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Sarango G, Richetta C, Pereira M, Kumari A, Ghosh M, Bertrand L, Pionneau C, Le Gall M, Grégoire S, Jeger‐Madiot R, Rosoy E, Subra F, Delelis O, Faure M, Esclatine A, Graff‐Dubois S, Stevanović S, Manoury B, Ramirez BC, Moris A. The Autophagy Receptor TAX1BP1 (T6BP) improves antigen presentation by MHC-II molecules. EMBO Rep 2022; 23:e55470. [PMID: 36215666 PMCID: PMC9724678 DOI: 10.15252/embr.202255470] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2022] [Revised: 09/16/2022] [Accepted: 09/23/2022] [Indexed: 12/12/2022] Open
Abstract
CD4+ T lymphocytes play a major role in the establishment and maintenance of immunity. They are activated by antigenic peptides derived from extracellular or newly synthesized (endogenous) proteins presented by the MHC-II molecules. The pathways leading to endogenous MHC-II presentation remain poorly characterized. We demonstrate here that the autophagy receptor, T6BP, influences both autophagy-dependent and -independent endogenous presentation of HIV- and HCMV-derived peptides. By studying the immunopeptidome of MHC-II molecules, we show that T6BP affects both the quantity and quality of peptides presented. T6BP silencing induces the mislocalization of the MHC-II-loading compartments and rapid degradation of the invariant chain (CD74) without altering the expression and internalization kinetics of MHC-II molecules. Defining the interactome of T6BP, we identify calnexin as a T6BP partner. We show that the calnexin cytosolic tail is required for this interaction. Remarkably, calnexin silencing replicates the functional consequences of T6BP silencing: decreased CD4+ T cell activation and exacerbated CD74 degradation. Altogether, we unravel T6BP as a key player of the MHC-II-restricted endogenous presentation pathway, and we propose one potential mechanism of action.
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Affiliation(s)
- Gabriela Sarango
- Université Paris‐Saclay, CEA, CNRSInstitute for Integrative Biology of the Cell (I2BC)Gif‐sur‐YvetteFrance,Sorbonne UniversitéINSERM, CNRS, Center for Immunology and Microbial Infections (CIMI‐Paris)ParisFrance
| | - Clémence Richetta
- Sorbonne UniversitéINSERM, CNRS, Center for Immunology and Microbial Infections (CIMI‐Paris)ParisFrance,LBPA, ENS‐Paris Saclay, CNRS UMR8113Université Paris SaclayGif‐sur‐YvetteFrance
| | - Mathias Pereira
- Université Paris‐Saclay, CEA, CNRSInstitute for Integrative Biology of the Cell (I2BC)Gif‐sur‐YvetteFrance,Sorbonne UniversitéINSERM, CNRS, Center for Immunology and Microbial Infections (CIMI‐Paris)ParisFrance
| | - Anita Kumari
- Université Paris‐Saclay, CEA, CNRSInstitute for Integrative Biology of the Cell (I2BC)Gif‐sur‐YvetteFrance,Sorbonne UniversitéINSERM, CNRS, Center for Immunology and Microbial Infections (CIMI‐Paris)ParisFrance
| | - Michael Ghosh
- Department of Immunology, Institute for Cell BiologyUniversity of TübingenTübingenGermany
| | - Lisa Bertrand
- Université Paris‐Saclay, CEA, CNRSInstitute for Integrative Biology of the Cell (I2BC)Gif‐sur‐YvetteFrance,Sorbonne UniversitéINSERM, CNRS, Center for Immunology and Microbial Infections (CIMI‐Paris)ParisFrance
| | - Cédric Pionneau
- Sorbonne UniversitéINSERM, UMS Production et Analyse de Données en Sciences de la vie et en Santé, PASS, Plateforme Post‐génomique de la Pitié SalpêtrièreParisFrance
| | - Morgane Le Gall
- 3P5 proteom'IC facilityUniversité de Paris, Institut Cochin, INSERM U1016, CNRS‐UMR 8104ParisFrance
| | - Sylvie Grégoire
- Université Paris‐Saclay, CEA, CNRSInstitute for Integrative Biology of the Cell (I2BC)Gif‐sur‐YvetteFrance,Sorbonne UniversitéINSERM, CNRS, Center for Immunology and Microbial Infections (CIMI‐Paris)ParisFrance
| | - Raphaël Jeger‐Madiot
- Sorbonne UniversitéINSERM, CNRS, Center for Immunology and Microbial Infections (CIMI‐Paris)ParisFrance,Present address:
Sorbonne Université, INSERM U959, Immunology‐Immunopathology‐Immunotherapy (i3)ParisFrance
| | - Elina Rosoy
- Sorbonne UniversitéINSERM, CNRS, Center for Immunology and Microbial Infections (CIMI‐Paris)ParisFrance
| | - Frédéric Subra
- LBPA, ENS‐Paris Saclay, CNRS UMR8113Université Paris SaclayGif‐sur‐YvetteFrance
| | - Olivier Delelis
- LBPA, ENS‐Paris Saclay, CNRS UMR8113Université Paris SaclayGif‐sur‐YvetteFrance
| | - Mathias Faure
- CIRI, Centre International de Recherche en Infectiologie, Université de Lyon, Inserm U1111Université Claude Bernard Lyon 1, CNRS, UMR5308, ENS de LyonLyonFrance,Equipe Labellisée par la Fondation pour la Recherche Médicale, FRM
| | - Audrey Esclatine
- Université Paris‐Saclay, CEA, CNRSInstitute for Integrative Biology of the Cell (I2BC)Gif‐sur‐YvetteFrance
| | - Stéphanie Graff‐Dubois
- Sorbonne UniversitéINSERM, CNRS, Center for Immunology and Microbial Infections (CIMI‐Paris)ParisFrance,Present address:
Sorbonne Université, INSERM U959, Immunology‐Immunopathology‐Immunotherapy (i3)ParisFrance
| | - Stefan Stevanović
- Department of Immunology, Institute for Cell BiologyUniversity of TübingenTübingenGermany
