B-raf and insulin synergistically prevent apoptosis and induce cell cycle progression in hematopoietic cells.
FDC-P1 hematopoietic cells were conditionally transformed to grow in response to (delta)B Raf:ER, (delta)Raf-1:ER or DA-Raf:ER in which the hormone binding domain of the estrogen receptor (ER) was linked to the N-terminal truncated (delta) Raf genes. When these cells were deprived of IL-3 or beta-estradiol for 24 hrs, they exited the cell cycle and underwent apoptosis. FD/(delta)Raf-1:ER and FD/(delta)A-Raf:ER, but not FD/(delta)B-Raf:ER cells, were readily induced to re-enter the cell cycle after addition of beta-estradiol or IL-3. Deprived FD/(delta)Raf-1:ER, but not FD/(delta)B-Raf:ER cells, expressed activated forms of MEK1 and ERK after beta-estradiol or IL-3 stimulation. Insulin or beta-estradiol alone did not induce FD/(delta)B-Raf:ER cells to re-enter the cell cycle, whereas cell cycle entry was observed upon their co-addition. Apoptosis was prevented in FD/(delta)B-Raf:ER cells when they were cultured in the presence of IL-3 or beta-estradiol, whereas they underwent apoptosis in their absence. Insulin by itself did not prevent apoptosis, however, upon DB-Raf:ER or DRaf-1:ER activation and addition of insulin, more than an additive effect was observed in both lines indicating that these path- ways synergized to prevent apoptosis. Raf isoforms differ in their abilities to control apoptosis and cell cycle progression and B-Raf requires insulin-activated pathways for full antiapoptotic and proliferative activity.
Shelton
John G
JG
Department of Microbiology and Immunology, Brody School of Medicine, East Carolina University, Greenville, North Carolina 27858, USA.
Chang
Fumin
F
Lee
John T
JT
Franklin
Richard A
RA
Steelman
Linda S
LS
McCubrey
James A
JA
D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D002453:Cell Cycle / Q000502:physiology*; D002455:Cell Division / Q000502:physiology; D016207:Cytokines / Q000378:metabolism; D006412:Hematopoietic Stem Cells / Q000378:metabolism*; D007328:Insulin / Q000378:metabolism*; D020935:MAP Kinase Signaling System / Q000502:physiology; D051379:Mice; D009154:Mutation; D010766:Phosphorylation; D019908:Proto-Oncogene Proteins c-raf / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D014407:Tumor Cells, Cultured
D016207:Cytokines; D007328:Insulin; D019908:Proto-Oncogene Proteins c-raf