MD Simulation Reveals a Trimerization-Enhanced Interaction of CD137L with CD137

Area of Science:

• Immunology
• Molecular Biology
• Computational Biology

Background:

• CD137 (4-1BB) is a key costimulatory receptor in the TNF superfamily, essential for T cell activation.
• CD137 ligand (CD137L) interactions with CD137 are critical for effective antitumor immune responses and cancer immunotherapy.
• The precise molecular mechanisms governing CD137L/CD137 bidirectional signaling remain incompletely understood.

Purpose of the Study:

• To investigate the structural and dynamic interactions between various oligomeric states of CD137L and CD137.
• To elucidate the role of CD137L oligomerization in modulating CD137 binding affinity and stability.
• To provide insights for designing novel CD137-based immunotherapeutic agents.

Main Methods:

• Construction and analysis of monomeric, dimeric, and trimeric CD137L constructs.
• Molecular dynamics simulations to explore CD137L/CD137 interactions.
• Assessment of thermal stability and binding affinities of different CD137L oligomers.

Main Results:

• Trimeric CD137L demonstrated greater thermal stability but lower binding affinity for CD137 compared to dimeric CD137L.
• The A'B' loop of CD137L was identified as crucial for structural stability and CD137 binding.
• Formation of hexameric CD137L structures significantly enhanced both binding affinity and complex stability.
• Oligomerization state critically influences CD137L/CD137 interaction dynamics and binding characteristics.

Conclusions:

• The oligomeric state of CD137L profoundly impacts its interaction with CD137, influencing T cell costimulation.
• Understanding these structure-function relationships is vital for optimizing CD137-targeted cancer immunotherapies.
• Hexameric CD137L represents a promising structural configuration for developing potent CD137 agonists to enhance antitumor immunity.