Interaction between SARS-CoV PBM and Cellular PDZ Domains Leading to Virus Virulence

Area of Science:

• Virology
• Molecular Biology
• Structural Biology

Background:

• Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV) utilizes PDZ-binding motifs (PBMs) to interact with host cellular PDZ domains, contributing to viral virulence.
• Over 400 cellular proteins with PDZ domains are potential binding partners for SARS-CoV 3a and envelope (E) proteins' PBMs.
• The specific roles of SARS-CoV 3a and E proteins in viral pathogenesis require detailed investigation.

Purpose of the Study:

• To elucidate the specific contributions of the PBMs in SARS-CoV 3a and E proteins to viral virulence and replication.
• To determine the necessity of the E protein's PBM for SARS-CoV pathogenicity and its interaction with host factors.
• To investigate the structural basis of the interaction between the SARS-CoV E protein PBM and the Syntenin-1 PDZ domain.

Main Methods:

• Generation of SARS-CoV mutants with deleted or altered PBMs in the 3a and E proteins.
• Assessment of viral titers and viability of generated SARS-CoV mutants.
• Mutagenesis analysis, including alanine and glycine scanning, of the SARS-CoV E protein PBM.
• In silico modeling and structural analysis of protein-protein interactions.

Main Results:

• Deletion of both 3a-PBM and E-PBM in SARS-CoV resulted in a one-logarithmic unit reduction in viral titer, with the virus remaining viable.
• Absence of E-PBM or its replacement prevented SARS-CoV rescue, indicating its critical role in virulence.
• The E protein PBM is essential for virulence, mediating p38-MAPK activation via Syntenin-1 PDZ domain interaction.
• The 3a protein's PBM is not essential for pathogenicity as it does not bind Syntenin-1.
• Mutagenesis identified specific amino acids in the E protein PBM crucial for optimal viral replication.
• Binding of the E protein to the Syntenin-1 PDZ2 domain induced conformational changes in both PDZ domains of the Syntenin-1 homodimer.

Conclusions:

• The PDZ-binding motif of the SARS-CoV envelope (E) protein is indispensable for viral virulence, primarily through interaction with Syntenin-1 and subsequent p38-MAPK activation.
• While the 3a protein's PBM is not critical for pathogenicity, the E protein's PBM is essential, highlighting differential roles in SARS-CoV pathogenesis.
• Structural insights reveal that E protein binding to Syntenin-1 induces significant conformational alterations, providing a basis for understanding virus-host interactions.