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Interaction of C-reactive protein with artificial phosphatidylcholine bilayers and complement
Journal of Immunology (Baltimore, Md. : 1950)
|May 1, 1981
Summary
C-reactive protein (CRP) binds to altered phosphatidylcholine membranes, requiring lysophosphatide. This binding, dependent on calcium ions, activates the complement system and is enhanced by specific glycolipids.
Area of Science:
- Biochemistry
- Immunology
- Membrane Biophysics
Background:
- C-reactive protein (CRP) is a key acute-phase protein involved in innate immunity.
- Understanding CRP's interaction with biological membranes is crucial for elucidating its functions.
Purpose of the Study:
- To investigate the binding requirements of CRP to model membranes.
- To determine the role of membrane composition and calcium ions in CRP binding.
- To assess the impact of CRP-membrane interactions on complement activation.
Main Methods:
- Utilized multilamellar and unilamellar liposomes composed of egg-phosphatidylcholine.
- Incorporated lysophosphatide and galactosyl cerebroside into liposomes.
- Measured CRP binding using binding constants and C1q binding assays.
- Investigated calcium ion dependence and inhibition by phosphocholine and galactose.
Main Results:
- CRP binding to phosphatidylcholine liposomes necessitates the presence of lysophosphatide, indicating a requirement for altered membrane organization.
- Binding is calcium-dependent and can be inhibited by phosphocholine.
- Incorporation of galactosyl cerebroside significantly enhanced CRP binding and subsequent C1q binding, suggesting a role for glycolipids.
- Calculated binding constants revealed stronger affinity for liposomes with glycolipids.
Conclusions:
- Altered phosphatidylcholine bilayer organization is essential for CRP binding.
- Galactosyl residues on membrane surfaces enhance CRP binding, potentially via a secondary binding site on CRP.
- CRP-membrane interactions are linked to the activation of the classical complement pathway.