Dephosphorylation of ribosomal protein P0 in response to troglitazone-induced cytotoxicity.
Troglitazone (TRO)-induced cytotoxicity was investigated in HepG2 cells. The cells were exposed to TRO as well as rosiglitazone (RSG) at concentrations of 0, 25, 50 and 75 microM for 48 h. Total proteins were separated by two-dimensional electrophoresis and visualized by silver staining. We focused on a protein spot at an approximate molecular weight of 35 kDa and isoelectric point (pI) of 5.7, which appeared only with the cytotoxic concentrations (50 and 75 microM) of TRO, but not with the low concentration (25 microM) of TRO or any concentrations of RSG. This protein spot was subjected to amino acid sequence analysis and identified as ribosomal protein P0 (P0). Interestingly, without any significant induction of its protein and mRNA, P0 was dephosphorylated depending on the concentration- and time-dependent manner of TRO-induced cytotoxicity. Pretreatment with a general caspase inhibitor, Z-VAD.fmk, prevented cleavage of caspase-3 but demonstrated a slight improvement of cytotoxicity induced by TRO. Thus, these effects could not prevent the dephosphorylation of P0. Our results strongly suggest that a post-translational modification, dephosphorylation, of P0 is associated with TRO-induced cytotoxicity.
Maniratanachote
Rawiwan
R
Drug Metabolism and Toxicology, Division of Pharmaceutical Sciences, Graduate School of Medical Science, Kanazawa University, Kakuma-machi, Kanazawa, Japan.
Minami
Keiichi
K
Katoh
Miki
M
Nakajima
Miki
M
Yokoi
Tsuyoshi
T
D000595:Amino Acid Sequence; D000970:Antineoplastic Agents / Q000633:toxicity*; D015153:Blotting, Western; D020169:Caspases / Q000378:metabolism; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D002839:Chromans / Q000633:toxicity*; D004452:Echocardiography; D006801:Humans; D006861:Hydrogen Peroxide / Q000633:toxicity; D047468:Immunoprecipitation; D007525:Isoelectric Focusing; D008969:Molecular Sequence Data; D008970:Molecular Weight; D016877:Oxidants / Q000633:toxicity; D010750:Phosphoproteins / Q000737:chemistry / Q000378:metabolism*; D010766:Phosphorylation; D040901:Proteomics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012269:Ribosomal Proteins / Q000737:chemistry / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D045162:Thiazolidinediones / Q000633:toxicity*; D000077288:Troglitazone
D000970:Antineoplastic Agents; D002839:Chromans; D016877:Oxidants; D010750:Phosphoproteins; D012269:Ribosomal Proteins; D045162:Thiazolidinediones; C054675:ribosomal protein P0; D006861:Hydrogen Peroxide; D020169:Caspases; D000077288:Troglitazone