Constitutively activated FLT3 phosphorylates BAD partially through pim-1.
Constitutively activating internal tandem duplication (ITD) mutations of the receptor tyrosine kinase FLT3 (Fms-like tyrosine kinase 3) play an important role in leukaemogenesis and their presence is associated with a poor prognosis in acute myeloid leukaemia (AML). Examining the anti- and proapoptotic proteins in constitutively activated FLT3 signalling in BaF3/ITD and MV4-11 cells, we found that the level of Bcl-2 antagonist of cell death (BAD) phosphorylation was greatly decreased in response to FLT3 inhibition. Both Ser-112 and Ser-136 of BAD are rapidly dephosphorylated after treatment with the FLT3 inhibitor CEP-701 in BaF3/ITD and MV4-11 cells. In confirmation of the cell line data, BAD was highly phosphorylated in both constitutively activated wild-type and mutant FLT3 primary AML samples, and rapidly dephosphorylated after treatment of the primary samples with CEP-701. Upstream proteins known to phosphorylate BAD include Akt, extracellular signal-regulated kinase/mitogen-activated protein kinase (Erk/ MAPK), Pim-1 and Pim-2. We and other groups have shown that constitutively activated FLT3 induces multiple signalling pathways, including phosphatidylinositol 3-kinase (PI3K)/Akt, Erk/MAPK and Janus kinase/signal transducers and activators of transcription (Jak/STAT). Thus, BAD may be a nexus point upon which these multiple signalling pathways converge in FLT3-mediated cell survival. In support of this, siRNA knockdown of BAD expression in MV4-11 cells conferred resistance to CEP-701-mediated apoptosis. Our data suggests that Pim-1 is one of the principal kinases mediating the anti-apoptotic function of FLT3/ITD signalling via the phosphorylation of BAD.
Kim
Kyu-Tae
KT
Department of Oncology, School of Medicine, Johns Hopkins University, Baltimore, MD 21231, USA.
Levis
Mark
M
Small
Donald
D
D000208:Acute Disease; D017209:Apoptosis / Q000187:drug effects; D002227:Carbazoles / Q000494:pharmacology; D049109:Cell Proliferation; D002470:Cell Survival; D002478:Cells, Cultured; D005663:Furans; D006801:Humans; D047468:Immunoprecipitation; D007211:Indoles / Q000494:pharmacology; D007951:Leukemia, Myeloid / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D051573:Proto-Oncogene Proteins c-pim-1 / Q000378:metabolism*; D034622:RNA Interference; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000502:physiology*; D014162:Transfection; D051025:bcl-Associated Death Protein / Q000378:metabolism*; D051941:fms-Like Tyrosine Kinase 3 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*
D002227:Carbazoles; D005663:Furans; D007211:Indoles; D051025:bcl-Associated Death Protein; C119379:lestaurtinib; C497970:FLT3 protein, human; D051941:fms-Like Tyrosine Kinase 3; D051057:Proto-Oncogene Proteins c-akt; D051573:Proto-Oncogene Proteins c-pim-1