1
|
Bonar MM, Tabler CO, Haqqani AA, Lapointe LE, Galiatsos JA, Joussef-Piña S, Quiñones-Mateu ME, Tilton JC. Nanoscale flow cytometry reveals interpatient variability in HIV protease activity that correlates with viral infectivity and identifies drug-resistant viruses. Sci Rep 2020; 10:18101. [PMID: 33093566 PMCID: PMC7583244 DOI: 10.1038/s41598-020-75118-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2020] [Accepted: 10/06/2020] [Indexed: 11/26/2022] Open
Abstract
HIV encodes an aspartyl protease that is activated during, or shortly after, budding of viral particles from the surface of infected cells. Protease-mediated cleavage of viral polyproteins is essential to generating infectious viruses, a process known as ‘maturation’ that is the target of FDA-approved antiretroviral drugs. Most assays to monitor protease activity rely on bulk analysis of millions of viruses and obscure potential heterogeneity of protease activation within individual particles. In this study we used nanoscale flow cytometry in conjunction with an engineered FRET reporter called VIral ProteasE Reporter (VIPER) to investigate heterogeneity of protease activation in individual, patient-derived viruses. We demonstrate previously unappreciated interpatient variation in HIV protease processing efficiency that impacts viral infectivity. Additionally, monitoring of protease activity in individual virions distinguishes between drug sensitivity or resistance to protease inhibitors in patient-derived samples. These findings demonstrate the feasibility of monitoring enzymatic processes using nanoscale flow cytometry and highlight the potential of this technology for translational clinical discovery, not only for viruses but also other submicron particles including exosomes, microvesicles, and bacteria.
Collapse
Affiliation(s)
- Michał M Bonar
- Center for Proteomics and Bioinformatics, Department of Nutrition, School of Medicine, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Caroline O Tabler
- Center for Proteomics and Bioinformatics, Department of Nutrition, School of Medicine, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Aiman A Haqqani
- Center for Proteomics and Bioinformatics, Department of Nutrition, School of Medicine, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Lauren E Lapointe
- Center for Proteomics and Bioinformatics, Department of Nutrition, School of Medicine, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Jake A Galiatsos
- Center for Proteomics and Bioinformatics, Department of Nutrition, School of Medicine, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Samira Joussef-Piña
- Department of Pathology, School of Medicine, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Miguel E Quiñones-Mateu
- Department of Pathology, School of Medicine, Case Western Reserve University, Cleveland, OH, 44106, USA.,Department of Microbiology and Immunology, University of Otago, Dunedin, 9016, New Zealand
| | - John C Tilton
- Center for Proteomics and Bioinformatics, Department of Nutrition, School of Medicine, Case Western Reserve University, Cleveland, OH, 44106, USA.
| |
Collapse
|
2
|
Kneller DW, Agniswamy J, Ghosh AK, Weber IT. Potent antiviral HIV-1 protease inhibitor combats highly drug resistant mutant PR20. Biochem Biophys Res Commun 2019; 519:61-66. [PMID: 31474336 PMCID: PMC7251940 DOI: 10.1016/j.bbrc.2019.08.126] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2019] [Accepted: 08/23/2019] [Indexed: 01/07/2023]
Abstract
Drug-resistance threatens effective treatment of HIV/AIDS. Clinical inhibitors, including darunavir (1), are ineffective for highly resistant protease mutant PR20, however, antiviral compound 2 derived from 1 with fused tricyclic group at P2, extended amino-benzothiazole P2' ligand and two fluorine atoms on P1 shows 16-fold better inhibition of PR20 enzyme activity. Crystal structures of PR20 and wild-type PR complexes reveal how the extra groups of 2 counteract the expanded ligand-binding pocket, dynamic flaps, and faster dimer dissociation of PR20.
