NMR: an essential structural tool for integrative studies of T cell development, pMHC ligand recognition and TCR mechanobiology

Abstract

Early studies of T cell structural biology using X-ray crystallography, surface plasmon resonance (SPR) and isothermal titration calorimetry (ITC) focused on a picture of the αβT cell receptor (αβTCR) component domains and their cognate ligands (peptides bound to MHC molecules, i.e. pMHCs) as static interaction partners. Moving forward requires integrating this corpus of data with dynamic technologies such as NMR, molecular dynamics (MD) simulations and real-time single molecule (SM) studies exemplified by optical tweezers (OT). NMR bridges relevant timescales and provides the potential for an all-atom dynamic description of αβTCR components *

Beyond detergent micelles: The advantages and applications of non-micellar and lipid-based membrane mimetics for solution-state NMR

“…Furthermore, refolding of disulfide bond-containing ectodomains, such as CD3 subunits of the T-cell receptor [126], for NMR is very difficult by itself. The presence of a TMH during refolding would be detrimental for the overall refolding yields.…”

The structure of a T-cell mechanosensor

“…Dynamic movement of TCRα and TCRβ protein segments has previously been visualized using a method called NMR 9 . The model of the TCR as a directional mechanosensor proposes that forces exerted by T-cell motility and the motion of components of a T cell's internal framework (the cytoskeleton) improve a T-cell's recognition of pMHC more than 1,000fold relative to recognition in the absence of force 6 .…”

“…The orientation of the variable domains and the positioning of the antigen-binding site favours a directional interaction of the TCR with a pMHC that is consistent with T-cell scanning motions that occur tangentially to the surface of the surveyed cell. The FG loop structure 5 of TCRβ's constant region controls the lifetime of a TCR-pMHC bond and also the extension of the TCRαβ heterodimer when it transitions from a compact to an extended form under force during antigen recognition 6,9 . The FG loop is located above CD3ε of CD3εγ.…”

“…Such forces might cause changes to parts of the TCR structure, and affect neighbouring lipids to expose key amino-acid sites on CD3 cytoplasmic tails. The addition of phosphate groups to these tyrosine amino-acid residues would trigger signalling cascades and other cellular changes needed for T-cell activation 6,9,12 . The abundance of interactions between the various connecting-peptide segments of the TCR would probably aid signalling 1,8,13 .…”

Integrative methods in structural biology

“…The mechanism of T cell signaling has been addressed by Reinherz, Wagner, and coworkers (Mallis et al 2019). Non-self peptides (p) are displayed on the cell surface by the major histocompatibility complex (MHC) for recognition by the αβT-cell antigen receptor (αβTCR).…”