Constitutive activation of c-kit in FMA3 murine mastocytoma cells caused by deletion of seven amino acids at the juxtamembrane domain.
A peculiar point mutation results in constitutive activation of c-kit receptor tyrosine kinase (KIT) in three different tumor mast cell lines; ie, the HMC-1, P-815, and RBL-2H3. Because constitutive activation of KIT was also observed in the FMA3 mouse mastocytoma cell line, we investigated the molecular mechanism. Sequencing of the whole coding region of the c-kit showed that the point mutation found in HMC-1, P-815, and RBL-2H3 cells was absent in FMA3 cells and that the c-kit cDNA of FMA3 cells carried an in-frame deletion of 21 base pairs (bp) encoding Thr-Gln-Leu-Pro-Tyr-Asp-His at codons 573 to 579 at the juxtamembrane domain. The FMA3-type c-kit cDNA with 21 bp deletion was introduced into the IC-2 cell line, which was derived from murine cultured mast cells. IC-2 cells were dependent on interleukin (IL)-3 and did not express KIT on the surface. In IC-2 cells introduced with the FMA3-type c-kit cDNA, KIT was constitutively phosphorylated on tyrosines and activated. Moreover, the FMA3-type KIT was dimerized without the stimulation by stem cell factor (SCF), a ligand for KIT. The spontaneously dimerized FMA3-type KIT without SCF binding was not internalized even after the activation. IC-2 cells expressing the FMA3-type KIT grew in suspension culture without IL-3 and SCF and became leukemic in nude athymic mice. The deletion of seven amino acids at the juxtamembrane domain appeared to be a new activating mutation of KIT that might be involved in neoplastic growth of mast cells.
Department of Pathology, Osaka University Medical School, Japan.
T
T
Tsujimura
M
M
Morimoto
K
K
Hashimoto
Y
Y
Moriyama
H
H
Kitayama
Y
Y
Matsuzawa
Y
Y
Kitamura
Y
Y
Kanakura
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002455:Cell Division / Q000187:drug effects; D004273:DNA, Neoplasm / Q000235:genetics; D004789:Enzyme Activation; D007377:Interleukin-3 / Q000494:pharmacology; D012515:Mast-Cell Sarcoma / Q000201:enzymology / Q000473:pathology*; D051379:Mice; D008810:Mice, Inbred C57BL; D008819:Mice, Nude; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D009368:Neoplasm Transplantation; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational; D017434:Protein Structure, Tertiary; D019009:Proto-Oncogene Proteins c-kit / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D011519:Proto-Oncogenes; D011994:Recombinant Proteins / Q000494:pharmacology; D016415:Sequence Alignment; D017384:Sequence Deletion; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity; D019089:Stem Cell Factor / Q000494:pharmacology; D014162:Transfection; D014407:Tumor Cells, Cultured; D014714:Vertebrates / Q000378:metabolism
D004273:DNA, Neoplasm; D007377:Interleukin-3; D009363:Neoplasm Proteins; D011994:Recombinant Proteins; D019089:Stem Cell Factor; D019009:Proto-Oncogene Proteins c-kit