Collapse
Affiliation(s)
- Daniel W. Kneller
- Department of Biology, Georgia State University, Atlanta, GA, 30303, USA
| | - Johnson Agniswamy
- Department of Biology, Georgia State University, Atlanta, GA, 30303, USA
| | - Arun K. Ghosh
- Department of Chemistry and Department of Medicinal Chemistry, Purdue University, West Lafayette, IN, 47907, USA
| | - Irene T. Weber
- Department of Biology, Georgia State University, Atlanta, GA, 30303, USA,Department of Chemistry, Georgia State University, Atlanta, GA, 30303, USA,Corresponding author: Phone: (+1) 404-413-5411
| |
Collapse
|
3
|
Huang L, Li L, Tien C, LaBarbera DV, Chen C. Targeting HIV-1 Protease Autoprocessing for High-throughput Drug Discovery and Drug Resistance Assessment. Sci Rep 2019; 9:301. [PMID: 30670786 PMCID: PMC6343032 DOI: 10.1038/s41598-018-36730-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2018] [Accepted: 11/23/2018] [Indexed: 01/28/2023] Open
Abstract
HIV-1 protease autoprocessing liberates the free mature protease from its Gag-Pol polyprotein precursor through a series of highly regulated autoproteolysis reactions. Herein, we report the development and validation (Z' ≥ 0.50) of a cell-based functional assay for high-throughput screening (HTS) of autoprocessing inhibitors using fusion precursors in combination with AlphaLISA (amplified luminescent proximity homogeneous assay ELISA). Through pilot screening of a collection of 130 known protease inhibitors, the AlphaLISA assay confirmed all 11 HIV protease inhibitors in the library capable of suppressing precursor autoprocessing at low micromolar concentrations. Meanwhile, other protease inhibitors had no impact on precursor autoprocessing. We next conducted HTS of ~23,000 compounds but found no positive hits. Such high selectivity is advantageous for large-scale HTS campaigns and as anticipated based on assay design because a positive hit needs simultaneously to be nontoxic, cell permeable, and inhibiting precursor autoprocessing. Furthermore, AlphaLISA quantification of fusion precursors carrying mutations known to cause resistance to HIV protease inhibitors faithfully recapitulated the reported resistance, suggesting that precursor autoprocessing is a critical step contributing to drug resistance. Taken together, this reported AlphaLISA platform will provide a useful tool for drug discovery targeting HIV-1 protease autoprocessing and for quantification of PI resistance.
Collapse
Affiliation(s)
- Liangqun Huang
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado, USA
| | - Linfeng Li
- Department of Pharmaceutical Sciences, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
| | - ChihFeng Tien
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado, USA
| | - Daniel V LaBarbera
- Department of Pharmaceutical Sciences, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
| | - Chaoping Chen
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado, USA.
| |
Collapse
|
4
|
Tien C, Huang L, Watanabe SM, Speidel JT, Carter CA, Chen C. Context-dependent autoprocessing of human immunodeficiency virus type 1 protease precursors. PLoS One 2018; 13:e0191372. [PMID: 29338056 PMCID: PMC5770051 DOI: 10.1371/journal.pone.0191372] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2017] [Accepted: 01/03/2018] [Indexed: 11/29/2022] Open
Abstract
HIV-1 protease autoprocessing is responsible for liberation of free mature protease (PR) from the Gag-Pol polyprotein precursor. A cell-based model system was previously developed to examine the autoprocessing mechanism of fusion precursors carrying the p6*-PR miniprecursor sandwiched between various proteins or epitopes. We here report that precursor autoprocessing is context-dependent as its activity and outcomes can be modulated by sequences upstream of p6*-PR. This was exemplified by the 26aa maltose binding protein (MBP) signal peptide (SigP) when placed at the N-terminus of a fusion precursor. The mature PRs released from SigP-carrying precursors are resistant to self-degradation whereas those released from SigP-lacking fusion precursors are prone to self-degradation. A H69D mutation in PR abolished autoprocessing of SigP-containing fusion precursors whereas it only partially suppressed autoprocessing of fusion precursors lacking SigP. An autoprocessing deficient GFP fusion precursor with SigP exhibited a subcellular distribution pattern distinct from the one without it in transfected HeLa cells. Furthermore, a SigP fusion precursor carrying a substitution at the P1 position released the mature PR and PR-containing fragments that were different from those released from the precursor carrying the same mutation but lacking SigP. We also examined autoprocessing outcomes in viral particles produced by a NL4-3 derived proviral construct and demonstrated the existence of several PR-containing fragments along with the mature PR. Some of these resembled the SigP precursor autoprocessing outcomes. This finding of context-dependent modulation reveals the complexity of precursor autoprocessing regulation that most likely accompanies sequence variation imposed by the evolution of the upstream Gag moiety.
