Interferon gamma-induced PNA-binding glycoproteins as markers of human keratinocyte differentiation: biological evidence using protein kinase C agonists, antagonists and retinoic acid

Abstract

Membrane glycoproteins (gps) play an important role in cell-cell interactions during epidermal maturation, and we have previously shown an up-regulation of PNA-binding gps in cultured human keratinocytes treated with interferon gamma (IFN-γ). The protein kinase C (PKC) pathway is known to play a key role in the regulation of proliferation and differentiation of keratinocytes and is also reported to be involved in some IFN-γ-mediated effects. In order to evaluate the cellular mechanisms and whether PNA-binding gp expression is related to the differentiative activity of the lymphokine, we studied the effects of PKC agonists and antagonists and the role of retinoic acid (RA), in the induction of these gps in cultured human keratinocytes stimulated with IFN-γ and processed for protein analysis. The expression of PNA-binding gps was revealed by incubation of SDS-polyacrylamide gels with ¹²⁵ I-PNA. The PKC antagonists (H7, sphingosine) as well as RA downgregulated the IFN-γ-induced PNA-reactive gps, whereas staurosporine and TPA upregulated their expression. These results provide evidence that PNA-reactive gps are late highly IFN-γ-sensitive markers of keratinocyte differentiation, drastically modulated through selective isoforms of PKC.