattern recognition receptors. TLRs are transmembrane receptors and that bind to specific molecular patterns in bacteria and viruses. To date 10 such receptors have been identified in humans and their pathogen-associated ligands include bacterial flagellin, viral DNA, lipopolysaccharides and CpG DNA motifs. TLRs either singly or as heterodimers form a complex with different combinations of adapter molecules like MyD88, TRAF6 and TIRAP to initiate signal transduction upon ligand binding.Binding of ligand to TLR triggers a cascade of signaling events via the TLR-adapter complex. Downstream signaling molecules like p38MAPK, JNK and NF-κB are activated and translocated into the nucleus where they activate transcription regulators like c-Fos and c-Jun leading to the induction of several pro-inflammatory cytokines eventually leading to antibacterial and antiviral responses.