Collapse
Affiliation(s)
- ChihFeng Tien
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado, United States of America
| | - Liangqun Huang
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado, United States of America
| | - Susan M. Watanabe
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, New York, United States of America
| | - Jordan T. Speidel
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado, United States of America
| | - Carol A. Carter
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, New York, United States of America
| | - Chaoping Chen
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado, United States of America
- * E-mail:
| |
Collapse
|
5
|
Fixman BB, Babcock IW, Minamide LS, Shaw AE, Oliveira da Silva MI, Runyan AM, Maloney MT, Field JJ, Bamburg JR. Modified Roller Tube Method for Precisely Localized and Repetitive Intermittent Imaging During Long-term Culture of Brain Slices in an Enclosed System. J Vis Exp 2017. [PMID: 29364208 DOI: 10.3791/56436] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Cultured rodent brain slices are useful for studying the cellular and molecular behavior of neurons and glia in an environment that maintains many of their normal in vivo interactions. Slices obtained from a variety of transgenic mouse lines or use of viral vectors for expression of fluorescently tagged proteins or reporters in wild type brain slices allow for high-resolution imaging by fluorescence microscopy. Although several methods have been developed for imaging brain slices, combining slice culture with the ability to perform repetitive high-resolution imaging of specific cells in live slices over long time periods has posed problems. This is especially true when viral vectors are used for expression of exogenous proteins since this is best done in a closed system to protect users and prevent cross contamination. Simple modifications made to the roller tube brain slice culture method that allow for repetitive high-resolution imaging of slices over many weeks in an enclosed system are reported. Culturing slices on photoetched coverslips permits the use of fiducial marks to rapidly and precisely reposition the stage to image the identical field over time before and after different treatments. Examples are shown for the use of this method combined with specific neuronal staining and expression to observe changes in hippocampal slice architecture, viral-mediated neuronal expression of fluorescent proteins, and the development of cofilin pathology, which was previously observed in the hippocampus of Alzheimer's disease (AD) in response to slice treatment with oligomers of amyloid-β (Aβ) peptide.
Collapse
Affiliation(s)
- Benjamin B Fixman
- Department of Biochemistry and Molecular Biology and Molecular, Cellular and Integrated Neuroscience Program, Colorado State University
| | - Isaac W Babcock
- Department of Biochemistry and Molecular Biology and Molecular, Cellular and Integrated Neuroscience Program, Colorado State University
| | - Laurie S Minamide
- Department of Biochemistry and Molecular Biology and Molecular, Cellular and Integrated Neuroscience Program, Colorado State University
| | - Alisa E Shaw
- Department of Biochemistry and Molecular Biology and Molecular, Cellular and Integrated Neuroscience Program, Colorado State University
| | - Marina I Oliveira da Silva
- Department of Biochemistry and Molecular Biology and Molecular, Cellular and Integrated Neuroscience Program, Colorado State University; IBMC-Instituto de Biologia Molecular e Celular, i3S-Instituto de Investigaçãoe Inovação em Saúde, ICBAS, Universidade do Porto
| | - Avery M Runyan
- Department of Biochemistry and Molecular Biology and Molecular, Cellular and Integrated Neuroscience Program, Colorado State University
| | - Michael T Maloney
- Department of Biochemistry and Molecular Biology and Molecular, Cellular and Integrated Neuroscience Program, Colorado State University; Denali Therapeutics
| | - Jeffrey J Field
- Department of Biochemistry and Molecular Biology and Molecular, Cellular and Integrated Neuroscience Program, Colorado State University
| | - James R Bamburg
- Department of Biochemistry and Molecular Biology and Molecular, Cellular and Integrated Neuroscience Program, Colorado State University;
