title: Control of myofibroblast differentiation by microtubule dynamics through a regulated localization of mDia2.
abstract: Myofibroblast differentiation plays a critical role in wound healing and in the pathogenesis of fibrosis. We have previously shown that myofibroblast differentiation is mediated by the activity of serum response factor (SRF), which is tightly controlled by the actin polymerization state. In this study, we investigated the role of the microtubule cytoskeleton in modulating myofibroblast phenotype. Treatment of human lung fibroblasts with the microtubule-destabilizing agent, colchicine, resulted in a formation of numerous stress fibers and expression of myofibroblast differentiation marker proteins. These effects of colchicine were independent of Smad signaling but were mediated by Rho signaling and SRF, as they were attenuated by the Rho kinase inhibitor, Y27632, or by the SRF inhibitor, CCG-1423. TGF-β-induced myofibroblast differentiation was not accompanied by gross changes in the microtubule polymerization state. However, microtubule stabilization by paclitaxel attenuated TGF-β-induced myofibroblast differentiation. Paclitaxel had no effect on TGF-β-induced Smad activation and Smad-dependent gene transcription but inhibited actin polymerization, nuclear accumulation of megakaryoblastic leukemia-1 protein, and SRF activation. The microtubule-associated formin, mDIA2, localized to actin stress fibers upon treatment with TGF-β, and paclitaxel prevented this localization. Treatment with the formin inhibitor, SMI formin homology 2 domain, inhibited stress fiber formation and myofibroblast differentiation induced by TGF-β, without affecting Smad-phosphorylation or microtubule polymerization. Together, these data suggest that (a) TGF-β promotes association of mDia2 with actin stress fibers, which further drives stress fiber formation and myofibroblast differentiation, and (b) microtubule polymerization state controls myofibroblast differentiation through the regulation of mDia2 localization.
authors.affiliation: Division of Allergy, Pulmonary, and Critical Care, University of Wisconsin, Madison, Wisconsin 53792, USA. nsandbo@medicine.wisc.edu
authors.forename: Nathan
authors.initials: N
authors.lastname: Sandbo
authors.forename: Caitlyn
authors.initials: C
authors.lastname: Ngam
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Torr
authors.forename: Steve
authors.initials: S
authors.lastname: Kregel
authors.forename: Jacob
authors.initials: J
authors.lastname: Kach
authors.forename: Nickolai
authors.initials: N
authors.lastname: Dulin
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D000577:Amides / Q000494:pharmacology; D000813:Anilides / Q000494:pharmacology; D001549:Benzamides / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology*; D002478:Cells, Cultured; D003078:Colchicine / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D000080865:Formins; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology; D006801:Humans; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D008870:Microtubules / Q000378:metabolism*; D058628:Myofibroblasts / Q000166:cytology / Q000378:metabolism*; D015514:Oncogene Proteins, Fusion / Q000378:metabolism; D017239:Paclitaxel / Q000494:pharmacology; D021381:Protein Transport / Q000187:drug effects / Q000502:physiology; D011725:Pyridines / Q000494:pharmacology; D026362:Serum Response Factor / Q000378:metabolism; D051785:Smad Proteins / Q000235:genetics / Q000378:metabolism; D022502:Stress Fibers / Q000378:metabolism; D015534:Trans-Activators; D016212:Transforming Growth Factor beta / Q000378:metabolism; D050257:Tubulin Modulators / Q000494:pharmacology
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D000577:Amides; D000813:Anilides; D001549:Benzamides; C523455:CCG 1423; C484571:DIAPH3 protein, human; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D000080865:Formins; C431575:MRTFA protein, human; D008869:Microtubule-Associated Proteins; D015514:Oncogene Proteins, Fusion; D011725:Pyridines; C476858:SRF protein, human; D026362:Serum Response Factor; D051785:Smad Proteins; D015534:Trans-Activators; D016212:Transforming Growth Factor beta; D050257:Tubulin Modulators; C108830:Y 27632; D017239:Paclitaxel; D003078:Colchicine
keywords: Actin; Cytoskeleton; Fibroblast; MKL1; Microtubules; Myofibroblast; SRF; Transforming Growth Factor Beta (TGFbeta)