Clusterin/apolipoprotein J is a novel biomarker of cellular senescence that does not affect the proliferative capacity of human diploid fibroblasts.
Normal human fibroblasts have a limited replicative potential in culture and eventually reach a state of irreversible growth arrest, termed senescence. In a previous study aiming to identify genes that are differentially regulated during cellular senescence we have cloned clusterin/apolipoprotein J (Apo J), a 80 kDa secreted glycoprotein. In the current report we pursue our studies and show that senescence of human diploid fibroblasts is accompanied by up-regulation of both Apo J mRNA and protein levels, but with no altered biogenesis, binding partner profile or intracellular distribution of the two Apo J forms detected. To analyze the causal relationship between senescence and Apo J protein accumulation, we stably overexpressed the Apo J gene in primary as well as in SV40 T antigen-immortalized human fibroblasts and we showed no alteration of the proliferative capacity of the transduced cells. Despite previous reports on tumor-derived cell lines, overexpression of Apo J in human fibroblasts did not provide protection against apoptosis or growth arrest induced by hydrogen peroxide. Overall, our results suggest that Apo J overexpression does not induce senescence but it is rather a secondary consequence of the senescence phenotype. To our knowledge this is the first report that provides a functional analysis of human Apo J during replicative senescence.
Petropoulou
C
C
Laboratory of Molecular and Cellular Aging, Institute of Biological Research and Biotechnology, National Hellenic Research Foundation, 48 Vas. Constantinou Ave., 116 35 Athens, Greece.
Trougakos
I P
IP
Kolettas
E
E
Toussaint
O
O
Gonos
E S
ES
D000943:Antigens, Differentiation / Q000096:biosynthesis / Q000235:genetics / Q000302:isolation & purification*; D016922:Cellular Senescence / Q000502:physiology*; D051152:Clusterin; D004171:Diploidy; D005347:Fibroblasts / Q000166:cytology / Q000502:physiology*; D006023:Glycoproteins / Q000096:biosynthesis / Q000235:genetics / Q000302:isolation & purification*; D006801:Humans; D018832:Molecular Chaperones / Q000096:biosynthesis / Q000235:genetics / Q000302:isolation & purification*; D018384:Oxidative Stress / Q000502:physiology; D011994:Recombinant Proteins / Q000096:biosynthesis; D015854:Up-Regulation
D000943:Antigens, Differentiation; C495242:CLU protein, human; D051152:Clusterin; D006023:Glycoproteins; D018832:Molecular Chaperones; D011994:Recombinant Proteins