title: Post-transcriptional regulation of autophagy in C2C12 myotubes following starvation and nutrient restoration.
abstract: In skeletal muscle, autophagy is activated in multiple physiological and pathological conditions, notably through the transcriptional regulation of autophagy-related genes by FoxO3. However, recent evidence suggests that autophagy could also be regulated by post-transcriptional mechanisms. The purpose of the study was therefore to determine the temporal regulation of transcriptional and post-transcriptional events involved in the control of autophagy during starvation (4h) and nutrient restoration (4h) in C2C12 myotubes. Starvation was associated with an activation of autophagy (decrease in mTOR activity, increase in AMPK activity and Ulk1 phosphorylation on Ser467), an increase in autophagy flux (increased LC3B-II/LC3B-I ratio, LC3B-II level and LC3B-positive punctate), and an increase in the content of autophagy-related proteins (Ulk1, Atg13, Vps34, and Atg5-Atg12 conjugate). Our data also indicated that the content of autophagy-related proteins was essentially maintained when nutrient sufficiency was restored. By contrast, mRNA level of Ulk1, Atg5, Bnip3, LC3B and Gabarapl1 did not increase in response to starvation. Accordingly, binding of FoxO3 transcription factor on LC3B promoter was only increased at the end of the starvation period, whereas mRNA levels of Atrogin1/MAFbx and MuRF1, two transcriptional targets of FoxO involved in ubiquitin-proteasome pathway, were markedly increased at this time. Together, these data provide evidence that target genes of FoxO3 are differentially regulated during starvation and that starvation of C2C12 myotubes is associated with a post-transcriptional regulation of autophagy.
authors.affiliation: Laboratoire de Physiologie de l'Exercice EA 4338, Université de Lyon, Université Jean Monnet, Saint Etienne, France.
authors.forename: Marine Maud
authors.initials: MM
authors.lastname: Desgeorges
authors.affiliation: Laboratoire de Physiologie de l'Exercice EA 4338, Université de Lyon, Université Jean Monnet, Saint Etienne, France. Electronic address: damien.freyssenet@univ-st-etienne.fr.
authors.forename: Damien
authors.initials: D
authors.lastname: Freyssenet
authors.affiliation: Laboratoire Carmen, Institut National de la Recherche Agronomique UMR1235, University Lyon-1, INSA-Lyon, F-69600 Oullins, France.
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Chanon
authors.affiliation: Laboratoire de Physiologie de l'Exercice EA 4338, Université de Lyon, Université Jean Monnet, Saint Etienne, France.
authors.forename: Josiane
authors.initials: J
authors.lastname: Castells
authors.affiliation: Pôle de Génomique, Institut de Recherche Biomédicale des Armées, Centre de Recherche du Service de Santé des Armées, La Tronche, France.
authors.forename: Pascal
authors.initials: P
authors.lastname: Pugnière
authors.affiliation: INRA UMR 1019, Unité Nutrition Humaine, St Genès Champanelle, France.
authors.forename: Daniel
authors.initials: D
authors.lastname: Béchet
authors.affiliation: Pôle de Génomique, Institut de Recherche Biomédicale des Armées, Centre de Recherche du Service de Santé des Armées, La Tronche, France.
authors.forename: André
authors.initials: A
authors.lastname: Peinnequin
authors.affiliation: Laboratoire de Physiologie de l'Exercice EA 4338, Université de Lyon, Université Jean Monnet, Saint Etienne, France.
authors.forename: Xavier
authors.initials: X
authors.lastname: Devillard
authors.affiliation: Laboratoire de Physiologie de l'Exercice EA 4338, Université de Lyon, Université Jean Monnet, Saint Etienne, France; Center for Genetic Medicine Research, Children's National Medical Center, Washington, DC 20010, USA.
authors.forename: Aurélia
authors.initials: A
authors.lastname: Defour
mesh_terms: D000818:Animals; D001343:Autophagy; D000071187:Autophagy-Related Protein 5; D000071189:Autophagy-Related Protein-1 Homolog; D015153:Blotting, Western; D002478:Cells, Cultured; D047369:Chromatin Immunoprecipitation; D005455:Fluorescent Antibody Technique; D005786:Gene Expression Regulation; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism; D018485:Muscle Fibers, Skeletal / Q000378:metabolism / Q000473:pathology*; D018482:Muscle, Skeletal / Q000378:metabolism / Q000473:pathology*; D009747:Nutritional Physiological Phenomena; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D012323:RNA Processing, Post-Transcriptional; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D013217:Starvation; D058570:TOR Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism
chemical_list: C495773:Atg5 protein, mouse; D000071187:Autophagy-Related Protein 5; C508686:BNip3 protein, mouse; C480859:Gabarapl1 protein, mouse; C480860:Map1lc3b protein, mouse; D008565:Membrane Proteins; D008869:Microtubule-Associated Proteins; D024101:Mitochondrial Proteins; D012333:RNA, Messenger; C546842:MTOR protein, human; D000071189:Autophagy-Related Protein-1 Homolog; D017346:Protein Serine-Threonine Kinases; D058570:TOR Serine-Threonine Kinases; C112444:Ulk1 protein, mouse
keywords: Autophagy–lysosome; Proteolysis; Skeletal muscle; Ubiquitin–proteasome