Structural and functional insights into RAGE activation by multimeric S100B.

Area of Science:

• Neuroscience
• Structural Biology
• Cell Biology

Background:

• Nervous system development and plasticity depend on extracellular factors regulating neuronal processes.
• The EF-hand protein S100B is abundant in the human brain and promotes neurite extension and neuron survival through the receptor for advanced glycation end products (RAGE).

Purpose of the Study:

• To elucidate the structural basis of S100B's function in the extracellular space.
• To investigate the binding affinity and functional consequences of different S100B oligomeric states with RAGE.

Main Methods:

• X-ray crystallography to determine the structure of Ca(2+)-loaded S100B.
• Size-exclusion chromatography to confirm multimeric forms in brain extracts.
• Purification and characterization of recombinant S100B oligomers (tetrameric, hexameric, octameric).
• Binding studies (e.g., analytical ultracentrifugation) to assess S100B-RAGE interactions.
• Cell-based assays to evaluate S100B's effect on cell growth and survival.

Main Results:

• The X-ray structure revealed an octameric S100B architecture composed of two tetramers.
• Multimeric S100B forms were confirmed in human brain extracts.
• Tetrameric S100B exhibited higher affinity for RAGE compared to dimeric S100B.
• Tetrameric S100B demonstrated enhanced activation of cell growth and promoted cell survival more effectively than dimeric S100B.
• S100B tetramer binding to RAGE likely involves two RAGE molecules, potentially through V-domain interactions.

Conclusions:

• The study reveals a tetrameric structure of S100B that binds RAGE with higher affinity, leading to enhanced neuronal support.
• These findings suggest that S100B oligomerization, particularly tetramer formation, is critical for its signaling function via RAGE in the brain.
• Tetrameric S100B likely triggers RAGE activation through receptor dimerization, playing a significant role in nervous system development and plasticity.