A Network of Protein Interactions around the Herpes Simplex Virus Tegument Protein VP22

Abstract

Assembly of the herpesvirus tegument is poorly understood but is believed to involve interactions between outer tegument proteins and the cytoplasmic domains of envelope glycoproteins. Here, we present the detailed characterization of a multicomponent glycoprotein-tegument complex found in herpes simplex virus 1 (HSV-1)-infected cells. We demonstrate that the tegument protein VP22 bridges a complex between glycoprotein E (gE) and glycoprotein M (gM). Glycoprotein I (gI), the known binding partner of gE, is also recruited into this gE-VP22-gM complex but is not required for its formation. Exclusion of the glycoproteins gB and gD and VP22's major binding partner VP16 demonstrates that recruitment of virion components into this complex is highly selective. The immediate-early protein ICP0, which requires VP22 for packaging into the virion, is also assembled into this gE-VP22-gM-gI complex in a VP22-dependent fashion. Although subcomplexes containing VP22 and ICP0 can be formed when either gE or gM are absent, optimal complex formation requires both glycoproteins. Furthermore, and in line with complex formation, neither of these glycoproteins is individually required for VP22 or ICP0 packaging into the virion, but deletion of gE and gM greatly reduces assembly of both VP22 and ICP0. Double deletion of gE and gM also results in small plaque size, reduced virus yield, and defective secondary envelopment, similar to the phenotype previously shown for pseudorabies virus. Hence, we suggest that optimal gE-VP22-gM-gI-ICP0 complex formation correlates with efficient virus morphogenesis and spread. These data give novel insights into the poorly understood process of tegument acquisition.T he herpesvirus virion is a complex particle consisting of a DNA genome-containing capsid surrounded by a compartment termed the tegument and an outer, host cell-derived lipid envelope that contains virus-encoded glycoproteins (29). The prototypic alphaherpesvirus herpes simplex virus 1 (HSV-1) packages at least 26 tegument proteins and up to 20 envelope proteins (35). Because of this complexity and previously recognized redundancy among the structural proteins, the molecular mechanisms involved in the assembly of this virus remain poorly understood. An attractive and widely accepted model proposes that viral glycoproteins embedded within membranes of the late secretory pathway recruit components of the outer tegument, through which viral capsids, surrounded by an inner tegument, bud to produce mature virions (25,33). In spite of this favored model, there are few examples in the literature of well-defined tegument-glycoprotein interactions shown to be involved in virus assembly. For example, the major tegument components VP16 and VP22 have been reported to interact with gH and gD, respectively, but the contribution these interactions make to tegument assembly and virus morphogenesis have not yet been proven (5,17,20).The nonessential glycoprotein gE is the only envelope protein thus far convincingly shown to interact directly with and be re...

Kaposi's Sarcoma-Associated Herpesvirus Inhibitor of cGAS (KicGAS), Encoded by ORF52, Is an Abundant Tegument Protein and Is Required for Production of Infectious Progeny Viruses

“…8C), which is reminiscent of the phenotype observed in HSV-1 VP22-null mutants (70,74). We speculate that KSHV ORF52 reinforces the interaction network between virion proteins, much as HSV-1 VP22 and HCMV pp65 do (62,72). The shared and unique structural features and functions of ORF52 homologues in KSHV, MHV-68, RRV, and EBV allude to the common, yet distinct strategies employed by these viruses to maintain persistent infection of their human host.…”

“…Besides binding to the tegument protein ICP0, VP22 interacts with its major binding partner VP16, which links to other alphaherpesvirus-specific tegument proteins (46,53). Furthermore, VP22 is also incorporated into the gE-VP22-gM complex, which may associate with the UL11-UL16 complex via its interaction with glycoproteins (72). If ORF52 and VP22 indeed share functional and structural similarities, a logical assumption is that ORF52 is similarly involved in virion assembly through its intricate interactions with other virion proteins.…”

ORF9p Phosphorylation by ORF47p Is Crucial for the Formation and Egress of Varicella-Zoster Virus Viral Particles

“…All these observations suggest an involvement of this tegument protein in the process of viral envelopment. Accordingly, HSV-1 VP22 was shown to be part of a glycoprotein-tegument network, interacting with the glycoproteins gE, gI, and gM, with the protein ICP0 (47,48), and with the transactivator VP16 (49); this last interaction seems to be important for VP22 virion incorporation, whose role is essential for the virion packaging of ICP0 (50).…”

Elucidation of the Block to Herpes Simplex Virus Egress in the Absence of Tegument Protein UL16 Reveals a Novel Interaction with VP22

“…Another tegument protein that has long been known to interact with the cytoplasmic tail of gE is VP22 (33,35,43). VP22 also interacts with tegument protein VP16, the product of the U L 48 gene, which is essential for virus replication and egress (28,34,51,52).…”

“…Unexpectedly, a defect in virion packaging was found for another tegument protein, VP22, which is encoded by the U L 49 gene (26). VP22 is a phosphorylated protein that is known to interact within a network that includes gE, gD, VP16, ICP0, and gM (8,9,(26)(27)(28)(29)(30)(31)(32)(33)(34)(35). It also binds to and negatively regulates "virion host shutoff" (VHS) protein, and thus, mutants that lack VP22 have defects in virus production and exhibit reduced protein synthesis (36, 37).…”