| | - Bénédicte Manoury
- Institut Necker Enfants Malades, INSERM U1151‐CNRS UMR 8253, Faculté de médecine NeckerUniversité de ParisParisFrance
| | - Bertha Cecilia Ramirez
- Université Paris‐Saclay, CEA, CNRSInstitute for Integrative Biology of the Cell (I2BC)Gif‐sur‐YvetteFrance,Sorbonne UniversitéINSERM, CNRS, Center for Immunology and Microbial Infections (CIMI‐Paris)ParisFrance
| | - Arnaud Moris
- Université Paris‐Saclay, CEA, CNRSInstitute for Integrative Biology of the Cell (I2BC)Gif‐sur‐YvetteFrance,Sorbonne UniversitéINSERM, CNRS, Center for Immunology and Microbial Infections (CIMI‐Paris)ParisFrance
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Cloutier M, Fortin JS, Thibodeau J. The transmembrane domain and luminal C-terminal region independently support invariant chain trimerization and assembly with MHCII into nonamers. BMC Immunol 2021; 22:56. [PMID: 34384367 PMCID: PMC8362237 DOI: 10.1186/s12865-021-00444-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2020] [Accepted: 07/20/2021] [Indexed: 05/31/2023] Open
Abstract
Background Invariant chain (CD74, Ii) is a multifunctional protein expressed in antigen presenting cells. It assists the ER exit of various cargos and serves as a receptor for the macrophage migration inhibitory factor. The newly translated Ii chains trimerize, a structural feature that is not readily understood in the context of its MHCII chaperoning function. Two segments of Ii, the luminal C-terminal region (TRIM) and the transmembrane domain (TM), have been shown to participate in the trimerization process but their relative importance and impact on the assembly with MHCII molecules remains debated. Here, we addressed the requirement of these domains in the trimerization of human Ii as well as in the oligomerization with MHCII molecules. We used site-directed mutagenesis to generate series of Ii and DR mutants. These were transiently transfected in HEK293T cells to test their cell surface expression and analyse their interactions by co-immunoprecipitations. Results Our results showed that the TRIM domain is not essential for Ii trimerization nor for intracellular trafficking with MHCII molecules. We also gathered evidence that in the absence of TM, TRIM allows the formation of multi-subunit complexes with HLA-DR. Similarly, in the absence of TRIM, Ii can assemble into high-order structures with MHCII molecules. Conclusions Altogether, our data show that trimerization of Ii through either TM or TRIM sustains nonameric complex formation with MHCII molecules. Supplementary Information The online version contains supplementary material available at 10.1186/s12865-021-00444-6.
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Affiliation(s)
- Maryse Cloutier
- Laboratoire d'Immunologie Moléculaire, Département de Microbiologie, Infectiologie et Immunologie, Faculté de Médecine, Université de Montréal, Succ Centre-Ville, CP 6128, Montréal, QC, H3C 3J7, Canada
| | - Jean-Simon Fortin
- Laboratoire d'Immunologie Moléculaire, Département de Microbiologie, Infectiologie et Immunologie, Faculté de Médecine, Université de Montréal, Succ Centre-Ville, CP 6128, Montréal, QC, H3C 3J7, Canada
| | - Jacques Thibodeau
- Laboratoire d'Immunologie Moléculaire, Département de Microbiologie, Infectiologie et Immunologie, Faculté de Médecine, Université de Montréal, Succ Centre-Ville, CP 6128, Montréal, QC, H3C 3J7, Canada.
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Borghese F, Clanchy FIL. CD74: an emerging opportunity as a therapeutic target in cancer and autoimmune disease. Expert Opin Ther Targets 2011; 15:237-51. [PMID: 21208136 DOI: 10.1517/14728222.2011.550879] [Citation(s) in RCA: 109] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
INTRODUCTION CD74, also known as the invariant chain, participates in several key processes of the immune system, including antigen presentation, B-cell differentiation and inflammatory signaling. Despite being described more than 3 decades ago, new functions and novel interactions for this evolutionarily conserved molecule are still being unraveled. As a participant in several immunological processes and an indicator of disease in some conditions, it has potential as a therapeutic target. AREAS COVERED The relationship between the structure of CD74 variants and their physiological functions is detailed in this review. The function of CD74 in several cell lineages is examined with a focus on the interactions with cathepsins and, in an inflammatory milieu, the pro-inflammatory cytokine macrophage migratory inhibitory factor. The role of CD74 signaling in inflammatory and carcinogenic processes is outlined as is the use of CD74 as a therapeutic target (in cancer) and tool (as a vaccine). EXPERT OPINION CD74 has several roles within the cell and throughout the immune system. Most prominent amongst these are the complex relationships with MIF and cathepsins. Modulation of CD74 function shows promise for the effective amelioration of disease.
