Signal peptidase complex mediates rotavirus VP7 processing and virion assembly

Area of Science:

• Virology
• Molecular Biology
• Cell Biology

Background:

• Viral glycoproteins require proper processing in the endoplasmic reticulum (ER) for infection.
• Rotavirus outer capsid protein VP7 is an ER-resident protein whose N-terminal signal peptide cleavage mechanism was unknown.

Purpose of the Study:

• To identify host factors involved in rotavirus VP7 processing and maturation.
• To elucidate the role of identified host factors in rotavirus infection and assembly.

Main Methods:

• Tandem affinity purification coupled with high-resolution mass spectrometry to identify VP7 interacting proteins.
• CRISPR/Cas9 gene editing and siRNA for gene knockdown of signal peptidase complex (SPC) subunits.
• Transmission electron microscopy (TEM) to analyze viral particle morphology.
• Site-directed mutagenesis to investigate VP7-SPC interaction.

Main Results:

• Members of the signal peptidase complex (SPC) were identified as host factors interacting with VP7.
• Knockout or knockdown of SPC subunits significantly reduced infectious rotavirus titers.
• Loss of SPC impaired VP7 signal peptide cleavage, leading to abnormal viral particles and defective virion maturation and assembly.
• Residue E256 in VP7 was identified as a key site for SPC binding; mutation reduced viral infectivity.

Conclusions:

• SPC is a novel regulator of rotavirus VP7 maturation and viral assembly.
• SPC plays a critical role in rotavirus infection, independent of viral transcription, translation, or replication.
• SPC represents a potential cellular target for broad-spectrum antiviral therapeutic development against rotavirus.