Specific S100 Proteins Bind Tumor Necrosis Factor and Inhibit Its Activity

Area of Science:

• Immunology
• Biochemistry
• Molecular Biology

Background:

• Tumor necrosis factor (TNF) inhibitors (anti-TNFs) are crucial for treating inflammatory diseases.
• Understanding TNF binding partners is key to predicting anti-TNF efficacy.
• The S100 protein family is multifunctional, with potential roles in inflammatory processes.

Purpose of the Study:

• To identify S100 proteins that interact with soluble TNF (sTNF).
• To characterize the binding kinetics and functional consequences of sTNF-S100 interactions.
• To explore the potential impact of these interactions on anti-TNF therapy.

Main Methods:

• Surface plasmon resonance spectroscopy to determine binding constants (K).
• Fluorimetric titrations for multimeric sTNF-S100 complexes.
• MTT assay to assess the cytotoxic activity of sTNF.
• Structural modeling and bioinformatics analysis.

Main Results:

• S100A11, S100A12, and S100A13 were found to interact with sTNF in vitro.
• Low equilibrium dissociation constants (2-28 nM for monomeric sTNF) indicate strong binding.
• S100A12/A13 suppressed sTNF's cytotoxic activity.
• Structural modeling suggests potential interference with anti-TNF binding.

Conclusions:

• Specific S100 proteins (S100A11, S100A12, S100A13) directly bind sTNF.
• These interactions may modulate sTNF activity and influence anti-TNF treatment efficacy.
• Dysregulation of TNF and these S100 proteins in diseases suggests a novel regulatory role.