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Affiliation(s)
- Federica Borghese
- Sapienza University of Rome, Department of Clinical Medicine, Clinical Immunology Unit, Umberto I Policlinico di Roma, 155 Viale del Policlinico, Rome, IT 00161
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Ye L, Liu X, Rout SN, Li Z, Yan Y, Lu L, Kamala T, Nanda NK, Song W, Samal SK, Zhu X. The MHC class II-associated invariant chain interacts with the neonatal Fc gamma receptor and modulates its trafficking to endosomal/lysosomal compartments. THE JOURNAL OF IMMUNOLOGY 2008; 181:2572-85. [PMID: 18684948 DOI: 10.4049/jimmunol.181.4.2572] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The neonatal Fc receptor for IgG (FcRn) transfers maternal IgG to the offspring and protects IgG from degradation. The FcRn resides in an acidic intracellular compartment, allowing it to bind IgG. In this study, we found the association of FcRn and invariant chain (Ii). The interaction was initiated within the endoplasmic reticulum by Ii binding to either the FcRn H chain alone or FcRn H chain-beta(2)-microglobulin complex and appeared to be maintained throughout the endocytic pathway. The CLIP in Ii was not required for FcRn-Ii association. The interaction was also detected in IFN-gamma-treated THP-1, epithelial and endothelial cells, and immature mouse DCs. A truncated FcRn without the cytoplasmic tail was unable to traffic to early endosomes; however, its location in early endosomes was restored by Ii expression. FcRn was also detected in the late endosome/lysosome only in the presence of Ii or on exposure to IFN-gamma. In immature human or mouse DCs, FcRn was barely detected in the late endosome/lysosome in the absence of Ii. Furthermore, the cytoplasmic tail of Ii conferred tailless FcRn to route to both the early endosome and late endosome/lysosome in a hybrid molecule. Because the FcRn is expressed in macrophages and DCs or epithelial and endothelial cells where Ii is induced under inflammation and infection, these results reveal the complexity of FcRn trafficking in which Ii is capable of expanding the boundary of FcRn trafficking. Taken together, the intracellular trafficking of FcRn is regulated by its intrinsic sorting information and/or an interaction with Ii chain.
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Affiliation(s)
- Lilin Ye
- Laboratory of Immunology, Virginia-Maryland Regional College of Veterinary Medicine, College Park, MD 20742, USA
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5
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Okiyoneda T, Kono T, Niibori A, Harada K, Kusuhara H, Takada T, Shuto T, Suico MA, Sugiyama Y, Kai H. Calreticulin facilitates the cell surface expression of ABCG5/G8. Biochem Biophys Res Commun 2006; 347:67-75. [PMID: 16806071 DOI: 10.1016/j.bbrc.2006.06.032] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2006] [Accepted: 06/08/2006] [Indexed: 11/18/2022]
Abstract
ATP-binding cassette (ABC) G5 (G5) and ABCG8 (G8) heterodimerize and function as sterol transporter that promote biliary excretion of neutral sterols. Both G5 and G8 interact with a lectin-like chaperone, calnexin (CNX), in the endoplasmic reticulum (ER) but the significance of this interaction remains unclear. Here, we show that not only CNX, but also its homologue calreticulin (CRT), is involved in the biosynthesis of G5/G8 sterol transporter. Both CNX and CRT interacted with immature forms of G5 and G8, and stimulated their productive folding by inhibiting their degradation. Interestingly, CRT predominantly enhanced the cell surface expression of mature G5/G8 whereas CNX did not have a similar effect. Inhibitors of N-glycan processing indicated that quality control of G5 and G8 might be differentially regulated in the ER. These findings clarify the role of CNX and CRT in the biosynthesis and quality control of G5/G8 sterol transporter.
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Affiliation(s)
- Tsukasa Okiyoneda
- Department of Molecular Medicine, Faculty of Medical and Pharmaceutical Sciences, Kumamoto University, Japan
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6
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Lee JA, Sinkovits RS, Mock D, Rab EL, Cai J, Yang P, Saunders B, Hsueh RC, Choi S, Subramaniam S, Scheuermann RH. Components of the antigen processing and presentation pathway revealed by gene expression microarray analysis following B cell antigen receptor (BCR) stimulation. BMC Bioinformatics 2006; 7:237. [PMID: 16670020 PMCID: PMC1479375 DOI: 10.1186/1471-2105-7-237] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2005] [Accepted: 05/02/2006] [Indexed: 12/28/2022] Open
Abstract
Background Activation of naïve B lymphocytes by extracellular ligands, e.g. antigen, lipopolysaccharide (LPS) and CD40 ligand, induces a combination of common and ligand-specific phenotypic changes through complex signal transduction pathways. For example, although all three of these ligands induce proliferation, only stimulation through the B cell antigen receptor (BCR) induces apoptosis in resting splenic B cells. In order to define the common and unique biological responses to ligand stimulation, we compared the gene expression changes induced in normal primary B cells by a panel of ligands using cDNA microarrays and a statistical approach, CLASSIFI (Cluster Assignment for Biological Inference), which identifies significant co-clustering of genes with similar Gene Ontology™ annotation. Results CLASSIFI analysis revealed an overrepresentation of genes involved in ion and vesicle transport, including multiple components of the proton pump, in the BCR-specific gene cluster, suggesting that activation of antigen processing and presentation pathways is a major biological response to antigen receptor stimulation. Proton pump components that were not included in the initial microarray data set were also upregulated in response to BCR stimulation in follow up experiments. MHC Class II expression was found to be maintained specifically in response to BCR stimulation. Furthermore, ligand-specific internalization of the BCR, a first step in B cell antigen processing and presentation, was demonstrated. Conclusion These observations provide experimental validation of the computational approach implemented in CLASSIFI, demonstrating that CLASSIFI-based gene expression cluster analysis is an effective data mining tool to identify biological processes that correlate with the experimental conditional variables. Furthermore, this analysis has identified at least thirty-eight candidate components of the B cell antigen processing and presentation pathway and sets the stage for future studies focused on a better understanding of the components involved in and unique to B cell antigen processing and presentation.
