CONSTITUTIVELY ACTIVATED NEU ONCOPROTEIN TYROSINE KINASE INTERFERES WITH GROWTH FACTOR-INDUCED SIGNALS FOR GENE ACTIVATION

L LEHTOLA, Lea Sistonen, P KOSKINEN, H LEHVÄSLAIHO, MF DIRENZO, PM COMOGLIO, K ALITALO

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    Abstract

    The neu receptor oncoprotein tyrosine kinase, capable of transforming cultured fibroblasts and causing mammary carcinomas in transgenic mice, carries a point mutation in its transmembrane domain and shows a constitutive tyrosine kinase activity. We analyzed the neu tyrosine kinase and its substrates in transfected NIH 3T3 fibroblasts by phosphotyrosine immunoblotting. Tryosine phosphorylated proteins were similar but not identical in epidermal growth factor (EGF)-stimulated cells expressing the human EGF receptor (EGFR) or a chimeric EGFR/neu receptor but differed from phosphotyrosyl proteins constitutively expressed in neu oncogene-transformed cells. The neu oncoprotein in the latter cells was phosphorylated in tyrosine in a ligand-independent manner and had a shortened half-life in comparison with the normal neu protein. Tumor promoter pretreatment inhibited ligand-induced receptor tyrosine phosphorylation and decreased tyrosine phosphorylated neu oncoprotein. Prolonged pretreatment with 12-O-tetradecanoyl-phorbol-13-acetate (TPA) also prevented the induction of immediate early growth factor-regulated genes in response to neu activation. Expression of the neu oncogene but not the protooncogene in NIH 3T3 cells was associated with enhanced levels of the jun and fos oncoproteins and loss of serum growth factor induction of immediate early mRNA responses. The constitutively activated neu oncoprotein tyrosine kinase thus deregulates cellular genomic responses to growth factors.
    Original languageUndefined/Unknown
    Pages (from-to)69–81
    Number of pages13
    JournalJournal of Cellular Biochemistry
    Volume45
    Issue number1
    Publication statusPublished - 1991
    MoE publication typeA1 Journal article-refereed

    Keywords

    • EGF
    • EPIDERMAL GROWTH FACTOR
    • RECEPTOR TYROSINE KINASE
    • TUMOR PROMOTER

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