Ligand-independent phosphorylation of Y869 (Y845) links mutant EGFR signaling to stat-mediated gene expression

    Authors

    S. Yanga; K. Parka; J. Turkson;C. L. Arteaga

    Comments

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    Abbreviated Journal Title

    Exp. Cell Res.

    Keywords

    EGFR; Src; lung cancer; STAT; phosphorylation; GROWTH-FACTOR RECEPTOR; TYROSINE KINASE INHIBITOR; CELL LUNG-CANCER; C-SRC; INCREASED SENSITIVITY; DOMAIN MUTATIONS; DOWN-REGULATION; GEFITINIB; PROTEINS; TRANSFORMATION; Oncology; Cell Biology

    Abstract

    Activating mutants of EGFR have been identified in a subset of non-small-cell lung cancers. To investigate mutant-driven signaling, we focused on Y869, a residue in the same activation loop where the L858R and L861Q mutations are located. We observed ligand-independent phosphorylation of Y869 in 32D cells EGFR(L858R) and EGFR(L861Q). The EGFR tyrosine kinase inhibitor (TKI) erlotinib inhibited Y869 P-EGFR in intact cells as well as in a cell-free kinase reaction. Expression of kinase domain of EGFR(L858R) and EGFR(L861Q) exhibited auto-phosphorylation of Y869; this was inhibited by EGFR TKIs but not by Src kinase inhibitor. P-Y859 of EGFR-mediated downstream component, STAT5, was also analyzed. Y694 P-STAT5 was eliminated by erlotinib treatment. Analysis of immune-complexes showed constitutive association of mutant EGFRs with STAT5 and Src which was unaffected by erlotinib or PP1. On the other hand, 32D-EGFR(WT) exhibited constitutive STAT5 phosphorylation and association of EGFR with JAK2. In these cells, a JAK2 inhibitor abrogated P-STAT5 whereas mutant EGFRs did not associate with JAK2. Expression of c-myc was regulated by EGFR/STAT5 signaling in cells expressing EGFR(L858R) and EGFR(L861Q). Our results suggest that ligand-independent and Src activity-independent phosphorylation of Y869 in mutant EGFR regulates STAT5 activation and c-myc expression. (C) 2007 Elsevier Inc. All rights reserved.

    Journal Title

    Experimental Cell Research

    Volume

    314

    Issue/Number

    2

    Publication Date

    1-1-2008

    Document Type

    Article

    Language

    English

    First Page

    413

    Last Page

    419

    WOS Identifier

    WOS:000251891300018

    ISSN

    0014-4827

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