1
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Lahola-Chomiak AA, Footz T, Nguyen-Phuoc K, Neil GJ, Fan B, Allen KF, Greenfield DS, Parrish RK, Linkroum K, Pasquale LR, Leonhardt RM, Ritch R, Javadiyan S, Craig JE, Allison WT, Lehmann OJ, Walter MA, Wiggs JL. Non-Synonymous variants in premelanosome protein (PMEL) cause ocular pigment dispersion and pigmentary glaucoma. Hum Mol Genet 2019; 28:1298-1311. [PMID: 30561643 DOI: 10.1093/hmg/ddy429] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2018] [Revised: 12/04/2018] [Accepted: 12/12/2018] [Indexed: 01/25/2023] Open
Abstract
Pigmentary glaucoma (PG) is a common glaucoma subtype that results from release of pigment from the iris, called pigment dispersion syndrome (PDS), and its deposition throughout the anterior chamber of the eye. Although PG has a substantial heritable component, no causative genes have yet been identified. We used whole exome sequencing of two independent pedigrees to identify two premelanosome protein (PMEL) variants associated with heritable PDS/PG. PMEL encodes a key component of the melanosome, the organelle essential for melanin synthesis, storage and transport. Targeted screening of PMEL in three independent cohorts (n = 394) identified seven additional PDS/PG-associated non-synonymous variants. Five of the nine variants exhibited defective processing of the PMEL protein. In addition, analysis of PDS/PG-associated PMEL variants expressed in HeLa cells revealed structural changes to pseudomelanosomes indicating altered amyloid fibril formation in five of the nine variants. Introduction of 11-base pair deletions to the homologous pmela in zebrafish by the clustered regularly interspaced short palindromic repeats (CRISPR)-Cas9 method caused profound pigmentation defects and enlarged anterior segments in the eye, further supporting PMEL's role in ocular pigmentation and function. Taken together, these data support a model in which missense PMEL variants represent dominant negative mutations that impair the ability of PMEL to form functional amyloid fibrils. While PMEL mutations have previously been shown to cause pigmentation and ocular defects in animals, this research is the first report of mutations in PMEL causing human disease.
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Affiliation(s)
| | - Tim Footz
- Department of Medical Genetics, University of Alberta, Edmonton AB, Canada
| | - Kim Nguyen-Phuoc
- Department of Medical Genetics, University of Alberta, Edmonton AB, Canada
| | - Gavin J Neil
- Department of Biological Sciences, University of Alberta, Edmonton AB, Canada
| | - Baojian Fan
- Ocular Genomics Institute and Department of Ophthalmology, Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, MA, USA
| | - Keri F Allen
- Ocular Genomics Institute and Department of Ophthalmology, Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, MA, USA
| | - David S Greenfield
- Department of Ophthalmology, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Palm Beach Gardens, FL, USA
| | - Richard K Parrish
- Anne Bates Leach Eye Hospital, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL, USA
| | - Kevin Linkroum
- Ocular Genomics Institute and Department of Ophthalmology, Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, MA, USA
| | - Louis R Pasquale
- Ocular Genomics Institute and Department of Ophthalmology, Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, MA, USA
| | - Ralf M Leonhardt
- Department of Immunobiology, Yale University School of Medicine, New Haven, CT, USA
| | - Robert Ritch
- Einhorn Clinical Research Center, New York Eye and Ear Infirmary of Mount Sinai, New York, NY, USA
| | - Shari Javadiyan
- Department of Ophthalmology, Flinders Medical Centre, Adelaide, South Australia, Australia
| | - Jamie E Craig
- Department of Ophthalmology, Flinders Medical Centre, Adelaide, South Australia, Australia
| | - W T Allison
- Department of Medical Genetics, University of Alberta, Edmonton AB, Canada.,Department of Biological Sciences, University of Alberta, Edmonton AB, Canada
| | - Ordan J Lehmann
- Department of Medical Genetics, University of Alberta, Edmonton AB, Canada.,Department of Ophthalmology, University of Alberta, Edmonton AB, Canada
| | - Michael A Walter
- Department of Medical Genetics, University of Alberta, Edmonton AB, Canada
| | - Janey L Wiggs
- Ocular Genomics Institute and Department of Ophthalmology, Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, MA, USA
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2
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Graham M, Tzika AC, Mitchell SM, Liu X, Leonhardt RM. Repeat domain-associated O-glycans govern PMEL fibrillar sheet architecture. Sci Rep 2019; 9:6101. [PMID: 30988362 PMCID: PMC6465243 DOI: 10.1038/s41598-019-42571-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2018] [Accepted: 02/06/2019] [Indexed: 12/20/2022] Open
Abstract
PMEL is a pigment cell-specific protein that forms a functional amyloid matrix in melanosomes. The matrix consists of well-separated fibrillar sheets on which the pigment melanin is deposited. Using electron tomography, we demonstrate that this sheet architecture is governed by the PMEL repeat (RPT) domain, which associates with the amyloid as an accessory proteolytic fragment. Thus, the RPT domain is dispensable for amyloid formation as such but shapes the morphology of the matrix, probably in order to maximize the surface area available for pigment adsorption. Although the primary amino acid sequence of the RPT domain differs vastly among various vertebrates, we show that it is a functionally conserved, interchangeable module. RPT domains of all species are predicted to be very highly O-glycosylated, which is likely the common defining feature of this domain. O-glycosylation is indeed essential for RPT domain function and the establishment of the PMEL sheet architecture. Thus, O-glycosylation, not amino acid sequence, appears to be the major factor governing the characteristic PMEL amyloid morphology.
