Oncogenic forms of the neu/HER2 tyrosine kinase are permanently coupled to phospholipase C gamma.
The neu/HER2 proto-oncogene encodes a transmembrane tyrosine kinase homologous to receptors for polypeptide growth factors. The oncogenic potential for the presumed receptor is released through multiple genetic mechanisms including a specific point mutation, truncation at the extracellular domain and overexpression of the protooncogene. Here we show that all these modes of oncogenic activation result in a constitutively phosphorylated neu protein and an increase in tyrosine phosphorylation of a phosphatidylinositol-specific phospholipase (PLC gamma). The examined transforming neu/HER2 proteins, unlike the normal gene product, also co-immunoprecipitated with PLC gamma molecules. A kinase-defective mutant of a transforming neu failed to mediate both tyrosine phosphorylation and association with PLC gamma, suggesting direct interaction of the neu kinase with PLC gamma. This possibility was examined by employing a chimeric protein composed of the extracellular ligand-binding domain of the epidermal growth factor receptor and the neu cytoplasmic portion. The chimeric receptor mediated rapid ligand-dependent modification of PLC gamma on tyrosine residues. It also physically associated, in a ligand-dependent manner, with the phosphoinositidase. Based on the presented results we suggest that the mechanism of cellular transformation by the neu/HER2 receptor involves tyrosine phosphorylation and activation of PLC gamma.
Department of Chemical Immunology, Weizmann Institute of Science, Rehovot, Israel.
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E
Peles
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Levy
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Or
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Ullrich
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Yarden
D001483:Base Sequence; D015153:Blotting, Western; D002471:Cell Transformation, Neoplastic; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D008969:Molecular Sequence Data; D009154:Mutation; D010716:Phosphatidylinositols / Q000378:metabolism; D010766:Phosphorylation; D011233:Precipitin Tests; D011505:Protein-Tyrosine Kinases / Q000235:genetics* / Q000378:metabolism; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins / Q000235:genetics* / Q000378:metabolism; D018719:Erb-b2 Receptor Tyrosine Kinases; D014407:Tumor Cells, Cultured; D010738:Type C Phospholipases / Q000378:metabolism*; D014638:Vanadates / Q000737:chemistry
D010716:Phosphatidylinositols; D011505:Protein-Tyrosine Kinases; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins; D018719:Erb-b2 Receptor Tyrosine Kinases; D010738:Type C Phospholipases; D014638:Vanadates; C000715470:MAS1 protein, human