| |
Collapse
|
6
|
Watanabe SM, Simon V, Durham ND, Kemp BR, Machihara S, Kemal KS, Shi B, Foley B, Li H, Chen BK, Weiser B, Burger H, Anastos K, Chen C, Carter CA. The HIV-1 late domain-2 S40A polymorphism in antiretroviral (or ART)-exposed individuals influences protease inhibitor susceptibility. Retrovirology 2016; 13:64. [PMID: 27600154 PMCID: PMC5011916 DOI: 10.1186/s12977-016-0298-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2016] [Accepted: 08/21/2016] [Indexed: 11/24/2022] Open
Abstract
Background The p6 region of the HIV-1 structural precursor polyprotein, Gag, contains two motifs, P7TAP11 and L35YPLXSL41, designated as late (L) domain-1 and -2, respectively. These motifs bind the ESCRT-I factor Tsg101 and the ESCRT adaptor Alix, respectively, and are critical for efficient budding of virus particles from the plasma membrane. L domain-2 is thought to be functionally redundant to PTAP. To identify possible other functions of L domain-2, we examined this motif in dominant viruses that emerged in a group of 14 women who had detectable levels of HIV-1 in both plasma and genital tract despite a history of current or previous antiretroviral therapy. Results Remarkably, variants possessing mutations or rare polymorphisms in the highly conserved L domain-2 were identified in seven of these women. A mutation in a conserved residue (S40A) that does not reduce Gag interaction with Alix and therefore did not reduce budding efficiency was further investigated. This mutation causes a simultaneous change in the Pol reading frame but exhibits little deficiency in Gag processing and virion maturation. Whether introduced into the HIV-1 NL4-3 strain genome or a model protease (PR) precursor, S40A reduced production of mature PR. This same mutation also led to high level detection of two extended forms of PR that were fairly stable compared to the WT in the presence of IDV at various concentrations; one of the extended forms was effective in trans processing even at micromolar IDV. Conclusions Our results indicate that L domain-2, considered redundant in vitro, can undergo mutations in vivo that significantly alter PR function. These may contribute fitness benefits in both the absence and presence of PR inhibitor. Electronic supplementary material The online version of this article (doi:10.1186/s12977-016-0298-1) contains supplementary material, which is available to authorized users.
Collapse
Affiliation(s)
- Susan M Watanabe
- Department of Molecular Genetics and Microbiology, Stony Brook University, Life Sciences Bldg., Stony Brook, NY, 11794-5222, USA
| | - Viviana Simon
- Department of Microbiology, Global Health and Emerging Pathogens Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Natasha D Durham
- Division of Infectious Diseases, Department of Medicine, Immunology Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Brittney R Kemp
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO, 80523-1870, USA
| | - Satoshi Machihara
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO, 80523-1870, USA
| | | | - Binshan Shi
- Department of Health Sciences, Albany College of Pharmacy and Health Sciences, Albany, NY, USA
| | - Brian Foley
- Los Alamos National Laboratory, Los Alamos, NM, USA
| | - Hongru Li
- Division of Infectious Diseases, Department of Medicine, Immunology Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Benjamin K Chen
- Division of Infectious Diseases, Department of Medicine, Immunology Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Barbara Weiser
- Department of Medicine, University of California Davis, Davis, CA, USA.,Department of Medicine, Sacramento VA Medical Center, Cordova, CA, USA
| | - Harold Burger
- Department of Medicine, University of California Davis, Davis, CA, USA.,Department of Medicine, Sacramento VA Medical Center, Cordova, CA, USA
| | - Kathryn Anastos
- Department of Medicine, Albert Einstein College of Medicine, Bronx, NY, USA
| | - Chaoping Chen
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO, 80523-1870, USA.
| | - Carol A Carter
- Department of Molecular Genetics and Microbiology, Stony Brook University, Life Sciences Bldg., Stony Brook, NY, 11794-5222, USA.
