Live-cell quantitative imaging of proteome degradation by stimulated Raman scattering.

Protein degradation is a regulatory process essential to cell viability and its dysfunction is implicated in many diseases, such as aging and neurodegeneration. In this report, stimulated Raman scattering microscopy coupled with metabolic labeling with (13)C-phenylalanine is used to visualize protein degradation in living cells with subcellular resolution. We choose the ring breathing modes of endogenous (12)C-phenylalanine and incorporated (13)C-phenylalanine as protein markers for the original and nascent proteomes, respectively, and the decay of the former wasquantified through (12)C/((12)C+(13)C) ratio maps. We demonstrate time-dependent imaging of proteomic degradation in mammalian cells under steady-state conditions and various perturbations, including oxidative stress, cell differentiation, and huntingtin protein aggregation.