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MicroED structures of HIV-1 Gag CTD-SP1 reveal binding interactions with the maturation inhibitor bevirimat.

ABSTRACT: HIV-1 protease (PR) cleavage of the Gag polyprotein triggers the assembly of mature, infectious particles. Final cleavage of Gag occurs at the junction helix between the capsid protein CA and the SP1 spacer peptide. Here we used MicroED to delineate the binding interactions of the maturation inhibitor bevirimat (BVM) using very thin frozen-hydrated, 3D microcrystals of a CTD-SP1 Gag construct with and without bound BVM. The 2.9-Å MicroED structure revealed that a single BVM molecule stabilizes the six-helix bundle via both electrostatic interactions with the dimethylsuccinyl moiety and hydrophobic interactions with the pentacyclic triterpenoid ring. These results provide insight into the mechanism of action of BVM and related maturation inhibitors that will inform further drug discovery efforts. This study also demonstrates the capabilities of MicroED for structure-based drug design.

SUBMITTER: Purdy MD

PROVIDER: S-EPMC6310804 | biostudies-literature | 2018 Dec

REPOSITORIES: biostudies-literature

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MicroED structures of HIV-1 Gag CTD-SP1 reveal binding interactions with the maturation inhibitor bevirimat.

Purdy Michael D MD Shi Dan D Chrustowicz Jakub J Hattne Johan J Gonen Tamir T Yeager Mark M

Proceedings of the National Academy of Sciences of the United States of America 20181210 52

HIV-1 protease (PR) cleavage of the Gag polyprotein triggers the assembly of mature, infectious particles. Final cleavage of Gag occurs at the junction helix between the capsid protein CA and the SP1 spacer peptide. Here we used MicroED to delineate the binding interactions of the maturation inhibitor bevirimat (BVM) using very thin frozen-hydrated, 3D microcrystals of a CTD-SP1 Gag construct with and without bound BVM. The 2.9-Å MicroED structure revealed that a single BVM molecule stabilizes t ...[more]

PMID: 30530702

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Project description:BackgroundMaturation inhibitors are an experimental class of antiretrovirals that inhibit Human Immunodeficiency Virus (HIV) particle maturation, the structural rearrangement required to form infectious virus particles. This rearrangement is triggered by the ordered cleavage of the precursor Gag polyproteins into their functional counterparts by the viral enzyme protease. In contrast to protease inhibitors, maturation inhibitors impede particle maturation by targeting the substrate of protease (Gag) instead of the protease enzyme itself. Direct cross-resistance between protease and maturation inhibitors may seem unlikely, but the co-evolution of protease and its substrate, Gag, during protease inhibitor therapy, could potentially affect future maturation inhibitor therapy. Previous studies showed that there might also be an effect of protease inhibitor resistance mutations on the development of maturation inhibitor resistance, but the exact mechanism remains unclear. We used wild-type and protease inhibitor resistant viruses to determine the impact of protease inhibitor resistance mutations on the development of maturation inhibitor resistance.ResultsOur resistance selection studies demonstrated that the resistance profiles for the maturation inhibitor bevirimat are more diverse for viruses with a mutated protease compared to viruses with a wild-type protease. Viral replication did not appear to be a major factor during emergence of bevirimat resistance. In all in vitro selections, one of four mutations was selected: Gag V362I, A364V, S368N or V370A. The impact of these mutations on maturation inhibitor resistance and viral replication was analyzed in different protease backgrounds. The data suggest that the protease background affects development of HIV-1 resistance to bevirimat and the replication profiles of bevirimat-selected HIV-1. The protease-dependent bevirimat resistance and replication levels can be explained by differences in CA/p2 cleavage processing by the different proteases.ConclusionsThese findings highlight the complicated interactions between the viral protease and its substrate. By providing a better understanding of these interactions, we aim to help guide the development of second generation maturation inhibitors.

Project description:BackgroundMaturation inhibitors (MIs) potently block HIV-1 maturation by inhibiting the cleavage of the capsid protein and spacer peptide 1 (CA-SP1). Bevirimat (BVM), a highly efficacious first-in-class MI against HIV-1 subtype B isolates, elicited sub-optimal efficacy in clinical trials due to polymorphisms in the CA-SP1 region of the Gag protein (SP1:V7A). HIV-1 subtype C inherently contains this polymorphism thus conferring BVM resistance, however it displayed sensitivity to second generation BVM analogs.ResultsIn this study, we have assessed the efficacy of three novel second-generation MIs (BVM analogs: CV-8611, CV-8612, CV-8613) against HIV-1 subtype B and C isolates. The BVM analogs were potent inhibitors of both HIV-1 subtype B (NL4-3) and subtype C (K3016) viruses. Serial passaging of the subtype C, K3016 virus strain in the presence of BVM analogs led to identification of two mutant viruses-Gag SP1:A1V and CA:I201V. While the SP1:A1V mutant was resistant to the MIs, the CA:I120V mutant displayed partial resistance and a MI-dependent phenotype. Further analysis of the activity of the BVM analogs against two additional HIV-1 subtype C strains, IndieC1 and ZM247 revealed that they had reduced sensitivity as compared to K3016. Sequence analysis of the three viruses identified two polymorphisms at SP1 residues 9 and 10 (K3016: N9, G10; IndieC1/ZM247: S9, T10). The N9S and S9N mutants had no change in MI-sensitivity. On the other hand, replacing glycine at residue 10 with threonine in K3016 reduced its MI sensitivity whereas introducing glycine at SP1 10 in place of threonine in IndieC1 and ZM247 significantly enhanced their MI sensitivity. Thus, the specific glycine residue 10 of SP1 in the HIV-1 subtype C viruses determined sensitivity towards BVM analogs.ConclusionsWe have identified an association of a specific glycine at position 10 of Gag-SP1 with an MI susceptible phenotype of HIV-1 subtype C viruses. Our findings have highlighted that HIV-1 subtype C viruses, which were inherently resistant to BVM, may also be similarly predisposed to exhibit a significant degree of resistance to second-generation BVM analogs. Our work has strongly suggested that genetic differences between HIV-1 subtypes may produce variable MI sensitivity that needs to be considered in the development of novel, potent, broadly-active MIs.

Dataset Information

MicroED structures of HIV-1 Gag CTD-SP1 reveal binding interactions with the maturation inhibitor bevirimat.

Publications

MicroED structures of HIV-1 Gag CTD-SP1 reveal binding interactions with the maturation inhibitor bevirimat.

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