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Affiliation(s)
- Morven Graham
- Department of Cell Biology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT, 06519, USA
| | - Athanasia C Tzika
- Department of Genetics & Evolution, Laboratory of Artificial & Natural Evolution (LANE), Sciences III Building, 1211, Geneva, 4, Switzerland
| | - Susan M Mitchell
- Department of Immunobiology, Yale University School of Medicine, 300 Cedar Street, New Haven, CT, 06519, USA
| | - Xinran Liu
- Department of Cell Biology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT, 06519, USA
| | - Ralf M Leonhardt
- Department of Immunobiology, Yale University School of Medicine, 300 Cedar Street, New Haven, CT, 06519, USA.
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3
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Vigneron N, Ferrari V, Van den Eynde BJ, Cresswell P, Leonhardt RM. Cytosolic Processing Governs TAP-Independent Presentation of a Critical Melanoma Antigen. J Immunol 2018; 201:1875-1888. [PMID: 30135181 DOI: 10.4049/jimmunol.1701479] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2017] [Accepted: 07/26/2018] [Indexed: 12/30/2022]
Abstract
Cancer immunotherapy has been flourishing in recent years with remarkable clinical success. But as more patients are treated, a shadow is emerging that has haunted other cancer therapies: tumors develop resistance. Resistance is often caused by defects in the MHC class I Ag presentation pathway critical for CD8 T cell-mediated tumor clearance. TAP and tapasin, both key players in the pathway, are frequently downregulated in human cancers, correlating with poor patient survival. Reduced dependence on these factors may promote vaccine efficiency by limiting immune evasion. In this study, we demonstrate that PMEL209-217, a promising phase 3 trial-tested antimelanoma vaccine candidate, is robustly presented by various TAP- and/or tapasin-deficient cell lines. This striking characteristic may underlie its potency as a vaccine. Surprisingly, cytosolic proteasomes generate the peptide even for TAP-independent presentation, whereas tripeptidyl peptidase 2 (TPP2) efficiently degrades the epitope. Consequently, inhibiting TPP2 substantially boosts PMEL209-217 presentation, suggesting a possible strategy to improve the therapeutic efficacy of the vaccine.
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Affiliation(s)
- Nathalie Vigneron
- Ludwig Institute for Cancer Research, Brussels B-1200, Belgium.,de Duve Institute, University of Louvain, Brussels B-1200, Belgium.,Walloon Excellence in Life Sciences and Biotechnology, Brussels B-1200, Belgium
| | - Violette Ferrari
- Ludwig Institute for Cancer Research, Brussels B-1200, Belgium.,de Duve Institute, University of Louvain, Brussels B-1200, Belgium.,Walloon Excellence in Life Sciences and Biotechnology, Brussels B-1200, Belgium
| | - Benoît J Van den Eynde
- Ludwig Institute for Cancer Research, Brussels B-1200, Belgium; .,de Duve Institute, University of Louvain, Brussels B-1200, Belgium.,Walloon Excellence in Life Sciences and Biotechnology, Brussels B-1200, Belgium
| | - Peter Cresswell
- Department of Immunobiology, Yale University, New Haven, CT 06519; and .,Department of Cell Biology, Yale University, New Haven, CT 06519
| | - Ralf M Leonhardt
- Department of Immunobiology, Yale University, New Haven, CT 06519; and
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4
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Radomski N, Rebbig A, Leonhardt RM, Knittler MR. Xenophagic pathways and their bacterial subversion in cellular self-defense - παντα ρει - everything is in flux. Int J Med Microbiol 2017; 308:185-196. [PMID: 29126745 DOI: 10.1016/j.ijmm.2017.10.012] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [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: 06/12/2017] [Revised: 10/24/2017] [Accepted: 10/29/2017] [Indexed: 01/09/2023] Open
Abstract
Autophagy is an evolutionarily ancient and highly conserved eukaryotic mechanism that targets cytoplasmic material for degradation. Autophagic flux involves the formation of autophagosomes and their degradation by lysosomes. The process plays a crucial role in maintaining cellular homeostasis and responds to various environmental conditions. While autophagy had previously been thought to be a non-selective process, it is now clear that it can also selectively target cellular organelles, such as mitochondria (referred to as mitophagy) and/or invading pathogens (referred to as xenophagy). Selective autophagy is characterized by specific substrate recognition and requires distinct cellular adaptor proteins. Here we review xenophagic mechanisms involved in the recognition and autolysosomal or autophagolysosomal degradation of different intracellular bacteria. In this context, we also discuss a recently discovered cellular self-defense pathway, termed mito-xenophagy, which occurs during bacterial infection of dendritic cells and depends on a TNF-α-mediated metabolic switch from oxidative phosphorylation to glycolysis.
