Binding and cellular activation studies reveal that toll-like receptor 2 can differentially recognize peptidoglycan from gram-positive and gram-negative bacteria

Jinkeng Asong, Margreet A. Wolfert, Kaustabh K. Maiti, Douglas Miller, Geert-Jan Boons

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

Although much progress has been made toward the identification of innate immune receptors, far less is known about how these receptors recognize specific microbial products. Such studies have been hampered by the need to purify compounds from microbial sources and a reliance on biological assays rather than direct binding to monitor recognition. We have employed surface plasmon resonance (SPR) binding studies using a wide range of well defined synthetic muropeptides derived from Gram-positive (lysine-containing) and Gram-negative (diaminopimelic acid (DAP)-containing) bacteria to demonstrate that Toll-like receptor 2 can recognize peptidoglycan (PGN). In the case of lysine-containing muropeptides, a limited number of compounds, which were derived from PGN remodeled by bacterial autolysins, was recognized. However, a wider range of DAP-containing muropeptides was bound with high affinity, and these compounds were derived from nascent and remodeled PGN. The difference in recognition of the two classes of muropeptides is proposed to be a strategy by the host to respond appropriately to Gram-negative and -positive bacteria, which produce vastly different quantities of PGN. It was also found that certain modifications of the carboxylic acids of isoglutamine and DAP can dramatically reduce binding, and thus, bacterial strains may employ such modifications to evade innate immune detection. Cellular activation studies employing highly purified PGN from Bacillus licheniformis, Bacillus subtilis, Escherichia coli, Lactobacillus plantarum, Micrococcus luteus, and Staphylococcus aureus support the structure binding relationship. The data firmly establish Toll-like receptor 2 as an innate immune sensor for PGN and provides an understanding of host-pathogen interactions at the molecular level. © 2009 by The American Society for Biochemistry and Molecular Biology, Inc.
Original languageEnglish
Pages (from-to)8643-8653
Number of pages11
JournalJournal of Biological Chemistry
Volume284
Issue number13
DOIs
Publication statusPublished - 27 Mar 2009
Externally publishedYes

Keywords

  • alpha amino acid
  • autolysin
  • bacterial protein
  • carboxylic acid
  • diaminopimelic acid
  • isoglutamine
  • muropeptide
  • peptidoglycan
  • toll like receptor 2
  • unclassified drug
  • article
  • Bacillus licheniformis
  • Bacillus subtilis
  • bacterial metabolism
  • bacterial strain
  • binding kinetics
  • HEK293 cell line
  • controlled study
  • Escherichia coli
  • Gram negative bacterium
  • Gram positive bacterium
  • host pathogen interaction
  • human
  • human cell
  • innate immunity
  • Lactobacillus plantarum
  • Micrococcus luteus
  • molecular recognition
  • nonhuman
  • priority journal
  • receptor binding
  • Staphylococcus aureus
  • surface plasmon resonance

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