Molecular basis of EphA2 recognition by gHgL from gammaherpesviruses

Abstract

The human γ-herpesviruses Kaposi sarcoma associated herpesvirus (KSHV) and Epstein-Barr virus (EBV) are associated with many human malignancies. Viral glycoprotein H (gH) and glycoprotein L (gL) are crucial for the cell tropism by binding to specific receptors. Recently, EphA2 was identified as the specific entry receptor for both KSHV and EBV. Here, we characterized the crystal structures of KSHV gHgL or EBV gHgL in complex with the ligand binding domain (LBD) of EphA2. Both KSHV and EBV gHgL bind to the channel and peripheral regions of LBD primarily using gL. Extensive interactions with more contacts contribute to the higher affinity of KSHV gHgL to LBD than that of EBV gHgL. These binding characteristics were verified using cell-based fusion assays with mutations in key EphA2 residues. Our experiments suggest that multiple animal γ-herpesviruses could use EphA2 as an entry receptor, implying a potential threat to human health.

Plxdc family members are novel receptors for the rhesus monkey rhadinovirus (RRV)

“…In contrast, recombinant overexpression of Plxdc2, but not of Plxdc1 enhanced infection with RRV 17577 (Fig 2F and 2I), which was paralleled in our fusion assay: RRV 17577 gH/gB/gL effector cells fused readily with Plxdc2 overexpressing target cells, but not in the absence of gL or with Plxcd1 overexpressing target cells (Fig 6E). These features of Plxdc1/2 binding specificities appear similar to the interaction of the gH/gL complex with Eph receptors, wherein mutation of the strictly conserved Eph interaction motif is sufficient to abrogate receptor binding, but differences in KSHV and RRV affinities for A-and B-type Eph RTKs indicate the existence of additional regions in gH or gL that contribute to or modulate the interaction, which is corroborated by a recent crystal structure of KSHV gH/gL in complex with EphA2 [36]. Whether these preferences for different members of conserved receptor families also influence e.g.…”

Human herpesvirus 8 molecular mimicry of ephrin ligands facilitates cell entry and triggers EphA2 signaling

“…In our structure the R103 EphA2 forms 2 hydrogen bonds and 1 salt bridge with the E52 gH , which is substantially less than the gL contribution (14 HB and extensive buried surface area) (Table S2). In EBV gH/gL the equivalent residue E30 gH is located away from the EphA2 binding interface due to a different organization of the N-terminal part of gH compared to the HHV-8 gH, possibly contributing to the reported weaker affinity with a Kd in the M range 52 (the EBV gH and EphA2 in fact do not form any contacts). To determine to what extent the HHV-8 E52 gH influences interactions with EphA2, we performed biophysical (gH/gL and EphA2 ectodomains in solution) and cellular assays (EphA2 full-length membrane bound and gH/gL ectodomains in solution).…”

“…The structures of several Eph receptor -ephrin ligand complexes have been determined 39,40,42,44,45 , but how viral antigens such as HHV-8 gH/gL interact with EphA2 was completely unknown until recently. The 3.2Å X-ray structure of a HHV8 gH/gL-EphA2 complex was published while we were preparing this manuscript 52 . Our goal has been to explore the events that emulate the early stages of HHV-8 entry.…”

Cellular Receptors Involved in KSHV Infection

“…A recent high-resolution structural investigation into the complex formation between KSHV gH-gL and the ligand binding domain (LBD) of EPHA2 revealed primarily gL protein binding to LBD [ 78 ]. It was further revealed that many amino acids of EPHA2′s LBD are potentially recognized by other γ-herpesviruses, thereby providing the structural basis of EPHA2 recognition by γ-herpesvirus gHgL [ 78 ].…”

“…A recent high-resolution structural investigation into the complex formation between KSHV gH-gL and the ligand binding domain (LBD) of EPHA2 revealed primarily gL protein binding to LBD [ 78 ]. It was further revealed that many amino acids of EPHA2′s LBD are potentially recognized by other γ-herpesviruses, thereby providing the structural basis of EPHA2 recognition by γ-herpesvirus gHgL [ 78 ]. Recently, an investigation of EPHA2 sequence variants in the protein coding region of the gene in South African HIV positive individuals revealed that certain variants, primarily located in the functionally important tyrosine kinase domain, affected patient’s susceptibility to KSHV infection or KS development [ 79 ].…”