E2F1 stability is regulated by a novel-PKC/p38beta MAP kinase signaling pathway during keratinocyte differentiation.
E2F transcription factors regulate proliferation, differentiation, DNA repair and apoptosis. Tight E2F regulation is crucial for epidermal formation and regeneration. However, virtually nothing is known about the molecular events modulating E2F during epidermal keratinocyte differentiation. Elucidation of these events is essential to understand epidermal morphogenesis, transformation and repair. Here we show that, in differentiating keratinocytes, Ca(2+)-induced protein kinase C (PKC) activation downregulates E2F1 protein levels. Further, we have identified PKC delta and eta as those isoforms specifically involved in induction of E2F1 proteasomal degradation. We also demonstrate that E2F1 downregulation by novel PKC isozymes requires activation of p38beta mitogen-activated protein kinase (MAPK). This is the first example of regulation in the E2F transcription factor family by activation of PKC and MAPK in the context of biologically significant differentiation stimuli in epithelia.
Ivanova
I A
IA
Department of Physiology and Pharmacology, University of Western Ontario, London Ontario, Canada N6A 5C1.
D'Souza
S J A
SJ
Dagnino
L
L
D000818:Animals; D002454:Cell Differentiation; D050687:E2F1 Transcription Factor / Q000378:metabolism*; D004789:Enzyme Activation; D015603:Keratinocytes / Q000166:cytology* / Q000201:enzymology / Q000378:metabolism; D051379:Mice; D011493:Protein Kinase C / Q000378:metabolism*; D015398:Signal Transduction; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
D050687:E2F1 Transcription Factor; C493754:E2f1 protein, mouse; D011493:Protein Kinase C; D048051:p38 Mitogen-Activated Protein Kinases