The Infectious Bronchitis Virus Coronavirus Envelope Protein Alters Golgi pH to Protect Spike Protein and Promote Release of Infectious Virus

Jason W. Westerbeck; Carolyn E. Machamer

Attempts to rescue IBV EG3 by manipulation of Golgi pH. Despite intense efforts we were unable to conclusively determine whether an increase in Golgi pH could rescue the deficiencies of the IBV EG3 virus. We tried drugs that neutralize acidic compartments (baflinomycin A1, monensin and ammonium chloride), as well as overexpression of influenza A M2, a pH activated proton channel (4). However, the drugs inhibited exocytosis at all concentrations used (during short or long infections), and, we were unable to obtain a high percentage of M2transfected cells that were subsequently infected with IBV-EG3. In several experiments where the percent of transfected and infected cells was greater than 40%, we obtained 40-75% increases in release of infectious IBV-EG3 virus, but most experiments failed to show a reasonable overlap of transfection and infection and rescue of IBV-EG3 infectivity (data not shown). Additionally, attempts to make stable lines expressing M2 and pHluorin did not yield lines expressing M2 at a high enough level to alter the Golgi pH. We thus turned to another approach to assess the role of neutralization of the Golgi by IBV E during infection. The copyright holder for this preprint (which was not peer-reviewed) is the author/funder. It . https://doi.org/10.1101/440628 doi: bioRxiv preprint