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Affiliation(s)
- Jamie A Lee
- Department of Pathology, Laboratory of Molecular Pathology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
| | - Robert S Sinkovits
- San Diego Supercomputer Center, University of California, San Diego, California 92122, USA
| | - Dennis Mock
- San Diego Supercomputer Center, University of California, San Diego, California 92122, USA
| | - Eva L Rab
- Department of Pathology, Laboratory of Molecular Pathology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
| | - Jennifer Cai
- Department of Pathology, Laboratory of Molecular Pathology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
| | - Peng Yang
- Department of Pathology, Laboratory of Molecular Pathology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
| | - Brian Saunders
- San Diego Supercomputer Center, University of California, San Diego, California 92122, USA
| | - Robert C Hsueh
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
| | - Sangdun Choi
- Division of Biology, California Institute of Technology, Pasadena, CA, USA
| | - Shankar Subramaniam
- San Diego Supercomputer Center, University of California, San Diego, California 92122, USA
- Department of Bioengineering, University of California, San Diego, California 92122, USA
| | - Richard H Scheuermann
- Department of Pathology, Laboratory of Molecular Pathology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
- San Diego Supercomputer Center, University of California, San Diego, California 92122, USA
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Thammavongsa V, Mancino L, Raghavan M. Polypeptide Substrate Recognition by Calnexin Requires Specific Conformations of the Calnexin Protein. J Biol Chem 2005; 280:33497-505. [PMID: 16061483 DOI: 10.1074/jbc.m503648200] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Calnexin is an endoplasmic reticulum chaperone that binds to substrates containing monoglucosylated oligosaccharides. Whether calnexin can also directly recognize polypeptide components of substrates is controversial. We found that calnexin displayed significant conformational lability for a chaperone and that heat treatment and calcium depletion induced the formation of calnexin dimers and higher order oligomers. These conditions enhanced the chaperone activity of calnexin toward glycosylated and non-glycosylated major histocompatibility complex (MHC) class I heavy chains, and enhanced calnexin binding to MHC class I heavy chains. In contrast to these observations, calnexin binding to oligosaccharide substrates has been reported to be impaired under calcium-depleting conditions. Calnexin dimers were induced in HeLa cells upon heat shock and under calcium-depleting conditions, and heat shock enhanced calnexin binding to MHC class I heavy chains in HeLa cells. Virus-induced endoplasmic reticulum stress also resulted in the appearance of calnexin dimers. Tunicamycin treatment of HeLa cells induced a slow accumulation of calnexin dimers, the appearance of which correlated with enhanced calnexin binding to deglycosylated MHC class I heavy chains. In vitro, the presence of calnexin-specific oligosaccharides inhibited the formation of calnexin dimers and higher order structures. Together, these data indicate that polypeptide binding is favored by conditions that induce partial unfolding of calnexin monomers, whereas oligosaccharide binding is favored by conditions that enhance the structural stability (folding) of calnexin monomers. Conditions that induce the calnexin "polypeptide-binding" conformation also induce self-association of calnexin if the concentration is sufficiently high; however, calnexin dimerization/oligomerization per se is not essential for polypeptide substrate binding.
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Affiliation(s)
- Vilasack Thammavongsa
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan 48109-0620, USA
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8
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Pu Z, Lovitch SB, Bikoff EK, Unanue ER. T Cells Distinguish MHC-Peptide Complexes Formed in Separate Vesicles and Edited by H2-DM. Immunity 2004; 20:467-76. [PMID: 15084275 DOI: 10.1016/s1074-7613(04)00073-1] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2003] [Revised: 02/04/2004] [Accepted: 03/01/2004] [Indexed: 11/24/2022]
Abstract
The peptide spanning residues 48-61 of hen egg white lysozyme (HEL) presented by I-A(k) gives rise to two T cell populations, referred to as type A and B, that distinguish the complex generated intracellularly upon processing of HEL from that formed with exogenous peptide. Here, we ascribe this difference to recognition of distinct conformers of the complex and show that formation of the two complexes results from antigen processing in different intracellular compartments and is dependent upon H2-DM. While the type A complex preferentially formed in a lysosome-like late vesicle, the type B complex failed to form in this compartment; this distinction was abolished in antigen-presenting cells lacking DM. Experiments in vitro indicated that H2-DM acts directly on the complex to eliminate the type B conformation. We conclude that different antigen-processing pathways generate distinct MHC-peptide conformers, priming T cells with distinct specificity that may play unique roles in immunity.
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Affiliation(s)
- Zheng Pu
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63110, USA
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9
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Trombetta ES, Parodi AJ. N-glycan processing and glycoprotein folding. ADVANCES IN PROTEIN CHEMISTRY 2002; 59:303-44. [PMID: 11868276 DOI: 10.1016/s0065-3233(01)59010-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
- E S Trombetta
- Instituto de Investigaciones Biotecnológicas, Universidad de San Martín, (1650) San Martin, Pcia. de Buenos Aires, Argentina
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10
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Neumann J, Schach N, Koch N. Glycosylation signals that separate the trimerization from the mhc class II-binding domain control intracellular degradation of invariant chain. J Biol Chem 2001; 276:13469-75. [PMID: 11278714 DOI: 10.1074/jbc.m010629200] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Invariant chain (Ii) serves as a chaperone for folding and intracellular transport of major histocompatibility complex class II (MHCII) molecules. Early in biosynthesis, Ii associates with MHCII molecules and directs their intracellular transport to endocytic compartments where vesicular proteinases sequentially release Ii from the MHCII heterodimer. The detachment of Ii makes the MHCII groove susceptible for binding of antigenic peptides. We investigated the role of N-linked glycosylation in the controlled intracellular degradation of Ii. Motifs for asparagine-linked glycosylation were altered, and mutated Ii (IiNmut) was transiently expressed in COS cells. The half-life of IiNmut was strongly reduced compared with wild-type Ii although the sensitivity of the N glycan-free polypeptide to in vitro proteinase digestion was not substantially increased. Inhibition of vesicular proteinases revealed endosomal degradation of IiNmut. Intracellular proteolysis of IiNmut is substantially impaired by serine proteinase inhibitors. Thus, a considerable amount of IiNmut is degraded in nonacidic intracellular compartments. The data suggest that N-linked glycosylation of Ii hinders premature proteolysis in nonacidic vesicles resulting in Ii degradation in acidic MHC class II-processing compartments.
