Cytokine-induced protein kinase B activation and Bad phosphorylation do not correlate with cell survival of hemopoietic cells.
Activation of phosphoinositide-3 kinases (PI3Ks), their downstream target protein kinase B (PKB), and phosphorylation of Bad have all been implicated in survival signaling in many systems. However, it is not known whether these events are sufficient or necessary to universally prevent apoptosis. To address this issue, we have used three different factor-dependent hemopoietic cell lines, MC/9, BaF/3, and factor-dependent (FD)-6, which respond to a range of cytokines, to investigate the relationship between PI3K, PKB, and Bad activity with survival. The cytokines IL-3, IL-4, stem cell factor (SCF), GM-CSF, and insulin all induced the rapid and transient activation of PKB in responsive cell lines. In all cases, cytokine-induced PKB activation was sensitive to inhibition by the PI3K inhibitor, LY294002. However, dual phosphorylation of the proapoptotic protein Bad was found not to correlate with PKB activation. In addition, we observed cell-type-specific differences in the ability of the same cytokine to induce Bad phosphorylation. Whereas IL-4 induced low levels of dual phosphorylation of Bad in FD-6, it was unable to in MC/9 or BaF/3. Insulin, which was the most potent inducer of PKB in FD-6, induced barely detectable Bad phosphorylation. In addition, the ability of a particular cytokine to induce PKB activity did not correlate with its ability to promote cell survival and/or proliferation. These data demonstrate that, in hemopoietic cells, activation of PKB does not automatically confer a survival signal or result in phosphorylation of Bad, implying that other survival pathways must be involved.
Hinton
H J
HJ
Department of Pharmacology, University of Bath, United Kingdom.
Welham
M J
MJ
D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D002455:Cell Division / Q000276:immunology; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects / Q000276:immunology; D002867:Chromones / Q000494:pharmacology; D016207:Cytokines / Q000502:physiology*; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006412:Hematopoietic Stem Cells / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism; D051379:Mice; D009025:Morpholines / Q000494:pharmacology; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D012694:Serine / Q000378:metabolism; D051025:bcl-Associated Death Protein
C494820:Bad protein, mouse; D002352:Carrier Proteins; D002867:Chromones; D016207:Cytokines; D004791:Enzyme Inhibitors; D009025:Morpholines; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D051025:bcl-Associated Death Protein; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; D012694:Serine; D011505:Protein-Tyrosine Kinases; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt