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Ligand‐induced protein tyrosine kinase activity in living cells coexpressing intact EGF receptors and receptors with an extensive cytosolic deletion
Author(s) -
Dou Yi,
Hoffman Patricia,
Hoffman Brian L.,
Carlin Cathleen
Publication year - 1992
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.1041530220
Subject(s) - autophosphorylation , tyrosine kinase , biology , receptor tyrosine kinase , receptor , tropomyosin receptor kinase c , microbiology and biotechnology , epidermal growth factor , biochemistry , platelet derived growth factor receptor , protein kinase a , kinase , growth factor
A population of stable NIH 3T3 transfectants with two molecular weight classes of membrane‐bound EGF receptors encoded by a human EGF receptor cDNA has been identified and characterized. In addition to intact EGF receptors, these cells also express a molecule with an extensive cytosolic deletion. This deletion includes the ligand‐activated intrinsic protein tyrosine kinase catalytic domain. Treatment with EGF caused dimerization of intact and truncated receptors, allowing us to assess protein tyrosine kinase activity in the heterodimer isolated from living cells. In contrast to homodimeric complexes with intact EGF receptor only, heterodimers were deficient in protein tyrosine kinase activity. Moreover, physical association between intact and truncated molecules suppressed receptor autophosphorylation by EGF receptor protein tyrosine kinase activated by antibody binding in vitro. Evidence presented here supports the idea that protein tyrosine kinase activation is facilitated by interaction between adjacent receptor molecules with intact catalytic domains. Furthermore, molecules with cytoplasmic deletions that are physically associated with kinase‐active EGF receptors appear to behave as dominant negative mutations. The HerC cl cells used in this study were selected with methotrexate to amplify the EGF receptor cDNA, and in that sense may resemble certain tumor‐derived cells characterized by overexpressed and rearranged EGF receptor genes. © 1992 Wiley‐Liss, Inc.