Stressor-Actuated Proximity Labeling for Reporting Cellular Interaction

Cell-cell interactions determine the activation state and function of cells. When host cells are exposed to stressors such as microorganisms, immune defense machinery is activated to release H₂O₂, providing direct evidence of the relevant cellular physiological processes. Inspired by the fact that peroxidase can catalyze proximity labeling in the presence of exogenous H₂O₂, a stressor-actuated proximity labeling (SAPL) strategy is developed to report the process information on cell-cell interactions by recording stress levels. The stressors are covalently modified with horseradish peroxidase (HRP) and the H₂O₂ released by the host cells in response to the stressors triggers HRP-based proximity labeling. Using a fungal mimic or live fungi as stressors, the stress levels of different host cells are compared by in situ imaging of the labeling signals. The ability to accumulate stress signals allows SAPL to more sensitively differentiate between interactions involving different macrophage phenotypes. SAPL is also a powerful tool for real-time, in situ monitoring of the effects of surface modifications on cellular interactions. Thus, the SAPL strategy represents a new perspective in the monitoring of cell-cell interactions using endogenous effector molecules.