a, Diagram for proximity labelling and proteomic discovery of trafficking cofactors using Sting1−/− MEFs stably expressing STING–APEX2. b, Representative microscopy images of STING–APEX2 trafficking at various time points after stimulation (HT-DNA, 1 μg ml−1). BFA blocks the exit of STING from the ER; BafA1 blocks the degradation of STING by lysosomes. Scale bars, 10 μm. c, Immunoblot analysis of cell lysates. STING–APEX2 MEFs were mock-treated or stimulated with HT-DNA (1 μg ml−1) for the indicated times with or without treatment with BFA or BafA1 (top). Then, proximity labelling was performed and biotinylated proteins were detected by streptavidin–HRP. Immunoblot is representative of at least three independent experiments. d, TMT-MS quantitative proteomics data filtering from two independent experiments and candidate discovery. e, Diagram of the STING trafficking route after stimulation, including time points (top) and organelles. f, Heat map showing selected STING trafficking cofactor candidates at each organelle (top). MS value was normalized to the 0-h time point. Data are representative of three independent experiments.