TLR Signalling: Beyond Immunity

Abstract

The ability of multicellular organisms to detect and eliminate pathogens is key to their survival. Toll‐like receptors (TLRs) are one of the key components of the immune response in invertebrates and vertebrates. Although the general families of TLRs are conserved between species in the detection of microbe‐associated molecular patterns, their specific role may be altered in these distinct organisms. Beyond the vast role of TLRs in immunity, they are also involved in development, metabolic homoeostasis and pain sensation.

Key Concepts

  • The role of TLRs in facilitating the innate immune response is well established, but they are now known to be involved in development, metabolic homoeostasis and nociception.
  • TLRs are functionally conserved between species but can play different roles depending on the tissue in which they are expressed as well as the nature of the activating ligand and downstream effectors.
  • TLRs use two main adaptor proteins to facilitate their downstream signalling pathways: Myd88 dependent and TRIF.
  • The ligands recognised by TLRs can be described as microbe‐associated molecular patterns (MAMPs) and damage‐associated molecular patterns (DAMPs).
  • TLRs have been targeted for therapeutic applications, but a balance must be struck between their inhibition and activation to maintain homoeostasis.

Keywords: Toll‐like receptors; damage‐associated molecular patterns; microbe‐associated molecular pattern; Myd88

Figure 1. Schematic of TLR and PRR pathways in metazoans and plants, respectively. There are two main pathways utilised in TLR signalling for metazoans: myd88 dependent/independent. The figure depicts both pathways as well as the ligands which activate them for metazoans, while only myd88 is found in invertebrates, and plants forgo myd88 altogether. Homologous intermediates that function in these pathways are coloured similarly as well and signal through similar downstream transcription factors to bring about conserved outcomes related to immunity such as inflammation.
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How to Cite close
Guessoum, Omar, Tang, Qijun, Agorsor, Israel DK, Ke, Wenfan, Li, Renyu, Danna, Cristian H, and Deppmann, Christopher D(Aug 2017) TLR Signalling: Beyond Immunity. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0027502]