The Identification and Characterization of Fusogenic Domains in Herpes Virus Glycoprotein B Molecules

Abstract

The molecular mechanism of entry of herpes viruses requires a multicomponent fusion system. Virus entry and cell-cell fusion of Herpes simplex virus (HSV) requires four glycoproteins: gD, gB and gH/gL. The role of gB remained elusive until recently, when the crystal structure of HSV-1 gB became available. Glycoprotein B homologues represent the most highly conserved group of herpes virus glycoproteins; however, despite the high degree of sequence and structural conservation, differences in post-translational processing are observed for different members of this virus family. Whereas gB of HSV is not proteolytically processed after oligomerization, most other gB homologues are cleaved by a cellular protease into subunits that remain linked through disulfide bonds. Proteolytic cleavage is common for activation of many other viral fusion proteins, so it remains difficult to envisage a common role for different herpes virus gB structures in the fusion mechanism. We selected bovine herpes virus type 1 (BoHV-1) and herpes simplex virus type 1 (HSV-1) as representative viruses expressing cleaved and uncleaved gBs, and have screened their amino acid sequences for regions of highly interfacial hydrophobicity. Synthetic peptides corresponding to such regions were tested for their ability to induce the fusion of large unilamellar vesicles and to inhibit herpes virus infection. These results underline that several regions of the gB protein are involved in the mechanism of membrane interaction.

Analysis of a Membrane Interacting Region of Herpes Simplex Virus Type 1 Glycoprotein H

“…Moreover, recent data have shown that peptides spanning the heptad-repeat region of gH inhibit the entry of both human cytomegalovirus (31) and HSV-1 (29,30), similar to the corresponding entry inhibitors identified for viruses that have a class I membrane-fusion protein.…”

“…gH has been reported to have certain features that are characteristic of class I fusion proteins, such as the presence of heptad repeats and a putative fusion peptide region (21,29,30). Moreover, recent data have shown that peptides spanning the heptad-repeat region of gH inhibit the entry of both human cytomegalovirus (31) and HSV-1 (29,30), similar to the corresponding entry inhibitors identified for viruses that have a class I membrane-fusion protein.…”

“…The fusogenic properties of gB are well established (1,16,17), and its structure displays features of both class I and class II membrane-fusion proteins (18). In fact, the crystal structure of HSV-1 gB (9) revealed an unexpected structural homology to the envelope glycoprotein of the vesicular stomatitis virus (19).…”

Herpes Simplex Virus gD Forms Distinct Complexes with Fusion Executors gB and gH/gL in Part through the C-terminal Profusion Domain

“…Thus, gH carries elements typical of fusion glycoproteins, i.e. hydrophobic regions able to interact with target cells or artificial membranes and two heptad repeats potentially able to form a coiled coil (13)(14)(15)(16)(17)(18). Peptides mimicking the hydrophobic regions of gH promote fusion of artificial membranes (19,20).…”

Peptide gH625 enters into neuron and astrocyte cell lines and crosses the blood–brain barrier in rats

“…10,11 The intrinsic ability of virus-derived peptides to induce membrane perturbation may be useful in the design of delivery vehicles. [12][13][14] The peptide gH625, previously identified as a membraneperturbing domain in glycoprotein H (gH) of herpes simplex virus 1, has been demonstrated to be able to traverse the membrane bilayer. 15 Further, gH625 has been used extensively for vector-mediated strategies that enable passage of a large variety of small molecules as well as proteins across cell membranes in vitro.…”