Activation of epidermal growth factor receptor promotes late terminal differentiation of cell-matrix interaction-disrupted keratinocytes

The biological effects of epidermal growth factor receptor (EGFR) activatio n may differ between epidermal suprabasal and basal keratinocytes, since gr owth factors are mitogenic in adherent cells only in the presence of cell-e xtracellular matrix (ECM) interaction, To investigate biological effects of EGFR activation on keratinocytes without cell-ECM interaction, we cultured normal human keratinocytes on polyhydroxyethyl-methacrylate-coated plates, which disrupt cell-ECM but not cell-cell interaction. The cells initially expressed keratin 10 (K10) and then profilaggrin, mimicking sequential diff erentiation of epidermal suprabasal keratinocytes, The addition of EGF or t ransforming growth factor-alpha promoted late terminal differentiation (pro filaggrin expression, type 1 transglutaminase expression and activity, and cornified envelope formation) of the suspended keratinocytes, while suppres sing K10 expression, an early: differentiation marker. These effects were a ttenuated by EGFR tyrosine kinase inhibitor PD153035 or an anti-EGFR monocl onal antibody, whereas protein kinase C inhibitors H7 and bisindolylmaleimi de I or mitogen-activated protein kinase/extracellular signal-regulated kin ase kinase inhibitor PD98059 abolished profilaggrin up-regulation but not K 10 suppression. Since the antidifferentiative role of EGFR on cell-ECM inte raction-conserved keratinocytes has been well documented, our results indic ate that the biological effects of EGFR:on keratinocytes are influenced by cell-ECM interaction and suggest that EGFR activation promotes rather than inhibits the terminal differentiation of suprabasal epidermal keratinocytes .