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Affiliation(s)
- J Neumann
- Section of Immunobiology, University of Bonn, 53117 Bonn, Römerstrasse 164, Germany
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11
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Abstract
Our understanding of eukaryotic protein folding in the endoplasmic reticulum has increased enormously over the last 5 years. In this review, we summarize some of the major research themes that have captivated researchers in this field during the last years of the 20th century. We follow the path of a typical protein as it emerges from the ribosome and enters the reticular environment. While many of these events are shared between different polypeptide chains, we highlight some of the numerous differences between proteins, between cell types, and between the chaperones utilized by different ER glycoproteins. Finally, we consider the likely advances in this field as the new century unfolds and we address the prospect of a unified understanding of how protein folding, degradation, and translation are coordinated within a cell.
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Affiliation(s)
- A M Benham
- Department of Bio-Organic Chemistry, Utrecht University, The Netherlands
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12
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Affiliation(s)
- J Pieters
- Basel Institute for Immunology, Switzerland
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13
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Tokunaga F, Brostrom C, Koide T, Arvan P. Endoplasmic reticulum (ER)-associated degradation of misfolded N-linked glycoproteins is suppressed upon inhibition of ER mannosidase I. J Biol Chem 2000; 275:40757-64. [PMID: 10984471 DOI: 10.1074/jbc.m001073200] [Citation(s) in RCA: 99] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
To examine the role of early carbohydrate recognition/trimming reactions in targeting endoplasmic reticulum (ER)-retained, misfolded glycoproteins for ER-associated degradation (ERAD), we have stably expressed the cog thyroglobulin (Tg) mutant cDNA in Chinese hamster ovary cells. We found that inhibitors of ER mannosidase I (but not other glycosidases) acutely suppressed Cog Tg degradation and also perturbed the ERAD process for Tg reduced with dithiothreitol as well as for gamma-carboxylation-deficient protein C expressed in warfarin-treated baby hamster kidney cells. Kifunensine inhibition of ER mannosidase I also suppressed ERAD in castanospermine-treated cells; thus, suppression of ERAD does not require lectin-like binding of ER chaperones calnexin and calreticulin to monoglucosylated oligosaccharides. Notably, the undegraded protein fraction remained completely microsome-associated. In pulse-chase studies, kifunensine-sensitive degradation was still inhibitable even 1 h after Tg synthesis. Intriguingly, chronic treatment with kifunensine caused a 3-fold accumulation of Cog Tg in Chinese hamster ovary cells and did not lead to significant induction of the ER unfolded protein response. We hypothesize that, in a manner not requiring lectin-like activity of calnexin/calreticulin, the recognition or processing of a specific branched N-linked mannose structure enhances the efficiency of glycoprotein retrotranslocation from the ER lumen.
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Affiliation(s)
- F Tokunaga
- Department of Life Science, Himeji Institute of Technology, Harima Science Garden City, Hyogo 678-1277, Japan
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14
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Chillarón J, Adán C, Haas IG. Mannosidase action, independent of glucose trimming, is essential for proteasome-mediated degradation of unassembled glycosylated Ig light chains. Biol Chem 2000; 381:1155-64. [PMID: 11209750 DOI: 10.1515/bc.2000.143] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
In order to study the role of N-glycans in the ER-associated degradation of unassembled immunoglobulin light (Ig L) chains, we introduced N-glycan acceptor sites into the variable domain of the murine Ig L chain kappaNS1, which is unfolded in unassembled molecules. We investigated the fate of kappaNS1 glycosylated at position 70 (K70) and of a double mutant (kappa18/70) in stably transfected HeLa cells. Degradation of both chains was impaired by lactacystin, a specific inhibitor of the proteasome. The mannosidase inhibitor dMNJ also blocked degradation in a step preceding proteasome action, as did two protein synthesis inhibitors, cycloheximide and puromycin. In contrast, ER glucosidase inhibitors dramatically accelerated the degradation of the chains when added either pre- or posttranslationally. The accelerated degradation was sensitive to lactacystin, dMNJ and cycloheximide, too. None of these drugs, except lactacystin, affected the degradation of unglycosylated kappaNS1 chains. We conclude that ER mannosidases and proteasome activities, but not glucose trimming (and therefore, most likely not the calnexin/calreticulin UDP:glucose glycoprotein glucosyl transferase cycle), are essential for ER-associated degradation (ERAD) of soluble glycoproteins. A role for a short-lived protein, acting before or simultaneously to ER mannosidases, is suggested.
