A difference between plasma and cellular fibronectins located with monoclonal antibodies

Area of Science:

• Immunology
• Biochemistry
• Cell Biology

Background:

• Fibronectin is a crucial extracellular matrix protein involved in cell adhesion, migration, and wound healing.
• Cellular fibronectin (cFN) and plasma fibronectin (pFN) are distinct isoforms with differing biological roles.
• Understanding the structural differences between cFN and pFN is essential for elucidating their specific functions.

Purpose of the Study:

• To characterize two novel monoclonal antibodies against hamster cellular fibronectin.
• To identify specific epitopes recognized by these antibodies on the fibronectin molecule.
• To investigate structural differences between cellular and plasma fibronectin.

Main Methods:

• Production and characterization of monoclonal antibodies.
• Immunological assays to determine antibody specificity (cFN vs. pFN).
• Proteolytic digestion (tryptic and chymotryptic) to map antibody-binding sites.
• Analysis of antibody recognition in relation to fibronectin glycosylation.

Main Results:

• One antibody showed high specificity for cellular fibronectin, while the other recognized both cellular and plasma fibronectin.
• Both antibodies bind to a common, restricted region near the C-terminus of cellular fibronectin.
• This region is released as a 40 kDa fragment upon digestion and contains a free sulfhydryl group.
• Antibody recognition is independent of fibronectin carbohydrate residues.

Conclusions:

• The developed monoclonal antibodies are valuable tools for distinguishing between cellular and plasma fibronectin.
• A specific structural domain near the C-terminus of fibronectin has been identified and characterized.
• These findings provide a basis for further investigation into the structural and functional divergence of fibronectin isoforms.