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Affiliation(s)
- Nadine Radomski
- Institute of Immunology, Friedrich-Loeffler-Institut, Institute of Immunology, Federal Research Institute of Animal Health, D-17493 Greifswald, Isle of Riems, Germany
| | - Annica Rebbig
- Institute of Immunology, Friedrich-Loeffler-Institut, Institute of Immunology, Federal Research Institute of Animal Health, D-17493 Greifswald, Isle of Riems, Germany
| | - Ralf M Leonhardt
- Department of Immunobiology, Yale University School of Medicine, New Haven, CT 06519, USA
| | - Michael R Knittler
- Institute of Immunology, Friedrich-Loeffler-Institut, Institute of Immunology, Federal Research Institute of Animal Health, D-17493 Greifswald, Isle of Riems, Germany.
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5
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Rufer E, Kägebein D, Leonhardt RM, Knittler MR. Hydrophobic Interactions Are Key To Drive the Association of Tapasin with Peptide Transporter Subunit TAP2. J Immunol 2015; 195:5482-94. [PMID: 26519531 DOI: 10.4049/jimmunol.1500246] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2015] [Accepted: 09/29/2015] [Indexed: 11/19/2022]
Abstract
The transporter associated with Ag processing (TAP) translocates proteasomally derived cytosolic peptides into the endoplasmic reticulum. TAP is a central component of the peptide-loading complex (PLC), to which tapasin (TPN) recruits MHC class I (MHC I) and accessory chaperones. The PLC functions to facilitate and optimize MHC I-mediated Ag presentation. The heterodimeric peptide transporter consists of two homologous subunits, TAP1 and TAP2, each of which contains an N-terminal domain (N-domain) in addition to a conserved transmembrane (TM) core segment. Each N-domain binds to the TM region of a single TPN molecule, which recruits one MHC I molecule to TAP1 and/or TAP2. Although both N-domains act as TPN-docking sites, various studies suggest a functional asymmetry within the PLC resulting in greater significance of the TAP2/TPN interaction for MHC loading. In this study, we demonstrate that the leucine-rich hydrophobic sequence stretches (with the central leucine residues L20 and L66) in the first and second TM helix of TAP2 form a functional unit acting as a docking site for optimal TPN/MHC I recruitment, whereas three distinct highly conserved arginine and/or aspartate residues inside or flanking these TM helices are dispensable. Moreover, we show that the physical interaction between TAP2 and TPN is disrupted by benzene, a compound known to interfere with hydrophobic interactions, such as those between pairing leucine zippers. No such effects were observed for the TAP1/TAP2 interaction or the complex formation between TPN and MHC I. We propose that TAP/TPN complex formation is driven by hydrophobic interactions via leucine zipper-like motifs.