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15
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Ayalon-Soffer M, Shenkman M, Lederkremer GZ. Differential role of mannose and glucose trimming in the ER degradation of asialoglycoprotein receptor subunits. J Cell Sci 1999; 112 ( Pt 19):3309-18. [PMID: 10504336 DOI: 10.1242/jcs.112.19.3309] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
To gain insight into how sugar chain processing events modulate endoplasmic reticulum (ER)/proteasomal degradation we looked at human asialoglycoprotein receptor polypeptides H2a and H2b, variants which differ only by an extra pentapeptide (EGHRG) present in H2a. Membrane-bound H2a is a precursor of a soluble secreted form while H2b reaches the plasma membrane. Uncleaved precursor H2a molecules are completely retained in the ER and degraded as well as a portion of H2b. Inhibition of N-linked sugar chain mannose trimming stabilized both variants. In contrast, inhibition of glucose trimming with castanospermine greatly enhanced the degradation rate of H2a but not that of H2b. We studied a possible involvement of the ER chaperone calnexin, as inhibitors of glucose trimming are known to prevent calnexin binding. Incubation of cells with low concentrations of castanospermine (30 microg/ml) did not interfere with calnexin binding to H2a while causing the same accelerated degradation as high concentrations (>100 microg/ml) which did inhibit the association. Castanospermine treatment after calnexin binding blocked the dissociation of the chaperone but still caused accelerated degradation. The increased degradation could be blocked by a specific proteasome inhibitor, ZL(3)VS. Our results suggest that extensive mannose trimming or retention of glucose residues due to lack of glucose trimming are signals for ER/proteasomal degradation independent of interaction with calnexin.
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Affiliation(s)
- M Ayalon-Soffer
- Department of Cell Research and Immunology, George Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel, 69978
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16
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Ashman JB, Miller J. A Role for the Transmembrane Domain in the Trimerization of the MHC Class II-Associated Invariant Chain. THE JOURNAL OF IMMUNOLOGY 1999. [DOI: 10.4049/jimmunol.163.5.2704] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Abstract
MHC class II and invariant chain (Ii) associate early in biosynthesis to form a nonameric complex. Ii first assembles into a trimer and then associates with three class II αβ heterodimers. Although the membrane-proximal region of the Ii luminal domain is structurally disordered, the C-terminal segment of the luminal domain is largely α-helical and contains a major interaction site for the Ii trimer. In this study, we show that the Ii transmembrane domain plays an important role in the formation of Ii trimers. The Ii transmembrane domain contains an unusual patch of hydrophilic residues near the luminal interface. Substitution of these polar residues with nonpolar amino acids resulted in a decrease in the efficiency of Ii trimerization and subsequent class II association. Moreover, N-terminal fragments of Ii were found to trimerize independently of the luminal α-helical domain. Progressive C-terminal truncations mapped a homotypic association site to the first 80 aa of Ii. Together, these results implicate the Ii transmembrane domain as a site of trimer interaction that can play an important role in the initiation of trimer formation.
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Affiliation(s)
| | - Jim Miller
- *Committee on Immunology and
- †Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637
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17
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Keller SH, Lindstrom J, Taylor P. Inhibition of glucose trimming with castanospermine reduces calnexin association and promotes proteasome degradation of the alpha-subunit of the nicotinic acetylcholine receptor. J Biol Chem 1998; 273:17064-72. [PMID: 9642271 DOI: 10.1074/jbc.273.27.17064] [Citation(s) in RCA: 84] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
To identify factors involved in the expression of ligand-gated ion channels, we expressed nicotinic acetylcholine receptors in HEK cells to characterize roles for oligosaccharide trimming, calnexin association, and targeting to the proteasome. The homologous subunits of the acetylcholine receptor traverse the membrane four times, contain at least one oligosaccharide, and are retained in the endoplasmic reticulum until completely assembled into the circular arrangement of subunits of delta-alpha-gamma-alpha-beta to enclose the ion channel. We previously demonstrated that calnexin is associated with unassembled subunits of the receptor, but appears to dissociate when subunits are assembled in various combinations. We used the glucosidase inhibitor castanospermine to block oligosaccharide processing, and thereby inhibit calnexin's interaction with the oligosaccharides in the receptor subunits. Castanospermine treatment reduces the association of calnexin with the alpha-subunit of the receptor, and diminishes the intracellular accumulation of unassembled receptor subunit protein. However, treatment with castanospermine does not appear to alter subunit folding or assembly. In contrast, co-treatment with proteasome inhibitors and castanospermine enhances the accumulation of polyubiquitin-conjugated alpha-subunits, and generally reverses the castanospermine induced loss of alpha-subunit protein. Co-transfection of cDNAs encoding the alpha- and delta-subunits, which leads to the expression of assembled alpha- and delta- subunits, also inhibits the loss of alpha-subunits expressed in the presence of castanospermine. Taken together, these observations indicate that calnexin association reduces the degradation of unassembled receptor subunits in the ubiquitin-proteasome pathway.
