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Zhu H, Mathew E, Connelly SM, Zuber J, Sullivan M, Piepenbrink MS, Kobie JJ, Dumont ME. Identification of variant HIV envelope proteins with enhanced affinities for precursors to anti-gp41 broadly neutralizing antibodies. PLoS One 2019; 14:e0221550. [PMID: 31504041 PMCID: PMC6736307 DOI: 10.1371/journal.pone.0221550] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2019] [Accepted: 08/09/2019] [Indexed: 11/19/2022] Open
Abstract
HIV envelope protein (Env) is the sole target of broadly neutralizing antibodies (BNAbs) that are capable of neutralizing diverse strains of HIV. While BNAbs develop spontaneously in a subset of HIV-infected patients, efforts to design an envelope protein-based immunogen to elicit broadly neutralizing antibody responses have so far been unsuccessful. It is hypothesized that a primary barrier to eliciting BNAbs is the fact that HIV envelope proteins bind poorly to the germline-encoded unmutated common ancestor (UCA) precursors to BNAbs. To identify variant forms of Env with increased affinities for the UCA forms of BNAbs 4E10 and 10E8, which target the Membrane Proximal External Region (MPER) of Env, libraries of randomly mutated Env variants were expressed in a yeast surface display system and screened using fluorescence activated cell sorting for cells displaying variants with enhanced abilities to bind the UCA antibodies. Based on analyses of individual clones obtained from the screen and on next-generation sequencing of sorted libraries, distinct but partially overlapping sets of amino acid substitutions conferring enhanced UCA antibody binding were identified. These were particularly enriched in substitutions of arginine for highly conserved tryptophan residues. The UCA-binding variants also generally exhibited enhanced binding to the mature forms of anti-MPER antibodies. Mapping of the identified substitutions into available structures of Env suggest that they may act by destabilizing both the initial pre-fusion conformation and the six-helix bundle involved in fusion of the viral and cell membranes, as well as providing new or expanded epitopes with increased accessibility for the UCA antibodies.
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Affiliation(s)
- Hong Zhu
- Department of Biochemistry and Biophysics, University of Rochester Medical Center, Rochester, NY, United States of America
| | - Elizabeth Mathew
- Department of Biochemistry and Biophysics, University of Rochester Medical Center, Rochester, NY, United States of America
| | - Sara M. Connelly
- Department of Biochemistry and Biophysics, University of Rochester Medical Center, Rochester, NY, United States of America
| | - Jeffrey Zuber
- Department of Biochemistry and Biophysics, University of Rochester Medical Center, Rochester, NY, United States of America
| | - Mark Sullivan
- Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, NY, United States of America
| | - Michael S. Piepenbrink
- Infectious Diseases Division, University of Rochester Medical Center, Rochester, NY United States of America
| | - James J. Kobie
- Infectious Diseases Division, University of Rochester Medical Center, Rochester, NY United States of America
| | - Mark E. Dumont
- Department of Biochemistry and Biophysics, University of Rochester Medical Center, Rochester, NY, United States of America
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Chen W, Guo J, Cai Y, Fu Q, Chen B, Chou JJ. Unidirectional Presentation of Membrane Proteins in Nanoparticle-Supported Liposomes. Angew Chem Int Ed Engl 2019; 58:9866-9870. [PMID: 30990942 PMCID: PMC6660371 DOI: 10.1002/anie.201903093] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2019] [Indexed: 12/30/2022]
Abstract
Presentation of membrane proteins to host immune systems has been a challenging problem owing to complexity arising from the poor in vivo stability of the membrane-mimetic media often used for solubilizing the membrane proteins. The use of functionalized, biocompatible nanoparticles as substrates is shown to guide the formation of proteoliposomes, which can present many copies of membrane proteins in a unidirectional manner. The approach was demonstrated to present the membrane-proximal region of the HIV-1 envelope glycoprotein. These nanoparticle-supported liposomes are broadly applicable as membrane antigen vehicles for inducing host immune responses.
