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Heterodimerization of c-erbB2 with different epidermal growth factor receptor mutants elicits stimulatory or
T Spivak-Kroizman1, D Rotin, D Pinchasi
1Department of Pharmacology, New York University Medical Center, New York 10016.
Abstract:
Ligand-induced dimerization of growth factor receptors is crucial for stimulation of their intrinsic protein tyrosine kinase activity promoting receptor autophosphorylation by an intermolecular mechanism. Moreover, the suppressive and negative dominant action of defective epidermal growth factor receptor (EGFR) was shown to be caused by formation of inactive heterodimers with normal EGFR leading to diminished biological signaling. In this report we explore the structural requirements and functional significance of heterodimerization between EGFR and HER2. HER2 (also called c-erbB-2 or neu) is a member of the EGFR family whose natural ligand is still unknown. We show that in response to EGF, wild type EGFR and various EGFR mutants were able to undergo heterodimerization with HER2. Addition of EGF to transfected cells co-expressing HER2 with a kinase negative point mutant of EGFR (K721A) stimulated heterodimer formation, tyrosine phosphorylation of K721A and HER2, and tyrosine phosphorylation of one of their known substrates, phospholipase C gamma. However, the binding of EGF to transfected cells co-expressing HER2 together with another EGFR mutant CD533 (a deletion mutant lacking most of the cytoplasmic domain of EGFR) caused heterodimerization and inhibition of tyrosine kinase activity. It appears therefore that EGF-induced heterodimerization of EGFR and HER2 can promote either stimulatory or inhibitory influences on kinase activity. We propose that the nature of receptor interactions on the cell surface can either activate or inhibit the initiation of growth factor-controlled cellular signaling.
Insights
Epidermal growth factor receptor (EGFR) and HER2 form heterodimers upon EGF binding. This interaction can either activate or inhibit cellular signaling pathways, depending on receptor structure and interactions.
Area of Science:
- Molecular Biology
- Cell Signaling
- Biochemistry
Background:
- Ligand-induced dimerization of growth factor receptors activates protein tyrosine kinase activity.
- Defective epidermal growth factor receptor (EGFR) can exhibit dominant-negative effects through inactive heterodimer formation.
- HER2 (also known as c-erbB-2 or neu) is a member of the EGFR family with an unknown natural ligand.
Purpose of the Study:
- To investigate the structural requirements and functional significance of heterodimerization between EGFR and HER2.
- To explore how EGFR-HER2 heterodimerization influences tyrosine kinase activity and downstream signaling.
Main Methods:
- Co-expression of wild-type EGFR, kinase-negative mutants (K721A), and a cytoplasmic domain deletion mutant (CD533) of EGFR with HER2 in transfected cells.
- Stimulation with epidermal growth factor (EGF).
- Analysis of heterodimer formation, receptor tyrosine phosphorylation, and substrate phosphorylation (e.g., phospholipase C gamma).
Main Results:
- EGF stimulation induced heterodimerization between wild-type EGFR and HER2, as well as with EGFR mutants.
- Co-expression of HER2 with EGFR (K721A) mutant led to EGF-stimulated heterodimer formation, tyrosine phosphorylation of both receptors, and substrate phosphorylation.
- Co-expression of HER2 with EGFR mutant CD533 resulted in heterodimerization but inhibited tyrosine kinase activity.
Conclusions:
- EGF-induced heterodimerization of EGFR and HER2 can exert both stimulatory and inhibitory effects on tyrosine kinase activity.
- The nature of receptor interactions at the cell surface dictates whether growth factor-controlled signaling is activated or inhibited.