1
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Hargett AA, Azurmendi HF, Crawford CJ, Wear MP, Oscarson S, Casadevall A, Freedberg DI. The structure of a C. neoformans polysaccharide motif recognized by protective antibodies: A combined NMR and MD study. Proc Natl Acad Sci U S A 2024; 121:e2315733121. [PMID: 38330012 PMCID: PMC10873606 DOI: 10.1073/pnas.2315733121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2023] [Accepted: 12/02/2023] [Indexed: 02/10/2024] Open
Abstract
Cryptococcus neoformans is a fungal pathogen responsible for cryptococcosis and cryptococcal meningitis. The C. neoformans' capsular polysaccharide and its shed exopolysaccharide function both as key virulence factors and to protect the fungal cell from phagocytosis. Currently, a glycoconjugate of these polysaccharides is being explored as a vaccine to protect against C. neoformans infection. In this study, NOE and J-coupling values from NMR experiments were consistent with a converged structure of the synthetic decasaccharide, GXM10-Ac3, calculated from MD simulations. GXM10-Ac3 was designed as an extension of glucuronoxylomannan (GXM) polysaccharide motif (M2) which is common in the clinically predominant serotype A strains and is recognized by protective forms of GXM-specific monoclonal antibodies. The M2 motif is a hexasaccharide with a three-residue α-mannan backbone, modified by β-(1→2)-xyloses (Xyl) on the first two mannoses (Man) and a β-(1→2)-glucuronic acid (GlcA) on the third Man. Combined NMR and MD analyses reveal that GXM10-Ac3 adopts an extended structure, with Xyl/GlcA branches alternating sides along the α-mannan backbone. O-acetyl esters also alternate sides and are grouped in pairs. MD analysis of a twelve M2-repeating unit polymer supports the notion that the GXM10-Ac3 structure is uniformly represented throughout the polysaccharide. This derived GXM model displays high flexibility while maintaining a structural identity, yielding insights to further explore intermolecular interactions between polysaccharides, interactions with anti-GXM mAbs, and the cryptococcal polysaccharide architecture.
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Affiliation(s)
- Audra A. Hargett
- Laboratory of Bacterial Polysaccharides, Office of Vaccines Research and Review, Center for Biologics Evaluation and Research, U.S. Food and Drug Administration, Silver Spring, MD 20993
| | - Hugo F. Azurmendi
- Laboratory of Bacterial Polysaccharides, Office of Vaccines Research and Review, Center for Biologics Evaluation and Research, U.S. Food and Drug Administration, Silver Spring, MD 20993
| | - Conor J. Crawford
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, The Johns Hopkins Bloomberg School of Public Health, Baltimore, MD21205
- Centre for Synthesis and Chemical Biology, University College Dublin, Dublin 4, Ireland
| | - Maggie P. Wear
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, The Johns Hopkins Bloomberg School of Public Health, Baltimore, MD21205
| | - Stefan Oscarson
- Centre for Synthesis and Chemical Biology, University College Dublin, Dublin 4, Ireland
| | - Arturo Casadevall
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, The Johns Hopkins Bloomberg School of Public Health, Baltimore, MD21205
| | - Darón I. Freedberg
- Laboratory of Bacterial Polysaccharides, Office of Vaccines Research and Review, Center for Biologics Evaluation and Research, U.S. Food and Drug Administration, Silver Spring, MD 20993
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2
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Crawford C, Guazzelli L, McConnell SA, McCabe O, d’Errico C, Greengo SD, Wear MP, Jedlicka AE, Casadevall A, Oscarson S. Synthetic Glycans Reveal Determinants of Antibody Functional Efficacy against a Fungal Pathogen. ACS Infect Dis 2024; 10:475-488. [PMID: 37856427 PMCID: PMC10862557 DOI: 10.1021/acsinfecdis.3c00447] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2023] [Indexed: 10/21/2023]
Abstract
Antibodies play a vital role in the immune response to infectious diseases and can be administered passively to protect patients. In the case of Cryptococcus neoformans, a WHO critical priority fungal pathogen, infection results in antibodies targeting capsular glucuronoxylomannan (GXM). These antibodies yield protective, non-protective, and disease-enhancing outcomes when administered passively. However, it was unknown how these distinct antibodies recognized their antigens at the molecular level, leading to the hypothesis that they may target different GXM epitopes. To test this hypothesis, we constructed a microarray containing 26 glycans representative of those found in highly virulent cryptococcal strains and utilized it to study 16 well-characterized monoclonal antibodies. Notably, we found that protective and non-protective antibodies shared conserved reactivity to the M2 motif of GXM, irrespective of the strain used in infection or GXM-isolated to produce a conjugate vaccine. Here, only two antibodies, 12A1 and 18B7, exhibited diverse trivalent GXM motif reactivity. IgG antibodies associated with protective responses showed cross-reactivity to at least two GXM motifs. This molecular understanding of antibody binding epitopes was used to map the antigenic diversity of two Cryptococcus neoformans strains, which revealed the exceptional complexity of fungal capsular polysaccharides. A multi-GXM motif vaccine holds the potential to effectively address this antigenic diversity. Collectively, these findings underscore the context-dependent nature of antibody function and challenge the classification of anti-GXM epitopes as either "protective" or "non-protective".
