Structural glycoprotein E2 of classical swine fever virus critically interacts with host protein Torsin-1A during the virus infectious cycle

Authors: VUONO, ELIZABETH - University Of Mississippi; RAMIREZ-MEDIA, ELIZABETH - University Of Connecticut; VELAZQUEZ-SALINAS, LAURO - University Of Kansas; BERGGREN, KEITH - University Of Princeton; RAI, AYUSHI - Oak Ridge Institute For Science And Education (ORISE); Pruitt, Sarah; Espinoza, Nallely; Gladue, Douglas; Borca, Manuel

Submitted to: Journal of Virology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/23/2021
Publication Date: 5/24/2021
Citation: Vuono, E., Ramirez-Media, E., Velazquez-Salinas, L., Berggren, K., Rai, A., Pruitt, S.E., Espinoza, N.N., Gladue, D.P., Borca, M.V. 2021. Structural glycoprotein E2 of classical swine fever virus critically interacts with host protein Torsin-1A during the virus infectious cycle. Virology Journal. https://doi.org/10.1128/JVI.00314-21.
DOI: https://doi.org/10.1128/JVI.00314-21

Interpretive Summary: Classical swine fever virus (CSFV) causes a devastating disease in swine, one protein of this virus called E2 is probably the most important component of virus due to its involvement in many virus activities, particularly interacting with the hosts i.e. pig cells. Here we identified a protein in pig cells that interact with E2, this protein is called Torsin-1A. The E2 amino acid residues mediating the interaction with Torsin-1A, were also identified. A genetically modified CSFV was created harboring mutations disrupting E2- Torsin-1A interaction. Disruption of the E2- Torsin-1A interaction resulted in a non-viable CSFV.

Technical Abstract: The classical swine fever virus (CSFV) glycoprotein E2 is the major structural component of the virus particle. E2 is involved in several functions such as virus adsorption to the cell, the elicitation of protective immune responses, and virus virulence in swine. Using a yeast two-hybrid system, we previously identified the swine host protein Torsin-1A, an ATPase protein residing in the endoplasmic reticulum and inner nucleus membrane of the cell, as a specific binding partner for E2. The interaction between Torsin-1A and E2 proteins was confirmed to occur in CSFV-infected swine cells using three independent methodologies: co-immunoprecipitation, confocal microscopy and proximity ligation assay (PLA). Furthermore, the E2 residue critical to mediate the protein-protein interaction with Torsin-1A was identified by a reverse yeast two-hybrid using a randomly mutated E2 library. A recombinant CSFV E2 mutant protein with a Q316L substitution failed to bind swine Torsin-1A in the yeast two-hybrid model. In addition, a CSFV infectious clone harboring the E2 Q316L substitution, although expressing substantial levels of E2 protein, repetitively failed to produce virus progeny when the corresponding RNA was transfected into susceptible SK6 cells. Importantly, PLA analysis of the transfected cells demonstrated an abolishment of the interaction between E2 and Torsin-1A, indicating a critical role for that interaction during CSFV replication.