title: The EGF-like protein dlk1 inhibits notch signaling and potentiates adipogenesis of mesenchymal cells.
abstract: The EGF-like homeotic gene Dlk1 appears to function as an inhibitor of adipogenesis. Overexpression of Dlk1 prevents adipogenesis of 3T3-L1 cells. Dlk1-deficient mice are obese; however, adipose tissue still develops in Fc-dlk1 transgenic mice, suggesting that Dlk1 is not a strict inhibitor of adipogenesis. To clarify the role of Dlk1 in adipogenesis, we studied whether Dlk1 could act differently on this process depending upon the differentiation state of the precursor cells. We found that Dlk1 is a potentiator of adipogenesis for mesenchymal C3H10T1/2 cells. This potentiating effect can be triggered by overexpressing the entire protein or the extracellular EGF-like-containing region, but not by overexpressing the intracellular dlk1 sequence. In addition, coculture of C3H10T1/2 cells with other cells expressing Dlk1, but not with cells lacking Dlk1 expression, enhances their adipogenic response. Potentiation of adipogenesis by Dlk1 was associated with changes in the activation of ERK1/2 after IGFI/insulin induction. Finally, as reported with other cells, dlk1 functioned as a Notch signaling inhibitor in C3H10T1/2 cells, but inhibition of Notch1 expression prevented the potentiating effects of Dlk1 in adipogenesis. These data suggest that Dlk1 may potentiate or inhibit adipogenesis depending upon the cellular context, and that Notch1 expression and activation are important factors in this context.
authors.affiliation: Department of Inorganic and Organic Chemistry and Biochemistry, Medical School, Regional Center for Biomedical Research, University of Castilla-La Mancha, Albacete, Spain.
authors.forename: María-Luisa
authors.initials: ML
authors.lastname: Nueda
authors.forename: Victoriano
authors.initials: V
authors.lastname: Baladrón
authors.forename: Beatriz
authors.initials: B
authors.lastname: Sánchez-Solana
authors.forename: María-Angeles
authors.initials: MA
authors.lastname: Ballesteros
authors.forename: Jorge
authors.initials: J
authors.lastname: Laborda
mesh_terms: D041721:3T3-L1 Cells; D050156:Adipogenesis / Q000187:drug effects / Q000235:genetics*; D000818:Animals; D002135:Calcium-Binding Proteins; D002460:Cell Line; D007328:Insulin / Q000494:pharmacology; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics / Q000502:physiology*; D059630:Mesenchymal Stem Cells / Q000166:cytology* / Q000187:drug effects; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D051881:Receptor, Notch1 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D015398:Signal Transduction; D014162:Transfection
chemical_list: D002135:Calcium-Binding Proteins; C512925:Dlk1 protein, mouse; D007328:Insulin; D036341:Intercellular Signaling Peptides and Proteins; C497762:Notch1 protein, mouse; D051881:Receptor, Notch1; D007334:Insulin-Like Growth Factor I; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3