Dynamics Determine Signaling in a Multicomponent System Associated with Rheumatoid Arthritis

Strategies that target multiple components are usually required for treatment of diseases originating from complex biological systems. The multicomponent system consisting of the DR4 major histocompatibility complex type II molecule, the glycopeptide CI1259-273 from type II collagen, and a T-cell receptor is associated with development of rheumatoid arthritis (RA). We introduced non-native amino acids and amide bond isosteres into CI1259-273 and investigated the effect on binding to DR4 and the subsequent T-cell response. Molecular dynamics simulations revealed that complexes between DR4 and derivatives of CI1259-273 were highly dynamic. Signaling in the overall multicomponent system was found to depend on formation of an appropriate number of dynamic intramolecular hydrogen bonds between DR4 and CI1259-273, together with the positioning of the galactose moiety of CI1259-273 in the DR4 binding groove. Interestingly, the system tolerated modifications at several positions in CI1259-273, indicating opportunities to use analogues to increase our understanding of how rheumatoid arthritis develops and for evaluation as vaccines to treat RA.