Covalent N-arylation by the pollutant 1,2-naphthoquinone activates the EGF receptor

Abstract

The epidermal growth factor receptor (EGFR) is the most intensively investigated receptor tyrosine kinase. Several EGFR mutations and modifications have been shown to lead to abnormal self-activation, which plays a critical role in carcinogenesis. Environmental air pollutants, which are associated with cancer and respiratory diseases, can also activate EGFR. Specifically, the environmental electrophile 1,2-naphthoquinone (1,2-NQ), a component of diesel exhaust particles and particulate matter more generally, has previously been shown to impact EGFR signaling. However, the detailed mechanism of 1,2-NQ function is unknown. Here, we demonstrate that 1,2-NQ is a novel chemical activator of EGFR but not other EGFR family proteins. We found that 1,2-NQ forms a covalent bond, in a reaction referred to as N -arylation, with Lys80, which is in the ligand-binding domain. This modification activates the EGFR–Akt signaling pathway, which inhibits serum deprivation–induced cell death in a human lung adenocarcinoma cell line. Our study reveals a novel mode of EGFR pathway activation and suggests a link between abnormal EGFR activation and environmental pollutant–associated diseases such as cancer.

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

“…In particular, electrophilic environmental chemicals should be given priority for evaluation not only because they are routinely and chronically exposed in daily life but also because they form protein adducts and disrupt the functions of proteins ( 78 , 79 ). We previously reported that 1,2-naphthoquinone, which is found in air pollutants such as particulate matter 2.5, activates EGFR via N -arylation and induces PI3K–Akt signaling ( 80 ). Our studies indicate that the disruption of signaling homeostasis by 1,2-naphthoquinone, MVK, and MVK analogs leads to adverse physiological effects and demonstrate the importance of protein adduct formation by environmental electrophiles as a model for exposome research.…”

“…After quantification of protein concentration by the bicinchoninic acid (BCA) assay (Takara, T930A) method, protein samples were boiled in 1×Laemmli SDS sample buffer (62.5 mM Tris–HCl [pH 6.8], 5% [v/v] 2-mercaptoethanol, 2% [w/v] SDS, and 10% [v/v] glycerol) for 5 min. The samples were subjected to SDS–PAGE and Western blotting as previously described ( 80 ).…”