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Serum amyloid P component binds to histones and activates the classical complement pathway.
P S Hicks1, L Saunero-Nava, T W Du Clos
1Department of Microbiology, University of New Mexico School of Medicine, Albuquerque 87131.
Journal of Immunology (Baltimore, Md. : 1950)
|December 1, 1992
Summary
C-reactive protein (CRP) and serum amyloid P component (SAP) bind to histones and chromatin. Both pentraxins activate the classical complement pathway after binding, revealing shared and distinct interactions.
Area of Science:
- Immunology
- Biochemistry
- Molecular Biology
Background:
- Pentraxins like CRP and SAP bind nuclear material, potentially aiding clearance.
- CRP interacts with chromatin via histones; SAP's histone binding was uncharacterized.
- Both CRP and SAP can activate the complement system.
Purpose of the Study:
- To investigate CRP and SAP binding to histones H1 and H2A.
- To determine complement activation following pentraxin-histone binding.
- To compare SAP and CRP interactions with chromatin and histones.
Main Methods:
- Chromatin and histone binding assays for CRP and SAP.
- Complement activation assays using SAP-depleted serum.
- Analysis of complement component deposition (C4d, C3).
Main Results:
- SAP binds to histones H1, H2A, and chromatin, independent of H1 for chromatin binding.
- SAP partially inhibits CRP binding to chromatin and H1, but not H2A.
- Binding of CRP or SAP to H2A activates the classical complement pathway via C1q.
Conclusions:
- CRP and SAP share binding sites on histones and chromatin.
- Both pentraxins activate the classical complement pathway upon ligand binding.
- Distinct binding mechanisms exist for CRP and SAP with chromatin components.