Transcriptional and posttranslational regulation of clusterin by the two main cellular proteolytic pathways.
Clusterin/apolipoprotein J (CLU) is a secreted glycoprotein associated with many severe physiological disturbances that represent states of increased oxidative stress, such as aging, cancer, atherosclerosis, diabetes, and renal and neurodegenerative diseases. The aim of our work was to examine the effect of proteasome and lysosome inhibition on CLU expression and to determine whether those proteolytic pathways are implicated in CLU gene regulation and protein degradation. To this end we used two different model systems, namely the U-2 OS osteosarcoma cell line and the WI38 primary human embryonic lung fibroblasts. We report that proteasome inhibition promotes both heat-shock factor 1 (HSF-1)-dependent CLU gene expression induction and protein accumulation due to reduced degradation. In contrast, lysosome inhibition results in elevated levels of CLU protein but does not affect the CLU mRNA levels. We also provide direct evidence that both the intracellular precursor, psCLU, and the mature secreted, sCLU, isoforms constitute proteolytic substrates of the proteasome and the lysosome. Overall our findings indicate that CLU overexpression after proteasome inhibition relates to both positive gene transcriptional regulation by HSF-1 and posttranslational protein accumulation due to reduced proteasomal and lysosomal degradation.
Balantinou
Eirini
E
National Hellenic Research Foundation, Institute of Biological Research and Biotechnology, 48 Vas. Constantinou Avenue, Athens, Greece.
Trougakos
Ioannis P
IP
Chondrogianni
Niki
N
Margaritis
Lukas H
LH
Gonos
Efstathios S
ES
D019138:Antibodies, Blocking / Q000378:metabolism; D045744:Cell Line, Tumor; D051152:Clusterin / Q000737:chemistry / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism; D005347:Fibroblasts / Q000378:metabolism* / Q000648:ultrastructure; D005786:Gene Expression Regulation / Q000187:drug effects; D000076249:Heat Shock Transcription Factors; D006801:Humans; D006868:Hydrolysis; D007976:Leupeptins / Q000494:pharmacology; D008247:Lysosomes / Q000201:enzymology; D008297:Male; D009842:Oligopeptides / Q000494:pharmacology; D012516:Osteosarcoma / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D061988:Proteasome Inhibitors; D011499:Protein Processing, Post-Translational; D014157:Transcription Factors / Q000378:metabolism; D015533:Transcriptional Activation / Q000187:drug effects; D014162:Transfection; D025801:Ubiquitin / Q000235:genetics / Q000378:metabolism
D019138:Antibodies, Blocking; C495242:CLU protein, human; D051152:Clusterin; D004268:DNA-Binding Proteins; D000076249:Heat Shock Transcription Factors; D007976:Leupeptins; D009842:Oligopeptides; D061988:Proteasome Inhibitors; D014157:Transcription Factors; D025801:Ubiquitin; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde; C078846:epoxomicin