title: The small Rho GTPase Rac1 controls normal human dermal fibroblasts proliferation with phosphorylation of the oncoprotein c-myc.
abstract: Proliferation of dermal fibroblasts is crucial for the maintenance of skin. The small Rho GTPase, Rac1, has been identified as a key transducer of proliferative signals in various cell types, but in normal human dermal fibroblasts its significance to cell growth control has not been studied. In this study, we applied the method of RNA interference to suppress endogenous Rac1 expression and examined the consequences on human skin fibroblasts. Rac1 knock-down resulted in inhibition of DNA synthesis. This effect was not mediated by inhibition of the central transducer of proliferative stimuli, ERK1/2 or by activation of the pro-apoptotic p38. Rather, as a consequence of the suppressed Rac1 expression we observed a significant decrease in phosphorylation of c-myc, revealing for the first time that in human fibroblasts Rac1 exerts control on proliferation through c-myc phosphorylation. Thus Rac1 activates proliferation of normal fibroblasts through stimulation of c-myc phosphorylation without affecting ERK1/2 activity.
authors.affiliation: Cell and Tissue Laboratory, URPHYM, University of Namur (FUNDP), B-5000 Namur, Belgium.
authors.forename: Ekaterina
authors.initials: E
authors.lastname: Nikolova
authors.forename: Vanio
authors.initials: V
authors.lastname: Mitev
authors.forename: Nikolai
authors.initials: N
authors.lastname: Zhelev
authors.forename: Christophe F
authors.initials: CF
authors.lastname: Deroanne
authors.forename: Yves
authors.initials: Y
authors.lastname: Poumay
mesh_terms: D049109:Cell Proliferation; D002478:Cells, Cultured; D005347:Fibroblasts; D006801:Humans; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D010766:Phosphorylation; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics; D012867:Skin / Q000166:cytology* / Q000378:metabolism*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism; D020830:rac1 GTP-Binding Protein / Q000235:genetics / Q000378:metabolism*
chemical_list: D016271:Proto-Oncogene Proteins c-myc; D034741:RNA, Small Interfering; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D048051:p38 Mitogen-Activated Protein Kinases; D020830:rac1 GTP-Binding Protein