Substrate mediated mechanical forces enable optimal kinetic proofreading by T-cell receptors

Abstract

T-cells use molecular reactions with nonequilibrium error correction, i.e., proofreading, to discriminate between nearly identical antigens with high specificity and sensitivity. These receptor binding events are known to be force sensitive, yet traditional schemes of proofreading focus on reaction kinetics alone and do not consider the role of force dependent catch/slip bond behavior or interactions with mechanically engaged coreceptors such as adhesion molecules. To address this, we propose a minimal framework for proofreading of ligand discrimination by T-cell receptors (TCRs) that uses endogenous TCR mechanosensation and substrate-mediated mechanical interactions with adhesive proteins (load sharing) to improve recognition fidelity. We leverage the catch bond behavior of cognate antigens to delay decision making and amplify TCR signaling while discarding noncognate slip bond ligands in the presence of a force. By integrating our model with existing structural and molecular data, we show that substrate mechanics regulates the transmission of active cytoskeletal forces through a molecular clutch and controls the energization of bound TCRs needed for optimal proofreading. Our work demonstrates how mechanical forces and substrate properties can augment kinetic proofreading in T-cells, suggesting biomaterial design strategies for immunotherapies that tune the mechanical microenvironment of T-cells to achieve high fidelity TCR-ligand discrimination, antigen recognition, and activation.