Mechanism of phosphatidylinositol 3-kinase-dependent increases in BAC1.2F5 macrophage-like cell density in response to M-CSF: phosphatidylinositol 3-kinase inhibitors increase the rate of apoptosis rather than inhibit DNA synthesis.
OBJECTIVE
To determine the role of phosphatidylinositol 3-kinase (PI 3-kinase) in macrophagecolony stimulating factor (M-CSF)-induced macrophage proliferation.


METHODS
The M-CSF-dependent BAC1.2F5 murine macrophage cell line was used.


METHODS
PI 3-kinase activity, Protein kinase B activation, increased cell numbers, induction of DNA synthesis and apoptosis were measured in response to serum, M-CSF and PI 3-kinase inhibitors.


RESULTS
Wortmannin or LY294002 inhibited M-CSF-stimulated increases in BAC1.2F5 cell density. Further analysis showed that inhibition of PI 3-kinase had an insignificant effect on DNA synthesis, but significantly induced apoptosis. Other co-factors in serum mediated cell survival and prevented programmed cell death, in a PI 3-kinase-dependent manner. Stimulation of BAC1.2F5 macrophages with M-CSF induced phosphorylation of PKB/Akt as detected by activation-specific antibodies. Activation of PKB/Akt correlated with PI 3-kinase activation, suggesting that the protection from apoptosis in these cells is mediated by PKB/Akt.


CONCLUSIONS
These results indicate that the lack of increase in cell numbers when cells are stimulated with M-CSF in the presence of PI 3-kinase inhibitors is due to a preferential PI 3-kinase requirement for protection against apoptosis, rather than a requirement for PI 3-kinase activation during the proliferation signal.
Murray
J T
JT
Yamanouchi Research Institute, Oxford, UK.
Craggs
G
G
Wilson
L
L
Kellie
S
S
D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D002452:Cell Count; D002455:Cell Division; D002460:Cell Line; D002470:Cell Survival; D002867:Chromones / Q000494:pharmacology; D016895:Culture Media, Serum-Free / Q000494:pharmacology; D004261:DNA Replication / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D016173:Macrophage Colony-Stimulating Factor / Q000494:pharmacology*; D008264:Macrophages / Q000166:cytology / Q000187:drug effects / Q000276:immunology*; D051379:Mice; D009025:Morpholines / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000276:immunology; D051057:Proto-Oncogene Proteins c-akt; D000077191:Wortmannin
D000730:Androstadienes; D002867:Chromones; D016895:Culture Media, Serum-Free; D004791:Enzyme Inhibitors; D016173:Macrophage Colony-Stimulating Factor; D009025:Morpholines; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D000077191:Wortmannin; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one