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Affiliation(s)
- S H Keller
- Department of Pharmacology, University of California, San Diego, La Jolla, California 92093-0636, USA
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18
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Chen Y, Le Cahérec F, Chuck SL. Calnexin and other factors that alter translocation affect the rapid binding of ubiquitin to apoB in the Sec61 complex. J Biol Chem 1998; 273:11887-94. [PMID: 9565615 DOI: 10.1074/jbc.273.19.11887] [Citation(s) in RCA: 81] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Several secretory proteins, including apolipoprotein B, have been shown to undergo degradation by proteasomes. We found that the rapid degradation of nascent apolipoprotein B in HepG2 cells was diminished but not abolished by the addition of any of three different inhibitors of proteasomes. Ubiquitin is conjugated to apolipoprotein B that is not assembled with sufficient lipids either during or soon after synthesis. In addition, we found that apolipoprotein B that has entered the endoplasmic reticulum sufficiently to become glycosylated can be degraded by proteasomes. Furthermore, we detected ubiquitin-apolipoprotein B that is associated with the Sec61 complex, the major constituent of the translocational channel. Treatment of cells with monomethylethanolamine or dithiothreitol decreased the translocation of apolipoprotein B and increased the proportion of ubiquitin-conjugated molecules associated with Sec61. Conversely, treatment of cells with oleic acid, which increased the proportion of translocated apolipoprotein B, decreased the amount of ubiquitin-apolipoprotein B in the Sec61 complex. Finally, we found that inhibition of the interaction between calnexin and apolipoprotein B decreases the translocation of apolipoprotein B, increases the ubiquitin-apolipoprotein B in the Sec61 complex, and increases the proteasomal degradation of glycosylated apolipoprotein B. Thus, ubiquitin can be attached to unassembled apolipoprotein B in the Sec61 complex, and this process is affected by factors including calnexin that alter the translocation of apolipoprotein B.
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Affiliation(s)
- Y Chen
- Molecular Medicine Unit, Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts 02215, USA
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19
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Zhang Q, Salter RD. Distinct Patterns of Folding and Interactions with Calnexin and Calreticulin in Human Class I MHC Proteins with Altered N-Glycosylation. THE JOURNAL OF IMMUNOLOGY 1998. [DOI: 10.4049/jimmunol.160.2.831] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Abstract
Calnexin is a lectin-like chaperone that binds to class I MHC molecules soon after their synthesis, retaining unassembled heavy chains and also assisting their folding. Following association with β2-microglobulin (β2m) in the endoplasmic reticulum, a large proportion of human class I molecules release from calnexin, whereas mouse class I molecules do not. We asked whether addition of a second N-glycan to the human class I molecule A*0201 at position 176, a site present in mouse, would affect its binding to calnexin. The 176dg mutant with N-glycans at positions 86 and 176, when transfected into CIR cells, demonstrated increased binding to calnexin, detectable both before and after association with β2m, and reduced interaction with calreticulin and TAP relative to wild-type protein bearing a single N-glycan at position 86. Cell surface levels of the mutant were decreased only slightly relative to the wild type, suggesting that the protein is not misfolded or grossly altered structurally. A subpopulation of mutant molecules was retained in the endoplasmic reticulum, and surprisingly, these molecules reacted with w6/32, which recognizes an epitope present on transport-competent class I HLA complexes. Transfection into Daudi cells demonstrated that 176dg reacts with w6/32 in the absence of β2m, suggesting that the Ab epitope can be induced by binding of calnexin. These data may explain previously noted differences between mouse and human class I MHC proteins and demonstrate that the location of N-oligosaccharides within proteins can influence their folding and interactions with chaperones such as calnexin and calreticulin.
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Affiliation(s)
- Qing Zhang
- Department of Pathology and University of Pittsburgh Cancer Institute, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213
| | - Russell D. Salter
- Department of Pathology and University of Pittsburgh Cancer Institute, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213
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20
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Chang W, Gelman MS, Prives JM. Calnexin-dependent enhancement of nicotinic acetylcholine receptor assembly and surface expression. J Biol Chem 1997; 272:28925-32. [PMID: 9360963 DOI: 10.1074/jbc.272.46.28925] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The muscle-type nicotinic acetylcholine receptor (AChR)2 is a pentameric membrane ion channel assembled in the endoplasmic reticulum from four homologous subunits by mechanisms that are insufficiently understood. Nascent AChR subunits were recently found to form complexes with the endoplasmic reticulum-resident molecular chaperone calnexin. To determine the contribution of this interaction to AChR assembly and surface expression, we have now used transient transfection of mouse AChR subunits and calnexin into non-muscle cells. Co-transfection of calnexin along with AChR subunits into COS and HEK 293 cells was found to enhance AChR subunit folding and assembly, and to decrease degradation rates of newly synthesized AChR alpha-subunits, resulting in elevated surface expression of assembled AChR. Moreover, inhibition of the interaction between endogenous calnexin and AChR by castanospermine resulted in decreased AChR subunit folding, assembly, and surface expression in muscle and HEK 293 cells. Together, these findings provide evidence that calnexin directly contributes to AChR biogenesis by promoting subunit folding and assembly.
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Affiliation(s)
- W Chang
- Department of Pharmacological Sciences, State University of New York at Stony Brook, Stony Brook, New York 11794, USA
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21
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Abstract
Presentation of antigenic peptides by MHC class II molecules to CD4(+) T cells requires many events in both the biosynthetic and endocytic pathways that must all occur in a controlled and coordinated fashion. In recent years the roles of two important chaperones, the invariant chain and the HLA-DM dimer, in promoting the acquisition of peptides by MHC class II molecules have largely been elucidated. The different compartments within the endosomal/lysosomal pathway that are involved in peptide loading are now being characterized. In addition to the specialized MHC class II compartments that exist in antigen-presenting cells, other intracellular compartments may also be involved in peptide loading. The precise mechanisms and intracellular sites of MHC class II peptide loading appear to dictate the nature of the T-cell epitopes presented by the antigen-presenting cell.
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Affiliation(s)
- J Pieters
- Basel Institute for Immunology, Grenzacherstrasse 487, Postfach CH-4005 Basel, Switzerland.
