μMap-Interface:\nTemporal Photoproximity Labeling\nIdentifies F11R as a Functional Member of the Transient Phagocytic\nSurfaceome

Phagocytosis is usually carried out by professional phagocytic\ncells in the context of pathogen response or wound healing. The transient\nsurface proteins that regulate phagocytosis pose a challenging proteomics\ntarget; knowledge thereof could lead to new therapeutic insights.\nHerein, we describe a novel photocatalytic proximity labeling method:\n“μMap-Interface”, allowing for spatiotemporal\nmapping of phagocytosis. Utilizing photocatalyst-conjugated IGG-opsonized\nbeads and initiating phagocytosis in a synchronized manner, we capture\nphagocytic interactome “snapshots” at the interface\nof the phagocyte and its target. This allows profiling of the dynamic\nsurface proteome of human macrophages during the engulfment process.\nWe reveal previously known phagocytic mediators as well as potential\nnovel interactors and validate their presence with super-resolution\nmicroscopy. This includes F11R, an important cancer target yet to\nbe investigated in the context of phagocytosis. Further, we demonstrate\nthat knocking down F11R leads to an increased degree of phagocytosis;\nthis insight could contribute to explaining its oncogenic activity.\nLastly, we show capture of orthogonal phagocytic surfaceomes across\ndifferent cells, using a neutrophil-like model. We believe this method\nwill enable new insights into phagocytic processes in a variety of\ncontexts.