SARS-CoV-2 ORF3a-Mediated NF-κB Activation Is Not Dependent on TRAF-Binding Sequence.

Area of Science:

• Virology
• Immunology
• Molecular Biology

Background:

• Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) causes COVID-19, characterized by excessive inflammation.
• SARS-CoV-2 accessory protein ORF3a is implicated in COVID-19 pathology and inflammation.
• Nuclear factor kappa B (NF-κB) is a critical inflammatory pathway.

Purpose of the Study:

• To investigate the role of SARS-CoV-2 ORF3a protein in binding to TNF receptor-associated factor (TRAF) proteins.
• To determine ORF3a's capacity to induce NF-κB activation.
• To elucidate the mechanisms by which ORF3a influences inflammatory pathways.

Main Methods:

• X-ray crystallography to analyze protein structures.
• Fluorescence polarization assay to assess protein-ligand binding.
• Dual-luciferase assay to measure NF-κB activation.
• Site-directed mutagenesis to study protein function.

Main Results:

• Low-affinity binding was observed between an ORF3a N-terminal peptide and TRAF proteins.
• ORF3a demonstrated the ability to activate NF-κB.
• Mutating the N-terminal TRAF-binding sequence (PIQAS) in ORF3a did not significantly reduce NF-κB activation.

Conclusions:

• SARS-CoV-2 ORF3a protein can activate NF-κB.
• The interaction with TRAF proteins via the N-terminal PIQAS sequence is not the primary mechanism for ORF3a-induced NF-κB activation.
• Alternative mechanisms likely mediate ORF3a's role in activating NF-κB and contributing to COVID-19 pathology.