Cross-talk between Akt, p53 and Mdm2: possible implications for the regulation of apoptosis.
The p53 tumor suppressor protein and the Akt/PKB kinase play important roles in the transduction of pro-apoptotic and anti-apoptotic signals, respectively. We provide evidence that conflicting signals transduced by Akt and p53 are integrated via negative feedback between the two pathways. On the one hand, the combination of ionizing radiation and survival factor deprivation, which leads to rapid apoptosis of IL-3 dependent DA-1 cells, entails a caspase- and p53-dependent destruction of Akt. This destruction of Akt is not a secondary consequence of apoptosis, since it is not seen when the same cells are triggered to undergo apoptosis under different conditions. On the other hand upon serum stimulation, when Akt becomes active and enhances cell survival, phosphorylation occurs at an Akt consensus site (serine 166) within the Mdm2 protein, a key regulator of p53 function. Taken together, our findings suggest that depending on the balance of signals, p53-dependent downregulation of Akt may promote an irreversible commitment to apoptotic cell death, whereas effective recruitment of Akt by appropriate survival signals may lead to activation of Mdm2, inactivation of p53, and eventually inhibition of p53-dependent apoptosis.
Gottlieb
Tanya M
TM
Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot 76100, Israel.
Leal
Juan Fernando Martinez
JF
Seger
Rony
R
Taya
Yoichi
Y
Oren
Moshe
M
D000818:Animals; D017209:Apoptosis / Q000528:radiation effects; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism; D002460:Cell Line; D002470:Cell Survival / Q000528:radiation effects; D015536:Down-Regulation / Q000528:radiation effects; D025461:Feedback, Physiological / Q000528:radiation effects; D007377:Interleukin-3 / Q000494:pharmacology; D051379:Mice; D009687:Nuclear Proteins; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D051736:Proto-Oncogene Proteins c-mdm2; D011839:Radiation, Ionizing; D015398:Signal Transduction / Q000528:radiation effects; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*
D061945:Caspase Inhibitors; D007377:Interleukin-3; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; D016159:Tumor Suppressor Protein p53; C497207:Mdm2 protein, mouse; D051736:Proto-Oncogene Proteins c-mdm2; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D020169:Caspases