Related Experiment Videos
Decay-accelerating factor (DAF/CD55) is a functional active element of the LPS receptor complex.
H Heine1, A J Ulmer, V T El-Samalouti
1Center for Medicine and Biosciences, Research Center Borstel, Borstel, Germany.
Journal of Endotoxin Research
|October 3, 2001
Summary
We discovered that CD55, also known as decay accelerating factor (DAF), binds to lipopolysaccharide (LPS) and lipid A. This finding reveals a new role for CD55 in mediating LPS-induced cellular activation.
Area of Science:
- Immunology
- Cell Biology
- Complement System
Background:
- Lipopolysaccharide (LPS) and lipid A are key components of Gram-negative bacteria, triggering potent immune responses.
- Lipid-binding protein (LBP) and soluble CD14 (sCD14) are known to facilitate LPS recognition by cellular receptors.
- An 80 kDa membrane protein (LMP80) was previously identified for its ability to bind LPS and lipid A.
Purpose of the Study:
- To identify the protein LMP80 and elucidate its function in LPS recognition.
- To investigate the role of CD55 in cellular activation pathways induced by LPS and lipid A.
Main Methods:
- Immuno-coprecipitation assays to confirm physical interaction between LMP80 and LPS/lipid A.
- Peptide sequencing and protein analysis to identify LMP80.
- Transfection of LPS-hyporesponsive Chinese hamster ovary (CHO) cells with human CD55.
- Stimulation of transfected cells with LPS or lipid A and subsequent analysis of NF-κB translocation.
Main Results:
- LMP80 was identified as CD55 (decay accelerating factor, DAF), a known regulator of the complement cascade.
- CD55 directly interacts with LPS and lipid A in the presence of LBP and sCD14.
- Transfection of CD55 into LPS-hyporesponsive cells conferred responsiveness to LPS and lipid A.
- LPS and lipid A stimulation induced NF-κB translocation in CD55-expressing cells.
Conclusions:
- CD55 plays a novel role in mediating cellular activation in response to LPS and lipid A.
- CD55 may function as a component of a multimeric LPS receptor complex.
- These findings expand our understanding of innate immune recognition of bacterial components.