Signal peptidase complex mediates rotavirus VP7 processing and virion assembly

Area of Science:

• Virology
• Molecular Biology
• Cell Biology

Background:

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

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 mass spectrometry to identify VP7 interacting proteins.
• CRISPR/Cas9 gene editing and siRNA for gene knockdown of candidate host factors.
• Transmission electron microscopy (TEM) to analyze viral particle morphology.
• Site-directed mutagenesis to investigate protein-protein interactions.

Main Results:

• Members of the signal peptidase complex (SPC) were identified as host factors interacting with VP7.
• Knockdown or knockout of SPC subunits significantly reduced rotavirus titers independently of viral strain and cell type.
• Loss of SPC impaired VP7 signal peptide cleavage, leading to abnormal viral particles and defects in virion maturation and assembly.
• Residue E256 in VP7 was identified as a key binding site for SPC, and mutation of this site reduced viral infectivity.

Conclusions:

• SPC is a novel regulator of rotavirus VP7 maturation and virion assembly.
• SPC facilitates efficient cleavage of the VP7 signal peptide, essential for viral infectivity.
• SPC represents a potential cellular target for broad-spectrum antiviral therapeutic development against rotavirus.