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Affiliation(s)
- Wen Chen
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 250 Longwood Avenue, Boston, MA 02115, United States
| | - Junling Guo
- Department of Biomass Science and Engineering, Sichuan University, 252 Shuncheng Street, Chengdu, Sichuan 610065, China
| | - Yongfei Cai
- Division of Molecular Medicine, Boston Children’s Hospital, Department of Pediatrics, Harvard Medical School, 3 Blackfan Street, Boston, MA 02115, United States
| | - Qingshan Fu
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 250 Longwood Avenue, Boston, MA 02115, United States
| | - Bing Chen
- Division of Molecular Medicine, Boston Children’s Hospital, Department of Pediatrics, Harvard Medical School, 3 Blackfan Street, Boston, MA 02115, United States
| | - James J. Chou
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 250 Longwood Avenue, Boston, MA 02115, United States
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Chen W, Cai Y, Fu Q, Chen B, Guo J, Chou JJ. Unidirectional Presentation of Membrane Proteins in Nanoparticle‐Supported Liposomes. Angew Chem Int Ed Engl 2019. [DOI: 10.1002/ange.201903093] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Wen Chen
- Department of Biological Chemistry and Molecular PharmacologyHarvard Medical School 250 Longwood Avenue Boston MA 02115 USA
| | - Yongfei Cai
- Division of Molecular MedicineBoston Children's HospitalDepartment of PediatricsHarvard Medical School 3 Blackfan Street Boston MA 02115 USA
| | - Qingshan Fu
- Department of Biological Chemistry and Molecular PharmacologyHarvard Medical School 250 Longwood Avenue Boston MA 02115 USA
| | - Bing Chen
- Division of Molecular MedicineBoston Children's HospitalDepartment of PediatricsHarvard Medical School 3 Blackfan Street Boston MA 02115 USA
| | - Junling Guo
- Department of Biomass Science and EngineeringSichuan University 24 South Section Yihuan Road Chengdu Sichuan 610065 China
| | - James J. Chou
- Department of Biological Chemistry and Molecular PharmacologyHarvard Medical School 250 Longwood Avenue Boston MA 02115 USA
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Fu Q, Piai A, Chen W, Xia K, Chou JJ. Structure determination protocol for transmembrane domain oligomers. Nat Protoc 2019; 14:2483-2520. [PMID: 31270510 DOI: 10.1038/s41596-019-0188-9] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2018] [Accepted: 04/30/2019] [Indexed: 01/08/2023]
Abstract
The transmembrane (TM) anchors of cell surface proteins have been one of the 'blind spots' in structural biology because they are generally very hydrophobic, sometimes dynamic, and thus difficult targets for structural characterization. A plethora of examples show these membrane anchors are not merely anchors but can multimerize specifically to activate signaling receptors on the cell surface or to stabilize envelope proteins in viruses. Through a series of studies of the TM domains (TMDs) of immune receptors and viral membrane proteins, we have established a robust protocol for determining atomic-resolution structures of TM oligomers by NMR in bicelles that closely mimic a lipid bilayer. Our protocol overcomes hurdles typically encountered by structural biology techniques such as X-ray crystallography and cryo-electron microscopy (cryo-EM) when studying small TMDs. Here, we provide the details of the protocol, covering five major technical aspects: (i) a general method for producing isotopically labeled TM or membrane-proximal (MP) protein fragments that involves expression of the protein (which is fused to TrpLE) into inclusion bodies and releasing the target protein by cyanogen bromide (CNBr) cleavage; (ii) determination of the oligomeric state of TMDs in bicelles; (iii) detection of intermolecular contacts using nuclear Overhauser effect (NOE) experiments; (iv) structure determination; and (v) paramagnetic probe titration (PPT) to characterize the membrane partition of the TM oligomers. This protocol is broadly applicable for filling structural gaps of many type I/II membrane proteins. The procedures may take 3-6 months to complete, depending on the complexity and stability of the protein sample.
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Affiliation(s)
- Qingshan Fu
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, USA
| | - Alessandro Piai
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, USA
| | - Wen Chen
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, USA
| | - Ke Xia
- Department of Chemistry and Chemical Biology, Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY, USA
| | - James J Chou
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, USA.
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Chen B. Molecular Mechanism of HIV-1 Entry. Trends Microbiol 2019; 27:878-891. [PMID: 31262533 DOI: 10.1016/j.tim.2019.06.002] [Citation(s) in RCA: 161] [Impact Index Per Article: 32.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2019] [Revised: 05/20/2019] [Accepted: 06/05/2019] [Indexed: 11/19/2022]
Abstract
HIV-1 envelope glycoprotein [Env; trimeric (gp160)3 cleaved to (gp120/gp41)3] attaches the virion to a susceptible cell and induces fusion of viral and cell membranes to initiate infection. It interacts with the primary receptor CD4 and coreceptor (e.g., chemokine receptor CCR5 or CXCR4) to allow viral entry by triggering large structural rearrangements and unleashing the fusogenic potential of gp41 to induce membrane fusion. Recent advances in structural biology of HIV-1 Env and its complexes with the cellular receptors have revealed molecular details of HIV-1 entry and yielded new mechanistic insights. In this review, I summarize our latest understanding of the HIV-1 membrane fusion process and discuss possible pathways for productive viral entry.
