Signal peptide cleavage from GP3 enabled by removal of adjacent glycosylation sites does not impair replication of equine arteritis virus in cell culture, but the hydrophobic C-terminus is essential.

The research investigates the role of a specific protein, GP3, in the development of equine arteritis virus (EAV). It was found that removing certain glycosylation sites – places where sugars attach – near GP3 enables a critical cut or cleavage of the protein. This modified GP3 doesn’t hamper the spread of the virus, but removing the protein’s hydrophobic – or water-repelling – ending does.

Background and Purpose

• The study was conducted to explore the function and relevance of the GP3 protein in the replication of the equine arteritis virus (EAV), a disease primarily affecting horses.
• Previous studies showed that in laboratory conditions, when carbohydrates (sugars) that attach near the GP3 signal peptide (a specific part of the protein) are removed, this enables the protein to be cleaved or separated more efficiently. The goal was to confirm this phenomenon in actual viruses amended to disable the glycosylation sites – places on a protein where carbohydrates can attach – adjacent to GP3.

Methods and Results

• The researchers investigated the infectivity of EAV that contains a GP3 protein whose signal peptide has been cut or cleaved. The results pointed out that the virus’s ability to infect cells was not weakened or impaired.
• Additionally, the modified GP3 protein, with a cleaved signal peptide, was found to associate with two other proteins, GP2 and GP4, in the virus particles.
• Nevertheless, the study found contrasting results when the hydrophobic C-terminus of GP3 – the end part of the protein that repels water – was deleted or removed. In those cases, the viruses quickly turned back to their original, wild type form.

Conclusions and Implications

• This study underscores that the hydrophobic C-terminus of GP3 is crucial for maintaining the stability and function of the equine arteritis virus.
• The research also reveals that the signal peptide on GP3 is revealed or exposed to the stirring of the endoplasmic reticulum (ER), a part of the cell where protein synthesis occurs, and the C-terminus binds GP3 to membranes externally or peripherally.
• The findings are significant for our understanding of how the EAV develops and potentially progresses, which is crucial for developing more effective strategies to impede or control the virus’s replication and spread.