ErbB-1 and ErbB-2 Acquire Distinct Signaling Properties Dependent upon Their Dimerization Partner

Abstract

The different epidermal growth factor (EGF)-related peptides elicit a diverse array of biological responses as the result of their ability to activate distinct subsets of ErbB receptor dimers, leading to the recruitment of different intracellular signaling networks. To specifically examine dimerization-dependent modulation of receptor signaling, we constructed NIH 3T3 cell lines expressing ErbB-1 and ErbB-2 singly and in pairwise combinations with each other ErbB family member. This model system allowed the comparison of EGFactivated ErbB-1 with ErbB-1 activated by Neu differentiation factor (NDF)-induced heterodimerization with ErbB-4. In both cases, ErbB-1 coupled to the adaptor protein Shc, but only when activated by EGF was it able to interact with Grb2. Compared to the rapid internalization of EGF-activated ErbB-1, NDF-activated ErbB-1 showed delayed internalization characteristics. Furthermore, the p85 subunit of phosphatidylinositol kinase (PI3-K) associated with EGF-activated ErbB-1 in a biphasic manner, whereas association with ErbB-1 transactivated by ErbB-4 was monophasic. The signaling properties of ErbB-2 following heterodimerization with the other ErbB receptors or homodimerization induced by point mutation or monoclonal antibody treatment were also analyzed. ErbB-2 binding to peptides containing the Src homology 2 domain of Grb2 or p85 and the phosphotyrosine binding domain of Shc varied according to the mode of receptor activation. Finally, tryptic phosphopeptide mapping of both ErbB-1 and ErbB-2 revealed that receptor phosphorylation is dependent on the dimerization partner. Differential receptor phosphorylation may, therefore, be the basis for the differences in the signaling properties observed.The ErbB family of receptor tyrosine kinases has four members: epidermal growth factor (EGF) receptor (ErbB-1), ErbB-2, ErbB-3, and ErbB-4. The ErbB receptors are expressed in epithelial, mesenchymal, and neuronal tissue and play fundamental roles during development. Two of the family members, ErbB-1 and ErbB-2, are involved in the development of many types of human cancer (reviewed in references 29 and 44).A large family of growth factors, the EGF-related peptides, serve as ligands for ErbB receptors (42,44). The ligands fall into three groups: EGF, amphiregulin (AR), and transforming growth factor ␣, which bind ErbB-1; betacellulin, epiregulin, and heparin binding EGF-like growth factor, which bind both ErbB-1 and ErbB-4; and Neu differentiation factors (NDFs) or heregulins, which are ligands for ErbB-3 and ErbB-4.Ligand binding promotes ErbB receptor homo-and heterodimerization. Although no direct ligand for ErbB-2 has been identified, it appears to be the preferred heterodimerization partner of all ErbB proteins (21,30,48). Despite the lack of an ErbB-2-specific ligand, homodimerization of this receptor can be achieved by mutating a single amino acid residue in the transmembrane domain (1), leading to constitutive ErbB-2 dimerization and activation. Alternatively, antibody binding to the extracellul...

Overexpression of ErbB2 enhances ethanol-stimulated intracellular signaling and invasion of human mammary epithelial and breast cancer cells in vitro

“…ErbB2 is the preferred heterodimerization partner of all activated ErbB family members (Graus-Porta et al, 1997). Although no identified ligand, ErbB2 can be transactivated by dimerization with ErbB family members, and its transactivation allows the recruitment of distinct effector molecules leading to diversification of signal transduction response (Olayioye et al, 1998). ErbB2 amplification in breast cancer cells leads to an association with adaptor proteins and downstream effectors (Olayioye et al, 1998;Spencer et al, 2000 …”

Gene expression profiling of ErbB receptor and ligand-dependent transcription

“…The weaker receptor activation elicited by HB-EGF in SUM44 cells compared to NRG induction may contribute to (Sartor et al, 2001). Hence, differences arising from homomeric versus heteromeric signaling may also contribute to distinct patterns of gene regulation (Olayioye et al, 1998). In fact, heterodimers of ErbBs overexpressed in NIH3T3 cells result in overlapping but distinct expression profiles from single-receptor homodimers (Alaoui-Jamali et al, 2003).…”

Feedback inhibition by RALT controls signal output by the ErbB network

“…Combinatorial dimerization among ErbB RTKs generates additional signalling potential via integration of the signalling competence of individual protomers as well as the generation of novel signalling profiles (Olayioye et al, 1998). Finally, ErbB RTKs share some signalling pathways, such as those leading to Ras-ERK and PI-3K-AKT activation.…”