| |
Collapse
|
7
|
Park JH, Sayer JM, Aniana A, Yu X, Weber IT, Harrison RW, Louis JM. Binding of Clinical Inhibitors to a Model Precursor of a Rationally Selected Multidrug Resistant HIV-1 Protease Is Significantly Weaker Than That to the Released Mature Enzyme. Biochemistry 2016; 55:2390-400. [PMID: 27039930 DOI: 10.1021/acs.biochem.6b00012] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We have systematically validated the activity and inhibition of a HIV-1 protease (PR) variant bearing 17 mutations (PR(S17)), selected to represent high resistance by machine learning on genotype-phenotype data. Three of five mutations in PR(S17) correlating with major drug resistance, M46L, G48V, and V82S, and five of 11 natural variations differ from the mutations in two clinically derived extreme mutants, PR20 and PR22 bearing 19 and 22 mutations, respectively. PR(S17), which forms a stable dimer (<10 nM), is ∼10- and 2-fold less efficient in processing the Gag polyprotein than the wild type and PR20, respectively, but maintains the same cleavage order. Isolation of a model precursor of PR(S17) flanked by the 56-amino acid transframe region (TFP-p6pol) at its N-terminus, which is impossible upon expression of an analogous PR20 precursor, allowed systematic comparison of inhibition of TFP-p6pol-PR(S17) and mature PR(S17). Resistance of PR(S17) to eight protease inhibitors (PIs) relative to PR (Ki) increases by 1.5-5 orders of magnitude from 0.01 to 8.4 μM. Amprenavir, darunavir, atazanavir, and lopinavir, the most effective of the eight PIs, inhibit precursor autoprocessing at the p6pol/PR site with IC50 values ranging from ∼7.5 to 60 μM. Thus, this process, crucial for stable dimer formation, shows inhibition ∼200-800-fold weaker than that of the mature PR(S17). TFP/p6pol cleavage, which occurs faster, is inhibited even more weakly by all PIs except darunavir (IC50 = 15 μM); amprenavir shows a 2-fold increase in IC50 (∼15 μM), and atazanavir and lopinavir show increased IC50 values of >42 and >70 μM, respectively.
Collapse
Affiliation(s)
- Joon H Park
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Department of Health and Human Services , Bethesda, Maryland 20892, United States
| | - Jane M Sayer
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Department of Health and Human Services , Bethesda, Maryland 20892, United States
| | - Annie Aniana
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Department of Health and Human Services , Bethesda, Maryland 20892, United States
| | | | | | | | - John M Louis
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Department of Health and Human Services , Bethesda, Maryland 20892, United States
| |
Collapse
|
8
|
Ambrosio AL, Boyle JA, Di Pietro SM. TPC2 mediates new mechanisms of platelet dense granule membrane dynamics through regulation of Ca2+ release. Mol Biol Cell 2015. [PMID: 26202466 PMCID: PMC4569316 DOI: 10.1091/mbc.e15-01-0058] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
TPC2 is a component of the platelet dense granule membrane and regulates the formation of perigranular Ca2+ nanodomains that correlate with “kiss-and-run” events and tubule connections. These membrane contacts allow material transfer between organelles and are likely involved in granule maturation. Platelet dense granules (PDGs) are acidic calcium stores essential for normal hemostasis. They develop from late endosomal compartments upon receiving PDG-specific proteins through vesicular trafficking, but their maturation process is not well understood. Here we show that two-pore channel 2 (TPC2) is a component of the PDG membrane that regulates PDG luminal pH and the pool of releasable Ca2+. Using a genetically encoded Ca2+ biosensor and a pore mutant TPC2, we establish the function of TPC2 in Ca2+ release from PDGs and the formation of perigranular Ca2+ nanodomains. For the first time, Ca2+ spikes around PDGs—or any organelle of the endolysosome family—are visualized in real time and revealed to precisely mark organelle “kiss-and-run” events. Further, the presence of membranous tubules transiently connecting PDGs is revealed and shown to be dramatically enhanced by TPC2 in a mechanism that requires ion flux through TPC2. “Kiss-and-run” events and tubule connections mediate transfer of membrane proteins and luminal content between PDGs. The results show that PDGs use previously unknown mechanisms of membrane dynamics and content exchange that are regulated by TPC2.
