Cleavage Inhibition of the Murine Coronavirus Spike Protein by a Furin-Like Enzyme Affects Cell-Cell but Not Virus-Cell Fusion

Cleavage of the mouse hepatitis coronavirus strain A59 spike protein was blocked in a concentration-dependent manner by a peptide furin inhibitor, indicating that furin or a furin-like enzyme is responsible for this process. While cell-cell fusion was clearly affected by preventing spike protein cleavage, virus-cell fusion was not, indicating that these events have different requirements.