The phosphorylation status and anti-apoptotic activity of Bcl-2 are regulated by ERK and protein phosphatase 2A on the mitochondria.
Bcl-2 protein play important roles in the regulation of apoptosis. We previously reported that the phosphorylation of Bcl-2 was augmented by treatment with protein phosphatase 2A (PP2A) inhibitor; however, the kinase responsible for Bcl-2 phosphorylation had not yet been identified. In this study, we identified extracellular-signal-regulated kinase (ERK) as the responsible kinase for the phosphorylation of Bcl-2. We also found that the transmembrane region (TM) deleted form of Bcl-2 (Bcl-2DeltaTM), which was unable to localize on the mitochondria was constitutively phosphorylated, whereas wild-type Bcl-2 that localized on the mitochondria, was present in its hypophosphorylated form. The phosphorylation of Bcl-2DeltaTM was retarded by treatment with MAP kinase ERK kinase (MEK) inhibitor and PP2A did not bind to Bcl-2DeltaTM. These observations suggest that Bcl-2DeltaTM is constitutively phosphorylated by ERK, but is not dephosphorylated by PP2A in human tumor cell lines. The phosphorylation of Bcl-2 resulted in a reduction in anti-apoptotic function, implying that dephosphorylation promoted the anti-apoptotic activity of Bcl-2 protein in human tumor cell lines. Thus, the present findings suggest that ERK and PP2A are physiological regulators of Bcl-2 phosphorylation, and these enzymes exert an influence on the anti-apoptotic function of Bcl-2.
Tamura
Yuki
Y
Antibiotics Laboratory, Discovery Research Institute, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.
Simizu
Siro
S
Osada
Hiroyuki
H
D017209:Apoptosis / Q000502:physiology*; D006528:Carcinoma, Hepatocellular; D045744:Cell Line, Tumor; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006367:HeLa Cells; D006801:Humans; D007700:Kinetics; D008113:Liver Neoplasms; D008928:Mitochondria / Q000378:metabolism*; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D016296:Mutagenesis; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D010766:Phosphorylation; D010957:Plasmids; D054648:Protein Phosphatase 2; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics* / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D017384:Sequence Deletion
D004791:Enzyme Inhibitors; D019253:Proto-Oncogene Proteins c-bcl-2; D011994:Recombinant Proteins; D019950:Mitogen-Activated Protein Kinase 1; D020928:Mitogen-Activated Protein Kinases; D010749:Phosphoprotein Phosphatases; D054648:Protein Phosphatase 2