title: Translocation of p53 to mitochondria is regulated by its lipid binding property to anionic phospholipids and it participates in cell death control.
abstract: p53, can regulate cell apoptosis in both transcription-dependent and -independent manners. The transcription-independent pathway was demonstrated by the translocation of p53 to mitochondria. Our study showed that p53 mitochondrial translocation was found in mitomycin C (MMC)-treated HepG2. The p53 C-terminal domain is clustered with potential nuclear leading sequences and showed strong electrostatic ion-ion interactions with cardiolipin, phosphatidylglycerol and phosphatidic acid in vitro. Disruption of cardiolipin biosynthesis by phosphatidylglycero-phosphate synthase (PGS) or CDP-diacylglycerol synthase 2 (CDS-2) short hairpin RNA (shRNA) transfection eliminated the MMC-induced translocation of mitochondrial p53. The elimination of mitochondrial p53 translocation also reduced Bcl-xL and Bcl-2 mitochondrial distribution. In HEK 293T models with saturated p53 expression, the mitochondrial partition of p53, Bcl-xL, and Bcl-2 obviously decreased in their PGS shRNA- or CDS-2 shRNA-expressing stable clones. In p53-null H1299 models, both the mitochondrial partitions of Bcl-xL and Bcl-2 were strongly reduced in relation to the HEK 293T models. The Bcl-xL mitochondrial partition was elevated in H1299 models expressing pCEP4-p53wt suggesting the direct carrier role of p53 in transporting Bcl-xL to the mitochondria. We also found that the cytosolic pool of Bcl-xL and Bcl-2 remained unaffected in the low-dose MMC treatment but decreased in the high-dose MMC treatment. The cytosolic pool of Bcl-2 and Bcl-xL directly regulated their amounts in p53-dependent mitochondrial distribution. In the low-dose MMC treatment, the increased mitochondrial p53, Bcl-xL, and Bcl-2 could attenuate apoptosis. However, in the high-dose MMC treatment, only the p53 translocated to the mitochondria and resulted in apoptosis progression. On the basis of this study, we thought mitochondrial p53 might regulate apoptosis in a biphasic manner.
authors.affiliation: Institute of Toxicology, College of Medicine, National Taiwan University, Taipei, Taiwan.
authors.forename: Ching-Hao
authors.initials: CH
authors.lastname: Li
authors.forename: Yu-Wen
authors.initials: YW
authors.lastname: Cheng
authors.forename: Po-Ling
authors.initials: PL
authors.lastname: Liao
authors.forename: Jaw-Jou
authors.initials: JJ
authors.lastname: Kang
mesh_terms: D017209:Apoptosis / Q000502:physiology*; D015153:Blotting, Western; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D006801:Humans; D018613:Microscopy, Confocal; D008928:Mitochondria / Q000378:metabolism*; D010743:Phospholipids / Q000378:metabolism; D021381:Protein Transport / Q000502:physiology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D014162:Transfection; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*; D051020:bcl-X Protein / Q000378:metabolism
chemical_list: D010743:Phospholipids; D019253:Proto-Oncogene Proteins c-bcl-2; D016159:Tumor Suppressor Protein p53; D051020:bcl-X Protein