title: Reduced autophagy leads to an impaired ferritin turnover in senescent fibroblasts.
abstract: Changes in the two main intracellular degradation systems, the Ubiquitin-Proteasome System and the Autophagy-Lysosome pathway (ALP) are widely discussed as a hallmark of the aging process. To follow the age-related behavior of both degradation systems we examined their impact on ferritin, known to be degradable by both. Ferritin H was analyzed in young and senescent human fibroblasts, revealing a higher steady-state level in the senescent cells. By blocking both proteolytic systems, we confirmed that particularly the ALP plays a crucial role in ferritin H turnover. However, an unexpected increase in lysosomal activity in the senescent cells, suggests a dysregulation in the autophagy pathway. To further investigate the impaired ferritin H turnover, confocal microscopic colocalization studies of ferritin H with lysosomal-associated membrane protein 2a (Lamp2a) and monodansylcadaverine (MDC) were performed and clearly revealed the degradation of ferritin by macroautophagy. By induction of autophagy via inhibition of mTOR using rapamycin an increase of ferritin H turnover was obtained in senescent cells, demonstrating a mTOR dependent reduction of autophagy in senescent human fibroblasts.
authors: Department of Molecular Toxicology, German Institute of Human Nutrition, Potsdam-Rehbruecke, Germany. Electronic address: Christiane.Ott@dife.de.
authors: Christiane
authors: C
authors: Ott
authors: Department of Molecular Toxicology, German Institute of Human Nutrition, Potsdam-Rehbruecke, Germany. Electronic address: Jeannette.Koenig@dife.de.
authors: Jeannette
authors: J
authors: König
authors: Department of Molecular Toxicology, German Institute of Human Nutrition, Potsdam-Rehbruecke, Germany; German Center for Diabetes Research (DZD), 85764 München-Neuherberg, Germany. Electronic address: Annika.Hoehn@dife.de.
authors: Annika
authors: A
authors: Höhn
authors: Department of Molecular Toxicology, German Institute of Human Nutrition, Potsdam-Rehbruecke, Germany; German Center for Cardiovascular Research (DZHK), 10117 Berlin, Germany. Electronic address: Tobias.Jung@dife.de.
authors: Tobias
authors: T
authors: Jung
authors: Department of Molecular Toxicology, German Institute of Human Nutrition, Potsdam-Rehbruecke, Germany; German Center for Diabetes Research (DZD), 85764 München-Neuherberg, Germany; German Center for Cardiovascular Research (DZHK), 10117 Berlin, Germany. Electronic address: scientific.director@dife.de.
authors: Tilman
authors: T
authors: Grune
mesh_terms: D001052:Apoferritins / Q000378:metabolism*; D001343:Autophagy / Q000187:drug effects* / Q000235:genetics; D002103:Cadaverine / Q000031:analogs & derivatives / Q000494:pharmacology; D016922:Cellular Senescence / Q000187:drug effects; D003676:Deferoxamine / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D052816:Foreskin / Q000166:cytology / Q000378:metabolism; D015870:Gene Expression; D006427:Hemin / Q000494:pharmacology; D006801:Humans; D007700:Kinetics; D052119:Lysosomal-Associated Membrane Protein 2 / Q000235:genetics / Q000378:metabolism; D008247:Lysosomes / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D061251:Primary Cell Culture; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D059748:Proteolysis / Q000187:drug effects; D020123:Sirolimus / Q000494:pharmacology; D058570:TOR Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism
chemical_list: D004791:Enzyme Inhibitors; C497811:LAMP2 protein, human; D052119:Lysosomal-Associated Membrane Protein 2; D006427:Hemin; D001052:Apoferritins; C546842:MTOR protein, human; D058570:TOR Serine-Threonine Kinases; D046988:Proteasome Endopeptidase Complex; C008542:monodansylcadaverine; D003676:Deferoxamine; D002103:Cadaverine; D020123:Sirolimus
keywords: 20S proteasome; ATGs; Aging; Autophagy-lysosome pathway; Ferritin; Fibroblasts; Rapamycin; Senescence; mTOR