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Affiliation(s)
- Conor
J. Crawford
- Centre
for Synthesis and Chemical Biology, University
College Dublin, Belfield D04 V1W8, Dublin 4, Ireland
- Department
of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, 615 North Wolfe Street, Baltimore, Maryland 21205, United States
| | - Lorenzo Guazzelli
- Centre
for Synthesis and Chemical Biology, University
College Dublin, Belfield D04 V1W8, Dublin 4, Ireland
| | - Scott A. McConnell
- Department
of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, 615 North Wolfe Street, Baltimore, Maryland 21205, United States
| | - Orla McCabe
- Centre
for Synthesis and Chemical Biology, University
College Dublin, Belfield D04 V1W8, Dublin 4, Ireland
| | - Clotilde d’Errico
- Centre
for Synthesis and Chemical Biology, University
College Dublin, Belfield D04 V1W8, Dublin 4, Ireland
| | - Seth D. Greengo
- Department
of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, 615 North Wolfe Street, Baltimore, Maryland 21205, United States
| | - Maggie P. Wear
- Department
of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, 615 North Wolfe Street, Baltimore, Maryland 21205, United States
| | - Anne E. Jedlicka
- Department
of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, 615 North Wolfe Street, Baltimore, Maryland 21205, United States
| | - Arturo Casadevall
- Department
of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, 615 North Wolfe Street, Baltimore, Maryland 21205, United States
| | - Stefan Oscarson
- Centre
for Synthesis and Chemical Biology, University
College Dublin, Belfield D04 V1W8, Dublin 4, Ireland
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3
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Crawford CJ, Liporagi-Lopes L, Coelho C, Santos SR, Nicola AM, Wear MP, Vij R, Oscarson S, Casadevall A. Semi-synthetic glycoconjugate vaccine candidate against Cryptococcus neoformans. bioRxiv 2024:2024.02.02.578725. [PMID: 38352552 PMCID: PMC10862886 DOI: 10.1101/2024.02.02.578725] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 02/24/2024]
Abstract
Cryptococcus neoformans is a fungus classified by the World Health Organization as a critically important pathogen, posing a significant threat to immunocompromised individuals. In this study, we present the chemical synthesis and evaluation of two semi-synthetic vaccine candidates targeting the capsular polysaccharide glucuronoxylomannan (GXM) of C. neoformans. These semi-synthetic glycoconjugate vaccines contain the identical synthetic decasaccharide (M2 motif) antigen. This motif is present in serotype A strains, which constitute 95% of clinical cryptococcosis cases. This synthetic oligosaccharide was conjugated to two proteins (CRM197 and Anthrax 63 kDa PA) and tested for immunogenicity in mice. The conjugates elicited a specific antibody response that bound to the M2 motif but also exhibited additional cross-reactivity towards M1 and M4 GXM motifs. Both glycoconjugates produced antibodies that bound to GXM in ELISA assays and to live fungal cells. Mice immunized with the CRM197 glycoconjugate produced opsonic antibodies and displayed trends toward increased median survival relative to mice given a mock PBS injection (18 vs 15 days, p = 0.06). While these findings indicate promise, achieving a successful vaccine demands further optimization of the glycoconjugate. It could serve as a component in a multi-valent GXM motif vaccine, enhancing both strength and breadth of immune responses.
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Affiliation(s)
- Conor J Crawford
- Centre for Synthesis and Chemical Biology, University College Dublin, Belfield, Dublin, Ireland
- Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health 615 North Wolfe Street, Baltimore, MD 21205, USA
- Present Address: Max Planck Institute of Colloids and Interfaces, Am Mühlenberg1, 14476 Potsdam, Germany
| | - Livia Liporagi-Lopes
- Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health 615 North Wolfe Street, Baltimore, MD 21205, USA
- Present Address: Departamento de Análises Clínicas e Toxicológicas, Faculdade de Farmácia, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Carolina Coelho
- Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health 615 North Wolfe Street, Baltimore, MD 21205, USA
- Present Address: MRC Centre for Medical Mycology, University of Exeter, Exeter Devon UK
| | - Samuel R Santos
- Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health 615 North Wolfe Street, Baltimore, MD 21205, USA
| | - André Moraes Nicola
- Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health 615 North Wolfe Street, Baltimore, MD 21205, USA
- Present Address: Faculty of Medicine, University of Brasília, Brasília, Brazil
| | - Maggie P Wear
- Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health 615 North Wolfe Street, Baltimore, MD 21205, USA
| | - Raghav Vij
- Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health 615 North Wolfe Street, Baltimore, MD 21205, USA
- Present address: Leibniz Institute for Natural Product Research and Infection Biology, Jena, Germany
| | - Stefan Oscarson
- Centre for Synthesis and Chemical Biology, University College Dublin, Belfield, Dublin, Ireland
| | - Arturo Casadevall
- Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health 615 North Wolfe Street, Baltimore, MD 21205, USA
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4
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Hargett AA, Azurmendi HF, Crawford CJ, Wear MP, Oscarson S, Casadevall A, Freedberg DI. The structure of a C. neoformans polysaccharide motif recognized by protective antibodies: A combined NMR and MD study. bioRxiv 2023:2023.09.06.556507. [PMID: 37732210 PMCID: PMC10508755 DOI: 10.1101/2023.09.06.556507] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/22/2023]
Abstract
Cryptococcus neoformans is a fungal pathogen responsible for cryptococcosis and cryptococcal meningitis. The C. neoformans capsular polysaccharide and shed exopolysaccharide functions both as a key virulence factor and to protect the fungal cell from phagocytosis. Currently, a glycoconjugate of these polysaccharides is being explored as a vaccine to protect against C. neoformans infection. In this combined NMR and MD study, experimentally determined NOEs and J-couplings support a structure of the synthetic decasaccharide, GXM10-Ac3, obtained by MD. GXM10-Ac3 was designed as an extension of glucuronoxylomannan (GXM) polysaccharide motif (M2) which is common in the clinically predominant serotype A strains and is recognized by protective forms of GXM-specific monoclonal antibodies. The M2 motif is characterized by a 6-residue α-mannan backbone repeating unit, consisting of a triad of α-(1→3)-mannoses, modified by β-(1→2)-xyloses on the first two mannoses and a β-(1→2)-glucuronic acid on the third mannose. The combined NMR and MD analyses reveal that GXM10-Ac3 adopts an extended structure, with xylose/glucuronic acid branches alternating sides along the α-mannan backbone. O-acetyl esters also alternate sides and are grouped in pairs. MD analysis of a twelve M2-repeating unit polymer supports the notion that the GXM10-Ac3 structure is uniformly represented throughout the polysaccharide. This experimentally consistent GXM model displays high flexibility while maintaining a structural identity, yielding new insights to further explore intermolecular interactions between polysaccharides, interactions with anti-GXM mAbs, and the cryptococcal polysaccharide architecture.
