Fluorogenic photocatalyzed proximity labelling with visible light to map the interactome in living cells

Living processes are primarily governed by transient and dynamic interactions betweenbiomacromolecules or cells. It is therefore essential to study these interactions to understand themechanisms they regulate. These are identified using proximity labeling techniques, where thelabelling agent is usually a enzyme fused to the protein of interest (e.g. the APEX approach).1,2Although effective, this technique sometimes has limitations in terms of labelling speed, toxicity andprecision. The use of photocatalytic proximity labelling has improved the spatial precision ofproximity labelling, while using bio-compatible wavelengths.3 A limitation common to all thesemethods is their inability to mark and follow the evolution of these dynamic interactions from theproduct of interest (POI) on living cells. In this communication, we will present our latest work on thedevelopment of a fluorogenic photocatalyzed proximity labelling that provides a simple solution tothis problem. This new method is based on the use of organic photocatalyst and fluorogenic photo-crosslinking agents. Proof of concept was first demonstrated in living bacteria (Streptococcuspneumoniae) by spatiotemporally controlled fluorescent labelling of teichoic acids, a majorcomponent of the cell wall in Gram-positive bacteria, monitored by epifluorescent microscopy. Wesubsequently demonstrated that this method is effective for the selective fluorescent labelling ofproteins that interact with teichoic acids. Once again, direct fluorescent labelling of the interactomesimplifies characterization procedures.