Proteolytic processing of human cytomegalovirus glycoprotein B (gpUL55) is mediated by the human endoprotease furin.

Inhibition of endoproteolytic cleavage of glycoprotein B (gB; gpUL55) of human cytomegalovirus was achieved by treatment of infected fibroblasts with decanoyl peptidyl chloromethyl ketone (decRVKR-CMK), which inhibits the action of cellular subtilisin-like endoproteases with the amino acid recognition motif R x K/R R. Uncleaved gB precursor molecules of 160 kDa that were accumulated were endoglycosidase H resistant, suggesting that correct cellular transport occurred in the presence of the drug. The inhibitor also prevented endoproteolytic gB processing in CV-1 cells infected with a recombinant vaccinia virus-gB construct (VVgB). Evidence for direct involvement of the ubiquitous subtilisin-like endoprotease furin in gB cleavage was obtained from the observation that coinfection of CV-1 cells with WgB and a recombinant vaccinia-human furin construct reestablished endoproteolytic activity which was normally absent late after infection with WgB alone.