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22
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Mey-Tal SV, Schechter C, Ehrlich R. Synthesis and turnover of beta2-microglobulin in Ad12-transformed cells defective in assembly and transport of class I major histocompatibility complex molecules. J Biol Chem 1997; 272:353-61. [PMID: 8995269 DOI: 10.1074/jbc.272.1.353] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
In primary embryonal fibroblasts from transgenic mice expressing H-2 genes and a miniature swine class I transgene (PD1), transformation with the highly oncogenic Ad12 results in a reduction in peptide transporter and proteasome-associated (LMP2 and LMP7) gene expression, and suppression in transport and cell surface expression of all class I antigens. The selective suppression in transport of H-2 (but not of PD1) molecules in cells reconstituted for the expression of peptide transporter and LMP genes implied that an additional factor(s) is involved in the assembly of class I complexes. Here we show that the beta2m, H-2Db, and H-2Kb genes are transcribed and translated in Ad12-transformed cells. However, unlike normal and E1Ad5-transformed cells, in which beta2m is either secreted unbound or bound to class I heavy chains, in Ad12-transformed cells significant amounts of beta2m are retained in the cell bound to the membrane, but free of class I heavy chains. This abnormal turnover of beta2m in the Ad12-transformed cells suggests the existence of a novel beta2m-binding molecule(s) that sequesters beta2m, and this process may provide a mechanism by which transformation with Ad12 may subvert class I complex formation.
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Affiliation(s)
- S V Mey-Tal
- Department of Cell Research and Immunology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Ramat Aviv, Israel
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23
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Rodan AR, Simons JF, Trombetta ES, Helenius A. N-linked oligosaccharides are necessary and sufficient for association of glycosylated forms of bovine RNase with calnexin and calreticulin. EMBO J 1996; 15:6921-30. [PMID: 9003768 PMCID: PMC452518] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Calnexin and calreticulin are lectin-like molecular chaperones that promote folding and assembly of newly synthesized glycoproteins in the endoplasmic reticulum. While it is well established that they interact with substrate monoglucosylated N-linked oligosaccharides, it has been proposed that they also interact with polypeptide moieties. To test this notion, glycosylated forms of bovine pancreatic ribonuclease (RNase) were translated in the presence of microsomes and their folding and association with calnexin and calreticulin were monitored. When expressed with two N-linked glycans in the presence of micromolar concentrations of deoxynojirimycin, this small soluble protein was found to bind firmly to both calnexin and calreticulin. The oligosaccharides were necessary for association, but it made no difference whether the RNase was folded or not. This indicated that unlike other chaperones, calnexin and calreticulin do not select their substrates on the basis of folding status. Moreover, enzymatic removal of the oligosaccharide chains using peptide N-glycosidase F or removal of the glucoses by ER glucosidase II resulted in dissociation of the complexes. This indicated that the lectin-like interaction, and not a protein-protein interaction, played the central role in stabilizing RNase-calnexin/calreticulin complexes.
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Affiliation(s)
- A R Rodan
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06520-8002, USA
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24
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Zheng Z, Maidji E, Tugizov S, Pereira L. Mutations in the carboxyl-terminal hydrophobic sequence of human cytomegalovirus glycoprotein B alter transport and protein chaperone binding. J Virol 1996; 70:8029-40. [PMID: 8892927 PMCID: PMC190876 DOI: 10.1128/jvi.70.11.8029-8040.1996] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Human cytomegalovirus glycoprotein B (gB) plays a role in the fusion of the virion envelope with the host cell membrane and in syncytium formation in infected cells. Hydrophobic sequences at the carboxyl terminus, amino acids (aa) 714 to 771, anchor gB in the lipid bilayer, but the unusual length of this domain suggests that it may serve another role in gB structure. To explore the function(s) of this region, we deleted aa 717 to 747 (gB deltaI mutation), aa 751 to 771 (gB deltaII mutation), and aa 717 to 772 (gB deltaI-II mutation) and constructed a substitution mutation, Lys-748 to Val (Lys748Val)-Asn749Ala-Pro750Ile (gB KNPm). Mutated forms of gB were expressed in U373 glioblastoma cells and subjected to analysis by flow cytometry, confocal microscopy, and immunoprecipitation. Mutations gB deltaI-II and gB deltaII alone caused secretion of gB into the medium, confirming that aa 751 to 771 function as a membrane anchor. In contrast, mutations gB deltaI and gB KNPm blocked cell surface expression and arrested gB transport in the endoplasmic reticulum (ER). Detailed examination of gB deltaI and gB KNPm with a panel of monoclonal antibodies showed that the mutated forms were indistinguishable from wild-type gB in conformation and formed oligomers; however, they remained sensitive to endoglycosidase H and did not undergo endoproteolytic cleavage. Analysis of protein complexes formed by gB and molecular chaperones in the ER showed that calnexin and calreticulin, lectin-like chaperones, bound equal amounts of uncleaved wild-type gB, gB deltaI, and gB KNPm, but the glucose-regulated proteins 78 (BiP) and 94 formed stable complexes only with the mutated forms, causing their retention in the ER. Our studies show that aa 714 to 750 are key residues in the architecture of gB molecules and that the ER chaperones, which facilitate gB folding and monitor the quality of glycoproteins, detect subtle changes in folding intermediates that are conferred by mutations in this region.
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Affiliation(s)
- Z Zheng
- Department of Stomatology, School of Dentistry, University of California, San Francisco 94143-0512, USA
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25
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German RN, Castellino F, Han R, Reis e Sousa C, Romagnoli P, Sadegh-Nasseri S, Zhong GM. Processing and presentation of endocytically acquired protein antigens by MHC class II and class I molecules. Immunol Rev 1996; 151:5-30. [PMID: 8872483 DOI: 10.1111/j.1600-065x.1996.tb00701.x] [Citation(s) in RCA: 82] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- R N German
- Lymphocyte Biology Section, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892-1892, USA.
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