MHC class I-restricted antigen processing is essential for making CD8+ T cell responses. It must function correctly for effective immune recognition of pathogens, and aberrations can lead to autoimmunity. The overall aim of this proposal is to understand the quality control processes regulating MHC class I- restricted antigen processing of conventional antigens, translated in the cytosol, and of exogenous antigens internalized by cross-presenting cells. The latter process is particularly poorly characterized, yet it is essential for priming CD8+ T cell responses. We wish to understand how these two different processing mechanisms drive the assembly of essentially the same pool of MHC-I peptide complexes. A critical quality control process in the endoplasmic reticulum (ER) that remains ill understood is the action of the enzyme UDP-glucose glycoprotein transferase (UGT1), which produces the correct monoglucosylated glycan structure that allows MHC-I molecules to maintain an interaction with the Peptide Loading Complex (PLC) via the lectin chaperone calreticulin, facilitating tapasin-mediated peptide exchange. This promotes the expression by the cell of complexes of MHC-I with peptides of high affinity. We will test the hypothesis that structural flexibility in the MHC-I peptide binding domain serves as a recognition signal for UGT1. A second component, which is found in both the ER and the endocytic pathway, is the tapasin homologue TAPBPR. In vitro, TAPBPR can induce peptide exchange by MHC-I molecules outside of the PLC, and it has also been shown to interact with UGT1. A second major goal is to determine whether TAPBPR mediates peptide exchange by MHC class I molecules in intact cells, whether this can occur both in the ER and the phagosomes of cross-presenting cells, and whether in either of these intracellular compartments the simultaneous interaction of TAPBPR with UGT1 focuses the enzymatic activity of UGT1 onto MHC-I molecules associated with low affinity peptides, facilitating their exchange for optimal peptides. The final goal is to determine how cross-presented intact antigens encounter proteasomes, which are essential for both conventional MHC-I antigen processing and cross- presentation. We have evidence that this interaction occurs proximal to, and probably within, phagosomes of cross-presenting cells. The mechanisms that regulate this interaction at both the cell biological and biochemical level will be investigated.

Public Health Relevance

CD8+ T cells can recognize and kill tumor cells as well as cells infected with viruses. Expanding their numbers in the body is critical for the elimination of viruses during an infection, and their emergence is important for fighting cancer. They recognize molecules called MHC class I molecules associated with fragments of proteins that come from the tumor or the virus, and this proposal is aimed to understand how the association of the fragments with the MHC class I molecules occurs.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
5R01AI097206-08
Application #
9703860
Study Section
Cellular and Molecular Immunology - B Study Section (CMIB)
Program Officer
Gondre-Lewis, Timothy A
Project Start
2012-06-15
Project End
2021-05-31
Budget Start
2019-06-01
Budget End
2020-05-31
Support Year
8
Fiscal Year
2019
Total Cost
Indirect Cost
Name
Yale University
Department
Microbiology/Immun/Virology
Type
Schools of Medicine
DUNS #
043207562
City
New Haven
State
CT
Country
United States
Zip Code
06520
Arshad, Najla; Cresswell, Peter (2018) Tumor-associated calreticulin variants functionally compromise the peptide loading complex and impair its recruitment of MHC-I. J Biol Chem 293:9555-9569
Lu, Qiao; Grotzke, Jeff E; Cresswell, Peter (2018) A novel probe to assess cytosolic entry of exogenous proteins. Nat Commun 9:3104
Grotzke, Jeff E; Kozik, Patrycja; Morel, Jean-David et al. (2017) Sec61 blockade by mycolactone inhibits antigen cross-presentation independently of endosome-to-cytosol export. Proc Natl Acad Sci U S A 114:E5910-E5919
Grotzke, Jeff E; Sengupta, Debrup; Lu, Qiao et al. (2017) The ongoing saga of the mechanism(s) of MHC class I-restricted cross-presentation. Curr Opin Immunol 46:89-96
Grotzke, Jeff E; Cresswell, Peter (2015) Are ERAD components involved in cross-presentation? Mol Immunol 68:112-5
Samie, Mohammad; Cresswell, Peter (2015) The transcription factor TFEB acts as a molecular switch that regulates exogenous antigen-presentation pathways. Nat Immunol 16:729-36
Leonhardt, Ralf M; Abrahimi, Parwiz; Mitchell, Susan M et al. (2014) Three tapasin docking sites in TAP cooperate to facilitate transporter stabilization and heterodimerization. J Immunol 192:2480-94
Grotzke, Jeff E; Lu, Qiao; Cresswell, Peter (2013) Deglycosylation-dependent fluorescent proteins provide unique tools for the study of ER-associated degradation. Proc Natl Acad Sci U S A 110:3393-8
Blum, Janice S; Wearsch, Pamela A; Cresswell, Peter (2013) Pathways of antigen processing. Annu Rev Immunol 31:443-73
Panter, Michaela S; Jain, Ankur; Leonhardt, Ralf M et al. (2012) Dynamics of major histocompatibility complex class I association with the human peptide-loading complex. J Biol Chem 287:31172-84

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