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Affiliation(s)
- Elke Rufer
- Institute of Immunology, Federal Research Institute of Animal Health, Friedrich Loeffler Institute, D-17493 Greifswald-Isle of Riems, Germany
| | - Danny Kägebein
- Institute of Immunology, Federal Research Institute of Animal Health, Friedrich Loeffler Institute, D-17493 Greifswald-Isle of Riems, Germany
| | - Ralf M Leonhardt
- Howard Hughes Medical Institute, New Haven, CT 06519; and Department of Immunobiology, Yale University School of Medicine, New Haven, CT 06519
| | - Michael R Knittler
- Institute of Immunology, Federal Research Institute of Animal Health, Friedrich Loeffler Institute, D-17493 Greifswald-Isle of Riems, Germany;
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6
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Leonhardt RM, Abrahimi P, Mitchell SM, Cresswell P. Three tapasin docking sites in TAP cooperate to facilitate transporter stabilization and heterodimerization. J Immunol 2014; 192:2480-94. [PMID: 24501197 DOI: 10.4049/jimmunol.1302637] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The TAP translocates peptide Ags into the lumen of the endoplasmic reticulum for loading onto MHC class I molecules. MHC class I acquires its peptide cargo in the peptide loading complex, an oligomeric complex that the chaperone tapasin organizes by bridging TAP to MHC class I and recruiting accessory molecules such as ERp57 and calreticulin. Three tapasin binding sites on TAP have been described, two of which are located in the N-terminal domains of TAP1 and TAP2. The third binding site is present in the core transmembrane (TM) domain of TAP1 and is used only by the unassembled subunits. Tapasin is required to promote TAP stability, but through which binding site(s) it is acting is unknown. In particular, the role of tapasin binding to the core TM domain of TAP1 single chains is mysterious because this interaction is lost upon TAP2 association. In this study, we map the respective binding site in TAP1 to the polar face of the amphipathic TM helix TM9 and identify key residues that are essential to establish the interaction. We find that this interaction is dispensable for the peptide transport function but essential to achieve full stability of human TAP1. The interaction is also required for proper heterodimerization of the transporter. Based on similar results obtained using TAP mutants that lack tapasin binding to either N-terminal domain, we conclude that all three tapasin-binding sites in TAP cooperate to achieve high transporter stability and efficient heterodimerization.
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7
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Leonhardt RM, Vigneron N, Hee JS, Graham M, Cresswell P. Critical residues in the PMEL/Pmel17 N-terminus direct the hierarchical assembly of melanosomal fibrils. Mol Biol Cell 2013; 24:964-81. [PMID: 23389629 PMCID: PMC3608505 DOI: 10.1091/mbc.e12-10-0742] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Asp-73, Pro-75, Trp-153, and Trp-160 are essential residues in the PMEL NTR that are required for functional fibril formation. The NTR is necessary in cis to drive the downstream PKD into an amyloid core matrix, which subsequently incorporates and stabilizes the RPT domain–containing, MαC fibril–associated fragment. PMEL (also called Pmel17 or gp100) is a melanocyte/melanoma-specific glycoprotein that plays a critical role in melanosome development by forming a fibrillar amyloid matrix in the organelle for melanin deposition. Although ultimately not a component of mature fibrils, the PMEL N-terminal region (NTR) is essential for their formation. By mutational analysis we establish a high-resolution map of this domain in which sequence elements and functionally critical residues are assigned. We show that the NTR functions in cis to drive the aggregation of the downstream polycystic kidney disease (PKD) domain into a melanosomal core matrix. This is essential to promote in trans the stabilization and terminal proteolytic maturation of the repeat (RPT) domain–containing MαC units, precursors of the second fibrillogenic fragment. We conclude that during melanosome biogenesis the NTR controls the hierarchical assembly of melanosomal fibrils.
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Affiliation(s)
- Ralf M Leonhardt
- Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT, USA.
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8
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Panter MS, Jain A, Leonhardt RM, Ha T, Cresswell P. Dynamics of major histocompatibility complex class I association with the human peptide-loading complex. J Biol Chem 2012; 287:31172-84. [PMID: 22829594 PMCID: PMC3438949 DOI: 10.1074/jbc.m112.387704] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Although the human peptide-loading complex (PLC) is required for optimal major histocompatibility complex class I (MHC I) antigen presentation, its composition is still incompletely understood. The ratio of the transporter associated with antigen processing (TAP) and MHC I to tapasin, which is responsible for MHC I recruitment and peptide binding optimization, is particularly critical for modeling of the PLC. Here, we characterized the stoichiometry of the human PLC using both biophysical and biochemical approaches. By means of single-molecule pulldown (SiMPull), we determined a TAP/tapasin ratio of 1:2, consistent with previous studies of insect-cell microsomes, rat-human chimeric cells, and HeLa cells expressing truncated TAP subunits. We also report that the tapasin/MHC I ratio varies, with the PLC population comprising both 2:1 and 2:2 complexes, based on mutational and co-precipitation studies. The MHC I-saturated PLC may be particularly prevalent among peptide-selective alleles, such as HLA-C4. Additionally, MHC I association with the PLC increases when its peptide supply is reduced by inhibiting the proteasome or by blocking TAP-mediated peptide transport using viral inhibitors. Taken together, our results indicate that the composition of the human PLC varies under normal conditions and dynamically adapts to alterations in peptide supply that may arise during viral infection. These findings improve our understanding of the quality control of MHC I peptide loading and may aid the structural and functional modeling of the human PLC.
