Nordén R, Nyström K, Adamiak B, Halim A, Nilsson J, Larson G, Trybala E, Olofsson S. Involvement of viral glycoprotein gC-1 in expression of the selectin ligand sialyl-Lewis X induced after infection with herpes simplex virus type 1 APMIS 2013; 121: 280–89.
Several herpesviruses induce expression of the selectin receptor sialyl-Lewis X (sLex) by activating transcription of one or more of silent host FUT genes, each one encoding a fucosyltransferase that catalyses the rate-limiting step of sLex synthesis. The aim here was to identify the identity of the glycoconjugate associated with sLex glycoepitope in herpes simplex virus type 1 (HSV-1) infected human diploid fibroblasts, using immunofluorescence confocal microscopy. Cells infected with all tested HSV-1 strains analysed demonstrated bright sLex fluorescence, except for two mutant viruses that were unable to induce proper expression of viral glycoprotein gC-1: One gC-1 null mutant and another mutant expressing gC-1 devoid of its major O-glycan-containing region (aa 33–116). The sLex reactivity of HSV-1 infected cells was abolished by mild alkali treatment. Altogether the results indicated that the detectable sLex was associated with O-linked glycans, situated in the mucin region of gC-1. No evidence for sLex (i) in other HSV-1 glycoproteins with mucin domains such as gI-1 or (ii) in host cell glycoproteins/glycolipids was found. Thus, the mucin domain of HSV-1 gC-1 may support expression of selectin ligands such as sLex and other larger O-linked glycans in cell types lacking endogenous mucin domain-containing glycoproteins, optimized for O-glycan expression, provided that the adequate host glycosyltransferase genes are activated.