Central role of the proteasome in senescence and survival of human fibroblasts: induction of a senescence-like phenotype upon its inhibition and resistance to stress upon its activation.
Normal human fibroblasts undergo a limited number of divisions in culture and progressively they reach a state of irreversible growth arrest, a process termed as replicative senescence. The proteasome is the major cellular proteolytic machinery, the function of which is impaired during replicative senescence. However, the exact causes of its malfunction in these conditions are unknown. Using WI38 fibroblasts as a model for cellular senescence we have observed reduced levels of proteasomal peptidase activities coupled with increased levels of both oxidized and ubiquitinated proteins in senescent cells. We have found the catalytic subunits of the 20 S complex and subunits of the 19 S regulatory complex to be down-regulated in senescent cells. This is accompanied by a decrease in the level of both 20 S and 26 S complexes. Partial inhibition of proteasomes in young cells caused by treatment with specific inhibitors induced a senescence-like phenotype, thus demonstrating the fundamental importance of the proteasome for retaining cellular maintenance and homeostasis. Stable overexpression of beta1 and beta5 subunits in WI38 established cell lines was shown to induce elevated expression levels of beta1 subunit in beta5 transfectants and vice versa. Transfectants possess increased proteasome activities and most importantly, increased capacity to cope better with various stresses. In summary these data demonstrate the central role of the proteasome during cellular senescence and survival as well as provide insights toward a better understanding of proteasome regulation.
National Hellenic Research Foundation, Institute of Biological Research and Biotechnology, 48 Vas. Constantinou Ave., Athens 11635, Greece.
Niki
N
Chondrogianni
Fiona L L
FL
Stratford
Ioannis P
IP
Trougakos
Bertrand
B
Friguet
A Jennifer
AJ
Rivett
Efstathios S
ES
Gonos
D002455:Cell Division; D002460:Cell Line; D002470:Cell Survival; D016922:Cellular Senescence; D002850:Chromatography, Gel; D003546:Cysteine Endopeptidases / Q000378:metabolism / Q000502:physiology*; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004247:DNA / Q000096:biosynthesis; D015536:Down-Regulation; D015180:Electrophoresis, Gel, Two-Dimensional; D005347:Fibroblasts / Q000378:metabolism*; D006801:Humans; D007976:Leupeptins / Q000494:pharmacology; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D009097:Multienzyme Complexes / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000502:physiology*; D009842:Oligopeptides / Q000494:pharmacology; D018384:Oxidative Stress; D010447:Peptide Hydrolases / Q000502:physiology*; D010641:Phenotype; D011233:Precipitin Tests; D046988:Proteasome Endopeptidase Complex; D013997:Time Factors; D014162:Transfection; D001616:beta-Galactosidase / Q000378:metabolism
D015853:Cysteine Proteinase Inhibitors; D007976:Leupeptins; D009097:Multienzyme Complexes; D009842:Oligopeptides; D004247:DNA; D001616:beta-Galactosidase; D010447:Peptide Hydrolases; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde; C078846:epoxomicin