Identification of oxidized cysteine residues in signaling proteins in U937 cells at basal levels and upon diamide and hypochlorous acid stimulations.

Here, we report a detection of oxidative post-translational modifications (ox-PTM) of Cys residues in the U937 cell line either non-stimulated or stimulated with diamide, a thiol-oxidizing agent at 0.5mM for 20min or HOCl at 100µM for 10min. Reversible Cys ox-PTMs were labelled using a bioswitch method using a Maleimide-(Polyethylene Glycol)2-Biotin (Mal-PEG2-Bio) probe independently of the oxidation type. Labeled proteins were analyzed by Mass spectrometry. We identified Cys ox-PTMs encompassing 1473 proteins containing at least ox-PTM-modified Cys. These sites include ox-PTM sites previously described in vitro validating the approach. Numerous novel Cys susceptible to ox-PTMs were identified including signaling proteins, including kinases, phosphatases and transcription and translation factors and proteins relevant to virus-host interactions.