Tyrosine phosphorylation of a 120-kilodalton pp60src substrate upon epidermal growth factor and platelet-derived growth factor receptor stimulation and in polyomavirus middle-T-antigen-transformed cells.
The monoclonal antibody 2B12 is directed toward p120, a 120-kDa cellular protein originally identified as a protein tyrosine kinase substrate in cells expressing membrane-associated oncogenic variants of pp60src. In this report, we show that p120 was tyrosine phosphorylated in avian cells expressing membrane-associated, enzymatically activated variants of c-src, including variants having structural alterations in the src homology regions 2 and 3. In contrast, p120 was not tyrosine phosphorylated in cells expressing enzymatically activated, nonmyristylated pp60src. Furthermore, p120 was tyrosine phosphorylated in avian cells expressing middle T antigen, the transforming protein of polyomavirus, as well as in rodent cells stimulated with either epidermal growth factor (EGF) or platelet-derived growth factor. Analysis of the time course of p120 tyrosine phosphorylation in EGF-stimulated cells revealed a rapid onset of tyrosine phosphorylation. In addition, both the extent and duration of p120 phosphorylation increased when cells overexpressing the EGF receptor were stimulated with EGF. Biochemical analysis showed that p120 (in both normal and src-transformed cells) was membrane associated, was myristylated, and was phosphorylated on serine and threonine residues. Hence, p120 appears to be a substrate of both nonreceptor- and ligand-activated transmembrane receptor tyrosine kinases and of serine/threonine kinases and is perhaps a component of both mitogen-stimulated and tyrosine kinase oncogene-induced signaling pathways.
Kanner
S B
SB
Department of Microbiology and Cancer Center, University of Virginia Health Sciences Center, Charlottesville 22908.
Reynolds
A B
AB
Parsons
J T
JT
D000818:Animals; D000952:Antigens, Polyomavirus Transforming / Q000235:genetics*; D002460:Cell Line; D002471:Cell Transformation, Neoplastic; D002642:Chick Embryo; D066246:ErbB Receptors / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D008970:Molecular Weight; D008979:Moloney murine leukemia virus / Q000235:genetics; D019814:Myristic Acid; D009227:Myristic Acids / Q000378:metabolism; D019308:Palmitic Acid; D010169:Palmitic Acids / Q000378:metabolism; D010710:Phosphates / Q000378:metabolism; D010766:Phosphorylation; D010982:Platelet-Derived Growth Factor / Q000378:metabolism*; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000235:genetics* / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000378:metabolism*; D017479:Receptors, Platelet-Derived Growth Factor; D014443:Tyrosine
D000952:Antigens, Polyomavirus Transforming; D009227:Myristic Acids; D010169:Palmitic Acids; D010710:Phosphates; D010982:Platelet-Derived Growth Factor; D011956:Receptors, Cell Surface; D019814:Myristic Acid; D019308:Palmitic Acid; D014443:Tyrosine; D066246:ErbB Receptors; D017479:Receptors, Platelet-Derived Growth Factor; D016392:Proto-Oncogene Proteins pp60(c-src)