Transformation-specific tyrosine phosphorylation of a novel cellular protein in chicken cells expressing oncogenic variants of the avian cellular src gene.
We used myristylated and nonmyristylated c-src-based variants and phosphotyrosine-specific antibodies to reevaluate the role of tyrosine phosphorylation in cellular transformation by pp60src. Prior methods used to detect tyrosine-phosphorylated proteins failed to discriminate predicted differences in tyrosine phosphorylation which are clearly observed with phosphotyrosine-specific antibodies and Western blotting (immunoblotting). Here we report the observation of a 120,000-Mr protein whose phosphorylation on tyrosine correlates with the induction of morphological transformation. p120 was not observed in cells overexpressing the regulated, nononcogenic pp60c-src, whereas phosphorylation of p120 was greatly enhanced in cells expressing activated, oncogenic pp60527F. Furthermore, phosphorylation of p120 was not induced by expression of the activated but nonmyristylated src variant pp602A/527F, which is transformation defective. p120 partitioned preferentially with cellular membranes, consistent with the observation that transforming src proteins are membrane associated. Although a number of additional putative substrates were identified and partially characterized with respect to intracellular localization, tyrosine phosphorylation of these proteins was not tightly linked to transformation.
Reynolds
A B
AB
Department of Microbiology, University of Virginia School of Medicine, Charlottesville 22908.
Roesel
D J
DJ
Kanner
S B
SB
Parsons
J T
JT
D000818:Animals; D002478:Cells, Cultured; D014644:Genetic Variation; D006651:Histocytochemistry; D008970:Molecular Weight; D009857:Oncogenes; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D019000:Phosphotyrosine; D011518:Proto-Oncogene Proteins / Q000235:genetics; D016392:Proto-Oncogene Proteins pp60(c-src); D014170:Transformation, Genetic; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000378:metabolism
D010750:Phosphoproteins; D011518:Proto-Oncogene Proteins; D019000:Phosphotyrosine; D014443:Tyrosine; D016392:Proto-Oncogene Proteins pp60(c-src)