Opposite effects of Ras or PKC activation on the expression of the SPRR2A keratinocyte terminal differentiation marker.
Epidermal growth factor (EGF) enhances the expression of the keratinocyte terminal differentiation marker SPRR2A, when added to monolayers of basal keratinocytes, induced to stratify by increasing the extracellular calcium concentration. A similar stimulation is found during suspension-induced differentiation in methylcellulose. This effect, which is observed after several hours of EGF addition, is restricted to terminally differentiating keratinocytes and is dependent on PKC signaling. EGF also transiently activates the Ras signaling pathway, with a maximum induction after 10 min (Medema et al., 1994, Mol. Cell. Biol. 14, 7078-7085). The cellular effects of activated Ras were determined by transient transfection of Ha-ras(Leu-61) into normal human keratinocytes. Activated Ras completely inhibited PKC-mediated expression of SPRR2A. This inhibition is mediated via c-Jun as it is reversed by a dominant-negative c-Jun mutant (cJunDelta6/194) and c-Jun can substitute for activated Ras. The inhibitory effect is targeted to a 150-bp minimal promoter region, which is essential and sufficient for SPRR2A expression during keratinocyte terminal differentiation. This indicates that the Ras and PKC pathways, which both can be triggered by EGF, although at different time points, have opposite effects on SPRR2A gene expression.
Leiden Institute of Chemistry, Leiden University, Leiden, 2333 CC, The Netherlands.
M W
MW
Sark
A M
AM
Borgstein
J P
JP
Medema
P
P
van de Putte
C
C
Backendorf
D002118:Calcium / Q000037:antagonists & inhibitors / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects; D002478:Cells, Cultured; D055233:Cornified Envelope Proline-Rich Proteins; D004789:Enzyme Activation; D004815:Epidermal Growth Factor / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects; D016762:Genes, fos / Q000235:genetics; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D015603:Keratinocytes / Q000166:cytology / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D008301:Maleimides / Q000494:pharmacology; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D009154:Mutation; D015689:Oncogene Protein p21(ras) / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000235:genetics; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011498:Protein Precursors / Q000235:genetics* / Q000378:metabolism; D016755:Proto-Oncogene Proteins c-jun / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014158:Transcription, Genetic / Q000187:drug effects
D055233:Cornified Envelope Proline-Rich Proteins; D007211:Indoles; D008301:Maleimides; D008565:Membrane Proteins; D011498:Protein Precursors; D016755:Proto-Oncogene Proteins c-jun; D012333:RNA, Messenger; C101744:SPRR2A protein, human; D004815:Epidermal Growth Factor; D011493:Protein Kinase C; D015689:Oncogene Protein p21(ras); C070515:bisindolylmaleimide I; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium