Protein carbonylation, known as one of the most harmful oxidative post-translational modifications (PTMs), plays a significant role in aetiology and/or progression of several pathological conditions. Basically, the high level of reactive oxygen species (ROS) induced by redox imbalance in pathological states are deemed to be the main cause of protein carbonylation. The oxidative PTMs initiated by ROS is an irreversible modification, involving the formation of aldehyde, ketone, or lactam groups at the side chains of amino acid residues. Most importantly, as a major hallmark for oxidative stress, protein carbonylation has been found to be associated with a number of diseases such as malaria, neurodegeneration and pulmonary disease. Also, it should be noted that although the leading factors of protein carbonylation have been widely reported, its degradation mechanisms and pathways have not yet been studied.
Hence, the development of effective tools and methods to detect protein carbonylation in live cells has become a research focus in recent years. Hydrazine derivates are most widely used to identify the specific carbonylated groups on biomolecules since 2,4-dinitrophenyl hydrazine (DNPH) was firstly introduced by Levine et al. However, most of the current tools are not compatible with live context or significantly lack specificity. Herein, we design an easily accessible aggregation-induced emission (AIE) probe that incorporates a hydrazine group as the recognition unit, which has opened up new possibilities for measuring the carbonylated protein load in live cells as well as further analysis utilizing mass spectrometry (MS)-based proteomics. This tailor-made probe has been proven to be applicable in cells treated with different oxidative stressors or oxidative inhibitors, showing significant enhancement or reduction in fluorescence, respectively. Besides, through the influenza A virus (IAV) infection, we found and further verified that autophagy is a main degradation pathway for carbonylated proteins, which provides a novel method to conduct the real-time tracking of autophagosomes in various intracellular processes.