DNA-based nanoparticle tension sensors reveal that T-cell receptors transmit defined pN forces to their antigens for enhanced fidelity

Abstract

T cells are triggered when the T-cell receptor (TCR) encounters its antigenic ligand, the peptide-major histocompatibility complex (pMHC), on the surface of antigen presenting cells (APCs). Because T cells are highly migratory and antigen recognition occurs at an intermembrane junction where the T cell physically contacts the APC, there are long-standing questions of whether T cells transmit defined forces to their TCR complex and whether chemomechanical coupling influences immune function. Here we develop DNA-based gold nanoparticle tension sensors to provide, to our knowledge, the first pN tension maps of individual TCR-pMHC complexes during T-cell activation. We show that naïve T cells harness cytoskeletal coupling to transmit 12–19 pN of force to their TCRs within seconds of ligand binding and preceding initial calcium signaling. CD8 coreceptor binding and lymphocyte-specific kinase signaling are required for antigen-mediated cell spreading and force generation. Lymphocyte function-associated antigen 1 (LFA-1) mediated adhesion modulates TCR-pMHC tension by intensifying its magnitude to values >19 pN and spatially reorganizes the location of TCR forces to the kinapse, the zone located at the trailing edge of migrating T cells, thus demonstrating chemomechanical crosstalk between TCR and LFA-1 receptor signaling. Finally, T cells display a dampened and poorly specific response to antigen agonists when TCR forces are chemically abolished or physically “filtered” to a level below ∼12 pN using mechanically labile DNA tethers. Therefore, we conclude that T cells tune TCR mechanics with pN resolution to create a checkpoint of agonist quality necessary for specific immune response.

Mechanosensing drives acuity of αβ T-cell recognition

“…2A). We expect that the high densities provide a stabilizing interface to create multiple points against which internal cytoskeletal forces can pull to activate TCR-pMHC mechanosensors (40,61). Consistent with this notion, triggered cells are associated with large bead displacements along the shear direction (SI Appendix, Fig.…”

“…This paradoxical extension of αβ TCR-pMHC-bond lifetime under force, so-called catch bond behavior, was then observed experimentally (19,33). The importance of force on TCR triggering has been confirmed in other work (34)(35)(36)(37)(38)(39)(40). However, during the initial T-cell surface contact, external (scanning) and internal (retrograde flow) force appear to operate in opposing directions (41).…”

Cytoskeletal control of B cell responses to antigens

“…Mechanosensitivity has been extensively explored in the case of the TCR and several types of experiments suggest that TCR triggering involves mechanical stimulation [135][136][137][138][139] . The mechanosensitive component of BCR signalling has not been identified, but B cell activation involves phosphorylation of the adaptor protein NEDD9, which is known as a mechanosensor 140,141 .…”

Lipid-dependent conformational dynamics underlie the functional versatility of T-cell receptor

“…Therefore we mainly used AFM to measure the dynamics of CD3ε-membrane interaction rather than the absolute force values and binding energies. Our force value cannot be directly compared with the TCR-pMHC interaction forces measured by other systems because of the setup difference [2,38,43]. Nevertheless, our force value is within the physiological range.…”

“…Mutation of a Cys residue in the CD3ε stalk region to prevent the outside-in conformational transition leads to the blockade of αβ T cell development and impaired peripheral T cell function due to abnormal pre-TCR and TCR signaling [18,19,37]. Fourth, mechanical force has been shown to be critical for TCR signaling and might directly cause CD3 conformational change [2,[38][39][40][41][42][43][44]. These studies highlight the importance of conformational change in TCR triggering.…”