ABSTRACT
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is responsible for the pandemic that has affected millions of people worldwide. This virus contains a unique polybasic insertion (PRRA) within the spike protein, resulting in a novel furin cleavage site that has been shown to influence viral infectivity and syncytia formation in cell culture. This insertion also generates novel putative sites of O-glycosylation, a protein modification that has been shown in other proteins to influence furin cleavage. Here, we define the specific members of the UDP-GalNAc:polypeptide N-acetylgalactosaminyltransferase (GALNT) family that are capable of glycosylating the novel SARS-CoV-2 coronavirus spike and examine their presence in human respiratory cells that are targets for SARS-CoV-2 infection. Moreover, we show that O-glycosylation by specific members of the GALNT enzyme family modulates furin cleavage of the spike in vivo. Given the well-established role of O-glycosylation in the regulation of proteolysis, our results suggest that O-glycosylation of SARS-CoV-2 may play roles in aspects of spike stability/processing, which may influence viral infectivity and tropism.