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Affiliation(s)
- Michaela S Panter
- Department of Immunobiology, Yale University School of Medicine, New Haven, Connecticut 06520-8011, USA
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9
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Stroobant V, Demotte N, Luiten RM, Leonhardt RM, Cresswell P, Bonehill A, Michaux A, Ma W, Mulder A, Van den Eynde BJ, van der Bruggen P, Vigneron N. Inefficient exogenous loading of a tapasin-dependent peptide onto HLA-B*44:02 can be improved by acid treatment or fixation of target cells. Eur J Immunol 2012; 42:1417-28. [PMID: 22678898 PMCID: PMC3766947 DOI: 10.1002/eji.201141954] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [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: 01/12/2023]
Abstract
Antitumor cytolytic T lymphocytes (CTLs) recognize peptides derived from cellular proteins and presented on MHC class I. One category of peptides recognized by these CTLs is derived from proteins encoded by "cancer-germline" genes, which are specifically expressed in tumors, and therefore represent optimal targets for cancer immunotherapy. Here, we identify an antigenic peptide, which is derived from the MAGE-A1-encoded protein (160-169) and presented to CTLs by HLA-B*44:02. Although this peptide is encoded by MAGE-A1, processed endogenously and presented by tumor cells, the corresponding synthetic peptide is hardly able to sensitize target cells to CTL recognition when pulsed exogenously. Endogenous processing and presentation of this peptide is strictly dependent on the presence of tapasin, which is believed to help peptide loading by stabilizing a peptide-receptive form of HLA-B*44:02. Exogenous loading of the peptide can be dramatically improved by paraformaldehyde fixation of surface molecules or by peptide loading at acidic pH. Either strategy allows efficient exogenous loading of the peptide, presumably by generating or stabilizing a peptide-receptive, empty conformation of the HLA. Altogether, our results indicate a potential drawback of short peptide-based vaccination strategies and offer possible solutions regarding the use of problematic epitopes such as the one described here.
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Affiliation(s)
- Vincent Stroobant
- Ludwig Institute for Cancer Research, Brussels Branch, Brussels, Belgium
- Welbio and de Duve Institute, Université catholique de Louvain, Brussels, Belgium
| | - Nathalie Demotte
- Ludwig Institute for Cancer Research, Brussels Branch, Brussels, Belgium
- Welbio and de Duve Institute, Université catholique de Louvain, Brussels, Belgium
| | | | - Ralf M. Leonhardt
- Yale University School of Medicine, Department of Immunobiology, 300 Cedar Street, P.O. Box 208011, New Haven CT 06520-8011, USA
| | - Peter Cresswell
- Yale University School of Medicine, Department of Immunobiology, 300 Cedar Street, P.O. Box 208011, New Haven CT 06520-8011, USA
- Howard Hughes Medical Institute
| | - Aude Bonehill
- Laboratory of Molecular and Cellular Therapy, Department of Physiology and Immunology, Medical School of Vrije Universiteit Brussel (VUB), Brussels, Belgium
| | - Alexandre Michaux
- Ludwig Institute for Cancer Research, Brussels Branch, Brussels, Belgium
- Welbio and de Duve Institute, Université catholique de Louvain, Brussels, Belgium
| | - Wenbin Ma
- Ludwig Institute for Cancer Research, Brussels Branch, Brussels, Belgium
- Welbio and de Duve Institute, Université catholique de Louvain, Brussels, Belgium
| | - Arend Mulder
- Department of immunohematology, Leiden University Medical Center, 2333 ZA Leiden, The Netherlands
| | - Benoît J. Van den Eynde
- Ludwig Institute for Cancer Research, Brussels Branch, Brussels, Belgium
- Welbio and de Duve Institute, Université catholique de Louvain, Brussels, Belgium
| | - Pierre van der Bruggen
- Ludwig Institute for Cancer Research, Brussels Branch, Brussels, Belgium
- Welbio and de Duve Institute, Université catholique de Louvain, Brussels, Belgium
| | - Nathalie Vigneron
- Ludwig Institute for Cancer Research, Brussels Branch, Brussels, Belgium
- Welbio and de Duve Institute, Université catholique de Louvain, Brussels, Belgium
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10
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Dimberu PM, Leonhardt RM. Cancer immunotherapy takes a multi-faceted approach to kick the immune system into gear. Yale J Biol Med 2011; 84:371-380. [PMID: 22180675 PMCID: PMC3238317] [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] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Cancer accounts for about every fourth death in the United States, with approximately 1,500 people dying each day as a result of this disease. Despite some progress in the last decades, these numbers alone undoubtedly demonstrate the urgent need for new and more efficient treatments. Immunotherapy aims to activate an efficient immune response against tumors or even prevent cancers from occurring in the first place. It is a growing field currently flourishing with several successful trials, some of which have led to the recent approval of new anti-cancer drugs by the Food and Drug Administration (FDA). This review addresses the manifold strategies that immunotherapy has taken in the past and discusses the most recent achievements in the field.
