SARS-CoV-2 and MERS-CoV disrupt host protein synthesis via nsp1 with differential effects on the integrated stress...

Area of Science:

• Virology
• Molecular Biology
• Immunology

Background:

• Coronaviruses, including SARS-CoV-2 and MERS-CoV, pose significant public health threats, necessitating the development of antiviral strategies.
• Understanding how these viruses evade host defenses and establish infection is crucial for therapeutic development.
• The conserved coronavirus nonstructural protein 1 (nsp1) plays a key role in modulating host cellular processes, including protein synthesis and mRNA stability.

Purpose of the Study:

• To investigate the differential interactions of SARS-CoV-2 and MERS-CoV nsp1 proteins with the host integrated stress response (ISR) kinases.
• To elucidate the mechanisms by which nsp1 from these distinct coronaviruses affects host protein synthesis and mRNA degradation.
• To compare the impact of SARS-CoV-2 and MERS-CoV nsp1 on host cellular responses, specifically focusing on the ISR pathway and GADD34 expression.

Main Methods:

• Utilized recombinant SARS-CoV-2 and MERS-CoV expressing nsp1 mutants with alterations in conserved domains.
• Infected wildtype (WT) and knockout (KO) cell lines (PKR KO, PERK KO) to assess the role of specific ISR kinases.
• Employed single-molecule fluorescence in situ hybridization (smFISH) to analyze host mRNA degradation.
• Monitored host protein synthesis inhibition and GADD34 expression levels.

Main Results:

• SARS-CoV-2 nsp1 induced host protein synthesis shutoff via ISR activation (p-eIF2α), which was dependent on PERK kinase.
• MERS-CoV nsp1 infection did not lead to significant eIF2α phosphorylation, and translation was rescued in WT cells.
• Both SARS-CoV-2 and MERS-CoV nsp1 proteins were found to promote host mRNA degradation, a process dependent on functional nsp1.
• SARS-CoV-2 nsp1 suppressed GADD34 expression, while SARS-CoV-2 nsp1 mutants and MERS-CoV WT infection induced GADD34.

Conclusions:

• SARS-CoV-2 and MERS-CoV exhibit distinct strategies in manipulating the host ISR pathway via their nsp1 proteins.
• nsp1's role in inhibiting host protein synthesis differs significantly between SARS-CoV-2 and MERS-CoV, with SARS-CoV-2 heavily relying on PERK-mediated ISR activation.
• Both viruses' nsp1 proteins contribute to host mRNA degradation, highlighting a conserved mechanism of viral evasion.
• These findings provide critical insights into coronavirus pathogenesis and offer potential targets for antiviral therapies.