Two Mechanisms Regulate Keratin K15 Expression in Keratinocytes: Role of PKC/AP-1 and FOXM1 Mediated Signaling

The study investigated the regulation of keratin K15 expression in keratinocytes, identifying two primary mechanisms: PKC/AP-1 and FOXM1 mediated signaling pathways. PKC/AP-1 signaling was crucial for K15 upregulation during terminal differentiation, particularly under high cell density and phorbol ester treatment, and involved PKCδ and AP-1 activation. FOXM1 mediated basal-specific K15 expression, confirmed by its binding to the K15 promoter. These findings underscored the complexity of K15 regulation and suggested caution in using K15 as a stem cell marker due to its context-dependent expression.