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Affiliation(s)
- Audra A. Hargett
- Laboratory of Bacterial Polysaccharides, Office of Vaccines Research and Review, Center for Biologics Evaluation and Research, U.S. Food and Drug Administration, Silver Spring, MD, USA
| | - Hugo F. Azurmendi
- Laboratory of Bacterial Polysaccharides, Office of Vaccines Research and Review, Center for Biologics Evaluation and Research, U.S. Food and Drug Administration, Silver Spring, MD, USA
| | - Conor J. Crawford
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
- Centre for Synthesis and Chemical Biology, University College Dublin, Belfield, Dublin 4, Ireland
- Current address: Department of Biomolecular Systems, Max Planck Institute of Colloids and Interfaces, Potsdam, Germany
| | - Maggie P. Wear
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | - Stefan Oscarson
- Centre for Synthesis and Chemical Biology, University College Dublin, Belfield, Dublin 4, Ireland
| | - Arturo Casadevall
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | - Darόn I. Freedberg
- Laboratory of Bacterial Polysaccharides, Office of Vaccines Research and Review, Center for Biologics Evaluation and Research, U.S. Food and Drug Administration, Silver Spring, MD, USA
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5
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McConnell SA, Sachithanandham J, Mudrak NJ, Zhu X, Farhang PA, Cordero RJB, Wear MP, Shapiro JR, Park HS, Klein SL, Tobian AAR, Bloch EM, Sullivan DJ, Pekosz A, Casadevall A. Spike-protein proteolytic antibodies in COVID-19 convalescent plasma contribute to SARS-CoV-2 neutralization. Cell Chem Biol 2023; 30:726-738.e4. [PMID: 37354908 PMCID: PMC10288624 DOI: 10.1016/j.chembiol.2023.05.011] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2022] [Revised: 03/23/2023] [Accepted: 05/26/2023] [Indexed: 06/26/2023]
Abstract
Understanding the mechanisms of antibody-mediated neutralization of SARS-CoV-2 is critical in combating the COVID-19 pandemic. Based on previous reports of antibody catalysis, we investigated the proteolysis of spike (S) by antibodies in COVID-19 convalescent plasma (CCP) and its contribution to viral neutralization. Quenched fluorescent peptides were designed based on S epitopes to sensitively detect antibody-mediated proteolysis. We observed epitope cleavage by CCP from different donors which persisted when plasma was heat-treated or when IgG was isolated from plasma. Further, purified CCP antibodies proteolyzed recombinant S domains, as well as authentic viral S. Cleavage of S variants suggests CCP antibody-mediated proteolysis is a durable phenomenon despite antigenic drift. We differentiated viral neutralization occurring via direct interference with receptor binding from that occurring by antibody-mediated proteolysis, demonstrating that antibody catalysis enhanced neutralization. These results suggest that antibody-catalyzed damage of S is an immunologically relevant function of neutralizing antibodies against SARS-CoV-2.
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Affiliation(s)
- Scott A McConnell
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, USA
| | - Jaiprasath Sachithanandham
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, USA
| | - Nathan J Mudrak
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, USA
| | - Xianming Zhu
- Department of Pathology, Johns Hopkins School of Medicine, Baltimore, MD 21287, USA
| | - Parsa Alba Farhang
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, USA
| | - Radames J B Cordero
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, USA
| | - Maggie P Wear
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, USA
| | - Janna R Shapiro
- Department of International Health, Johns Hopkins School of Public Health, Baltimore, MD 21205, USA
| | - Han-Sol Park
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, USA
| | - Sabra L Klein
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, USA; Department of International Health, Johns Hopkins School of Public Health, Baltimore, MD 21205, USA; Department of Biochemistry and Molecular Biology, Johns Hopkins School of Public Health, Baltimore, MD 21205, USA
| | - Aaron A R Tobian
- Department of Pathology, Johns Hopkins School of Medicine, Baltimore, MD 21287, USA
| | - Evan M Bloch
- Department of Pathology, Johns Hopkins School of Medicine, Baltimore, MD 21287, USA
| | - David J Sullivan
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, USA
| | - Andrew Pekosz
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, USA
| | - Arturo Casadevall
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, USA.
