Monomeric C-reactive protein regulates fibronectin mediated monocyte adhesion

Area of Science:

• Biochemistry
• Immunology
• Cell Biology

Background:

• C-reactive protein (CRP) interacts with fibronectin (FN), but binding is pH and calcium-dependent, creating in vivo uncertainty.
• CRP can dissociate into monomeric CRP (mCRP) under inflammatory conditions (low pH, no calcium).

Purpose of the Study:

• To investigate the binding characteristics of different CRP isoforms to fibronectin.
• To determine the role of mCRP in monocyte adhesion and inflammatory processes.

Main Methods:

• Surface plasmon resonance and ELISA assays to study CRP-FN binding.
• Peptide competition, deletion mutant assays, and protein docking to identify binding sites.
• In vitro assays for monocyte adhesion and endothelial cell adhesion molecule expression.
• In vivo studies using DSS-induced colitis model in mice.

Main Results:

• Monomeric CRP (mCRP) binds with high affinity to fibronectin (FN), independent of calcium and pH.
• The binding site of mCRP to FN was identified as residues a.a.35-47.
• mCRP significantly enhances monocyte adhesion to FN and upregulates endothelial adhesion molecules.
• In vivo, mCRP colocalizes with FN in inflamed tissue, unlike native CRP.

Conclusions:

• mCRP, formed locally from circulating CRP, is the primary isoform interacting with FN.
• mCRP regulates FN-mediated monocyte adhesion, contributing to inflammatory processes.
• These findings clarify CRP-FN interactions in vivo and highlight mCRP's role in inflammation.