title: Smooth muscle alpha-actin expression and myofibroblast differentiation by TGFbeta are dependent upon MK2.
abstract: Fibroblasts play a major role in processes such as wound repair, scarring, and fibrosis. Differentiation into myofibroblasts, characterized by upregulation of smooth muscle alpha-actin (smalpha) in response to profibrotic agents such as TGFbeta is believed to be an important step in fibrosis. Therefore, elucidating mechanisms of myofibroblast differentiation might reveal novel targets in treating diseases such as idiopathic pulmonary fibrosis (IPF). MK2 is a kinase substrate of p38 MAP kinase that mediates some effects of p38 activation on the actin cytoskeleton. Using mouse embryonic fibroblasts (MEF) from MK2 knockout (MK2(-/-)) mice, we demonstrate that disrupting expression of MK2 expression reduces filamentous actin and stress fibers. It also causes MK2(-/-) MEF to express less smalpha than their corresponding wild-type (WT) MEF at baseline and in response to TGFbeta. Furthermore, TGFbeta causes downregulation of smalpha in MK2(-/-) MEF, instead of upregulation observed in WT MEF. Expression of other fibroblast markers, such as collagen, is not altered in MK2(-/-) MEF. Our results further suggest that downregulation of smalpha in MK2(-/-) MEF is not due to lack of activation of serum responsive promoter elements, but probably due to reduced smalpha message stability in these cells. These results indicate that MK2 plays a key role in regulation of smalpha expression, and that targeting MK2 might present a therapeutic approach in managing conditions such as pulmonary fibrosis.
authors.affiliation: Pulmonary and Critical Care Division, Department of Medicine/Tupper Research Institute, Tufts-New England Medical Center, and Tufts University School of Medicine, Boston, Massachusetts 02111, USA.
authors.forename: Anne Marie
authors.initials: AM
authors.lastname: Sousa
authors.forename: Tiegang
authors.initials: T
authors.lastname: Liu
authors.forename: Oscar
authors.initials: O
authors.lastname: Guevara
authors.forename: Joanne
authors.initials: J
authors.lastname: Stevens
authors.forename: Barry L
authors.initials: BL
authors.lastname: Fanburg
authors.forename: Matthias
authors.initials: M
authors.lastname: Gaestel
authors.forename: Deniz
authors.initials: D
authors.lastname: Toksoz
authors.forename: Usamah S
authors.initials: US
authors.lastname: Kayyali
mesh_terms: D000199:Actins / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects*; D002478:Cells, Cultured; D004591:Electrophoresis, Polyacrylamide Gel; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D015870:Gene Expression / Q000187:drug effects; D007093:Imidazoles / Q000494:pharmacology; D015151:Immunoblotting; D047908:Intracellular Signaling Peptides and Proteins; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009130:Muscle, Smooth / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D009154:Mutation; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases; D011725:Pyridines / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D027602:Serum Response Element / Q000235:genetics; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000494:pharmacology*; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D000099190:MAP-Kinase-Activated Kinase 2
chemical_list: D000199:Actins; D007093:Imidazoles; D047908:Intracellular Signaling Peptides and Proteins; D008156:Luciferases; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases; D011725:Pyridines; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D016212:Transforming Growth Factor beta; D048051:p38 Mitogen-Activated Protein Kinases; D000099190:MAP-Kinase-Activated Kinase 2; C093642:SB 203580