TLR2 recognizes a bacterial lipopeptide through direct binding.
The TLRs play an important role in the initiation of cellular innate immune responses to a wide range of bacterial products, including LPS and lipoproteins. Although rapid progress has been made on signaling functions of activated TLRs, the molecular mechanisms that lead to TLR activation are still poorly understood. We report in this study that the extracellular domain of TLR2 interacts directly with synthetic bacterial lipopeptide (sBLP), a potent analog of bacterial lipoproteins. Using fluorescently labeled sBLP complexed to soluble recombinant CD14 (rsCD14), we observed specific binding of sBLP to the surface of cells expressing TLR2 transgenes and to a recombinant soluble form of the TLR2 ectodomain. TLR2-mediated binding of sBLP at the cell surface did not require prior induction of intracellular signals. In addition, using a chimeric TLR2/TLR4 construct, we showed that the leucine-rich region of TLR2 carries the specificity for binding of the agonist and for initiating signaling. Specific binding of fluorescent sBLP to purified sTLR2 required sCD14. However, sCD14 was not part of the complex formed by soluble TLR2 and sBLP. Together, these data provide evidence that TLR2 recognizes sBLP through direct binding.
Vasselon
Thierry
T
Institut National de la Santé et de la Recherche Médicale Unité 396, Paris, France. vasselon@histo.chu-stlouis.fr
Detmers
Patricia A
PA
Charron
Dominique
D
Haziot
Alain
A
D000215:Acylation; D001426:Bacterial Proteins / Q000138:chemical synthesis / Q000378:metabolism*; D002460:Cell Line; D002462:Cell Membrane / Q000276:immunology / Q000378:metabolism; D000939:Epitopes / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D005110:Extracellular Space / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D007930:Leucine / Q000378:metabolism; D018950:Lipopolysaccharide Receptors / Q000378:metabolism; D008074:Lipoproteins / Q000138:chemical synthesis / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D010455:Peptides / Q000138:chemical synthesis / Q000378:metabolism*; D011485:Protein Binding / Q000235:genetics / Q000276:immunology; D017434:Protein Structure, Tertiary / Q000235:genetics; D011956:Receptors, Cell Surface / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D020449:Repetitive Sequences, Amino Acid; D015398:Signal Transduction / Q000235:genetics / Q000276:immunology; D012995:Solubility; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors; D014162:Transfection
D001426:Bacterial Proteins; D000939:Epitopes; D018950:Lipopolysaccharide Receptors; D008074:Lipoproteins; D008562:Membrane Glycoproteins; D010455:Peptides; D011956:Receptors, Cell Surface; D011994:Recombinant Proteins; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors; C061108:N-palmitoyl-S-(2,3-bis(palmitoyloxy)propyl)cysteinyl-seryl-lysyl-lysyl-lysyl-lysine; D007930:Leucine