Tuning the sensitivity of mechanosensory receptors through histidine scanning.

T cell receptor (TCR)-T cell therapy is effective for solid tumors, yet identifying potent, specific TCRs for tumor antigens is challenging. Conventional affinity maturation may cause fatal off-target toxicity. Catch bonds play a crucial role in mechanosensory receptor signaling, including the TCR, but their formation and potential to mitigate the challenges of TCR-T remain unclear. Here, we demonstrate that histidine scanning can identify TCR hotspots capable of forming additional catch bonds, which can be randomized to create TCR libraries for screening low-affinity, higher-potency variants. Mechanistically, histidine facilitates the formation of hydrogen bonds and salt bridges and fortifies the intracellular signaling cascade. Using this approach, we engineered different TCRs specific for various antigens, without off-target toxicity or on-target toxicity. Our findings introduce a universal method of engineering low-affinity, high-potency TCRs for safe TCR-T cell therapy, without requiring the structure for designing TCR libraries. Additionally, histidine scanning can be broadly applied to other mechanosensory ligand-receptor systems.