Early onset senescence occurs when fibroblasts lack the glutamate-cysteine ligase modifier subunit.
Cellular senescence is the irreversible entry of cells into growth arrest. Senescence of primary cells in culture has long been used as an in vitro model for aging. Glutamate-cysteine ligase (GCL) controls the synthetic rate of the important cellular antioxidant glutathione (GSH). The catalytic subunit of GCL, GCLC, is catalytically active and essential for life. By contrast the modifier subunit of GCL, GCLM, is dispensable in mice. Although it is recognized that GCLM increases the rate of GSH synthesis, its physiological role is unclear. Herein, we show that loss of Gclm leads to premature senescence of primary murine fibroblasts as characterized by: (a) diminished growth rate, (b) cell morphology consistent with senescence, (c) increases in senescence-associated beta-galactosidase activity, and (d) cell cycle arrest at the G(1)/S and G(2)/M boundaries. These changes are accompanied by increased intracellular ROS, accumulation of DNA damage, and induction of p53 and p21 proteins. We also found that N-acetylcysteine increases intracellular GSH and prevents premature senescence in Gclm(-/-) cells. These results suggest that the control of GCLM, which in turn controls aspects of the cellular redox environment via GSH, is important in determining the replicative capacity of the cell.
Department of Environmental Health and Center for Environmental Genetics, University of Cincinnati Medical Center, Cincinnati, OH 45267-0056, USA. ying.chen@ucdenver.edu
Ying
Y
Chen
Elisabet
E
Johansson
Yunxia
Y
Fan
Howard G
HG
Shertzer
Vasilis
V
Vasiliou
Daniel W
DW
Nebert
Timothy P
TP
Dalton
D000111:Acetylcysteine / Q000494:pharmacology; D000818:Animals; D018929:Cell Culture Techniques; D002453:Cell Cycle / Q000187:drug effects / Q000235:genetics; D048708:Cell Growth Processes / Q000187:drug effects / Q000235:genetics; D016922:Cellular Senescence / Q000187:drug effects / Q000235:genetics; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000235:genetics / Q000378:metabolism; D004249:DNA Damage; D005260:Female; D005333:Fetus; D005347:Fibroblasts / Q000378:metabolism* / Q000473:pathology; D016166:Free Radical Scavengers / Q000494:pharmacology; D005721:Glutamate-Cysteine Ligase / Q000235:genetics / Q000378:metabolism*; D005978:Glutathione / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D011247:Pregnancy; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism; D001616:beta-Galactosidase / Q000378:metabolism
D050759:Cyclin-Dependent Kinase Inhibitor p21; D016166:Free Radical Scavengers; D021122:Protein Subunits; D017382:Reactive Oxygen Species; D016159:Tumor Suppressor Protein p53; D001616:beta-Galactosidase; D005721:Glutamate-Cysteine Ligase; D005978:Glutathione; D000111:Acetylcysteine