Background Paper Functions of Coronavirus Glycoproteins

Abstract

For coronaviruses, the glycoproteins have both historical and biological significance (1,2). Because some coronaviruses were difficult to isolate and propagate, their characteristic large, petal-shaped spikes first allowed coronaviruses to be identified as related agents in a common family. Viral glycoproteins play important roles throughout the life cycle of coronaviruses. Viral glycoproteins interact with receptors on the host cell membrane and are required for penetration of the viral genome into cells by fusion of the viral envelope with the plasma membrane or endosomal membranes. In virus-infected cells, Coronavirus glycoproteins may be glycosylated, acylated, oligomerized, cleaved into subunits by proteases, and transported to specific membrane compartments. The viral glycoproteins participate in assembly of virions, and the intracellular location of viral glycoproteins may determine the location of Coronavirus budding. Viral glycoproteins on the surface of infected cells may permit fusion with adjacent cells, and may make the cell susceptible to immune cytolysis or cell-mediated cytotoxicity, or permit hemadsorption. Epitopes of viral glycoproteins may be recognized by neutralizing, non-neutralizing or hemagglutination-inhibiting antibodies. Thus, elucidation of the structure and functions of Coronavirus glycoproteins is of central importance in understanding the replicative cycle and pathogenesis of coronaviruses.