title: AMP-activated protein kinase inhibits transforming growth factor-beta-induced Smad3-dependent transcription and myofibroblast transdifferentiation.
abstract: In wound healing, myofibroblast transdifferentiation (MFT) is a metaplastic change in phenotype producing profibrotic effector cells that secrete and remodel the extracellular matrix. Unlike pathways that induce MFT, the molecular mechanisms that negatively regulate MFT are poorly understood. Here, we report that AMP-activated protein kinase (AMPK) blocks MFT in response to transforming growth factor-beta (TGFbeta). Pharmacological activation of AMPK inhibited TGFbeta-induced secretion of extracellular matrix proteins collagen types I and IV and fibronectin. AMPK activation also prevented induction of the myofibroblast phenotype markers alpha-smooth muscle actin and the ED-A fibronectin splice variant. AMPK activators did not prevent MFT in cells transduced with an adenovirus expressing dominant negative, kinase-dead AMPKalpha2. Moreover, AMPK activators did not inhibit MFT induction in AMPK(alpha1,2)(-/-) fibroblasts, demonstrating a requirement for AMPK(alpha) expression. Adenoviral transduction of constitutively active AMPK(alpha2) was sufficient to prevent TGFbeta-induced collagen I, alpha-smooth muscle actin, and ED-A fibronectin. AMPK did not reduce TGFbeta-stimulated Smad3 COOH-terminal phosphorylation and nuclear translocation, which are necessary for MFT. However, AMPK activation inhibited TGFbeta-induced transcription driven by Smad3-binding cis-elements. Consistent with a role for AMPK in transcriptional regulation, nuclear translocation of AMPKalpha2 correlated with the appearance of active AMPKalpha in the nucleus. Collectively, these results demonstrate that AMPK inhibits TGFbeta-induced transcription downstream of Smad3 COOH-terminal phosphorylation and nuclear translocation. Furthermore, activation of AMPK is sufficient to negatively regulate MFT in vitro.
authors.affiliation: Division of Nephrology and Hypertension, Department of Medicine, Case Western Reserve University and University Hospitals Case Medical Center, Cleveland, Ohio 44106, USA.
authors.forename: Rangnath
authors.initials: R
authors.lastname: Mishra
authors.forename: Barbara L
authors.initials: BL
authors.lastname: Cool
authors.forename: Keith R
authors.initials: KR
authors.lastname: Laderoute
authors.forename: Marc
authors.initials: M
authors.lastname: Foretz
authors.forename: Benoit
authors.initials: B
authors.lastname: Viollet
authors.forename: Michael S
authors.initials: MS
authors.lastname: Simonson
mesh_terms: D055372:AMP-Activated Protein Kinases; D021581:Active Transport, Cell Nucleus; D000256:Adenoviridae / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D054338:Cell Transdifferentiation; D003094:Collagen / Q000378:metabolism; D004789:Enzyme Activation; D005109:Extracellular Matrix / Q000378:metabolism; D005347:Fibroblasts / Q000378:metabolism*; D005353:Fibronectins / Q000378:metabolism; D006801:Humans; D008954:Models, Biological; D009097:Multienzyme Complexes / Q000502:physiology*; D010641:Phenotype; D017346:Protein Serine-Threonine Kinases / Q000502:physiology*; D051900:Smad3 Protein / Q000502:physiology*; D014158:Transcription, Genetic; D016212:Transforming Growth Factor beta / Q000378:metabolism*
chemical_list: D005353:Fibronectins; D009097:Multienzyme Complexes; C497790:SMAD3 protein, human; D051900:Smad3 Protein; D016212:Transforming Growth Factor beta; D003094:Collagen; C526181:PRKAA2 protein, human; D017346:Protein Serine-Threonine Kinases; D055372:AMP-Activated Protein Kinases; C526180:PRKAA1 protein, human