The PD-1/PD-L1 complex resembles the antigen-binding Fv domains of antibodies and T cell receptors.Lin, D.Y., Tanaka, Y., Iwasaki, M., Gittis, A.G., Su, H.P., Mikami, B., Okazaki, T., Honjo, T., Minato, N., Garboczi, D.N.
(2008) Proc Natl Acad Sci U S A 105: 3011-3016
- PubMed: 18287011
- DOI: https://doi.org/10.1073/pnas.0712278105
- Primary Citation of Related Structures:
- PubMed Abstract:
Signaling through the programmed death 1 (PD-1) inhibitory receptor upon binding its ligand, PD-L1, suppresses immune responses against autoantigens and tumors and plays an important role in the maintenance of peripheral immune tolerance. Release from PD-1 inhibitory signaling revives "exhausted" virus-specific T cells in chronic viral infections. Here we present the crystal structure of murine PD-1 in complex with human PD-L1. PD-1 and PD-L1 interact through the conserved front and side of their Ig variable (IgV) domains, as do the IgV domains of antibodies and T cell receptors. This places the loops at the ends of the IgV domains on the same side of the PD-1/PD-L1 complex, forming a surface that is similar to the antigen-binding surface of antibodies and T cell receptors. Mapping conserved residues allowed the identification of residues that are important in forming the PD-1/PD-L1 interface. Based on the structure, we show that some reported loss-of-binding mutations involve the PD-1/PD-L1 interaction but that others compromise protein folding. The PD-1/PD-L1 interaction described here may be blocked by antibodies or by designed small-molecule drugs to lower inhibitory signaling that results in a stronger immune response. The immune receptor-like loops offer a new surface for further study and potentially the design of molecules that would affect PD-1/PD-L1 complex formation and thereby modulate the immune response.
Structural Biology Section, Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Twinbrook 2, 12441 Parklawn Drive, Rockville, MD 20852, USA.