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Seipp RP, Hoeffel G, Moise AR, Lok S, Ripoche AC, Marañón C, Hosmalin A, Jefferies WA. A secreted Tapasin isoform impairs cytotoxic T lymphocyte recognition by disrupting exogenous MHC class I antigen presentation. Front Immunol 2025; 15:1525136. [PMID: 40171019 PMCID: PMC11959276 DOI: 10.3389/fimmu.2024.1525136] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2024] [Accepted: 12/23/2024] [Indexed: 04/03/2025] Open
Abstract
Endogenous and exogenous antigen processing and presentation through the MHC class I peptide-loading complex (PLC) are essential for initiating cytotoxic T lymphocyte responses against pathogens and tumors. Tapasin, a key component of the PLC, is produced in multiple isoforms through alternative splicing, each isoform influencing the assembly and stability of MHC class I molecules differently. While the canonical Tapasin isoform plays a critical role in stabilizing MHC class I by facilitating optimal peptide loading in the endoplasmic reticulum (ER), the other isoforms function in distinct ways that impact immune regulation. This study aimed to investigate the role of Tapasin isoforms, particularly soluble isoform 3, in modulating antigen presentation and immune responses, focusing on their effects on MHC class I peptide loading and surface expression. Our findings show that isoforms 1 and 2 stabilize TAP and facilitate efficient peptide loading onto MHC class I in the ER, promoting optimal antigen presentation. In contrast, isoform 3, which lacks both the ER retention signal and the transmembrane domain, is secreted and acts as a negative regulator. Isoform 3 inhibits the loading of exogenous peptides onto MHC class I molecules at the cell surface, thereby playing a critical role in the spatial and temporal regulation of MHC class I antigen presentation. The secreted Tapasin isoform 3 likely regulates immune responses by preventing inappropriate T cell activation and cytotoxicity, which could otherwise lead to immune-mediated tissue damage and contribute to autoimmune disorders. Understanding the distinct functions of Tapasin isoforms provides insights into immune regulation and highlights the importance of fine-tuning peptide-loading processes to ensure proper immune responses and prevent immune-related pathologies.
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Affiliation(s)
- Robyn P. Seipp
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada
- Michael Smith Laboratories, University of British Columbia, Vancouver, BC, Canada
| | | | - Alexander R. Moise
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada
- Michael Smith Laboratories, University of British Columbia, Vancouver, BC, Canada
| | - Siri Lok
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada
- Michael Smith Laboratories, University of British Columbia, Vancouver, BC, Canada
| | | | | | - Anne Hosmalin
- Université Paris Cité, CNRS, Inserm, Institut Cochin, Paris, France
| | - Wilfred A. Jefferies
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada
- Michael Smith Laboratories, University of British Columbia, Vancouver, BC, Canada
- Vancouver Prostate Centre, Vancouver Coastal Health Research Institute, Vancouver, BC, Canada
- Centre for Blood Research, University of British Columbia, Vancouver, BC, Canada
- The Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, BC, Canada
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC, Canada
- Department of Medical Genetics, University of British Columbia, Vancouver, BC, Canada
- Department of Urological Science, University of British Columbia, Vancouver, BC, Canada
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Sironi L, Stella A, Lazzari B, Ramelli P, Gorni C, Mariani P. Molecular characterization of genes involved in chicken MHC class I antigen presentation pathway. ITALIAN JOURNAL OF ANIMAL SCIENCE 2016. [DOI: 10.4081/ijas.2007.1s.211] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Affiliation(s)
- L. Sironi
- Livestock Genomics 2 Unit. Parco Tecnologico Padano, Lodi, Italy
| | - A. Stella
- Statistical Genetics and Bioinformatic Unit. Parco Tecnologico Padano., Lodi, Italy
| | - B. Lazzari
- Statistical Genetics and Bioinformatic Unit. Parco Tecnologico Padano., Lodi, Italy
| | - P. Ramelli
- Livestock Genomics 2 Unit. Parco Tecnologico Padano, Lodi, Italy
| | - C. Gorni
- Livestock Genomics 2 Unit. Parco Tecnologico Padano, Lodi, Italy
| | - P. Mariani
- Livestock Genomics 2 Unit. Parco Tecnologico Padano, Lodi, Italy
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Panicker VP, Department of Veterinary Biochemistry, Faculty of Veterinary and Animal Sciences, Mannuthy, Thrissur, India, Uma R, Department of Veterinary Biochemistry, Faculty of Veterinary and Animal Sciences, Mannuthy, Thrissur, India. Identification and sequence analysis of Tapasin gene in guinea fowl. Vet World 2014. [DOI: 10.14202/vetworld.2014.1099-1102] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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Magor KE, Miranzo Navarro D, Barber MRW, Petkau K, Fleming-Canepa X, Blyth GAD, Blaine AH. Defense genes missing from the flight division. DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY 2013; 41:377-88. [PMID: 23624185 PMCID: PMC7172724 DOI: 10.1016/j.dci.2013.04.010] [Citation(s) in RCA: 127] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/18/2013] [Accepted: 04/16/2013] [Indexed: 05/12/2023]
Abstract
Birds have a smaller repertoire of immune genes than mammals. In our efforts to study antiviral responses to influenza in avian hosts, we have noted key genes that appear to be missing. As a result, we speculate that birds have impaired detection of viruses and intracellular pathogens. Birds are missing TLR8, a detector for single-stranded RNA. Chickens also lack RIG-I, the intracellular detector for single-stranded viral RNA. Riplet, an activator for RIG-I, is also missing in chickens. IRF3, the nuclear activator of interferon-beta in the RIG-I pathway is missing in birds. Downstream of interferon (IFN) signaling, some of the antiviral effectors are missing, including ISG15, and ISG54 and ISG56 (IFITs). Birds have only three antibody isotypes and IgD is missing. Ducks, but not chickens, make an unusual truncated IgY antibody that is missing the Fc fragment. Chickens have an expanded family of LILR leukocyte receptor genes, called CHIR genes, with hundreds of members, including several that encode IgY Fc receptors. Intriguingly, LILR homologues appear to be missing in ducks, including these IgY Fc receptors. The truncated IgY in ducks, and the duplicated IgY receptor genes in chickens may both have resulted from selective pressure by a pathogen on IgY FcR interactions. Birds have a minimal MHC, and the TAP transport and presentation of peptides on MHC class I is constrained, limiting function. Perhaps removing some constraint, ducks appear to lack tapasin, a chaperone involved in loading peptides on MHC class I. Finally, the absence of lymphotoxin-alpha and beta may account for the observed lack of lymph nodes in birds. As illustrated by these examples, the picture that emerges is some impairment of immune response to viruses in birds, either a cause or consequence of the host-pathogen arms race and long evolutionary relationship of birds and RNA viruses.
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Affiliation(s)
- Katharine E Magor
- Department of Biological Sciences, University of Alberta, Edmonton, Canada.
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