Metabolic stabilization of MAP kinase phosphatase-2 in senescence of human fibroblasts.
Cellular senescence is characterized by impaired cell proliferation. We have previously shown that, relative to the young counterpart, senescent WI-38 human fibroblasts display a decreased abundance of active phosphorylated ERK (p-ERK) in the nucleus. We have tested the hypothesis that this is due to elevated levels of nuclear MAP kinase phosphatase (MKP) activity in senescent cells. Our results indicate that the activity and abundance of MKP-2 is increased in senescent fibroblasts, compared to their young counterparts. Further analysis indicates that it is MKP-2 protein, but not MKP-2 mRNA level, that is increased in senescent cells. This increase is the result of the increased stability of MKP-2 protein against proteolytic degradation. The degradation of MKPs was impaired by proteasome inhibitors both in young and old WI-38 cells, indicating that proteasome activity is involved in the degradation of MKPs. Finally, our results indicate that proteasome activity, in general, is diminished in senescent fibroblasts. Taken together, these data indicate that the increased level and activity of MKP-2 in senescent WI-38 cells are the consequence of impaired proteosomal degradation, and this increase is likely to play a significant role in the decreased levels of p-ERK in the nucleus of senescent cells.
The Lankenau Institute for Medical Research, 100 Lancaster Avenue, Wynnewood, PA 19096, USA.
Claudio
C
Torres
Mary Kay
MK
Francis
Antonello
A
Lorenzini
Maria
M
Tresini
Vincent J
VJ
Cristofalo
D015153:Blotting, Western; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D016922:Cellular Senescence / Q000502:physiology*; D003546:Cysteine Endopeptidases / Q000378:metabolism; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D054637:Dual-Specificity Phosphatases; D005347:Fibroblasts / Q000201:enzymology*; D006801:Humans; D007976:Leupeptins / Q000494:pharmacology; D018613:Microscopy, Confocal; D054639:Mitogen-Activated Protein Kinase Phosphatases; D009097:Multienzyme Complexes / Q000378:metabolism; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D010766:Phosphorylation; D046988:Proteasome Endopeptidase Complex; D054648:Protein Phosphatase 2; D017027:Protein Tyrosine Phosphatases / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism
D015853:Cysteine Proteinase Inhibitors; D007976:Leupeptins; D009097:Multienzyme Complexes; D012333:RNA, Messenger; D054639:Mitogen-Activated Protein Kinase Phosphatases; D010749:Phosphoprotein Phosphatases; D054648:Protein Phosphatase 2; C490583:DUSP4 protein, human; D054637:Dual-Specificity Phosphatases; D017027:Protein Tyrosine Phosphatases; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde