Fibronectin interacts with Clq, a subcomponent of the first component of complement

Area of Science:

• Immunology
• Biochemistry
• Molecular Biology

Background:

• The complement system is a crucial part of innate immunity.
• Complement component 1 (Cl) initiates the classical complement pathway.
• Clq is the subcomponent of Cl that recognizes immune complexes and other targets.

Purpose of the Study:

• To investigate the interaction between human Clq and human fibronectin.
• To identify the regions and conditions influencing Clq-fibronectin binding.

Main Methods:

• Enzyme-linked immunosorbent assay (ELISA) was used to assess binding.
• Thermal denaturation and chain dissociation of Clq were employed.
• Enzymatic treatments (pepsin, collagenase) were performed on Clq.

Main Results:

• Clq binds to fibronectin, demonstrated by ELISA.
• Native Cl and reconstituted Cl show minimal fibronectin binding.
• Heating Clq above 51°C enhances fibronectin binding.
• The A chain of Clq mediates fibronectin binding.
• Collagen-like regions of Clq are involved, while globular regions are not essential.

Conclusions:

• Clq interacts with fibronectin, with binding modulated by Clq conformation.
• The A chain and collagen-like regions of Clq are critical for fibronectin binding.
• These findings provide insights into the molecular mechanisms of Clq-ligand interactions.