Subcellular protein profiling with far-red light mediated proximal labeling

Organelle specific protein identification is essential for understanding how cell functions on a subcellular level. Here, we report a light mediated proximal labeling (LIMPLA) strategy for organelle specific protein profiling in living cells. In this strategy, various commercial mitochondria-localized fluorescent trackers, such as Mitoview 405 and Rhodamine 123, can activate 2-Propynylamine (PA) to label proximal proteins in mitochondria under illumination. PA tagged proteins are subsequently derivatized via click chemistry with azido fluorescent dye for imaging or with azido biotin for further enrichment and mass-spec identification. This strategy can be generalized to other organelles specific protein labeling. For example, proteins in nucleus are labeled by utilizing the commercial nucleus tracker DRAQ5. As compared with other chemical strategies for subcellular protein labeling, there are several advantages for this LIMPLA strategy. First, this approach allows minimal interference to the cells status by avoiding exogenous gene tansduction and some special treatment such as hydrogen peroxide or serum starvation. Second, all reagents used in this strategy are commercially available without additional synthesis work. Further, this strategy holds the potential for analyzing proximal proteins of specific macromolecules that can be tagged with fluorescent dye by metabolic labeling strategy.