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6
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Wear MP, Hargett AA, Kelly JE, McConnell SA, Freedberg DI, Casadevall A, Crawford CJ, Stark RE. Fungal polysaccharides are altered by lyophilization resulting in decreased antibody binding. FASEB J 2022. [DOI: 10.1096/fasebj.2022.36.s1.r5955] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Maggie P. Wear
- Molecular Microbiology and ImmunologyJohns Hopkins University Bloomberg School of Public HealthBaltimoreMD
| | - Audra A. Hargett
- Laboratory of Bacterial PSs, Office of Vaccines Research and Review, Center for Biologics Evaluation and Research, U.S. Food and Drug AdministrationSilver SpringMD
| | - John E. Kelly
- The City College of New York and CUNY Institute for Macromolecular AssembliesNew YorkNY
| | - Scott A. McConnell
- Molecular Microbiology and ImmunologyJohns Hopkins University Bloomberg School of Public HealthBaltimoreMD
| | - Darón I. Freedberg
- Laboratory of Bacterial PSs, Office of Vaccines Research and Review, Center for Biologics Evaluation and Research, U.S. Food and Drug AdministrationSilver SpringMD
- Molecular Microbiology and ImmunologyLaboratory of Bacterial PSs, Office of Vaccines Research and Review, Center for Biologics Evaluation and Research, U.S. Food and Drug AdministrationSilver SpringMD
| | | | - Conor J. Crawford
- Molecular Microbiology and ImmunologyJohns Hopkins University Bloomberg School of Public HealthBaltimoreMD
- Johns Hopkins University Bloomberg School of Public HealthBaltimoreMD
| | - Ruth E. Stark
- The City College of New York and CUNY Institute for Macromolecular AssembliesNew YorkNY
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7
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Wear MP, Jacobs E, Wang S, McConnell S, Bowen A, Strother C, Cordero RJB, Crawford CJ, Casadevall A. Cryptococcus neoformans capsule regrowth experiments reveal dynamics of enlargement and architecture. J Biol Chem 2022; 298:101769. [PMID: 35218774 PMCID: PMC8942833 DOI: 10.1016/j.jbc.2022.101769] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2021] [Revised: 02/17/2022] [Accepted: 02/18/2022] [Indexed: 11/25/2022] Open
Abstract
The polysaccharide capsule of fungal pathogen Cryptococcus neoformans is a critical virulence factor that has historically evaded complete characterization. Cryptococcal polysaccharides are known to either remain attached to the cell as capsular polysaccharides (CPS) or to be shed into the extracellular space as exopolysaccharides (EPS). While many studies have examined the properties of EPS, far less is known about CPS. In this work, we detail the development of a new physical and enzymatic method for the isolation of CPS which can be used to explore the architecture of the capsule and isolated capsular material. We show that sonication or Glucanex enzyme cocktail digestion yields soluble CPS preparations, while use of a French pressure cell press and Glucanex digestion followed by cell disruption removed the capsule and produced cell wall-associated polysaccharide aggregates that we call 'capsule ghosts', implying an inherent organization that allows the CPS to exist independent of the cell wall surface. Since sonication and Glucanex digestion were non-cytotoxic, it was also possible to observe the cryptococcal cells rebuilding their capsule, revealing the presence of reducing-end glycans throughout the capsule. Finally, analysis of DMSO-extracted and sonicated CPS preparations revealed the conservation of previously identified GXM motifs only in the sonicated CPS. Together, these observations provide new insights into capsule architecture and synthesis, consistent with a model in which the capsule is assembled from the cell wall outwards using smaller polymers, which are then compiled into larger ones.
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Affiliation(s)
- Maggie P Wear
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA.
| | - Ella Jacobs
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | - Siqing Wang
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | - Scott McConnell
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | - Anthony Bowen
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | - Camilla Strother
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | - Radames J B Cordero
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | - Conor J Crawford
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | - Arturo Casadevall
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
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8
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Oliveira DSLD, Paredes V, Caixeta AV, Henriques NM, Wear MP, Albuquerque P, Felipe MSS, Casadevall A, Nicola AM. Hinge influences in murine IgG binding to Cryptococcus neoformans capsule. Immunology 2021; 165:110-121. [PMID: 34458991 DOI: 10.1111/imm.13411] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Revised: 08/07/2021] [Accepted: 08/19/2021] [Indexed: 11/30/2022] Open
Abstract
Decades of studies on antibody structure led to the tenet that the V region binds antigens while the C region interacts with immune effectors. In some antibodies, however, the C region affects affinity and/or specificity for the antigen. One example is the 3E5 monoclonal murine IgG family, in which the mIgG3 isotype has different fine specificity to the Cryptococcus neoformans capsule polysaccharide than the other mIgG isotypes despite their identical variable sequences. Our group serendipitously found another pair of mIgG1/mIgG3 antibodies based on the 2H1 hybridoma to the C. neoformans capsule that recapitulated the differences observed with 3E5. In this work, we report the molecular basis of the constant domain effects on antigen binding using recombinant antibodies. As with 3E5, immunofluorescence experiments show a punctate pattern for 2H1-mIgG3 and an annular pattern for 2H1-mIgG1; these binding patterns have been associated with protective efficacy in murine cryptococcosis. Also as observed with 3E5, 2H1-mIgG3 bound on ELISA to both acetylated and non-acetylated capsular polysaccharide, whereas 2H1-mIgG1 only bound well to the acetylated form, consistent with differences in fine specificity. In engineering hybrid mIgG1/mIgG3 antibodies, we found that switching the 2H1-mIgG3 hinge for its mIgG1 counterpart changed the immunofluorescence pattern to annular, but a 2H1-mIgG1 antibody with an mIgG3 hinge still had an annular pattern. The hinge is thus necessary but not sufficient for these changes in binding to the antigen. This important role for the constant region in antigen binding could affect antibody biology and engineering.
