Functional analysis of clusterin/apolipoprotein J in cellular death induced by severe genotoxic stress.
Clusterin/apolipoprotein J (CLU) is a secreted heterodimeric glycoprotein that is reportedly upregulated during tumorigenesis, as well as during cell injury or death. Despite extensive efforts, CLU function during cellular death remains largely elusive. We are using as a model system to study CLU function three human osteosarcoma (OS) cell lines, namely, Sa OS, KH OS, and U-2 OS cells, induced to die after exposure to severe genotoxic stress mediated by the chemotherapeutic drug doxorubicin (DXR). We initially applied small interfering RNA (siRNA)-mediated specific knockdown of the CLU protein in OS cells. In all three cell lines, CLU knockdown resulted in increased sensitization to DXR-induced apoptosis. Supportively, moderate levels of forced transgene-mediated CLU stable overexpression in KH OS cells could rescue them from DXR-mediated apoptosis. In contrast, stable overexpression of high CLU levels in Sa OS and U-2 OS cells augmented apoptosis induced by cell exposure to severe DXR-mediated genotoxic stress. In summary, our data provide evidence that, although CLU is essential for cellular homeostasis, it may become highly cytotoxic in certain cellular contexts when it accumulates in high amounts intracellularly either by direct synthesis or by uptake from the extracellular milieu.
Trougakos
Ioannis P
IP
Laboratory of Molecular and Cellular Aging, Institute of Biological Research and Biotechnology, National Hellenic Research Foundation, Athens 11635, Greece.
Gonos
Efstathios S
ES
D017209:Apoptosis; D016923:Cell Death; D002460:Cell Line; D045744:Cell Line, Tumor; D002470:Cell Survival; D051152:Clusterin; D003593:Cytoplasm / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004317:Doxorubicin / Q000494:pharmacology; D004797:Enzyme-Linked Immunosorbent Assay; D006023:Glycoproteins / Q000378:metabolism*; D006801:Humans; D018832:Molecular Chaperones / Q000378:metabolism*; D009841:Oligonucleotides / Q000737:chemistry; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D012313:RNA / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D019076:Transgenes; D015854:Up-Regulation
C495242:CLU protein, human; D051152:Clusterin; D018076:DNA, Complementary; D006023:Glycoproteins; D018832:Molecular Chaperones; D009841:Oligonucleotides; D016376:Oligonucleotides, Antisense; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D012313:RNA; D004317:Doxorubicin