SrcによるEphA2の発現亢進は細胞接着の喪失を相殺する

The receptor tyrosine kinase EphA2 is highly expressed in various cancers, and its elevated levels are associated with poor prognosis. Although Src has been shown to increase EphA2 expression partly through ERK signaling, the functional consequences of EphA2 upregulation remain unclear. In this study, we investigated the role of EphA2 upregulation by active Src in cell adhesion. We utilized HeLa S3-derived HeLa S3/v-Src cells, which allow inducible v-Src expression upon doxycycline (Dox) treatment. Dox treatment induced v-Src expression, cell rounding, and a marked increase in global tyrosine phosphorylation. Consistent with previously reports, EphA2 expression was upregulated following v-Src induction. Time-course analysis revealed that EphA2 knockdown accelerated v-Src-induced cell rounding. Similarly, c-Src also upregulated EphA2 and induced cell rounding. Paxillin staining demonstrated that c-Src expression increased both the number and area of focal adhesions, as well as paxillin intensity at these sites. All of these effects were abolished by EphA2 knockdown. In conclusion, Src activity upregulates EphA2 expression, and increased EphA2 counteracts Src-induced cell detachment. However, as Src signaling intensifies, it overrides the counteracting effect of EphA2, resulting in cell rounding and detachment. The balance between Src and EphA2 may act as a key regulator of cellular adhesion dynamics.