Tumor necrosis factor induces phosphorylation and translocation of BAD through a phosphatidylinositide-3-OH kinase-dependent pathway.
Tumor necrosis factor (TNF) induced the phosphorylation of BAD at serine 136 in HeLa cells under conditions that are not cytotoxic. BAD phosphorylation by TNF was dependent on phosphatidylinositide-3-OH kinase (PI3K) and was accompanied by the translocation of BAD from the mitochondria to the cytosol. Blocking the phosphorylation of BAD and its translocation to the cytosol with the PI3K inhibitor wortmannin activated caspase-3 and markedly potentiated the cytotoxicity of TNF. Transient transfection with a PI3K dominant negative mutant or a dominant negative mutant of the serine-threonine kinase Akt, the downstream target of PI3K and the enzyme that phosphorylates BAD, similarly potentiated the cytotoxicity of TNF. By contrast, transfection with a constitutively active Akt mutant protected against the cytotoxicity of TNF in the presence of wortmannin. Phosphorylation of BAD prevents its interaction with the antiapoptotic protein Bcl-XL. Transfection with a Bcl-XL expression vector protected against the cytotoxicity of TNF in the presence of wortmannin. The mechanism by which the inhibition of the phosphorylation of BAD is likely linked to the induction of lethal mitochondrial damage in TNF-intoxicated cells is discussed.
Pastorino
J G
JG
Department of Pathology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA.
Tafani
M
M
Farber
J L
JL
D000730:Androstadienes / Q000494:pharmacology; D001692:Biological Transport; D002352:Carrier Proteins / Q000378:metabolism*; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D016923:Cell Death; D002867:Chromones / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006367:HeLa Cells; D006801:Humans; D009025:Morpholines / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D010766:Phosphorylation; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*; D000077191:Wortmannin; D051025:bcl-Associated Death Protein; D051020:bcl-X Protein
D000730:Androstadienes; C494819:BAD protein, human; C494811:BCL2L1 protein, human; D002352:Carrier Proteins; D002867:Chromones; D004791:Enzyme Inhibitors; D009025:Morpholines; D019253:Proto-Oncogene Proteins c-bcl-2; D014409:Tumor Necrosis Factor-alpha; D051025:bcl-Associated Death Protein; D051020:bcl-X Protein; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; D019869:Phosphatidylinositol 3-Kinases; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; D000077191:Wortmannin