title: The complexity of ERK1 and ERK2 MAPKs in multiple hepatocyte fate responses.
abstract: Recent reports suggest that extracellular signal-regulated kinase (ERK1) and ERK2 mitogen-activated protein kinases (MAPK) may direct specific biological functions under certain contexts. In this study, we investigated the role of early and sustained epidermal growth factor (EGF) stimulation on long-term hepatocyte differentiation and the possible role of ERK1 and ERK2 in this process. We demonstrate a long-term survival and an elevated level of differentiation up to 3 weeks. The differentiation state of hepatocytes is supported by sustained expression of aldolase B, albumin, and the detoxifying enzymes CYP1A2, 2B2, and 3A23. Similarly to freshly isolated cells, cultured hepatocytes also retain the ability to respond to 3-methylcholanthrene (3MC) and phenobarbital (PB), two known CYP inducers. In addition, we show evidence that continuous MAPK/ERK kinase (MEK) inhibition enhances the level of differentiation. Using RNA interference approaches against ERK1 and ERK2, we demonstrate that this effect requires both ERK1 and ERK2 activity, whereas the specific ERK1 knockdown promotes cell survival and the specific ERK2 knockdown regulates cell proliferation. In conclusion, we demonstrate that early and sustained EGF stimulation greatly extends long-term hepatocyte survival and differentiation, and that inhibition of the ERK1/2 MAPK pathway potentiates these pro-survival/pro-differentiation phenotypes. We clearly attest that specific ERK1 and ERK2 MAPKs determine hepatocyte survival and proliferation, respectively, whereas dual inhibition is required to stabilize a highly differentiated state.
authors: EA 4427-SeRAIC, IRSET, IFR 140, Campus Biologie-Santé, F-35043 Rennes, France.
authors: Christophe
authors: C
authors: Frémin
authors: Frédéric
authors: F
authors: Ezan
authors: Jean-Philippe
authors: JP
authors: Guegan
authors: Luc
authors: L
authors: Gailhouste
authors: Maud
authors: M
authors: Trotard
authors: Jacques
authors: J
authors: Le Seyec
authors: Julie
authors: J
authors: Rageul
authors: Nathalie
authors: N
authors: Theret
authors: Sophie
authors: S
authors: Langouët
authors: Georges
authors: G
authors: Baffet
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000502:physiology*; D002470:Cell Survival / Q000502:physiology; D002478:Cells, Cultured; D004815:Epidermal Growth Factor / Q000378:metabolism; D022781:Hepatocytes / Q000166:cytology* / Q000502:physiology; D015151:Immunoblotting; D020935:MAP Kinase Signaling System / Q000502:physiology*; D008297:Male; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D034741:RNA, Small Interfering; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014162:Transfection
chemical_list: D034741:RNA, Small Interfering; D004815:Epidermal Growth Factor; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3