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Affiliation(s)
| | | | | | | | - Maggie P Wear
- Department of Molecular Microbiology & Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | | | - Maria Sueli Soares Felipe
- Graduate Program in Genomic Sciences and Biotechnology, Catholic University of Brasília, Brasília, Brazil
| | - Arturo Casadevall
- Department of Molecular Microbiology & Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | - André Moraes Nicola
- Faculty of Medicine, University of Brasília, Brasília, Brazil.,Graduate Program in Genomic Sciences and Biotechnology, Catholic University of Brasília, Brasília, Brazil
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9
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Derreth RT, Wear MP. Critical Online Service-Learning Pedagogy: Justice in Science Education. J Microbiol Biol Educ 2021; 22:22.1.61. [PMID: 33884083 PMCID: PMC8046651 DOI: 10.1128/jmbe.v22i1.2537] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2020] [Accepted: 02/05/2021] [Indexed: 05/17/2023]
Abstract
In the year 2020 the world changed dramatically. We went from busy lives spent largely away from home to spending most of our time at home while daily facing deepening national crises. With the violent, needless death of George Floyd, the simmering tensions around race in America boiled over, sending thousands into the streets to protest racial injustices. The world of science education has largely avoided discussing racism in our classes, but we can no longer ignore it. The events of the spring and summer have highlighted our need to integrate conversations and reflections on justice into science education. In this work, we argue that service learning can build this understanding from both theory and experience. Using a critical online service-learning framework, we have developed a service-learning course that incorporates dialogic communication, cross-contextual reflections, and positioning oneself as an ally. This perspective allows science and the community to prioritize relationships and humanity and reflect on our roles as professionals using the online interacting space. This course, taught at the beginning of the pandemic, focuses on critical online service learning for those studying public health. We discuss the challenges we faced moving critical service-learning pedagogy online and the compounding issues brought on by the pandemic itself.
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Affiliation(s)
- R. Tyler Derreth
- SOURCE, Community Engagement and Service-Learning Center at Johns Hopkins University, Schools of Public Health, Nursing, and Medicine, Baltimore, MD, 21205
- Health, Behavior and Society Department, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205
| | - Maggie P. Wear
- Molecular Microbiology and Immunology Department, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205
- R Center for Innovation in Science Education (RISE), Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205
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10
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Crawford CJ, Wear MP, Smith DFQ, d'Errico C, McConnell SA, Casadevall A, Oscarson S. A glycan FRET assay for detection and characterization of catalytic antibodies to the Cryptococcus neoformans capsule. Proc Natl Acad Sci U S A 2021; 118:e2016198118. [PMID: 33514659 PMCID: PMC7865134 DOI: 10.1073/pnas.2016198118] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Classic antibody functions include opsonization, complement activation, and enhancement of cellular antimicrobial function. Antibodies can also have catalytic activity, although the contribution of catalysis to their biological functions has been more difficult to establish. With the ubiquity of catalytic antibodies against glycans virtually unknown, we sought to advance this knowledge. The use of a glycan microarray allowed epitope mapping of several monoclonal antibodies (mAbs) against the capsule of Cryptococcus neoformans From this, we designed and synthesized two glycan-based FRET probes, which we used to discover antibodies with innate glycosidase activity and analyze their enzyme kinetics, including mAb 2H1, the most efficient identified to date. The validity of the FRET assay was confirmed by demonstrating that the mAbs mediate glycosidase activity on intact cryptococcal capsules, as observed by a reduction in capsule diameter. Furthermore, the mAb 18B7, a glycosidase hydrolase, resulted in the appearance of reducing ends in the capsule as labeled by a hydroxylamine-armed fluorescent (HAAF) probe. Finally, we demonstrate that exposing C. neoformans cells to catalytic antibodies results in changes in complement deposition and increased phagocytosis by macrophages, suggesting that the antiphagocytic properties of the capsule have been impaired. Our results raise questions over the ubiquity of antibodies with catalytic activity against glycans and establish the utility of glycan-based FRET and HAAF probes as tools for investigating this activity.
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Affiliation(s)
- Conor J Crawford
- Centre for Synthesis and Chemical Biology, University College Dublin, Dublin 4, Ireland
- Department of Molecular Microbiology and Immunology, The Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205
| | - Maggie P Wear
- Department of Molecular Microbiology and Immunology, The Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205
| | - Daniel F Q Smith
- Department of Molecular Microbiology and Immunology, The Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205
| | - Clotilde d'Errico
- Centre for Synthesis and Chemical Biology, University College Dublin, Dublin 4, Ireland
| | - Scott A McConnell
- Department of Molecular Microbiology and Immunology, The Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205
| | - Arturo Casadevall
- Department of Molecular Microbiology and Immunology, The Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205
| | - Stefan Oscarson
- Centre for Synthesis and Chemical Biology, University College Dublin, Dublin 4, Ireland;
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11
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Guazzelli L, Crawford CJ, Ulc R, Bowen A, McCabe O, Jedlicka AJ, Wear MP, Casadevall A, Oscarson S. A synthetic glycan array containing Cryptococcus neoformans glucuronoxylomannan capsular polysaccharide fragments allows the mapping of protective epitopes. Chem Sci 2020; 11:9209-9217. [PMID: 34123169 PMCID: PMC8163368 DOI: 10.1039/d0sc01249a] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2020] [Accepted: 07/29/2020] [Indexed: 01/12/2023] Open
Abstract
A convergent synthetic strategy to Cryptococcus neoformans glucuronoxylomannan (GXM) capsular polysaccharide part structures was developed based on di-, tri-, tetra-, penta- and hexasaccharide thioglycoside building blocks. The approach permitted the synthesis of a library of spacer-containing serotype A and D related GXM oligosaccharide structures, ranging from di- to octadecasaccharides. Ten deprotected GXM compounds (mono- to decasaccharide) were printed onto microarray plates and screened with seventeen mouse monoclonal antibodies (mAbs) to GXM. For the first time a GXM oligosaccharide structure (a serotype A decasaccharide), capable of being recognized by neutralizing forms of these GXM-specific mAbs, has been identified, offering insight into the binding epitopes of a range of protective monoclonal antibodies and furthering our efforts to develop semi-synthetic conjugate vaccine candidates against C. neoformans.
