Nanoscale Mechanical Force Primes NOD1-LRR for Efficient Pathogen Recognition

Detecting pathogens requires molecular sensors that can rapidly and precisely respond to local threats. While cytosolic innate immune receptors such as NOD1 are known as biochemical detectors, their ability to interpret physical cues remains a critical unknown. Here, we combine piconewton-resolution single-molecule manipulation, molecular dynamics simulations, and structural modeling to demonstrate that NOD1 is not a passive detector but an active nanomechanical sensor. We show that the receptor's LRR domain, with its curved, horseshoe-like nanoarchitecture, functions as a mechanical force concentrator. Physiologically relevant piconewton-scale forces, such as those at the membrane-cytosol interface, are concentrated into a high-stress hotspot that primes the domain for a conformational transition. This force-induced priming acts as an allosteric nanoswitch, transducing mechanical energy into a biochemical output: a dramatic increase in binding strength and sensitivity for its bacterial ligand iE-DAP. This mechanochemical coupling positions NOD1 as a force-responsive sensor, enabling rapid and spatially restricted immune activation. Our work establishes a new paradigm for cytosolic pathogen recognition and suggests that force-sensing LRR domains represent a generalizable design principle in nanobiology, bridging a conceptual gap between mechanobiology and innate immunity.