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Abstract
Viroporins are short polypeptides encoded by viruses. These small membrane proteins assemble into oligomers that can permeabilize cellular lipid bilayers, disrupting the physiology of the host to the advantage of the virus. Consequently, efforts during the last few decades have been focused towards the discovery of viroporin channel inhibitors, but in general these have not been successful to produce licensed drugs. Viroporins are also involved in viral pathogenesis by engaging in critical interactions with viral proteins, or disrupting normal host cellular pathways through coordinated interactions with host proteins. These protein-protein interactions (PPIs) may become alternative attractive drug targets for the development of antivirals. In this sense, while thus far most antiviral molecules have targeted viral proteins, focus is moving towards targeting host proteins that are essential for virus replication. In principle, this largely would overcome the problem of resistance, with the possibility of using repositioned existing drugs. The precise role of these PPIs, their strain- and host- specificities, and the structural determination of the complexes involved, are areas that will keep the fields of virology and structural biology occupied for years to come. In the present review, we provide an update of the efforts in the characterization of the main PPIs for most viroporins, as well as the role of viroporins in these PPIs interactions.
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Affiliation(s)
| | - David Bhella
- MRC-University of Glasgow Centre for Virus Research, Glasgow, UK
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Mahato DR, Fischer WB. Specification of binding modes between a transmembrane peptide mimic of ATP6V0C and polytopic E5 of human papillomavirus-16. J Biomol Struct Dyn 2017; 36:2618-2627. [DOI: 10.1080/07391102.2017.1364671] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- Dhani Ram Mahato
- Institute of Biophotonics, School of Biomedical Science and Engineering, National Yang-Ming University, 155, Li-Nong St., Sec. 2, Taipei 112, Taiwan
| | - Wolfgang B. Fischer
- Institute of Biophotonics, School of Biomedical Science and Engineering, National Yang-Ming University, 155, Li-Nong St., Sec. 2, Taipei 112, Taiwan
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Mahato DR, Fischer WB. Weak Selectivity Predicted for Modeled Bundles of Viral Channel-Forming Protein E5 of Human Papillomavirus-16. J Phys Chem B 2016; 120:13076-13085. [PMID: 27976908 DOI: 10.1021/acs.jpcb.6b10050] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Protein E5 is a polytopic 83 amino acid membrane protein with three transmembrane domains (TMDs), encoded by high-risk human papillomavirus-16 (HPV-16). HPV-16 is found to be the causative agent for cervical cancer. Protein E5, among other proteins (e.g., E6, E7), is expressed at an "early" (E) stage when the cell turns malignant. It has been experimentally found that E5 forms hexameric assemblies, which show the characteristics of the class of so-called channel-forming proteins by rendering lipid membranes permeable to ions and small molecules. Protein E5 is used to achieve structural models of the protein in assembled bundles using a force field-based docking approach. Extended molecular dynamics simulations of selected bundles in fully hydrated lipid bilayers suggest the second TMD to be pore-lining, allowing for water columns to exist within the lumen of the pore. Full correlation analysis indicates asymmetric dynamics within the monomers of the bundle. Potential of mean force calculations of a snapshot structure of the putative open pore of the protein bundle propose low selectivity.
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Affiliation(s)
- Dhani Ram Mahato
- Institute of Biophotonics and Biophotonics & Molecular Imaging Research Center (BMIRC), School of Biomedical Science and Engineering, National Yang-Ming University , Taipei 112, Taiwan
| | - Wolfgang B Fischer
- Institute of Biophotonics and Biophotonics & Molecular Imaging Research Center (BMIRC), School of Biomedical Science and Engineering, National Yang-Ming University , Taipei 112, Taiwan
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Novel Acylguanidine-Based Inhibitor of HIV-1. J Virol 2016; 90:9495-508. [PMID: 27512074 DOI: 10.1128/jvi.01107-16] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2016] [Accepted: 08/05/2016] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED The emergence of transmissible HIV-1 strains with resistance to antiretroviral drugs highlights a continual need for new therapies. Here we describe a novel acylguanidine-containing compound, 1-(2-(azepan-1-yl)nicotinoyl)guanidine (or SM111), that inhibits in vitro replication of HIV-1, including strains resistant to licensed protease, reverse transcriptase, and integrase inhibitors, without major cellular toxicity. At inhibitory concentrations, intracellular p24(Gag) production was unaffected, but virion release (measured as extracellular p24(Gag)) was reduced and virion infectivity was substantially impaired, suggesting that SM111 acts at a late stage of viral replication. SM111-mediated inhibition of HIV-1 was partially overcome by a Vpu I17R mutation alone or a Vpu W22* truncation in combination with Env N136Y. These mutations enhanced virion infectivity and Env expression on the surface of infected cells in the absence and presence of SM111 but also impaired Vpu's ability to downregulate CD4 and BST2/tetherin. Taken together, our results support acylguanidines as a class of HIV-1 inhibitors with a distinct mechanism of action compared to that of licensed antiretrovirals. Further research on SM111 and similar compounds may help to elucidate knowledge gaps related to Vpu's role in promoting viral egress and infectivity. IMPORTANCE New inhibitors of HIV-1 replication may be useful as therapeutics to counteract drug resistance and as reagents to perform more detailed studies of viral pathogenesis. SM111 is a small molecule that blocks the replication of wild-type and drug-resistant HIV-1 strains by impairing viral release and substantially reducing virion infectivity, most likely through its ability to prevent Env expression at the infected cell surface. Partial resistance to SM111 is mediated by mutations in Vpu and/or Env, suggesting that the compound affects host/viral protein interactions that are important during viral egress. Further characterization of SM111 and similar compounds may allow more detailed pharmacological studies of HIV-1 egress and provide opportunities to develop new treatments for HIV-1.
