Quantifying mitochondrial protein import by mePROD^mt proteomics

Mitochondrial protein import is crucial for maintaining cellular health and homeostasis. Disruptions in this process have been linked to various diseases. Traditional methods for studying mitochondrial protein import predominantly focus on individual proteins and lack the dynamic resolution needed to fully appreciate the complexity of mitochondrial proteostasis and protein trafficking. To address these limitations, we developed a technique called mitochondria-specific multiplexed enhanced protein dynamics (mePROD^mt). This method is a novel application of the mePROD methodology and utilizes pulsed stable isotope labeling with amino acids in cell culture (pSILAC)-based proteomics approach to study transient mitochondrial protein import. This chapter outlines the mePROD^mt protocol, which includes the preparation of heavy SILAC-labeled peptides for boosting overall mitochondrial peptide signals (booster), SILAC labeling of cultured cells under experimental conditions, mitochondria isolation, sample preparation for multiplex proteomics using tandem mass tags (TMT) for isobaric labeling, recommended liquid chromatography-mass spectrometry (LC-MS) settings for reporter ion quantitation and a data analysis pipeline to analyze pSILAC-TMT data.