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Affiliation(s)
- Peniel M Dimberu
- Department of Immunobiology, Yale School of Medicine, New Haven, Connecticut 06519, USA.
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11
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Heller C, Weisser T, Mueller-Schickert A, Rufer E, Hoh A, Leonhardt RM, Knittler MR. Identification of key amino acid residues that determine the ability of high risk HPV16-E7 to dysregulate major histocompatibility complex class I expression. J Biol Chem 2011; 286:10983-97. [PMID: 21321113 DOI: 10.1074/jbc.m110.199190] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
High risk human Papillomavirus (HPV) types are the major causative agents of cervical cancer. Reduced expression of major histocompatibility complex class I (MHC I) on HPV-infected cells might be responsible for insufficient T cell response and contribute to HPV-associated malignancy. The viral gene product required for subversion of MHC I synthesis is the E7 oncoprotein. Although it has been suggested that high and low risk HPVs diverge in their ability to dysregulate MHC I expression, it is not known what sequence determinants of HPV-E7 are responsible for this important functional difference. To investigate this, we analyzed the capability to affect MHC I of a set of chimeric E7 variants containing sequence elements from either high risk HPV16 or low risk HPV11. HPV16-E7, but not HPV11-E7, causes significant diminution of mRNA synthesis and surface presentation of MHC I, which depend on histone deacetylase activity. Our experiments demonstrate that the C-terminal region within the zinc finger domain of HPV-E7 is responsible for the contrasting effects of HPV11- and HPV16-E7 on MHC I. By using different loss- and gain-of-function mutants of HPV11- and HPV16-E7, we identify for the first time a residue variation at position 88 that is highly critical for HPV16-E7-mediated suppression of MHC I. Furthermore, our studies suggest that residues at position 78, 80, and 88 build a minimal functional unit within HPV16-E7 required for binding and histone deacetylase recruitment to the MHC I promoter. Taken together, our data provide new insights into how high risk HPV16-E7 dysregulates MHC I for immune evasion.
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Affiliation(s)
- Corina Heller
- Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Institute of Immunology, Tuebingen, Germany
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12
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Abstract
Pmel17 is a melanocyte/melanoma-specific protein that traffics to melanosomes where it forms a fibrillar matrix on which melanin gets deposited. Before being cleaved into smaller fibrillogenic fragments the protein undergoes processing by proprotein convertases, a class of serine proteases that typically recognize the canonical motif RX(R/K)R↓. The current model of Pmel17 maturation states that this processing step occurs in melanosomes, but in light of recent reports this issue has become controversial. We therefore addressed this question by thoroughly assessing the processing kinetics of either wild-type Pmel17 or a secreted soluble Pmel17 derivative. Our results demonstrate clearly that processing of Pmel17 occurs during secretion and that it does not require entry of the protein into the endocytic system. Strikingly, processing proceeds even in the presence of the secretion inhibitor monensin, suggesting that Pmel17 is an exceptionally good substrate. In line with this, we find that newly synthesized surface Pmel17 is already quantitatively cleaved. Moreover, we demonstrate that Pmel17 function is independent of the sequence identity of its unconventional proprotein convertase-cleavage motif that lacks arginine in P4 position. The data alter the current view of Pmel17 maturation and suggest that the multistep processing of Pmel17 begins with an early cleavage during secretion that primes the protein for later functional processing.
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Affiliation(s)
- Ralf M Leonhardt
- Department of Immunobiology, Yale University School of Medicine, New Haven, Connecticut 06519, USA.
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13
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Leonhardt RM, Vigneron N, Rahner C, Van den Eynde BJ, Cresswell P. Endoplasmic reticulum export, subcellular distribution, and fibril formation by Pmel17 require an intact N-terminal domain junction. J Biol Chem 2010; 285:16166-83. [PMID: 20231267 PMCID: PMC2871485 DOI: 10.1074/jbc.m109.097725] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Pmel17 is a melanocyte/melanoma-specific protein that subcellularly localizes to melanosomes, where it forms a fibrillar matrix that serves for the sequestration of potentially toxic reaction intermediates of melanin synthesis and deposition of the pigment. As a key factor in melanosomal biogenesis, understanding intracellular trafficking and processing of Pmel17 is of central importance to comprehend how these organelles are formed, how they mature, and how they function in the cell. Using a series of deletion and missense mutants of Pmel17, we are able to show that the integrity of the junction between the N-terminal region and the polycystic kidney disease-like domain is highly crucial for endoplasmic reticulum export, subcellular targeting, and fibril formation by Pmel17 and thus for establishing functional melanosomes.
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Affiliation(s)
- Ralf M Leonhardt
- Department of Immunobiology, Yale University School of Medicine, New Haven, Connecticut 06519, USA.