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Affiliation(s)
- Lorenzo Guazzelli
- Centre for Synthesis and Chemical Biology, UCD School of Chemistry, University College Dublin Belfield Dublin 4 Ireland
| | - Conor J Crawford
- Centre for Synthesis and Chemical Biology, UCD School of Chemistry, University College Dublin Belfield Dublin 4 Ireland
| | - Rebecca Ulc
- Centre for Synthesis and Chemical Biology, UCD School of Chemistry, University College Dublin Belfield Dublin 4 Ireland
| | - Anthony Bowen
- Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, The Johns Hopkins University 615 N. Wolfe St., Rm. E5132 Baltimore MD 21205 USA
| | - Orla McCabe
- Centre for Synthesis and Chemical Biology, UCD School of Chemistry, University College Dublin Belfield Dublin 4 Ireland
| | - Anne J Jedlicka
- Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, The Johns Hopkins University 615 N. Wolfe St., Rm. E5132 Baltimore MD 21205 USA
| | - Maggie P Wear
- Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, The Johns Hopkins University 615 N. Wolfe St., Rm. E5132 Baltimore MD 21205 USA
| | - Arturo Casadevall
- Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, The Johns Hopkins University 615 N. Wolfe St., Rm. E5132 Baltimore MD 21205 USA
| | - Stefan Oscarson
- Centre for Synthesis and Chemical Biology, UCD School of Chemistry, University College Dublin Belfield Dublin 4 Ireland
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12
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Crawford CJ, Cordero RJB, Guazzelli L, Wear MP, Bowen A, Oscarson S, Casadevall A. Exploring Cryptococcus neoformans capsule structure and assembly with a hydroxylamine-armed fluorescent probe. J Biol Chem 2020; 295:4327-4340. [PMID: 32005661 PMCID: PMC7105310 DOI: 10.1074/jbc.ra119.012251] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2019] [Revised: 01/30/2020] [Indexed: 11/06/2022] Open
Abstract
Chemical biology is an emerging field that enables the study and manipulation of biological systems with probes whose reactivities provide structural insights. The opportunistic fungal pathogen Cryptococcus neoformans possesses a polysaccharide capsule that is a major virulence factor, but is challenging to study. We report here the synthesis of a hydroxylamine-armed fluorescent probe that reacts with reducing glycans and its application to study the architecture of the C. neoformans capsule under a variety of conditions. The probe signal localized intracellularly and at the cell wall-membrane interface, implying the presence of reducing-end glycans at this location where the capsule is attached to the cell body. In contrast, no fluorescence signal was detected in the capsule body. We observed vesicle-like structures containing the reducing-end probe, both intra- and extracellularly, consistent with the importance of vesicles in capsular assembly. Disrupting the capsule with DMSO, ultrasound, or mechanical shear stress resulted in capsule alterations that affected the binding of the probe, as reducing ends were exposed and cell membrane integrity was compromised. Unlike the polysaccharides in the assembled capsule, isolated exopolysaccharides contained reducing ends. The reactivity of the hydroxylamine-armed fluorescent probe suggests a model for capsule assembly whereby reducing ends localize to the cell wall surface, supporting previous findings suggesting that this is an initiation point for capsular assembly. We propose that chemical biology is a promising approach for studying the C. neoformans capsule and its associated polysaccharides to unravel their roles in fungal virulence.
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Affiliation(s)
- Conor J Crawford
- Centre for Synthesis and Chemical Biology, University College Dublin, Belfield, Dublin 4, Ireland; Department of Molecular Microbiology and Immunology, Bloomberg School of Public Health, The Johns Hopkins University, Baltimore, Maryland 21205
| | - Radamés J B Cordero
- Department of Molecular Microbiology and Immunology, Bloomberg School of Public Health, The Johns Hopkins University, Baltimore, Maryland 21205
| | - Lorenzo Guazzelli
- Centre for Synthesis and Chemical Biology, University College Dublin, Belfield, Dublin 4, Ireland
| | - Maggie P Wear
- Department of Molecular Microbiology and Immunology, Bloomberg School of Public Health, The Johns Hopkins University, Baltimore, Maryland 21205
| | - Anthony Bowen
- Department of Molecular Microbiology and Immunology, Bloomberg School of Public Health, The Johns Hopkins University, Baltimore, Maryland 21205
| | - Stefan Oscarson
- Centre for Synthesis and Chemical Biology, University College Dublin, Belfield, Dublin 4, Ireland.
| | - Arturo Casadevall
- Department of Molecular Microbiology and Immunology, Bloomberg School of Public Health, The Johns Hopkins University, Baltimore, Maryland 21205.
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13
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Abstract
The capsule of Cryptococcus neoformans is its dominant virulence factor and plays a key role in the biology of this fungus. In this essay, we focus on the capsule as a cellular structure and note the limitations inherent in the current methodologies available for its study. Given that no single method can provide the structure of the capsule, our notions of what is the cryptococcal capsule must be arrived at by synthesizing information gathered from very different methodological approaches including microscopy, polysaccharide chemistry and physical chemistry of macromolecules. The emerging picture is one of a carefully regulated dynamic structure that is constantly rearranged as a response to environmental stimulation and cellular replication. In the environment, the capsule protects the fungus against desiccation and phagocytic predators. In animal hosts the capsule functions in both offensive and defensive modes, such that it interferes with immune responses while providing the fungal cell with a defensive shield that is both antiphagocytic and capable of absorbing microbicidal oxidative bursts from phagocytic cells. Finally, we delineate a set of unsolved problems in the cryptococcal capsule field that could provide fertile ground for future investigations.
