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Kinase-deficient neu proteins suppress epidermal growth factor receptor function and abolish cell transformation
X Qian1, W C Dougall, M E Hellman
1Department of Pathology and Laboratory Medicine, University of Pennsylvania, School of Medicine, Philadelphia 19104-6082.
Abstract:
p185c-neu and epidermal growth factor receptor (EGFR) associate into an active heterodimer, and overexpression of these two receptors leads to a transformed phenotype. However, the association of EGFR and kinase-deficient Neu proteins (point mutant N757 or cytoplasmic domain deletion mutant N691stop) results in a defective or inactive heterodimeric complex. In this report we explore the biological consequences of heterodimerization between EGFR and wild-type (WT) or kinase-deficient mutant Neu proteins in living cells. We show that co-expression of EGFR and kinase-deficient Neu proteins abolished the synergistic transformation and tumorigenicity. Moreover, the normal responses of EGFR to ligand were significantly suppressed, e.g., loss of EGF-dependent transformation, reduced rate of receptor endocytosis and turnover, diminished DNA synthesis, and decreased EGF binding affinity. These results provide the first evidence that kinase-deficient Neu proteins suppress normal EGFR function and display a dominant negative mutant phenotype. Together with the stimulatory effects observed in cells forming active heterodimers, these studies provide a role for heterodimerization of EGFR and Neu/c-erbB2 in interreceptor activation and synergistic signaling which may be responsible for the transition from normal receptor function into oncogenesis.
Insights
Kinase-deficient Neu proteins suppress epidermal growth factor receptor (EGFR) function when heterodimerized, blocking EGFR-driven transformation and tumorigenicity. This dominant-negative effect highlights the role of receptor heterodimerization in oncogenesis.
Area of Science:
- Cellular biology
- Molecular oncology
- Signal transduction
Background:
- p185c-neu and epidermal growth factor receptor (EGFR) form active heterodimers upon overexpression, driving a transformed phenotype.
- Kinase-deficient Neu proteins, when associated with EGFR, form defective or inactive heterodimeric complexes.
Purpose of the Study:
- To investigate the biological impact of heterodimerization between EGFR and wild-type or kinase-deficient Neu proteins in living cells.
- To elucidate the role of receptor heterodimerization in oncogenesis and signal transduction.
Main Methods:
- Co-expression of EGFR with wild-type or kinase-deficient Neu proteins in cellular models.
- Assessment of synergistic transformation, tumorigenicity, and EGFR ligand responses (e.g., EGF-dependent transformation, receptor endocytosis, DNA synthesis, EGF binding).
Main Results:
- Co-expression of EGFR and kinase-deficient Neu proteins abolished synergistic transformation and tumorigenicity.
- Normal EGFR responses to EGF were significantly suppressed, including loss of EGF-dependent transformation, reduced receptor endocytosis and turnover, diminished DNA synthesis, and decreased EGF binding affinity.
- Kinase-deficient Neu proteins exhibit a dominant-negative mutant phenotype, suppressing normal EGFR function.
Conclusions:
- Kinase-deficient Neu proteins suppress normal EGFR function, demonstrating a dominant-negative effect.
- Receptor heterodimerization between EGFR and Neu/c-erbB2 plays a crucial role in interreceptor activation and synergistic signaling.
- These interactions are implicated in the transition from normal receptor function to oncogenesis.