Disruption of molecular interactions between G3BP1 stress granule host protein and nucleocapsid (NTD-N) protein impedes SARS-CoV-2 virus replication

The Ras GTPase-activating protein SH3-domain-binding protein 1 (G3BP1) serves as a formidable barrier to viral replication by generating stress granules (SGs) in response to viral infections. Interestingly, viruses, including SARS-CoV-2, have evolved defensive mechanisms to hijack SG proteins like G3BP1 for the dissipation of SGs that lead to the evasion of host’s immune responses. Previous research has demonstrated that the interaction between the NTF2-like domain of G3BP1 (G3BP1 _NTF-2 ) and the intrinsically disordered N-terminal domain (NTD-N _1-25 ) of the N protein plays a crucial role in regulating viral replication and pathogenicity. Interestingly, the current study identified an additional upstream stretch of residues (128KDGIIWVATEG138) (N _128-138 ) within the N-terminal domain of the N protein (NTD-N _41-174 ) that also forms molecular contacts with the G3BP1 protein, as revealed through in silico analysis, site-directed mutagenesis and biochemical analysis. Remarkably, WIN-62577, and fluspirilene, the small molecules targeting the conserved peptide binding pocket in G3BP1 _NTF-2, not only disrupted the protein-protein interactions (PPIs) between the NTD-N _41-174 and G3BP1 _NTF-2 but also exhibited significant antiviral efficacy against SARS-CoV-2 replication with EC ₅₀ values of ∼1.8 µM and ∼1.3 µM, respectively. The findings of this study, validated by biophysical thermodynamics and biochemical investigations, advance the potential of developing therapeutics targeting the SG host protein against SARS-CoV-2, which may also serve as a broad-spectrum antiviral target.