Structure-Based Analysis of the Herpes Simplex Virus Glycoprotein D Binding Site Present on Herpesvirus Entry Mediator HveA (HVEM)

Abstract

Binding of herpes simplex virus (HSV) envelope glycoprotein D (gD) to a cell surface receptor is an essential step of virus entry. We recently determined the crystal structure of gD bound to one receptor, HveA. HveA is a member of the tumor necrosis factor receptor family and contains four characteristic cysteine-rich domains (CRDs). The first two CRDs of HveA are necessary and sufficient for gD binding. The structure of the gD-HveA complex reveals that 17 amino acids in HveA CRD1 and 4 amino acids in HveA CRD2 directly contact gD. To determine the contribution of these 21 HveA residues to virus entry, we constructed forms of HveA mutated in each of these contact residues. We determined the ability of the mutant proteins to bind gD, facilitate virus entry, and form HveA oligomers. Our results point to a binding hot spot centered around HveA-Y23, a residue that protrudes into a crevice on the surface of gD. Both the hydroxyl group and phenyl group of HveA-Y23 contribute to HSV entry. Our results also suggest that an intermolecular ␤-sheet formed between gD and HveA residues 35 to 37 contributes to binding and that a C37-C19 disulfide bond in CRD1 is a critical component of HveA structure necessary for gD binding. The results argue that CRD2 is required for gD binding mainly to provide structural support for a gD binding site in CRD1. Only one mutant, HveA-R75A, exhibited enhanced gD binding. While some mutations influenced complex formation, the majority did not affect HSV entry, suggesting that most contact residues contribute to HveA receptor function collectively rather than individually. This structure-based dissection of the gD-HveA binding site highlights the contribution of key residues within HveA to gD binding and HSV entry and defines a target region for the design of small-molecule inhibitors.In humans, herpes simplex virus (HSV) typically causes mucosal lesions and then spreads to the peripheral nervous system, where it establishes latent infections in sensory neurons. HSV encodes at least 11 membrane glycoproteins, and four of these (gD, gH, gL, and gB) are essential for entry of virions into mammalian cells. Expression of these four glycoproteins alone can facilitate cell fusion (4,33,37,41,44).The current model for virus entry posits the following series of events. Initially gC and/or gB binds cell surface heparan sulfate proteoglycans (41). Although binding of gC is a highaffinity interaction (K D ϭ 10 Ϫ8 M) (38), it is not essential for virus entry (41,42). This gC binding step is followed by binding of gD to one of several cell surface receptors. This essential step leads to pH-independent membrane fusion of the viral envelope with the cell plasma membrane, a process facilitated by gD, gH, gL, and gB (41). Some experiments suggest that the gH/gL heterodimer and/or gB is the viral fusogen, but how their fusogenic activity is triggered by the gD-receptor interaction is unknown (18,22).Several cellular receptors for HSV have been identified through expression cloning and homology searches, includin...

HSV trafficking and development of gene therapy vectors with applications in the nervous system

“…These results are in agreement with crystal structure data pinpointing the binding site for HveA and demonstrate that HveA binding to the N-terminus of gD results in a conformational change that may be responsible for inducing virus envelope fusion with the cell surface. 59,60 Together, these studies suggest that HveA is recognized by a folded part of gD that can be affected by mutations spanning a substantial portion of the molecule.…”

Separation of receptor-binding and profusogenic domains of glycoprotein D of herpes simplex virus 1 into distinct interacting proteins

“…At least some of the interactions of gD with its receptors have been mapped to the N terminus of gD, whereas the fusogenic determinant maps in the C-terminal portion of the ectodomain (residues 260-310). These residues (260-310) become actively engaged in membrane fusion after the interaction of the N-terminal domain with one of its cognate receptors (6)(7)(8)(10)(11)(12)(13)(14). gD also blocks apoptosis resulting from endocytosis of virus particles lacking gD.…”

The soluble ectodomain of herpes simplex virus gD contains a membrane-proximal pro-fusion domain and suffices to mediate virus entry

“…The four essential glycoproteins required for HSV entry are required and are also sufficient to induce fusion of cells that express a gD receptor (9). The gD-binding site on HVEM maps mainly to the N-terminal cysteine-rich domain 1, with a hot spot at Y23 (10,11). For nectin1, the N-terminal V domain, in particular its CCЈCЉ ridge (amino acids 64-104) is sufficient to mediate HSV entry (12)(13)(14)(15).…”