Human c-fgr induces a monocyte-specific enzyme in NIH 3T3 cells.
The mutant c-fgr protein (p58c-fgr/F523) containing Phe-523 instead of Tyr-523 exhibited transforming activity in NIH 3T3 cells like other protein-tyrosine kinases of the src family, but normal p58c-fgr (p58c-fgr/wt) did not. The mutant protein showed tyrosine kinase activity threefold higher than that of the normal protein in vitro. Surprisingly, transfection of the normal c-fgr gene into NIH 3T3 cells resulted in induction of sodium fluoride (NaF)-sensitive alpha-naphthyl butyrate esterase (alpha-NBE), a marker enzyme of cells of monocytic origin, which was not induced in v-src-, v-fgr-, or lyn-transfected NIH 3T3 cells. The NaF-sensitive alpha-NBE induced in c-fgr transfectants was shown by isoelectric focusing to have a pI of 5.2 to 5.4, a range which was the same as those for thioglycolate-induced murine peritoneal macrophages and 1 alpha,25-dihydroxyvitamin D3-treated WEHI-3B cells. Immunoblotting studies with antiphosphotyrosine antibodies revealed that 58-, 62-, 75-, 120-, 200-, and 230-kDa proteins were commonly phosphorylated at tyrosine residues in NIH 3T3 cells transfected with normal and mutated c-fgr, while 95-kDa protein was significantly phosphorylated at tyrosine residues in cells transfected with the mutated c-fgr. These findings suggest that tyrosine phosphorylation of specific cellular substrate proteins is important in induction of NaF-sensitive alpha-NBE and cell transformation by p58c-fgr.
Inoue
K
K
Department of Oncogene Research, Osaka University, Japan.
Wongsasant
B
B
Akiyama
T
T
Toyoshima
K
K
D016475:3T3 Cells; D000818:Animals; D001483:Base Sequence; D002265:Carboxylic Ester Hydrolases / Q000096:biosynthesis*; D003854:Deoxyribonucleotides; D006801:Humans; D015151:Immunoblotting; D007525:Isoelectric Focusing; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D014162:Transfection; D014170:Transformation, Genetic; D019061:src-Family Kinases
D003854:Deoxyribonucleotides; D011518:Proto-Oncogene Proteins; D011505:Protein-Tyrosine Kinases; C053102:proto-oncogene proteins c-fgr; D019061:src-Family Kinases; D002265:Carboxylic Ester Hydrolases; C021855:naphthylbutyrate esterase