Submitted to: Virus Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/23/2018
Publication Date: 8/28/2018
Citation: Gladue, D.P., Largo, E., Holinka-Patterson, L.G., Ramirez-Medina, E., Vuono, E.A., Berggren, K., Risatti, G.R., Nieva, J.L., Borca, M.V. 2018. Classical swine fever virus p7 protein interacts with host protein CAMLG and regulates calcium permeability at the endoplasmic reticulum. Virus Research. 10(9):E460. https://doi.org/10.3390/v10090460.
DOI: https://doi.org/10.3390/v10090460

Interpretive Summary: Classical swine fever (CSF) is a devastating disease in pigs. One of the viral proteins p7 creates a hole in the cellular membrane to promote replication of classical swine fever virus (CSFV). In this paper we studied the function of p7 and why it creates holes in cellular membranes. By using mutants of p7 we could conduct experiments that would measure what and how passes though the p7 pore. We discovered that CAMLG a host protein that regulates cellular calcium binds p7 during CSFV infection. By mapping where in p7 CAMLG binds, we were able to design specific mutants for p7, that interfered with CAMLG binding. Introducing these mutants into CSFV, resulted in inhibition of the virus being able to cause disease, from defects in the ability of the cell to regulate calcium levels during CSFV infection.

Technical Abstract: We have previously shown that Classical Swine Fever Virus (CSFV) p7 is an essential nonstructural protein with a viroporin activity, a critical function in the progression of virus infection. Also, we have identified p7 domains and amino acid residues being critical for pore formation. Here, we described that p7 specifically interacts with host protein CAMLG, an integral ER transmembrane protein involved in intracellular calcium release regulation and signal response generation. Detection of interaction as well as the identification of p7 areas mediating interaction with CAMLG was performed by yeast two-hybrid. p7-CAMLG interaction was further confirmed by confocal microscopy in eukaryotic cells co-expressing both proteins. Mutant forms of p7 having substituted native residues identified as mediating interaction with CAMLG showed a decreased co-localization compared with the native forms of p7. Furthermore, it is shown that native p7, but not the mutated forms of p7, failing to interact with CAMLG, efficiently mediates calcium permeability in the ER. Interestingly, viruses harboring some of those mutated forms of p7 have been previously shown to have a significantly decreased in virulence in swine.