Reactive oxygen species (ROS) control the expression of Bcl-2 family proteins by regulating their phosphorylation and ubiquitination.
We examined the influence of ROS on the phosphorylation and complex formation of Bcl-2 family proteins in Mn-superoxide dismutase (SOD) antisense-transfected squamous cell carcinoma cells, OSC-4 cells. The increase of intracellular ROS level induced by cis-diamminedichloroplatinum (CDDP) and gamma-ray treatment was greater in antisense-transfected cells than in control vector-transfected cells, and apoptosis was more extensively induced in the former. Antisense-transfected cells expressed high levels of Bax and Bak, but low levels of Bcl-2 and Bcl-XL when treated with CDDP, peplomycin, 5-fluorouracil or gamma-rays. After treatment with these agents, the phosphorylation of protein kinase A, Bcl-2 (Thr56) and Bad (Ser155) was increased, especially in antioxidant (N-acetylcysteine and pyrrolidine dithiocarbamate)-pretreated control cells, but the phosphorylation levels were very low in the antisense-transfected cells. Bcl-2 ubiquitination was increased, but ubiquitination of Bad and Bax was decreased in the antisense-transfected cells, although their ubiquitination was increased by the antioxidants. These results reveal that ROS induce apoptosis by regulating the phosphorylation and ubiquitination of Bcl-2 family proteins, resulting in increased proapoptotic protein levels and decreased antiapoptotic protein expression.
Department of Oral Oncology, Kochi Medical School, Kohasu, Nankoku City, 783-8505, Japan.
Dechao
D
Li
Eisaku
E
Ueta
Tsuyoshi
T
Kimura
Tetsuya
T
Yamamoto
Tokio
T
Osaki
D000970:Antineoplastic Agents / Q000633:toxicity; D017209:Apoptosis / Q000187:drug effects*; D002294:Carcinoma, Squamous Cell / Q000473:pathology*; D002945:Cisplatin / Q000633:toxicity; D006801:Humans; D009062:Mouth Neoplasms / Q000473:pathology*; D010766:Phosphorylation; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis* / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000494:pharmacology*; D014162:Transfection; D014407:Tumor Cells, Cultured / Q000473:pathology*; D014452:Ubiquitins / Q000378:metabolism
D000970:Antineoplastic Agents; D019253:Proto-Oncogene Proteins c-bcl-2; D017382:Reactive Oxygen Species; D014452:Ubiquitins; D002945:Cisplatin