Bcl-2 but not clusterin/apolipoprotein J protected human diploid fibroblasts and immortalized keratinocytes from ceramide-induced apoptosis: role of p53 in the ceramide response.
The role of clusterin/apolipoprotein J (Clu/ApoJ) and Bcl-2 on C(2)-ceramide-induced apoptosis of embryonic human diploid fibroblasts, MRC-5 and immortalized adult skin keratinocytes, HaCaT was investigated. C(2)-ceramide-induced apoptosis of HaCaT in a time- and dose-dependent manner, while in MRC-5 only at higher concentrations. There was a dose-dependent accumulation of Clu/ApoJ and downregulation of Bcl-2 which correlated with C(2)-ceramide-induced apoptosis of MRC-5. While overexpression of Bcl-2 suppressed C(2)-ceramide-mediated apoptosis in both cell types, Clu/ApoJ failed to do so, accessed by morphological changes, DNA fragmentation and PARP cleavage. There was no change in the expression of endogenous p53 or p21(Waf1/Cip1) upon C(2)-ceramide treatment of MRC-5. However, mutant p53(143ala) increased the sensitivity of MRC-5 to C(2)-ceramide-induced apoptosis by markedly downregulating Bcl-2, pointing to a role for p53. These results suggested that whereas downregulation of Bcl-2 may be a crucial factor involved in C(2)-ceramide-induced apoptosis, accumulation of Clu/ApoJ may be a signal of stress response. Moreover, the ceramide-activated apoptotic pathway may be regulated by p53.
Kolettas
Evangelos
E
Cell and Molecular Physiology Unit, Laboratory of Experimental Physiology, University of Ioannina Medical School, 45 110 Ioannina, Greece. ekoletas@cc.uoi.gr
Skoufos
Ioannis
I
Kontargiris
Evangelos
E
Markopoulou
Soultana
S
Tzavaras
Theodoros
T
Gonos
Efstathios S
ES
D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D002461:Cell Line, Transformed; D051152:Clusterin / Q000502:physiology*; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000502:physiology*; D004171:Diploidy; D015536:Down-Regulation; D005347:Fibroblasts / Q000187:drug effects / Q000502:physiology*; D006801:Humans; D015603:Keratinocytes / Q000187:drug effects / Q000502:physiology*; D009154:Mutation; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000502:physiology*; D015398:Signal Transduction; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000502:physiology; D016159:Tumor Suppressor Protein p53 / Q000502:physiology*
C493956:CDKN1A protein, human; C495242:CLU protein, human; D051152:Clusterin; D050759:Cyclin-Dependent Kinase Inhibitor p21; C064769:N-acetylsphingosine; D019253:Proto-Oncogene Proteins c-bcl-2; D016159:Tumor Suppressor Protein p53; D013110:Sphingosine