Production of multimeric forms of CD4 through a sugar-based cross-linking strategy

Area of Science:

• Biochemistry
• Molecular Biology
• Immunology

Background:

• Multivalent interactions are crucial for biological functions.
• Understanding these interactions requires methods to create protein homomultimers.
• CD4 protein interactions are key in viral infection pathways.

Purpose of the Study:

• To develop a novel, carbohydrate-targeted cross-linking procedure.
• To investigate the role of multivalent interactions in CD4 protein function.
• To produce soluble CD4 homomultimers for functional studies.

Main Methods:

• A three-step cross-linking procedure was developed: periodate oxidation of CD4 carbohydrate, cystamine modification of aldehydes to thiols, and bismaleimidohexane-mediated thiol cross-linking.
• The procedure was applied to CD4 protein.
• Functional activity was assessed via glycoprotein gp120 binding and an in vitro cellular assay for blocking HTLV-IIIB infection.

Main Results:

• Approximately 60% of CD4 was converted into soluble, higher molecular weight homomultimers (dimers and tetramers).
• These CD4 homomultimers retained their glycoprotein gp120 binding activity.
• CD4 dimers and tetramers demonstrated significantly enhanced activity (4x and 15x, respectively) in blocking HTLV-IIIB viral infection compared to CD4 monomers.

Conclusions:

• The developed cross-linking chemistry is an efficient method for producing glycoprotein homomultimers.
• CD4 homomultimerization enhances its ability to block viral infection, underscoring the functional significance of multivalent interactions.