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Leonhardt RM, Fiegl D, Rufer E, Karger A, Bettin B, Knittler MR. Post-endoplasmic reticulum rescue of unstable MHC class I requires proprotein convertase PC7. J Immunol 2010; 184:2985-98. [PMID: 20164418 DOI: 10.4049/jimmunol.0900308] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The function of the peptide-loading complex (PLC) is to facilitate loading of MHC class I (MHC I) molecules with antigenic peptides in the endoplasmic reticulum and to drive the selection of these ligands toward a set of high-affinity binders. When the PLC fails to perform properly, as frequently observed in virus-infected or tumor cells, structurally unstable MHC I peptide complexes are generated, which are prone to disintegrate instead of presenting Ags to cytotoxic T cells. In this study we show that a second quality control checkpoint dependent on the serine protease proprotein convertase 7 (PC7) can rescue unstable MHC I, whereas the related convertase furin is completely dispensable. Cells with a malfunctioning PLC and silenced for PC7 have substantially reduced MHC I surface levels caused by high instability and significantly delayed surface accumulation of these molecules. Instead of acquiring stability along the secretory route, MHC I appears to get largely routed to lysosomes for degradation in these cells. Moreover, mass spectrometry analysis provides evidence that lack of PLC quality control and/or loss of PC7 expression alters the MHC I-presented peptide profile. Finally, using exogenously applied peptide precursors, we show that liberation of MHC I epitopes may directly require PC7. We demonstrate for the first time an important function for PC7 in MHC I-mediated Ag presentation.
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Affiliation(s)
- Ralf M Leonhardt
- Department of Immunobiology, Yale University School of Medicine, New Haven, CT 06519, USA
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Vigneron N, Peaper DR, Leonhardt RM, Cresswell P. Functional significance of tapasin membrane association and disulfide linkage to ERp57 in MHC class I presentation. Eur J Immunol 2009; 39:2371-6. [PMID: 19701894 DOI: 10.1002/eji.200939536] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Tapasin is disulfide linked to ERp57 within the peptide loading complex. In cell-free assays, a soluble variant of the tapasin/ERp57 dimer recruits MHC class I molecules and promotes peptide binding to them, whereas soluble tapasin alone does not. Here we show that within cells, tapasin conjugation with ERp57 is as critical as its integration into the membrane for efficient MHC class I assembly, surface expression, and Ag presentation to CD8(+) T cells. Elimination of both of these properties severely compromises tapasin function, in keeping with predictions from in vitro studies.
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Affiliation(s)
- Nathalie Vigneron
- Department of Immunobiology, Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT 06520-8011, USA
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Rufer E, Leonhardt RM, Knittler MR. Molecular Architecture of the TAP-Associated MHC Class I Peptide-Loading Complex. J Immunol 2007; 179:5717-27. [DOI: 10.4049/jimmunol.179.9.5717] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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Leonhardt RM, Lee SJ, Kavathas PB, Cresswell P. Severe tryptophan starvation blocks onset of conventional persistence and reduces reactivation of Chlamydia trachomatis. Infect Immun 2007; 75:5105-17. [PMID: 17724071 PMCID: PMC2168275 DOI: 10.1128/iai.00668-07] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.1] [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: 11/20/2022] Open
Abstract
The intracellular survival of the bacterial pathogen Chlamydia trachomatis depends on protein synthesis by the microbe soon after internalization. Pharmacologic inhibition of bacterial translation inhibits early trafficking of the parasitophorous vacuole (inclusion) to the microtubule-organizing center (MTOC) and promotes its fusion with lysosomes, which is normally blocked by Chlamydia. Depletion of cellular tryptophan pools by gamma interferon-inducible indoleamine-2,3-dioxygenase (IDO) is believed to be the major innate immune mechanism controlling C. trachomatis infection in human cells, an action to which the bacteria can respond by converting into a nonreplicating but highly reactivatable persistent state. However, whether severe IDO-mediated tryptophan starvation can be sufficient to fully arrest the chlamydial life cycle and thereby counteract the onset of persistence is unknown. Here we demonstrate that at low exogenous tryptophan concentrations a substantial fraction of C. trachomatis bacteria fail to traffic to the MTOC or to switch into the conventional persistent state in gamma interferon-induced human cells. The organisms stay scattered in the cell periphery, do not retain infectivity, and display only low transcriptional activity. Importantly, the rate at which these aberrant Chlamydia bacteria become reactivated upon replenishment of cellular tryptophan pools is substantially lower. Thus, severe tryptophan depletion in cells with high IDO activity affects chlamydial development more rigorously than previously described.
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Affiliation(s)
- Ralf M Leonhardt
- Howard Hughes Medical Institute, Yale University School of Medicine, 300 Cedar Street, TAC S669/670, New Haven, CT 06519-1612, USA.
