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.

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Background] The epidermal growth factor receptor (EGFR) is the most intensively investigated receptor tyrosine kinase whose mutation or modification leads to abnormal self-activation, which plays a critical role in carcinogenesis. Although environmental air pollutants, which are associated with cancer and respiratory diseases, can activate EGFR, the detailed mechanisms remain unknown. In this study, we addressed to clarify the mechanisms by which the air pollutant 1,2-naphthoquinone (1,2-NQ) disrupts EGFR-Akt signaling and promotes oncogenic effects.[Methods] Phosphorylated forms of Akt, EGFR, IGF-IR, and Insulin receptor were detected by western blotting using specific antibodies. The modification sites in EGFR were identified by LC-MS/MS analysis. Cell viability was assessed by WST-8 assay.[Results] We found that 1,2-NQ stimulates the phosphorylation of EGFR, but not IGF-IR and Insulin receptor in A549 cells. LC-MS/MS analysis revealed that 1,2-NQ forms chemical modification with EGFR at ligand-binding domain I, Lys80. In addition, phosphorylation of Akt was observed by treatment with 1,2-NQ in a concentrationdependent manner. Activation of Akt by 1,2-NQ was suppressed by pretreatment with tyrphostinA25, a specific EGFR tyrosine kinase inhibitor. Moreover, 1,2-NQ exerted the cytoprotective effect against for serum deprivationinduced cell death through the activation of EGFR-Akt signaling.[Conclusions] These findings showed that 1,2-NQ directly activates EGFR-Akt signaling via chemical modification of EGFR.