[Molecular mechanism of EGFR signaling evoked by environmental pollutant 1,2-naphthoquinone].

The epidermal growth factor receptor (EGFR) is the most extensively examined receptor tyrosine kinase. Several EGFR mutations and modifications have been shown to induce self-activation, which plays a central role in carcinogenesis. Recently, environmental chemicals such as PM2.5 can also activate EGFR and become risk factors for cancer. Although, the detailed mechanism remains unknown. In this study, we focused on 1,2-naphthoquinone (1,2-NQ) which is a secondary metabolite of naphthalene. Humans are exposed to 1,2-NQ through the combustion of fossil and diesel fuel and from tobacco smoke and PM2.5. Here, we demonstrate that 1,2-NQ is a novel EGFR-specific activator. We found that 1,2-NQ forms a covalent bond called N-arylation with EGFR Lys80 which is in the extracellular domain by LC-MS/MS. This modification activates the EGFR-Akt signaling pathway, which inhibits serum deprivation-induced apoptosis in A549 cells. Our study reveals an original mode of EGFR activation via covalent binding. We propose the correlation between EGFR activation without ligands and environmental pollutant-associated diseases such as cancer.

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

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.