Collapse
Affiliation(s)
- Andrea L Ambrosio
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523-1870
| | - Judith A Boyle
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523-1870
| | - Santiago M Di Pietro
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523-1870
| |
Collapse
|
9
|
Counts CJ, Ho PS, Donlin MJ, Tavis JE, Chen C. A Functional Interplay between Human Immunodeficiency Virus Type 1 Protease Residues 77 and 93 Involved in Differential Regulation of Precursor Autoprocessing and Mature Protease Activity. PLoS One 2015; 10:e0123561. [PMID: 25893662 PMCID: PMC4404164 DOI: 10.1371/journal.pone.0123561] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2014] [Accepted: 03/04/2015] [Indexed: 11/18/2022] Open
Abstract
HIV-1 protease (PR) is a viral enzyme vital to the production of infectious virions. It is initially synthesized as part of the Gag-Pol polyprotein precursor in the infected cell. The free mature PR is liberated as a result of precursor autoprocessing upon virion release. We previously described a model system to examine autoprocessing in transfected mammalian cells. Here, we report that a covariance analysis of miniprecursor (p6*-PR) sequences derived from drug naïve patients identified a series of amino acid pairs that vary together across independent viral isolates. These covariance pairs were used to build the first topology map of the miniprecursor that suggests high levels of interaction between the p6* peptide and the mature PR. Additionally, several PR-PR covariance pairs are located far from each other (>12 Å Cα to Cα) relative to their positions in the mature PR structure. Biochemical characterization of one such covariance pair (77-93) revealed that each residue shows distinct preference for one of three alkyl amino acids (V, I, and L) and that a polar or charged amino acid at either of these two positions abolishes precursor autoprocessing. The most commonly observed 77V is preferred by the most commonly observed 93I, but the 77I variant is preferred by other 93 variances (L, V, or M) in supporting precursor autoprocessing. Furthermore, the 77I93V covariant enhanced precursor autoprocessing and Gag polyprotein processing but decreased the mature PR activity. Therefore, both covariance and biochemical analyses support a functional association between residues 77 and 93, which are spatially distant from each other in the mature PR structure. Our data also suggests that these covariance pairs differentially regulate precursor autoprocessing and the mature protease activity.
Collapse
Affiliation(s)
- Christopher J. Counts
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado, United States of America
| | - P. Shing Ho
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado, United States of America
| | - Maureen J. Donlin
- Department of Molecular Microbiology and Immunology, Saint Louis University School of Medicine, St. Louis, Missouri, United States of America
- Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, Missouri, United States of America
- Saint Louis University Liver Center, Saint Louis University School of Medicine, St. Louis, Missouri, United States of America
| | - John E. Tavis
- Department of Molecular Microbiology and Immunology, Saint Louis University School of Medicine, St. Louis, Missouri, United States of America
- Saint Louis University Liver Center, Saint Louis University School of Medicine, St. Louis, Missouri, United States of America
| | - Chaoping Chen
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado, United States of America
| |
Collapse
|
10
|
Understanding HIV-1 protease autoprocessing for novel therapeutic development. Future Med Chem 2014; 5:1215-29. [PMID: 23859204 DOI: 10.4155/fmc.13.89] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
In the infected cell, HIV-1 protease (PR) is initially synthesized as part of the GagPol polyprotein. PR autoprocessing is a virus-specific process by which the PR domain embedded in the precursor catalyzes proteolytic reactions responsible for liberation of free mature PRs, which then recognize and cleave at least ten different peptide sequences in the Gag and GagPol polyproteins. Despite extensive structure and function studies of the mature PRs as well as the successful development of ten US FDA-approved catalytic-site inhibitors, the precursor autoprocessing mechanism remains an intriguing yet-to-be-solved puzzle. This article discusses current understanding of the autoprocessing mechanism, in an effort to prompt the development of novel anti-HIV drugs that selectively target precursor autoprocessing.
