title: Stable incorporation of α-smooth muscle actin into stress fibers is dependent on specific tropomyosin isoforms.
abstract: α-Smooth Muscle Actin (α-SMA), a widely characterized cytoskeletal protein, represents the hallmark of myofibroblast differentiation. Transforming growth factorβ1 (TGFβ1) stimulates α-SMA expression and incorporation into stress fibers, thus providing an increased myofibroblast contractile force that participates in tissue remodeling. We have addressed the molecular mechanism by which α-SMA is stably incorporated into stress fibers in human myofibroblasts following exposure to TGFβ1. The unique N-terminal sequence AcEEED, which is critical for α-SMA incorporation into stress fibers, was used to screen for AcEEED binding proteins. Tropomyosins were identified as candidate binding proteins. We find that after TGFβ1 treatment elevated levels of the Tpm1.6/7 isoforms, and to a lesser extent Tpm2.1, precede the increase in α-SMA. RNA interference experiments demonstrate that α-SMA fails to stably incorporate into stress fibers of TGFβ1 treated fibroblasts depleted of Tpm1.6/7, but not other tropomyosins. This does not appear to be due to exclusive interactions between α-SMA and just the Tpm1.6/7 isoforms. We propose that an additional AcEEED binding factor may be required to generate α-SMA filaments containing just Tpm1.6/7 which result in stable incorporation of the resulting filaments into stress fibers.
authors.affiliation: Discovery Technologies, Roche Innovation Center Basel, F. Hoffmann-La Roche Ltd, Basel, Switzerland.
authors.forename: Marco
authors.initials: M
authors.lastname: Prunotto
authors.affiliation: Laboratorio Di Fisiopatologia Dell'uremia, Istituto Giannina Gaslini, Genoa, Italy.
authors.forename: Maurizio
authors.initials: M
authors.lastname: Bruschi
authors.affiliation: School of Medical Sciences, University of New South Wales, Sydney, Australia.
authors.forename: Peter
authors.initials: P
authors.lastname: Gunning
authors.affiliation: Department of Pathology and Immunology, Faculty of Medicine, University of Geneva, Geneva, Switzerland.
authors.forename: Giulio
authors.initials: G
authors.lastname: Gabbiani
authors.affiliation: Discovery Technologies, Roche Innovation Center Basel, F. Hoffmann-La Roche Ltd, Basel, Switzerland.
authors.forename: Franziska
authors.initials: F
authors.lastname: Weibel
authors.affiliation: Laboratorio Di Fisiopatologia Dell'uremia, Istituto Giannina Gaslini, Genoa, Italy.
authors.forename: Gian Marco
authors.initials: GM
authors.lastname: Ghiggeri
authors.affiliation: Laboratory of Mass Spectrometry, Core Facility, Istituto Giannina Gaslini, Genoa, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Petretto
authors.affiliation: Proteomics and Mass Spectrometry Laboratory, Istituto per Il Sistema Produzione Animale in Ambiente Mediterraneo (ISPAAM), National Research Council (CNR), Napoli, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Scaloni
authors.affiliation: School of Medical Sciences, University of New South Wales, Sydney, Australia.
authors.forename: Teresa
authors.initials: T
authors.lastname: Bonello
authors.affiliation: School of Medical Sciences, University of New South Wales, Sydney, Australia.
authors.forename: Galina
authors.initials: G
authors.lastname: Schevzov
authors.affiliation: School of Medical Sciences, University of New South Wales, Sydney, Australia.|Department of Electron Microscopy (IA) and Mathematical Methods in Biology (VD), A.N. Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russia.
authors.forename: Irina
authors.initials: I
authors.lastname: Alieva
authors.affiliation: Department of Pathology and Immunology, Faculty of Medicine, University of Geneva, Geneva, Switzerland.
authors.forename: Marie-Luce
authors.initials: ML
authors.lastname: Bochaton-Piallat
authors.affiliation: Laboratorio Di Fisiopatologia Dell'uremia, Istituto Giannina Gaslini, Genoa, Italy.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Candiano
authors.affiliation: Department of Pathology and Immunology, Faculty of Medicine, University of Geneva, Geneva, Switzerland.|Department of Electron Microscopy (IA) and Mathematical Methods in Biology (VD), A.N. Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russia.
authors.forename: Vera
authors.initials: V
authors.lastname: Dugina
authors.affiliation: Department of Pathology and Immunology, Faculty of Medicine, University of Geneva, Geneva, Switzerland.
authors.forename: Christine
authors.initials: C
authors.lastname: Chaponnier
mesh_terms: D005347:Fibroblasts / Q000378:metabolism*; D006801:Humans; D009130:Muscle, Smooth / Q000378:metabolism*; D058628:Myofibroblasts / Q000378:metabolism*; D020033:Protein Isoforms / Q000378:metabolism*; D040901:Proteomics; D022502:Stress Fibers; D014335:Tropomyosin / Q000378:metabolism*
chemical_list: D020033:Protein Isoforms; D014335:Tropomyosin
keywords: TGFβ; actin isoforms; myofibroblast; proteomic