ErbB-2, the preferred heterodimerization partner of all ErbB receptors, is a mediator of lateral signaling

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Abstract
We have analyzed ErbB receptor interplay induced by the epidermal growth factor (EGF)‐related peptides in cell lines naturally expressing the four ErbB receptors. Down‐regulation of cell surface ErbB‐1 or ErbB‐2 by intracellular expression of specific antibodies has allowed us to delineate the role of these receptors during signaling elicited by: EGF and heparin binding EGF (HB‐EGF), ligands of ErbB‐1; betacellulin (BTC), a ligand of ErbB‐1 and ErbB‐4; and neu differentiation factor (NDF), a ligand of ErbB‐3 and ErbB‐4. Ligand‐induced ErbB receptor heterodimerization follows a strict hierarchy and ErbB‐2 is the preferred heterodimerization partner of all ErbB proteins. NDF‐activated ErbB‐3 or ErbB‐4 heterodimerize with ErbB‐1 only when no ErbB‐2 is available. If all ErbB receptors are present, NDF receptors preferentially dimerize with ErbB‐2. Furthermore, EGF‐ and BTC‐induced activation of ErbB‐3 is impaired in the absence of ErbB‐2, suggesting that ErbB‐2 has a role in the lateral transmission of signals between other ErbB receptors. Finally, ErbB‐1 activated by all EGF‐related peptides (EGF, HB‐EGF, BTC and NDF) couples to SHC, whereas only ErbB‐1 activated by its own ligands associates with and phosphorylates Cbl. These results provide the first biochemical evidence that a given ErbB receptor has distinct signaling properties depending on its dimerization.