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Updated: Aug 20, 2026
Enrichment of Bacterial Lipoproteins and Preparation of N-terminal Lipopeptides for Structural Determination by Mass Spectrometry
Published on: May 21, 2018
TLR2 recognizes a bacterial lipopeptide through direct binding
Thierry Vasselon1, Patricia A Detmers, Dominique Charron
1Institut National de la Santé et de la Recherche Médicale Unité 396, Paris, France. vasselon@histo.chu-stlouis.fr
Abstract:
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.
Insights
Toll-like receptor 2 (TLR2) directly binds bacterial lipoproteins, initiating innate immune responses. This study reveals TLR2
Area of Science:
- Immunology
- Molecular Biology
Background:
- Toll-like receptors (TLRs) are crucial for innate immunity, recognizing bacterial products like LPS and lipoproteins.
- While TLR signaling is well-studied, the mechanisms of TLR activation remain unclear.
Purpose of the Study:
- To investigate the molecular mechanisms of TLR2 activation.
- To determine if TLR2 directly binds bacterial lipoproteins.
Main Methods:
- Used fluorescently labeled synthetic bacterial lipopeptide (sBLP) and soluble recombinant CD14 (rsCD14).
- Observed sBLP binding to cells expressing TLR2 transgenes and to soluble TLR2 ectodomain.
- Utilized a chimeric TLR2/TLR4 construct to identify the ligand-binding domain.
Main Results:
- Demonstrated direct interaction between the extracellular domain of TLR2 and sBLP.
- Showed TLR2-mediated sBLP binding occurs independently of intracellular signaling.
- Identified the leucine-rich region of TLR2 as responsible for agonist binding and signaling specificity.
- Confirmed that soluble CD14 is required for sBLP binding to purified TLR2, but not part of the final complex.
Conclusions:
- TLR2 directly recognizes synthetic bacterial lipopeptide (sBLP) through its extracellular domain.
- The leucine-rich region of TLR2 dictates specificity for sBLP binding and subsequent signaling initiation.
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