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Keusekotten K, Leonhardt RM, Ehses S, Knittler MR. Biogenesis of functional antigenic peptide transporter TAP requires assembly of pre-existing TAP1 with newly synthesized TAP2. J Biol Chem 2006; 281:17545-51. [PMID: 16624807 DOI: 10.1074/jbc.m602360200] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The transporter associated with antigen processing (TAP) is essential for the delivery of antigenic peptides from the cytosol into the endoplasmic reticulum (ER), where they are loaded onto major histocompatibility complex class I molecules. TAP is a heterodimeric transmembrane protein that comprises the homologous subunits TAP1 and TAP2. As for many other oligomeric protein complexes, which are synthesized in the ER, the process of subunit assembly is essential for TAP to attain a native functional state. Here, we have analyzed the individual requirements of TAP1 and TAP2 for the formation of a functional TAP complex. Unlike TAP1, TAP2 is very unstable when expressed in isolation. We show that heterodimerization of TAP subunits is required for maintaining a stable level of TAP2. By using an in vitro expression system we demonstrate that the biogenesis of functional TAP depends on the assembly of preexisting TAP1 with newly synthesized TAP2, but not vice versa. The pore forming core transmembrane domain (core TMD) of in vitro expressed TAP2 is necessary and sufficient to allow functional complex formation with pre-existing TAP1. We propose that the observed assembly mechanism of TAP protects newly synthesized TAP2 from rapid degradation and controls the number of transport active transporter molecules. Our findings open up new possibilities to investigate functional and structural properties of TAP and provide a powerful model system to address the biosynthetic assembly of oligomeric transmembrane proteins in the ER.
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Affiliation(s)
- Kirstin Keusekotten
- Institute for Genetics, University of Cologne, Zuelpicher Strasse 47, D-50674 Cologne, Germany
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Leonhardt RM, Keusekotten K, Bekpen C, Knittler MR. Critical role for the tapasin-docking site of TAP2 in the functional integrity of the MHC class I-peptide-loading complex. J Immunol 2005; 175:5104-14. [PMID: 16210614 DOI: 10.4049/jimmunol.175.8.5104] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The transporter associated with Ag processing (TAP) translocates antigenic peptides into the endoplasmic reticulum for binding onto MHC class I (MHC I) molecules. Tapasin organizes a peptide-loading complex (PLC) by recruiting MHC I and accessory chaperones to the N-terminal regions (N domains) of the TAP subunits TAP1 and TAP2. To investigate the function of the tapasin-docking sites of TAP in MHC I processing, we expressed N-terminally truncated variants of TAP1 and TAP2 in combination with wild-type chains, as fusion proteins or as single subunits. Strikingly, TAP variants lacking the N domain in TAP2, but not in TAP1, build PLCs that fail to generate stable MHC I-peptide complexes. This correlates with a substantially reduced recruitment of accessory chaperones into the PLC demonstrating their important role in the quality control of MHC I loading. However, stable surface expression of MHC I can be rescued in post-endoplasmic reticulum compartments by a proprotein convertase-dependent mechanism.
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Ehses S, Leonhardt RM, Hansen G, Knittler MR. Functional Role of C-Terminal Sequence Elements in the Transporter Associated with Antigen Processing. J Immunol 2004; 174:328-39. [PMID: 15611256 DOI: 10.4049/jimmunol.174.1.328] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
TAP delivers antigenic peptides into the endoplasmic reticulum (ER) that are subsequently bound by MHC class I molecules. TAP consists of two subunits (TAP1 and TAP2), each with a transmembrane (TMD) and a nucleotide-binding (NBD) domain. The two TAP-NBDs have distinct biochemical properties and control different steps during the peptide translocation process. We noted previously that the nonhomologous C-terminal tails of rat TAP1 and TAP2 determine the distinct functions of TAP-NBD1 and -NBD2. To identify the sequence elements responsible for the asymmetrical NBD function, we constructed chimeric rat TAP variants in which we systematically exchanged sequence regions of different length between the two TAP-NBDs. Our fine-mapping studies demonstrate that a nonhomologous region containing the alpha6/beta10-loop in conjunction with the downstream switch region is directly responsible for the functional separation of the TAP-NBDs. The alpha6/beta10-loop determines the nonsynonymous nucleotide binding of NBD1 and NBD2, whereas the switch region seems to play a critical role in regulating the functional cross-talk between the structural domains of TAP. Based on our findings, we postulate that these two sequence elements build a minimal functional unit that controls the asymmetry of the two TAP-NBDs.
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Affiliation(s)
- Sarah Ehses
- Institute for Genetics, University of Cologne, Zülpicher Strasse 47, 50674 Cologne, Germany
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