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Affiliation(s)
- Arturo Casadevall
- Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health , Baltimore , MD , USA
| | - Carolina Coelho
- Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health , Baltimore , MD , USA
| | - Radames J B Cordero
- Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health , Baltimore , MD , USA
| | - Quigly Dragotakes
- Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health , Baltimore , MD , USA
| | - Eric Jung
- Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health , Baltimore , MD , USA
| | - Raghav Vij
- Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health , Baltimore , MD , USA
| | - Maggie P Wear
- Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health , Baltimore , MD , USA
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14
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Bowen A, Wear MP, Cordero RJB, Oscarson S, Casadevall A. A Monoclonal Antibody to Cryptococcus neoformans Glucuronoxylomannan Manifests Hydrolytic Activity for Both Peptides and Polysaccharides. J Biol Chem 2016; 292:417-434. [PMID: 27872188 DOI: 10.1074/jbc.m116.767582] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2016] [Indexed: 11/06/2022] Open
Abstract
Studies in the 1980s first showed that some natural antibodies were "catalytic" and able to hydrolyze peptide or phosphodiester bonds in antigens. Many naturally occurring catalytic antibodies have since been isolated from human sera and associated with positive and negative outcomes in autoimmune disease and infection. The function and prevalence of these antibodies, however, remain unclear. A previous study suggested that the 18B7 monoclonal antibody against glucuronoxylomannan (GXM), the major component of the Cryptococcus neoformans polysaccharide capsule, hydrolyzed a peptide antigen mimetic. Using mass spectrometry and Förster resonance energy transfer techniques, we confirm and characterize the hydrolytic activity of 18B7 against peptide mimetics and show that 18B7 is able to hydrolyze an oligosaccharide substrate, providing the first example of a naturally occurring catalytic antibody for polysaccharides. Additionally, we show that the catalytic 18B7 antibody increases release of capsular polysaccharide from fungal cells. A serine protease inhibitor blocked peptide and oligosaccharide hydrolysis by 18B7, and a putative serine protease-like active site was identified in the light chain variable region of the antibody. An algorithm was developed to detect similar sites present in unique antibody structures in the Protein Data Bank. The putative site was found in 14 of 63 (22.2%) catalytic antibody structures and 119 of 1602 (7.4%) antibodies with no annotation of catalytic activity. The ability of many antibodies to cleave antigen, albeit slowly, supports the notion that this activity is an important immunoglobulin function in host defense. The discovery of GXM hydrolytic activity suggests new therapeutic possibilities for polysaccharide-binding antibodies.
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Affiliation(s)
- Anthony Bowen
- From the Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York 10461
| | - Maggie P Wear
- the Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland 21205, and
| | - Radames J B Cordero
- the Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland 21205, and
| | - Stefan Oscarson
- the Centre for Synthesis and Chemical Biology, UCD School of Chemistry and Chemical Biology, University College Dublin, Belfield, Dublin 4, Ireland
| | - Arturo Casadevall
- the Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland 21205, and
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15
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Wear MP, Kryndushkin D, O’Meally R, Sonnenberg JL, Cole RN, Shewmaker FP. Proteins with Intrinsically Disordered Domains Are Preferentially Recruited to Polyglutamine Aggregates. PLoS One 2015; 10:e0136362. [PMID: 26317359 PMCID: PMC4552826 DOI: 10.1371/journal.pone.0136362] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2015] [Accepted: 07/31/2015] [Indexed: 12/12/2022] Open
Abstract
Intracellular protein aggregation is the hallmark of several neurodegenerative diseases. Aggregates formed by polyglutamine (polyQ)-expanded proteins, such as Huntingtin, adopt amyloid-like structures that are resistant to denaturation. We used a novel purification strategy to isolate aggregates formed by human Huntingtin N-terminal fragments with expanded polyQ tracts from both yeast and mammalian (PC-12) cells. Using mass spectrometry we identified the protein species that are trapped within these polyQ aggregates. We found that proteins with very long intrinsically-disordered (ID) domains (≥100 amino acids) and RNA-binding proteins were disproportionately recruited into aggregates. The removal of the ID domains from selected proteins was sufficient to eliminate their recruitment into polyQ aggregates. We also observed that several neurodegenerative disease-linked proteins were reproducibly trapped within the polyQ aggregates purified from mammalian cells. Many of these proteins have large ID domains and are found in neuronal inclusions in their respective diseases. Our study indicates that neurodegenerative disease-associated proteins are particularly vulnerable to recruitment into polyQ aggregates via their ID domains. Also, the high frequency of ID domains in RNA-binding proteins may explain why RNA-binding proteins are frequently found in pathological inclusions in various neurodegenerative diseases.
