Methyl vinyl ketone and its analogs covalently modify PI3K and alter physiological functions by inhibiting PI3K signaling

Abstract

Reactive carbonyl species (RCS), which are abundant in the environment and are produced in vivo under stress, covalently bind to nucleophilic residues such as cysteine (Cys) in proteins. Disruption of protein function by RCS exposure is predicted to play a role in the development of various diseases such as cancer and metabolic disorders, but most studies on RCS have been limited to simple cytotoxicity validation, leaving their target proteins and resulting physiological changes unknown. In this study, we focused on methyl vinyl ketone (MVK), which is one of the main RCS found in cigarette smoke and exhaust gas. We found that MVK suppressed phosphatidylinositol-3 kinase (PI3K)–Akt signaling, which regulates processes involved in cellular homeostasis, including cell proliferation, autophagy, and glucose metabolism. Interestingly, MVK inhibits the interaction between the epidermal growth factor (EGF) receptor and PI3K. Cys656 in the SH2 domain of the PI3K p85 subunit, which is the covalently binding site of MVK, is important for this interaction. Suppression of PI3K–Akt signaling by MVK reversed EGF-induced negative regulation of autophagy, and attenuated glucose uptake. Furthermore, we analyzed the effects of the 23 RCS compounds with structures similar to MVK and showed that their analogs also suppressed PI3K–Akt signaling in a manner that correlated with their similarities to MVK. Our study demonstrates the mechanism of MVK and its analogs in suppressing PI3K–Akt signaling and modulating physiological functions, providing a model for future studies analyzing environmental reactive species.