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MD-2: the Toll 'gatekeeper' in endotoxin signalling
Monique Gangloff1, Nicholas J Gay
1Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge CB2 1GA, UK. mg308@cam.ac.uk
Trends in Biochemical Sciences
|July 28, 2004
Summary
Lipopolysaccharide (LPS) stimulates the innate immune system via Toll-like receptor 4 (TLR4) and myeloid differentiation-2 (MD-2). We propose two models for LPS recognition and signaling, considering lipid A structure and endotoxicity.
Area of Science:
- Immunology
- Microbiology
- Structural Biology
Background:
- Lipopolysaccharide (LPS) from Gram-negative bacteria activates the mammalian innate immune system.
- Toll-like receptor 4 (TLR4) and myeloid differentiation-2 (MD-2) are crucial for LPS recognition and inflammatory responses.
- The acylation and phosphorylation patterns of LPS influence its endotoxicity.
Purpose of the Study:
- To propose two novel mechanisms for LPS recognition and signaling by the TLR4-MD-2 complex.
- To integrate structural data of TLR4-MD-2 with LPS determinants of endotoxicity.
Main Methods:
- Computational modeling based on available structural information of TLR4 and MD-2.
- Analysis of LPS acylation and phosphorylation patterns related to endotoxicity.
Main Results:
- Model 1: LPS binding to two MD-2 molecules induces TLR4-MD-2 heterodimer association via lipid A acyl chains.
- Model 2: LPS binding to a single TLR4-MD-2 complex facilitates the recruitment of a second TLR4-MD-2 heterodimer.
- These proposed mechanisms differ from Drosophila Toll receptor activation.
Conclusions:
- The proposed models offer insights into LPS recognition and TLR4-MD-2 complex activation.
- Understanding these mechanisms can inform strategies to modulate inflammatory responses to LPS.