An Engineered Switch in T Cell Receptor Specificity Leads to an Unusual but Functional Binding Geometry

• Published in: Structure (London) 2016-07, Vol.24 (7), p.1142-1154
• Main Authors: Harris, Daniel T., Singh, Nishant K., Cai, Qi, Smith, Sheena N., Vander Kooi, Craig W., Procko, Erik, Kranz, David M., Baker, Brian M.
• Format: Article
• Language: English
• Subjects: Animals; BASIC BIOLOGICAL SCIENCES; Binding Sites, Antibody; HLA-A2 Antigen - chemistry; HLA-A2 Antigen - immunology; Humans; Mice; Molecular Docking Simulation; Mutation; Protein Binding; Receptors, Antigen, T-Cell - chemistry; Receptors, Antigen, T-Cell - genetics; Receptors, Antigen, T-Cell - immunology
• ISSN: 0969-2126; 1878-4186
• DOI: 10.1016/j.str.2016.04.011

Utilizing a diverse binding site, T cell receptors (TCRs) specifically recognize a composite ligand comprised of a foreign peptide and a major histocompatibility complex protein (MHC). To help understand the determinants of TCR specificity, we studied a parental and engineered receptor whose peptide specificity had been switched via molecular evolution. Altered specificity was associated with a significant change in TCR-binding geometry, but this did not impact the ability of the TCR to signal in an antigen-specific manner. The determinants of binding and specificity were distributed among contact and non-contact residues in germline and hypervariable loops, and included disruption of key TCR-MHC interactions that bias αβ TCRs toward particular binding modes. Sequence-fitness landscapes identified additional mutations that further enhanced specificity. Our results demonstrate that TCR specificity arises from the distributed action of numerous sites throughout the interface, with significant implications for engineering therapeutic TCRs with novel and functional recognition properties. [Display omitted] •Switching TCR specificity via in vitro evolution leads to an unusual binding mode•The engineered TCR still signals in an antigen-specific manner•Disruption of canonical TCR-MHC interactions catalyzes the specificity switch•Further contributions to the switch are distributed throughout the interface Harris et al. describe a TCR whose specificity was switched via in vitro molecular evolution and show it adopts an unusual binding mode over peptide/MHC but signals in an antigen-specific manner. Altered specificity was catalyzed by disrupting canonical interactions between TCR and MHC and was further influenced by changed interactions throughout the interface.