Analysis of interaction of Sendai virus V protein and melanoma differentiation-associated gene 5

Area of Science:

• Virology
• Immunology
• Molecular Biology

Background:

• Sendai virus (SeV) is a rodent pneumotropic virus.
• The SeV V protein inhibits IRF3 activation and interferon-β production by interacting with MDA5.
• The V unique (Vu) region is critical for viral pathogenicity.

Purpose of the Study:

• To investigate the interaction between SeV V protein and IRF3-activating proteins, particularly MDA5.
• To determine the role of the Vu region in V protein-MDA5 interaction and inhibition of IRF3 activation.
• To correlate viral pathogenicity with V protein-MDA5 binding and inhibitory function.

Main Methods:

• Co-immunoprecipitation assays were used to study protein interactions.
• Mutant V proteins with point mutations in the Vu region were analyzed.
• IRF3 reporter activation assays assessed the functional consequences of V protein interactions.

Main Results:

• SeV V protein interacted with multiple IRF3-activating proteins, including RIG-I, IKKε, and IRF3.
• Interaction with MDA5 was dependent on the Vu region and inhibited IRF3 activation.
• Mutations in the Vu region destabilized V protein or abolished MDA5 interaction.
• A stable mutant (V-R320G) interacted with MDA5 but did not inhibit IRF3 activation.

Conclusions:

• The interaction between SeV V protein and MDA5, mediated by the Vu region, is essential for inhibiting IRF3 activation.
• Viral pathogenicity of SeV is linked to the V protein's ability to inhibit MDA5, but not solely to the binding affinity.
• The Vu region's role in modulating MDA5 interaction and function is critical for SeV pathogenesis.