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Fischer WB, Kalita MM, Heermann D. Viral channel forming proteins--How to assemble and depolarize lipid membranes in silico. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1858:1710-21. [PMID: 26806161 PMCID: PMC7094687 DOI: 10.1016/j.bbamem.2016.01.018] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/17/2015] [Revised: 01/14/2016] [Accepted: 01/18/2016] [Indexed: 01/23/2023]
Abstract
Viral channel forming proteins (VCPs) have been discovered in the late 70s and are found in many viruses to date. Usually they are small and have to assemble to form channels which depolarize the lipid membrane of the host cells. Structural information is just about to emerge for just some of them. Thus, computational methods play a pivotal role in generating plausible structures which can be used in the drug development process. In this review the accumulation of structural data is introduced from a historical perspective. Computational performances and their predictive power are reported guided by biological questions such as the assembly, mechanism of function and drug–protein interaction of VCPs. An outlook of how coarse grained simulations can contribute to yet unexplored issues of these proteins is given. This article is part of a Special Issue entitled: Membrane Proteins edited by J.C. Gumbart and Sergei Noskov. Early references about the discovery of viral channel forming proteins. Latest structural information about the class of proteins. Identification of structural motifs, assembly mechanism of function and drug action using computational methods. Outlook for the use of coarse grained techniques to address assembly and integration into cellular processes.
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Affiliation(s)
- Wolfgang B Fischer
- Institute of Biophotonics, School of Biomedical Science and Engineering, National Yang-Ming University, Taipei 112, Taiwan; Biophotonics & Molecular Imaging Center (BMIRC), National Yang-Ming University, Taipei 112, Taiwan.
| | - Monoj Mon Kalita
- Institute of Biophotonics, School of Biomedical Science and Engineering, National Yang-Ming University, Taipei 112, Taiwan; Biophotonics & Molecular Imaging Center (BMIRC), National Yang-Ming University, Taipei 112, Taiwan
| | - Dieter Heermann
- Institute of Biophotonics, School of Biomedical Science and Engineering, National Yang-Ming University, Taipei 112, Taiwan; Biophotonics & Molecular Imaging Center (BMIRC), National Yang-Ming University, Taipei 112, Taiwan
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Abstract
Since the discovery that certain small viral membrane proteins, collectively termed as viroporins, can permeabilize host cellular membranes and also behave as ion channels, attempts have been made to link this feature to specific biological roles. In parallel, most viroporins identified so far are virulence factors, and interest has focused toward the discovery of channel inhibitors that would have a therapeutic effect, or be used as research tools to understand the biological roles of viroporin ion channel activity. However, this paradigm is being shifted by the difficulties inherent to small viral membrane proteins, and by the realization that protein-protein interactions and other diverse roles in the virus life cycle may represent an equal, if not, more important target. Therefore, although targeting the channel activity of viroporins can probably be therapeutically useful in some cases, the focus may shift to their other functions in following years. Small-molecule inhibitors have been mostly developed against the influenza A M2 (IAV M2 or AM2). This is not surprising since AM2 is the best characterized viroporin to date, with a well-established biological role in viral pathogenesis combined the most extensive structural investigations conducted, and has emerged as a validated drug target. For other viroporins, these studies are still mostly in their infancy, and together with those for AM2, are the subject of the present review.