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Affiliation(s)
- Bing Chen
- Division of Molecular Medicine, Boston Children's Hospital, and Department of Pediatrics, Harvard Medical School, 3 Blackfan Street, Boston, MA 02115, USA.
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Conformational Differences between Functional Human Immunodeficiency Virus Envelope Glycoprotein Trimers and Stabilized Soluble Trimers. J Virol 2019; 93:JVI.01709-18. [PMID: 30429345 DOI: 10.1128/jvi.01709-18] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2018] [Accepted: 11/07/2018] [Indexed: 01/11/2023] Open
Abstract
Binding to the receptor CD4 triggers entry-related conformational changes in the human immunodeficiency virus type 1 (HIV-1) envelope glycoprotein (Env) trimer, (gp120/gp41)3 Soluble versions of HIV-1 Env trimers (sgp140 SOSIP.664) stabilized by a gp120-gp41 disulfide bond and a change (I559P) in gp41 have been structurally characterized. Here, we use cross-linking/mass spectrometry to evaluate the conformations of functional membrane Env and sgp140 SOSIP.664. Differences were detected in the gp120 trimer association domain and C terminus and in the gp41 heptad repeat 1 (HR1) region. Whereas the membrane Env trimer exposes the gp41 HR1 coiled coil only after CD4 binding, the sgp140 SOSIP.664 HR1 coiled coil was accessible to the gp41 HR2 peptide even in the absence of CD4. Our results delineate differences in both gp120 and gp41 subunits between functional membrane Env and the sgp140 SOSIP.664 trimer and provide distance constraints that can assist validation of candidate structural models of the native HIV-1 Env trimer.IMPORTANCE HIV-1 envelope glycoprotein spikes mediate the entry of the virus into host cells and are a major target for vaccine-induced antibodies. Soluble forms of the envelope glycoproteins that are stable and easily produced have been characterized extensively and are being considered as vaccines. Here, we present evidence that these stabilized soluble envelope glycoproteins differ in multiple respects from the natural HIV-1 envelope glycoproteins. By pinpointing these differences, our results can guide the improvement of envelope glycoprotein preparations to achieve greater similarity to the viral envelope glycoprotein spike, potentially increasing their effectiveness as a vaccine.
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Fernandez MV, Freed EO. Meeting Review: 2018 International Workshop on Structure and Function of the Lentiviral gp41 Cytoplasmic Tail. Viruses 2018; 10:E613. [PMID: 30405009 PMCID: PMC6266243 DOI: 10.3390/v10110613] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2018] [Accepted: 11/03/2018] [Indexed: 01/09/2023] Open
Abstract
Recent developments in defining the role of the lentiviral envelope glycoprotein (Env) cytoplasmic tail (CT) in Env trafficking and incorporation into virus particles have advanced our understanding of viral replication and transmission. To stimulate additional progress in this field, the two-day International Workshop on Structure and Function of the Lentiviral gp41 Cytoplasmic Tail, co-organized by Eric Freed and James Hoxie, was held at the National Cancer Institute in Frederick, MD (26⁻27 April 2018). The meeting served to bring together experts focused on the role of gp41 in HIV replication and to discuss the emerging mechanisms of CT-dependent trafficking, Env conformation and structure, host protein interaction, incorporation, and viral transmission. The conference was organized around the following three main hot topics in gp41 research: the role of host factors in CT-dependent Env incorporation, Env structure, and CT-mediated trafficking and transmission. This review highlights important topics and the advances in gp41 research that were discussed during the conference.
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Affiliation(s)
- Melissa V Fernandez
- HIV Dynamics and Replication Program, Center for Cancer Research, National Cancer Institute, Frederick, MD 21702, USA.
| | - Eric O Freed
- HIV Dynamics and Replication Program, Center for Cancer Research, National Cancer Institute, Frederick, MD 21702, USA.
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