Ilaprazole and Other Novel Prazole-Based Compounds That Bind Tsg101 Inhibit Viral Budding of Herpes Simplex Virus 1 and 2 and Human Immunodeficiency Virus from Cells

Abstract

In many enveloped virus families, including HIV and HSV, a crucial, yet unexploited, step in the viral life cycle is releasing particles from the infected cell membranes. This release process is mediated by host ESCRT complex proteins, which are recruited by viral structural proteins and provides the mechanical means for membrane scission and subsequent viral budding. The prazole drug, tenatoprazole, was previously shown to bind to ESCRT complex member Tsg101 and to quantitatively block the release of infectious HIV-1 from cells in culture. In this report we show that tenatoprazole and a related prazole drug, ilaprazole, effectively block infectious Herpes Simplex Virus (HSV)-1/2 release from Vero cells in culture. By electron microscopy, we found that both prazole drugs block the transit of HSV particles through the cell nuclear membrane resulting in their accumulation in the nucleus. Ilaprazole also quantitatively blocks the release of HIV-1 from 293T cells with an EC50 of 0.8-1.2 μM, which is much more potent than tenatoprazole. Our results indicate that prazole-based compounds may represent a class of drugs with potential to be broad-spectrum antiviral agents against multiple enveloped viruses, by interrupting cellular Tsg101 interaction with maturing virus, thus blocking the budding process that releases particles from the cell. Importance These results provide the basis for the development of drugs that target enveloped virus budding that can be used ultimately to control multiple virus infections in humans.

Importance of Viral Late Domains in Budding and Release of Enveloped RNA Viruses

“…For example, it was observed that compounds that block the PPxY–NEDD4 interaction also efficiently inhibited the egress of MARV [ 175 , 176 ]. Similarly, recent studies have shown that prazole compounds can inhibit the release of some enveloped viruses, including HIV-1, EBOV, May aro v irus (MAYV), and HSV by covalently binding the UEV domain of TSG101, which results in the disruption of TSG101–ubiquitin interaction [ 177 , 178 , 179 ]. Such a class of inhibitors interfering with the budding machinery could thus resultingly be extremely useful for impairing the production of newly emerging RNA viruses for which no therapeutics are available.…”

Host and Viral Factors Involved in Nuclear Egress of Herpes Simplex Virus 1

“…In agreement with this observation, ALIX is required for recruitment of ESCRT-III to the NM during infection of cells with Epstein–Barr virus (EBV, a human gammaherpesvirus) [ 103 , 104 ]. In addition, a compound that binds to ESCRT-I protein TSG101 inhibits primary envelopment of HSV-1 in Vero cells [ 105 ], supporting the idea that ESCRT-III machinery is required for nuclear egress of HSV-1 capsids. The other ESCRT-III adaptor CHMP7 has a predominant role in reformation of the nuclear membrane in various situations [ 101 , 102 ].…”

Novel Tsg101 Binding Partners Regulate Viral L Domain Trafficking

“…Prazoles are small molecules that bind the UEV domain near the β-hairpin and disrupt Ub binding there ( [23]; Figure 4). As noted above, they interfere with the ability of HIV-1 Gag to recruit Tsg101 to the plasma membrane assembly site and with the ability of EBV and HSV to mobilize the factors required for immature capsid formation and egress from the nuclear membrane assembly site [25,70]. Through siRNA-mediated depletion/replacement experiments, residue Cys73 in Tsg101 was demonstrated to be the prazole target in the case of HIV-1 and EBV.…”

“…The UEV domain is the only region of the protein for which structural information is available at the resolution required for drug design. Most efforts targeting Tsg101 have focused primarily on the PTAP site in that domain and have led to the identification of both cyclic [61][62][63] and multidentate [64][65][66][67] peptide and small molecule inhibitors [24,25,68]. Interestingly, while peptide inhibitors targeting PTAP-dependent Gag budding had no effect on release of a PTAP mutant [61], the small molecule inhibitors targeting UEV Ub-binding inhibit release irrespective of PTAP engagement [23].…”

“…Budding of several of these susceptible viruses is Tsg101-independent, indicating that the Ub-and P(T/S)AP-binding functions of Tsg101 are not necessarily linked. An example is the nuclear egress of herpes simplex virus (HSV) types 1 and 2 [25], where the involvement of the protein is not critical [9] (reviewed in [26]). The structurally unique N-terminal helix (site 1) houses critical determinants that recognize tRNA (panel 1E; [15]) and one of the sites occupied by the proximal domain of di-Ub moieties (proximal site-1, Strickland submitted, panel 1G).…”