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Tietjen I, Ntie-Kang F, Mwimanzi P, Onguéné PA, Scull MA, Idowu TO, Ogundaini AO, Meva’a LM, Abegaz BM, Rice CM, Andrae-Marobela K, Brockman MA, Brumme ZL, Fedida D. Screening of the Pan-African natural product library identifies ixoratannin A-2 and boldine as novel HIV-1 inhibitors. PLoS One 2015; 10:e0121099. [PMID: 25830320 PMCID: PMC4382154 DOI: 10.1371/journal.pone.0121099] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2014] [Accepted: 02/09/2015] [Indexed: 11/29/2022] Open
Abstract
The continued burden of HIV in resource-limited regions such as parts of sub-Saharan Africa, combined with adverse effects and potential risks of resistance to existing antiretroviral therapies, emphasize the need to identify new HIV inhibitors. Here we performed a virtual screen of molecules from the pan-African Natural Product Library, the largest collection of medicinal plant-derived pure compounds on the African continent. We identified eight molecules with structural similarity to reported interactors of Vpu, an HIV-1 accessory protein with reported ion channel activity. Using in vitro HIV-1 replication assays with a CD4+ T cell line and peripheral blood mononuclear cells, we confirmed antiviral activity and minimal cytotoxicity for two compounds, ixoratannin A-2 and boldine. Notably, ixoratannin A-2 retained inhibitory activity against recombinant HIV-1 strains encoding patient-derived mutations that confer resistance to protease, non-nucleoside reverse transcriptase, or integrase inhibitors. Moreover, ixoratannin A-2 was less effective at inhibiting replication of HIV-1 lacking Vpu, supporting this protein as a possible direct or indirect target. In contrast, boldine was less effective against a protease inhibitor-resistant HIV-1 strain. Both ixoratannin A-2 and boldine also inhibited in vitro replication of hepatitis C virus (HCV). However, BIT-225, a previously-reported Vpu inhibitor, demonstrated antiviral activity but also cytotoxicity in HIV-1 and HCV replication assays. Our work identifies pure compounds derived from African plants with potential novel activities against viruses that disproportionately afflict resource-limited regions of the world.
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Affiliation(s)
- Ian Tietjen
- Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, BC, Canada
- Faculty of Health Sciences, Simon Fraser University, Burnaby, BC, Canada
- * E-mail: (IT)
| | - Fidele Ntie-Kang
- Department of Chemistry, Chemical and Bioactivity Information Centre, Faculty of Science, University of Buea, Buea, Cameroon
| | - Philip Mwimanzi
- Faculty of Health Sciences, Simon Fraser University, Burnaby, BC, Canada
| | - Pascal Amoa Onguéné
- Department of Chemistry, Faculty of Science, University of Douala, Douala, Cameroon
| | - Margaret A. Scull
- Laboratory of Virology and Infectious Disease, The Rockefeller University, New York, NY, United States of America
| | - Thomas Oyebode Idowu
- Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Obafemi Awolowo University, Ile-Ife, Nigeria
| | - Abiodun Oguntuga Ogundaini
- Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Obafemi Awolowo University, Ile-Ife, Nigeria
| | - Luc Mbaze Meva’a
- Department of Chemistry, Faculty of Science, University of Douala, Douala, Cameroon
| | | | - Charles M. Rice
- Laboratory of Virology and Infectious Disease, The Rockefeller University, New York, NY, United States of America
| | | | - Mark A. Brockman
- Faculty of Health Sciences, Simon Fraser University, Burnaby, BC, Canada
- Department of Molecular Biology and Biochemistry, Faculty of Science, Simon Fraser University, Burnaby, BC, Canada
- British Columbia Centre for Excellence in HIV/AIDS, Vancouver, BC, Canada
| | - Zabrina L. Brumme
- Faculty of Health Sciences, Simon Fraser University, Burnaby, BC, Canada
- British Columbia Centre for Excellence in HIV/AIDS, Vancouver, BC, Canada
| | - David Fedida
- Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, BC, Canada
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Atomistic detailed mechanism and weak cation-conducting activity of HIV-1 Vpu revealed by free energy calculations. PLoS One 2014; 9:e112983. [PMID: 25392993 PMCID: PMC4231112 DOI: 10.1371/journal.pone.0112983] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2014] [Accepted: 10/20/2014] [Indexed: 12/02/2022] Open
Abstract
The viral protein U (Vpu) encoded by HIV-1 has been shown to assist in the detachment of virion particles from infected cells. Vpu forms cation-specific ion channels in host cells, and has been proposed as a potential drug target. An understanding of the mechanism of ion transport through Vpu is desirable, but remains limited because of the unavailability of an experimental structure of the channel. Using a structure of the pentameric form of Vpu – modeled and validated based on available experimental data – umbrella sampling molecular dynamics simulations (cumulative simulation time of more than 0.4 µs) were employed to elucidate the energetics and the molecular mechanism of ion transport in Vpu. Free energy profiles corresponding to the permeation of Na+ and K+ were found to be similar to each other indicating lack of ion selection, consistent with previous experimental studies. The Ser23 residue is shown to enhance ion transport via two mechanisms: creating a weak binding site, and increasing the effective hydrophilic length of the channel, both of which have previously been hypothesized in experiments. A two-dimensional free energy landscape has been computed to model multiple ion permeation, based on which a mechanism for ion conduction is proposed. It is shown that only one ion can pass through the channel at a time. This, along with a stretch of hydrophobic residues in the transmembrane domain of Vpu, explains the slow kinetics of ion conduction. The results are consistent with previous conductance studies that showed Vpu to be a weakly conducting ion channel.
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Ahn S, Lim G, Nam S, Lee J. Structural modeling of Vpu from HIV-1 based on solid-state NMR observables. Chem Phys Lett 2014. [DOI: 10.1016/j.cplett.2014.03.033] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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