title: Elastin peptides activate extracellular signal-regulated kinase 1/2 via a Ras-independent mechanism requiring both p110gamma/Raf-1 and protein kinase A/B-Raf signaling in human skin fibroblasts.
abstract: Elastin peptides (EPs) produced during cancer progression bind to the elastin binding protein (EBP) found at the surface of dermal fibroblasts, leading to the expression of collagenase-1 gene. The production of this enzyme involved in stromal reaction is caused by the sustained activation of the extracellular signal-regulated kinases 1/2 (ERK1/2) pathway via cAMP/protein kinase A (PKA) and phosphatidylinositol 3-kinase (PI3K). However, the mechanism of these signaling events remains unknown. We show that kappa-elastin (kappaE), a commonly used EP, induces maximum phosphorylation of mitogen-activated protein kinase/extracellular signal-regulated kinase (MEK)1/2 and ERK1/2 after 30 min. The simultaneous inhibition of PKA and PI3K, by N-(2-(p-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide (H89) and 2-(4-morpholynil)-8-phenyl-4H-1-bemzopyran-4-one (LY294002), respectively, blocked MEK1/2 and ERK1/2 phosphorylation, as did lactose, an EBP antagonist. kappaE induced Raf-1 phosphorylation and activation in a PI3K-dependent manner. In our system, the PI3K p110gamma is expressed and activated by betagamma-derived subunits from a pertussis toxin-sensitive G protein after fibroblast stimulation. Pertussis toxin also blocks the Raf-1/MEK1/2/ERK1/2 phosphorylation cascade. In addition, we found that B-Raf is expressed in dermal fibroblasts and activated in a PKA-dependent manner after kappaE treatment, thereby integrating PKA signals to MEK1/2. It is noteworthy that Ras involvement was excluded because ERK1/2 activation by kappaE was not blocked in RasN17-transfected fibroblasts. Together, our results identify a novel Ras-independent ERK1/2 activation system in which p110gamma/Raf-1/MEK1/2 and PKA/B-Raf/MEK1/2 cooperate to activate ERK1/2. Thus, p110gamma and B-Raf seem to be important modulators of dermal fibroblasts physiology and should now qualify as therapeutic targets in strategies aiming at limiting elastin degradation contribution to cancer progression.
authors.affiliation: Laboratoire de Biochimie, UMR CNRS 6198, IFR53 Biomolécules, Faculty of Sciences, Université de Reims Champagne Ardenne, Moulin de la Housse, BP 1039, 51687 Reims Cedex 2, France.
authors.forename: Laurent
authors.initials: L
authors.lastname: Duca
authors.forename: Elise
authors.initials: E
authors.lastname: Lambert
authors.forename: Romain
authors.initials: R
authors.lastname: Debret
authors.forename: Bernard
authors.initials: B
authors.lastname: Rothhut
authors.forename: Charlotte
authors.initials: C
authors.lastname: Blanchevoye
authors.forename: Frédéric
authors.initials: F
authors.lastname: Delacoux
authors.forename: William
authors.initials: W
authors.lastname: Hornebeck
authors.forename: Laurent
authors.initials: L
authors.lastname: Martiny
authors.forename: Laurent
authors.initials: L
authors.lastname: Debelle
mesh_terms: D002478:Cells, Cultured; D017868:Cyclic AMP-Dependent Protein Kinases / Q000502:physiology*; D004549:Elastin / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects; D005347:Fibroblasts / Q000378:metabolism; D006801:Humans; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism*; D037342:Pertussis Toxin / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology*; D010766:Phosphorylation; D048493:Proto-Oncogene Proteins B-raf / Q000502:physiology*; D019908:Proto-Oncogene Proteins c-raf / Q000502:physiology*; D015398:Signal Transduction; D012867:Skin / Q000166:cytology / Q000378:metabolism; D018631:ras Proteins / Q000502:physiology
chemical_list: D004549:Elastin; D037342:Pertussis Toxin; D019869:Phosphatidylinositol 3-Kinases; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf; D019908:Proto-Oncogene Proteins c-raf; D017868:Cyclic AMP-Dependent Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D018631:ras Proteins