ERAP1 enzyme-mediated trimming and structural analyses of MHC I--bound precursor peptides yield novel insights into antigen processing and presentation.Li, L., Batliwala, M., Bouvier, M.
(2019) J.Biol.Chem. --: --
- PubMed: 31601650
- DOI: 10.1074/jbc.RA119.010102
- Primary Citation of Related Structures:
- PubMed Abstract:
Endoplasmic reticulum aminopeptidases 1 (ERAP1) and ERAP2 critically shape the major histocompatibility complex I (MHC I) immunopeptidome. The ERAPs remove N-terminal residues from antigenic precursor peptides and generate optimal-length peptides,i.e ...
Endoplasmic reticulum aminopeptidases 1 (ERAP1) and ERAP2 critically shape the major histocompatibility complex I (MHC I) immunopeptidome. The ERAPs remove N-terminal residues from antigenic precursor peptides and generate optimal-length peptides,i.e., 8-10mers, to fit into the MHC class I groove. It is therefore intriguing that MHC class I molecules can present N-terminally extended peptides on the cell surface that can elicit CD8+ T-cell responses. This observation likely reflects gaps in our understanding of how antigens are processed by the ERAP enzymes. To better understand ERAPs' function in antigen processing, here we generated a nested set of N-terminally extended 10-20mer peptides (RA)nAAKKKYCL covalently bound to the human leukocyte antigen (HLA)-B*0801. We used X-ray crystallography, thermostability assessments, and an ERAP1-trimming assay to characterize these complexes. The x-ray structures determined at 1.40-1.65 Å resolutions revealed that the residue extensions (RA)nunexpectedly protrude out of the A pocket of HLA-B*0801, whereas the AAKKKYCL core of all peptides adopts similar, bound conformations. HLA-B*0801 residue 62 was critical to open the A pocket. We also show that HLA-B*0801 and antigenic precursor peptides form stable complexes. Finally, ERAP1-mediated trimming of the MHC I-bound peptides required a minimal length of 14 amino acids. We propose a mechanistic model explaining how ERAP1-mediated trimming of MHC I-bound peptides in cells can generate peptides of canonical as well as noncanonical lengths that still serve as stable MHC I ligands. Our results provide a framework to better understand how the ERAP enzymes influence the MHC I immunopeptidome.
University of Illinois at Chicago, United States.,microbiology and immunology, University of Illinois at Chicago, United States.,Microbiology and Immunology, University of Illinois at Chicago, United States.