NOD1CARD Might Be Using Multiple Interfaces for RIP2-Mediated CARD-CARD Interaction: Insights from Molecular Dynamics...

Area of Science:

• Immunology
• Structural Biology
• Computational Biology

Background:

• Nucleotide-binding and oligomerization domain (NOD)-containing protein 1 (NOD1) is crucial for innate immunity, recognizing pathogen-associated molecular patterns like iE-DAP.
• NOD1 activation leads to self-oligomerization and interaction with receptor-interacting protein 2 (RIP2) via caspase-recruitment domains (CARDs) to initiate inflammatory signaling pathways, including NF-κB activation.
• The precise nature of the CARD-CARD interaction between NOD1 and RIP2 has been unclear due to conflicting experimental data.

Purpose of the Study:

• To elucidate the structural and dynamic mechanisms underlying the CARD-CARD interaction between NOD1 and RIP2.
• To identify specific interaction interfaces and oligomeric states involved in NOD1-RIP2 complex formation.
• To provide molecular insights into the initiation of NOD1-mediated innate immune responses.

Main Methods:

• Molecular dynamics (MD) simulations were employed to model and analyze the interactions between NOD1 CARD and RIP2 CARD.
• Heterodimeric and heterotrimeric complexes of NOD1 CARD and RIP2 CARD were computationally modeled.
• Analysis focused on identifying stable interfaces and oligomeric arrangements, including ratios of NOD1:RIP2 as 1:2 and 2:1.

Main Results:

• MD simulations suggested that the type-Ia interface of NOD1 CARD and the type-Ib interface of RIP2 CARD are likely interaction sites.
• Three dynamically stable heterotrimeric complexes were identified, involving NOD1:RIP2 ratios of 1:2 and 2:1.
• Specific interaction modes were observed, including heterodimers interacting with monomers and homodimers interacting with monomers via distinct interfaces (type-I, type-II, type-III).

Conclusions:

• This study provides crucial structural and dynamic insights into the formation of NOD1-RIP2 oligomers.
• The findings clarify the molecular basis of NOD1-mediated CARD-CARD interactions, essential for innate immune signaling.
• Understanding these interactions is vital for comprehending immune responses in both higher and lower eukaryotes.