The lectin-like interaction between recombinant tumor necrosis factor and uromodulin

Area of Science:

• Biochemistry
• Immunology
• Glycobiology

Background:

• Uromodulin (Tamm-Horsfall glycoprotein) is an immunosuppressive glycoprotein synthesized in the kidney.
• Uromodulin binds to recombinant murine interleukin 1 alpha, with binding inhibited by specific saccharides.

Purpose of the Study:

• To investigate the binding interaction between uromodulin and recombinant human tumor necrosis factor (rTNF).
• To elucidate the role of carbohydrate structures in uromodulin-rTNF binding and its biological implications.

Main Methods:

• High-affinity binding assays between uromodulin and rTNF.
• Inhibition studies using various saccharides, including diacetylchitobiose and specific mannose derivatives.
• Analysis of uromodulin oligosaccharide structures and their role in binding.
• Assessment of uromodulin's effect on rTNF cytotoxic activity and protection against lipopolysaccharide-induced lethality in mice.

Main Results:

• Uromodulin exhibits high-affinity binding to rTNF.
• Diacetylchitobiose and a specific mannose oligosaccharide effectively inhibit uromodulin-rTNF binding.
• Binding is independent of terminal sialic acid, galactose, and N-acetylhexosamine residues on uromodulin's N-linked chains.
• A lower molecular weight fraction of uromodulin digest inhibits rTNF binding.
• Uromodulin does not inhibit rTNF's cytotoxic activity but protects mice from lethal lipopolysaccharide challenge.

Conclusions:

• rTNF interacts with uromodulin via less processed carbohydrate chains than the major tetraantennary N-linked chains.
• This interaction may be crucial for enhancing the clearance and/or reducing the toxicity of TNF and other lymphokines in vivo.