Heparan Sulfate Proteoglycan Binding by Herpes Simplex Virus Type 1 Glycoproteins B and C, Which Differ in Their Contributions to Virus Attachment, Penetration, and Cell-to-Cell Spread

Abstract

Herpes simplex virus type 1 (HSV-1) mutants defective for envelope glycoprotein C (gC) and gB are highly impaired in the ability to attach to cell surface heparan sulfate (HS) moieties of proteoglycans, the initial virus receptor. Here we report studies aimed at defining the HS binding element of HSV-1 (strain KOS) gB and determining whether this structure is functionally independent of gB’s role in extracellular virus penetration or intercellular virus spread. A mutant form of gB deleted for a putative HS binding lysine-rich (pK) sequence (residues 68 to 76) was transiently expressed in Vero cells and shown to be processed normally, leading to exposure on the cell surface. Solubilized gBpK− also had substantially lower affinity for heparin-acrylic beads than did wild-type gB, confirming that the HS binding domain had been inactivated. The gBpK− gene was used to rescue a KOS gB null mutant virus to produce the replication-competent mutant KgBpK−. Compared with wild-type virus, KgBpK− showed reduced binding to mouse L cells (ca. 20%), while a gC null mutant virus in which the gC coding sequence was replaced by the lacZ gene (KCZ) was substantially more impaired (ca. 65%-reduced binding), indicating that the contribution of gC to HS binding was greater than that of gB. The effect of combining both mutations into a single virus (KgBpK−gC−) was additive (ca. 80%-reduced binding to HS) and displayed a binding activity similar to that observed for KOS virus attachment to sog9 cells, a glycosaminoglycan-deficient L-cell line. Cell-adsorbed individual and double HS mutant viruses exhibited a lower rate of virus entry following attachment, suggesting that HS binding plays a role in the process of virus penetration. Moreover, the KgBpK− mutant virus produced small plaques on Vero cells in the presence of neutralizing antibody where plaque formation depended on cell-to-cell virus spread. These studies permitted the following conclusions: (i) the pK sequence is not essential for gB processing or function in virus infection, (ii) the lysine-rich sequence of gB is responsible for HS binding, and (iii) binding to HS is cooperatively linked to the process of efficient virus entry and lateral spread but is not absolutely required for virus infectivity.

Structure-Based Mutations in the Herpes Simplex Virus 1 Glycoprotein B Ectodomain Arm Impart a Slow-Entry Phenotype

“…HSV-1 gB and gC bind to cell surface HS proteoglycans, and viruses with these glycoproteins deleted are impaired in the ability to attach to cells (21,26). HS binding was mapped to a lysine-rich region of gB (residues 68 to 76) (38). Mutation of this lysine-rich region disrupts HS binding, and the mutant virus is impaired but remains infectious, indicating that gB binding to HS is not essential for infection (38).…”

“…HS binding was mapped to a lysine-rich region of gB (residues 68 to 76) (38). Mutation of this lysine-rich region disrupts HS binding, and the mutant virus is impaired but remains infectious, indicating that gB binding to HS is not essential for infection (38). The gB 3A mutations are distant from the HS binding site, so these mutations were not expected to affect HS binding.…”

Crystal Structure of Herpes Simplex Virus 2 gD Bound to Nectin-1 Reveals a Conserved Mode of Receptor Recognition

“…As with other enveloped viruses, the initiation of virus infection by HSV requires, as a prerequisite, the specific interactions between viral surface glycoproteins and the host cellular receptors (7)(8)(9). Although multiple virus envelope proteins other than gD have been shown to be capable of recognizing host molecules (e.g., both gB and gC can engage HSPG [10,11] and gB also recognizes PILR␣ [59] and NMHC-IIA [60]), the gD-receptor interaction is considered a key step bridging the attachment and the fusion processes. Of the identified gD receptors, nectin-1 seems to play a more important role in mediating the infection by HSV-2, at least in in vivo murine models (28,29).…”

“…The current thesis indicates the involve-ment of at least 5 (of 11) virus envelope glycoproteins in HSV entry, including glycoproteins B, C, D, H, and L (gB, gC, gD, gH, and gL) (7)(8)(9). The initial attachment of the virus particles on the cell surface could be mediated by gB or gC, which can recognize sugar moieties like heparan sulfate proteoglycan (HSPG) (10,11). This is normally followed by a specific interaction between gD and its canonical receptors (12,13).…”

Bovine whey proteins – Overview on their main biological properties

“…Except in the case of simian rotavirus (Superti & Donelli, 1995), another mechanism hypothesized for binding of BLF to host cells is via a receptor (or co-receptor) -such as heparin sulphate proteoglycans (HSPG), which prevent binding of the virus thereto, and subsequent infection of the host cell (Laquerre et al, 1998). Recently, Marchetti, Trybala, Superti, Johansson, and Bergströ m (2004) elucidated the mechanism of BLF antiviral activity against HSV-1 infection initiates infection of cells via binding to it glycosaminoglycans (GAG) (WuDunn & Spear, 1989), which are composed of repeating (specifically sulphated) disaccharide units.…”