Chemoproteomic profiling of targets of lipid-derived electrophiles by bioorthogonal aminooxy probe

Redox imbalance in cells induces lipid peroxidation and generates a class of highly reactive metabolites known as lipid-derived electrophiles (LDEs) that can modify proteins and affects their functions. Identifying targets of LDEs is critical to understand how such modifications are functionally implicated in oxidative-stress associated diseases. Here we report a quantitative chemoproteomic method to globally profile protein targets and sites modified by LDEs. In this strategy, we designed and synthesized an alkyne-functionalized aminooxy probe to react with LDE-modified proteins for imaging and proteomic profiling. Using this probe, we successfully quantified >4000 proteins modified by 4-hydroxy-2-nonenal (HNE) of high confidence in mammalian cell lysate and combined with a tandem-orthogonal proteolysis activity-based protein profiling (TOP-ABPP) strategy, we identified ~400 residue sites targeted by HNE including reactive cysteines in peroxiredoxins, an important family of enzymes with anti-oxidant roles. Our method expands the toolbox to quantitatively profile protein targets of endogenous electrophiles and the enlarged inventory of LDE-modified proteins and sites will contribute to functional elucidation of cellular pathways affected by oxidative stress.