Collapse
|
11
|
Huang L, Li Y, Chen C. Flexible catalytic site conformations implicated in modulation of HIV-1 protease autoprocessing reactions. Retrovirology 2011; 8:79. [PMID: 21985091 PMCID: PMC3210109 DOI: 10.1186/1742-4690-8-79] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2011] [Accepted: 10/10/2011] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The HIV-1 protease is initially synthesized as part of the Gag-Pol polyprotein in the infected cell. Protease autoprocessing, by which the protease domain embedded in the precursor catalyzes essential cleavage reactions, leads to liberation of the free mature protease at the late stage of the replication cycle. To examine autoprocessing reactions in transfected mammalian cells, we previously described an assay using a fusion precursor consisting of the mature protease (PR) along with its upstream transframe region (p6*) sandwiched between GST and a small peptide epitope. RESULTS In this report, we studied two autoprocessing cleavage reactions, one between p6* and PR (the proximal site) and the other in the N-terminal region of p6* (the distal site) catalyzed by the embedded protease, using our cell-based assay. A fusion precursor carrying the NL4-3 derived protease cleaved both sites, whereas a precursor with a pseudo wild type protease preferentially autoprocessed the proximal site. Mutagenesis analysis demonstrated that several residues outside the active site (Q7, L33, N37, L63, C67 and H69) contributed to the differential substrate specificity. Furthermore, the cleavage reaction at the proximal site mediated by the embedded protease in precursors carrying different protease sequences or C-terminal fusion peptides displayed varied sensitivity to inhibition by darunavir, a catalytic site inhibitor. On the other hand, polypeptides such as a GCN4 motif, GFP, or hsp70 fused to the N-terminus of p6* had a minimal effect on darunavir inhibition of either cleavage reaction. CONCLUSIONS Taken together, our data suggest that several non-active site residues and the C-terminal flanking peptides regulate embedded protease activity through modulation of the catalytic site conformation. The cell-based assay provides a sensitive tool to study protease autoprocessing reactions in mammalian cells.
Collapse
Affiliation(s)
- Liangqun Huang
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado 80523-1870, USA
| | | | | |
Collapse
|
12
|
Inhibition of autoprocessing of natural variants and multidrug resistant mutant precursors of HIV-1 protease by clinical inhibitors. Proc Natl Acad Sci U S A 2011; 108:9072-7. [PMID: 21576495 DOI: 10.1073/pnas.1102278108] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Self-cleavage at the N terminus of HIV-1 protease from the Gag-Pol precursor (autoprocessing) is crucial for stabilizing the protease dimer required for onset of mature-like catalytic activity, viral maturation, and propagation. Among nine clinical protease inhibitors (PIs), darunavir and saquinavir were the most effective in inhibiting wild-type HIV-1 group M precursor autoprocessing, with an IC(50) value of 1-2 μM, 3-5 orders of magnitude higher than their binding affinities to the corresponding mature protease. Accordingly, both group M and N precursor-PI complexes exhibit T(m)s 17-21 °C lower than those of the corresponding mature protease-PI complexes suggestive of markedly reduced stabilities of the precursor dimer-PI ensembles. Autoprocessing of group N (natural variant) and three group M precursors bearing 11-20 mutations associated with multidrug resistance was either weakly responsive or fully unresponsive to inhibitors at concentrations up to a practical limit of approximately 150 μM PI. This observation parallels decreases of up to 8 × 10(3)-fold (e.g., 5 pM to 40 nM) in the binding affinity of darunavir and saquinavir to mature multidrug resistant proteases relative to wild type, suggesting that inhibition of some of these mutant precursors will occur only in the high μM to mM range in extreme PI-resistance, which is an effect arising from coordinated multiple mutations. An extremely darunavir-resistant mutant precursor is more responsive to inhibition by saquinavir. These findings raise the questions whether clinical failure of PI therapy is related to lack of inhibition of autoprocessing and whether specific inhibitors can be designed with low-nM affinity to target autoprocessing.
Collapse
|