Activation of ErbB4 by the Bifunctional Epidermal Growth Factor Family Hormone Epiregulin Is Regulated by ErbB2

David J Riese,Toshi Komurasaki,Gregory D Plowman,David F Stern

doi:10.1074/jbc.273.18.11288

David J Riese, Toshi Komurasaki + Show 2 more

Open Access

https://doi.org/10.1074/jbc.273.18.11288

Copy DOI

Abstract

Epiregulin (EPR) is a recently described member of the epidermal growth factor (EGF) family of peptide growth factors. The ever expanding size of the EGF family has made distinguishing the activities of these hormones paramount. We show here that EPR activates two members of the ErbB family of receptor tyrosine kinases, epidermal growth factor receptor (EGFR) and ErbB4. Therefore by these criteria, EPR is qualitatively similar to another EGF family hormone, betacellulin (BTC). Yet, here we also demonstrate quantitative differences between EPR and BTC. EPR stimulates higher levels of EGFR phosphorylation than does BTC, whereas BTC stimulates higher levels of ErbB4 phosphorylation than does EPR. Moreover, the EPR and BTC dose response curves show that although EGFR is more sensitive to EPR than is ErbB4, ErbB4 is more sensitive to BTC than is EGFR. Finally, ErbB2, which is not activated by EPR when expressed on its own, increases the sensitivity of ErbB4 for activation by EPR. Therefore, these results establish that EPR exhibits novel activities and modes of regulation, which may have significant implications for EPR function in vivo.

Highlights

The continuing discovery of novel members of the epidermal growth factor (EGF)1 family of peptide growth factors has led to an increased appreciation of the functional differences among these hormones, as well as a realization of the complex hormone-receptor interactions fostered by these peptides
EPR Activates EGF receptor (EGFR)—We first sought to identify which ErbB family receptors are activated by EPR when the receptors are expressed individually
We previously demonstrated that the EGF family of peptide growth factors can be divided into three distinct functional groups [8] (Fig. 8)

Summary

EXPERIMENTAL PROCEDURES

BaF3-derived cell lines expressing combinations of ErbB family receptors have been described previously [14]. The levels of ErbB3 expression are similiar in the BaF3/EGFRϩErbB3, BaF3/ErbB2ϩErbB3, and BaF3/ErbB3ϩErbB4 cell lines. The levels of ErbB4 expression are similiar in the BaF3/ EGFRϩErbB4, BaF3/NeuϩErbB4, and BaF3/ErbB3ϩErbB4 cell lines [7, 14]. CEM is an immortal human T-lymphoblastoid cell line that does not endogenously express EGF receptor, ErbB2, ErbB3, or ErbB4. Stimulation and Analysis of Receptor Phosphorylation—The conditions for stimulation of ErbB family receptor tyrosine phosphorylation have been described previously [7, 14]. The analysis of ErbB family receptor tyrosine phosphorylation by immunoprecipitation and antiphosphotyrosine immunoblotting has been described previously [7, 14]. Net receptor activation was calculated by subtracting the amount of tyrosine phosphorylation observed in samples from mock-stimulated cells

RESULTS

NTa NT

DISCUSSION