Phosphatidylinositol 3 kinase contributes to the transformation of hematopoietic cells by the D816V c-Kit mutant.
Stem cell factor (SCF) binds the receptor tyrosine kinase c-Kit and is critical for normal hematopoiesis. Substitution of valine for aspartic acid 816 (D816V) constitutively actives human c-Kit, and this mutation is found in patients with mastocytosis, leukemia, and germ cell tumors. Immortalized murine progenitor cells (MIHCs) transduced with wild-type c-Kit proliferate in response to SCF, whereas cells expressing D816V c-Kit (MIHC-D816V) are factor-independent and tumorigenic. However, the mechanisms mediating transformation by D816V c-Kit are unknown. The objective of this study was to identify signaling components that contribute to D816V c-Kit-mediated transformation. SCF stimulates association of p85PI3K with phosphorylated tyrosine 721 of wild-type c-Kit. Phosphatidylinositol 3 kinase (PI3K) subsequently contributes to the activation of Akt and Jnks. In contrast, these studies demonstrated that the D816V c-Kit mutant was constitutively associated with phosphorylated p85PI3K, and, downstream of PI3K, Jnk 1 and Jnk 2 were activated but Akt was not. Interestingly, Erks 1 and 2 were not constitutively activated by D816V c-Kit. Thus, D816V c-Kit maintains the activity of PI3K but not of all signaling pathways activated by wild-type c-Kit. Further, all pathways downstream of PI3K are not constitutively active in MIHC-D816V cells. Studies with a PI3K inhibitor and D816V/Y721F c-Kit, a mutant incapable of recruiting PI3K, indicate that constitutive activation of PI3K through direct recruitment by D816V c-Kit plays a role in factor-independent growth of MIHC and is critical for tumorigenicity.
Chian
R
R
Basic Research Laboratory and the Laboratory of Immunobiology, Division of Basic Sciences, National Cancer Institute-Frederick, MD 21702, USA.
Young
S
S
Danilkovitch-Miagkova
A
A
Rönnstrand
L
L
Leonard
E
E
Ferrao
P
P
Ashman
L
L
Linnekin
D
D
D019943:Amino Acid Substitution; D000818:Animals; D002455:Cell Division; D002471:Cell Transformation, Neoplastic / Q000378:metabolism*; D002478:Cells, Cultured; D002867:Chromones / Q000494:pharmacology; D004789:Enzyme Activation / Q000235:genetics; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D006412:Hematopoietic Stem Cells / Q000201:enzymology / Q000473:pathology*; D006801:Humans; D051379:Mice; D008808:Mice, Inbred CBA; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D048055:Mitogen-Activated Protein Kinase 8; D048056:Mitogen-Activated Protein Kinase 9; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009025:Morpholines / Q000494:pharmacology; D020125:Mutation, Missense; D019869:Phosphatidylinositol 3-Kinases / Q000737:chemistry / Q000502:physiology*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational; D017346:Protein Serine-Threonine Kinases; D017434:Protein Structure, Tertiary; D021122:Protein Subunits; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D019009:Proto-Oncogene Proteins c-kit / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D011993:Recombinant Fusion Proteins / Q000502:physiology; D015398:Signal Transduction; D019089:Stem Cell Factor / Q000502:physiology; D014162:Transfection
D002867:Chromones; D004791:Enzyme Inhibitors; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D048055:Mitogen-Activated Protein Kinase 8; D048056:Mitogen-Activated Protein Kinase 9; D020928:Mitogen-Activated Protein Kinases; D009025:Morpholines; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases; D021122:Protein Subunits; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D019009:Proto-Oncogene Proteins c-kit; D011993:Recombinant Fusion Proteins; D019089:Stem Cell Factor; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C494918:AKT1 protein, human