1
|
Erausquin E, Serra P, Parras D, Santamaria P, López-Sagaseta J. Structural plasticity in I-Ag7 links autoreactivity to hybrid insulin peptides in type I diabetes. Front Immunol 2022; 13:924311. [PMID: 35967292 PMCID: PMC9365947 DOI: 10.3389/fimmu.2022.924311] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2022] [Accepted: 07/04/2022] [Indexed: 11/13/2022] Open
Abstract
We recently provided evidence for promiscuous recognition of several different hybrid insulin peptides (HIPs) by the highly diabetogenic, I-Ag7-restricted 4.1-T cell receptor (TCR). To understand the structural determinants of this phenomenon, we solved the structure of an agonistic HIP/I-Ag7 complex, both in isolation as well as bound to the 4.1-TCR. We find that HIP promiscuity of the 4.1-TCR is dictated, on the one hand, by an amino acid sequence pattern that ensures I-Ag7 binding and, on the other hand, by the presence of three acidic residues at positions P5, P7 and P8 that favor an optimal engagement by the 4.1-TCR’s complementary determining regions. Surprisingly, comparison of the TCR-bound and unbound HIP/I-Ag7 structures reveals that 4.1-TCR binding triggers several novel and unique structural motions in both the I-Ag7 molecule and the peptide that are essential for docking. This observation indicates that the type 1 diabetes-associated I-Ag7 molecule is structurally malleable and that this plasticity allows the recognition of multiple peptides by individual TCRs that would otherwise be unable to do so.
Collapse
Affiliation(s)
- Elena Erausquin
- Unit of Protein Crystallography and Structural Immunology, Navarrabiomed, Navarra, Spain
- Public University of Navarra (UPNA), Pamplona, Spain
- Navarra University Hospital, Pamplona, Spain
| | - Pau Serra
- Institut D’Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain
| | - Daniel Parras
- Institut D’Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain
| | - Pere Santamaria
- Institut D’Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain
- Julia McFarlane Diabetes Research Centre (JMDRC) and Department of Microbiology, Immunology and Infectious Diseases, Snyder Institute for Chronic Diseases and Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
- *Correspondence: Jacinto López-Sagaseta, ; Pere Santamaria,
| | - Jacinto López-Sagaseta
- Unit of Protein Crystallography and Structural Immunology, Navarrabiomed, Navarra, Spain
- Public University of Navarra (UPNA), Pamplona, Spain
- Navarra University Hospital, Pamplona, Spain
- *Correspondence: Jacinto López-Sagaseta, ; Pere Santamaria,
| |
Collapse
|