Spatiotemporal tracking of cysteine fluctuations during organelle interactions with a lysosome-targeted fluorescent...

Cysteine (Cys) is a crucial amino acid and plays a protective role for cells by eliminating superfluous endogenous reactive oxygen species (ROS). Organelle interactions are consistently carried out during cellular physiological and pathological activities, and Cys levels change concomitantly with cell viability. Nevertheless, the dynamic fluctuations of Cys during organelle interactions remain largely unexplored to date. To address this issue, we developed a lysosome-targeted fluorescent probe, CSDC, by conjugating a 2,4-dinitrobenzenesulfonyl (DNBS) group onto a coumarin fluorophore, thereby achieving real-time imaging of Cys dynamics during mitochondrial and lysosomal fusion. The fluorescence of CSDC can be lightened by inhibiting the photoinduced electron transfer (PET) effect, and high sensitivity of 19 nM was achieved for CSDC. Leveraging the excellent fluorescence performance of CSDC, endogenous Cys under different cellular state was sensitively imaged. Furthermore, fluorescence imaging results exhibited that the content of Cys increased distinctly at the initial stage of mitophagy because of the cytoprotective effect, then gradually reduced to equilibrium during the following organelle interaction. This work not only provide a practically useful tool for sensing Cys, but also offered a direction in revealing the dynamic change of active molecule during organelle interaction with fluorescent probe.