Lipid rafts are required for Kit survival and proliferation signals.
In addition to its physiologic role as central regulator of the hematopoietic and reproductive systems, the Kit receptor tyrosine kinase (RTK) is pathologically overexpressed in some forms of leukemia and constitutively activated by oncogenic mutations in mast-cell proliferations and gastrointestinal stromal tumors. To gain insight into the general activation and signaling mechanisms of RTKs, we investigated the activation-dependent dynamic membrane distributions of wild-type and oncogenic forms of Kit in hematopoietic cells. Ligand-induced recruitment of wild-type Kit to lipid rafts after stimulation by Kit ligand (KL) and the constitutive localization of oncogenic Kit in lipid rafts are necessary for Kit-mediated proliferation and survival signals. KL-dependent and oncogenic Kit kinase activity resulted in recruitment of the regulatory phosphatidylinositol 3-kinase (PI3-K) subunit p85 to rafts where the catalytical PI3-K subunit p110 constitutively resides. Cholesterol depletion by methyl-beta-cyclodextrin prevented Kit-mediated activation of the PI3-K downstream target Akt and inhibited cellular proliferation by KL-activated or oncogenic Kit, including mutants resistant to the Kit inhibitor imatinib-mesylate. Our data are consistent with the notion that Kit recruitment to lipid rafts is required for efficient activation of the PI3-K/Akt pathway and Kit-mediated proliferation.
Jahn
Thomas
T
Division of Research Immunology and Bone Marrow Transplantation, Childrens Hospital Los Angeles, CA, USA. thahn@stanford.edu
Leifheit
Erica
E
Gooch
Stacie
S
Sindhu
Simran
S
Weinberg
Kenneth
K
D000818:Animals; D001549:Benzamides; D049109:Cell Proliferation; D002470:Cell Survival; D002478:Cells, Cultured / Q000187:drug effects / Q000378:metabolism; D002784:Cholesterol / Q000172:deficiency; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D006412:Hematopoietic Stem Cells / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D000068877:Imatinib Mesylate; D007700:Kinetics; D008407:Mast Cells / Q000187:drug effects / Q000378:metabolism; D021962:Membrane Microdomains / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D009154:Mutation / Q000235:genetics; D051059:PTEN Phosphohydrolase / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D010879:Piperazines / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism*; D019009:Proto-Oncogene Proteins c-kit / Q000235:genetics / Q000378:metabolism*; D011743:Pyrimidines / Q000494:pharmacology; D000081382:Pyruvate Dehydrogenase Acetyl-Transferring Kinase; D015398:Signal Transduction; D019089:Stem Cell Factor; D047392:beta-Cyclodextrins / Q000494:pharmacology
D001549:Benzamides; D002784:Cholesterol; D000068877:Imatinib Mesylate; D051059:PTEN Phosphohydrolase; D019869:Phosphatidylinositol 3-Kinases; D010879:Piperazines; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D019009:Proto-Oncogene Proteins c-kit; D011743:Pyrimidines; D000081382:Pyruvate Dehydrogenase Acetyl-Transferring Kinase; D019089:Stem Cell Factor; D047392:beta-Cyclodextrins; C108732:methyl-beta-cyclodextrin