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Affiliation(s)
- Maggie P. Wear
- Department of Pharmacology, Uniformed Services University of the Heath Sciences, Bethesda, Maryland, 20814, United States of America
| | - Dmitry Kryndushkin
- Department of Pharmacology, Uniformed Services University of the Heath Sciences, Bethesda, Maryland, 20814, United States of America
| | - Robert O’Meally
- Johns Hopkins Mass Spectrometry and Proteomic Facility, Johns Hopkins University, Baltimore, Maryland, 21218, United States of America
| | - Jason L. Sonnenberg
- Chemistry department, School of Sciences, Stevenson University, Stevenson, Maryland, 21153, United States of America
| | - Robert N. Cole
- Johns Hopkins Mass Spectrometry and Proteomic Facility, Johns Hopkins University, Baltimore, Maryland, 21218, United States of America
| | - Frank P. Shewmaker
- Department of Pharmacology, Uniformed Services University of the Heath Sciences, Bethesda, Maryland, 20814, United States of America
- * E-mail:
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16
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Abstract
The capacity to polymerize into amyloid fibrils is common to many proteins. While some proteins naturally form these fibrils to serve functional roles, amyloid is usually associated with pathogenic processes in which specific proteins aberrantly aggregate within cells or tissues. Though the contribution of amyloid fibrils to actual disease pathogenesis is not always clear, one possibility is that the titration of essential proteins from solution into aggregates contributes to the cellular degeneration common to many amyloid diseases. Using mammalian and yeast model systems, we recently showed that the common biophysical properties of amyloid aggregates--including strong resistance to dissolution--enable stringent purification and identification of both amyloid-forming and amyloid-associated proteins directly from cells. Strikingly, many proteins that were previously implicated in formation or clearance of intracellular aggregates, including several stress granule components, were found to co-aggregate with amyloid formed by a polyglutamine-expanded huntingtin fragment. This direct evaluation of proteins within aggregates can help identify new amyloid-forming proteins, as well as proteins that can indirectly contribute to disease mechanisms.
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Affiliation(s)
- Dmitry Kryndushkin
- Department of Pharmacology; Uniformed Services University of the Health Sciences; Bethesda, MD USA
| | - Maggie P Wear
- Department of Pharmacology; Uniformed Services University of the Health Sciences; Bethesda, MD USA
| | - Frank Shewmaker
- Department of Pharmacology; Uniformed Services University of the Health Sciences; Bethesda, MD USA
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17
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Prater CE, Saleh AD, Wear MP, Miller PS. Allosteric inhibition of the HIV-1 Rev/RRE interaction by a 3'-methylphosphonate modified antisense oligo-2'-O-methylribonucleotide. Oligonucleotides 2007; 17:275-90. [PMID: 17854268 DOI: 10.1089/oli.2007.0082] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The HIV-1 Rev response element (RRE), a highly structured RNA sequence consisting of five stemloops, is found in all spliced and partially spliced human immunodeficiency virus (HIV) mRNA transcripts. The RRE interacts with HIV-encoded Rev protein, which facilitates exit of the transcripts from the nucleus to the cytoplasm. Because the Rev/RRE interaction is critical to virus function, it is considered a potential target for therapeutic drugs. We have investigated the interactions of antisense oligonucleotides with stem-loop II, a region that contains the high-affinity binding site for Rev. Oligo-2'-O-methylribonucleotides terminating in a nuclease resistant 3'-methylphosphonate internucleotide linkage were targeted to the 5'- or 3'-side of stem-loop IIB, which is adjacent to the Rev binding site. Thermal denaturation experiments showed that oligonucleotides of this type form highly stable duplexes with complementary single-stranded RNA. Gel electrophoretic mobility shift assays (EMSA) showed that the oligonucleotides bound with high affinity and specificity at 37 degrees C to RRE stem-loop II RNA with apparent dissociation constants, K(D), in the low nM range. A 16-mer, 2-1mp, whose K(D) is 46 nM, competitively inhibited binding of Rev peptide to RRE stem-loop II RNA as shown by EMSA experiments. When transfected into HEK 293T cells, 2-1mp inhibited RRE mediated expression of chloramphenicol acetyl transferase (CAT) by 60% at a concentration of 300 nM oligonucleotide. These results are consistent with a mechanism by which 2-1mp blocks access of Rev to the RRE/CAT transcript thus preventing nuclear export and subsequent translation.
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Affiliation(s)
- Chrissy E Prater
- Laboratory of Respiratory Biology, National Institutes of Environmental Sciences, Research Triangle Park, North Carolina, USA
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18
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Prater CE, Saleh AD, Wear MP, Miller PS. Chimeric RNase H-competent oligonucleotides directed to the HIV-1 Rev response element. Bioorg Med Chem 2007; 15:5386-95. [PMID: 17566743 PMCID: PMC1987364 DOI: 10.1016/j.bmc.2007.05.066] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2007] [Revised: 05/23/2007] [Accepted: 05/29/2007] [Indexed: 11/26/2022]
Abstract
Chimeric oligo-2'-O-methylribonucleotides containing centrally located patches of contiguous 2'-deoxyribonucleotides and terminating in a nuclease resistant 3'-methylphosphonate internucleotide linkage were prepared. The oligonucleotides were targeted to the 3'-side of HIV Rev response element (RRE) stem-loop IIB RNA, which is adjacent to the high affinity Rev protein binding site and is critical to virus function. Thermal denaturation experiments showed that chimeric oligonucleotides form very stable duplexes with a complementary single-stranded RNA, and gel electrophoretic mobility shift assays (EMSA) showed that they bind with high affinity and specificity to RRE stem-loop II RNA (K(D) approximately 200 nM). The chimeric oligonucleotides promote RNase H-mediated hydrolysis of RRE stem-loop II RNA and have half-lives exceeding 24h when incubated in cell culture medium containing 10% fetal calf serum. One of the chimeric oligonucleotides inhibited RRE mediated expression of chloramphenicol acetyl transferase (CAT) approximately 60% at a concentration of 300 nM in HEK 293T cells co-transfected with p-RRE/CAT and p-Rev mammalian expression vectors.
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Affiliation(s)
| | | | | | - Paul S. Miller
- * Correspondence should be addressed to Paul S. Miller, . Phone: (410)-955-3489, Fax: (410)-955-2926
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