ACTIVATION OF PROTEIN-KINASE-C INHIBITS HUMAN KERATINOCYTE MIGRATION

The involvement of protein kinase C (PKC) in epidermal growth factor ( EGF)-induced human keratinocyte migration was studied with the phagoki netic assay. It was concluded that PKC activation does not mediate, bu t rather inhibits, EGF-induced keratinocyte migration. The following e xperimental observations support these conclusions: 1) The PKC inhibit or H-7 did not inhibit EGF-induced migration but instead led to a mode st enhancement. 2) PKC activators such as phorbol-12-myristate-13-acet ate (PMA), phorbol-12,13-dibutyrate (PDBu), and 1,2-dioctanoly-sn-glyc erol inhibited migration, but biologically inactive 4alpha-PMA had no effect. 3) PMA did not inhibit keratinocyte attachment and spreading b ut blocked migration almost immediately after addition. 4) Migration o f PKC-depleted cells, which were produced by prolonged treatment with PDBu, was enhanced similarly to normal cells by EGF. 5) PKC-depleted c ells were not susceptible to the inhibitory effects of phorbol esters on migration. Additional experiments, in which cells were preactivated with EGF, suggested that PKC inhibits the EGF effect at a post-recept or level. The inhibitory effect of PKC on keratinocyte migration was n ot restricted to EGF-induced migration; PKC activation also inhibited keratinocyte migration induced by bovine pituitary extract, insulin, i nsulin-like growth factor-1, and keratinocyte growth factor. (C) 1993 Wiley-Liss, Inc.