Identification of an interaction between the angiotensin II receptor sub-type AT2 and the ErbB3 receptor, a member of the epidermal growth factor receptor family

To identify the proteins that interact and mediate angiotensin II receptor AT2-specific signaling, a random peptide library was screened by yeast-base d Two-Hybrid protein-protein interaction assay technique. A peptide that sh ared significant homology with the amino acids located between the residues Gly-Xaa-Gly-Xaa-Xaa-Gly721 and Lys742, the residues predicted to be import ant for ATP binding of the ErbB3 and ErbB2 receptors, was identified to be interacting with the AT2 receptor. The interaction between the human ErbB3 receptor and the AT2 receptor was further confirmed using the cytoplasmic d omain (amino acids 671-782) of the human ErbB3 receptor. Moreover, an AT2 r eceptor peptide that spans the amino acids 226-363, (spans the third ICL an d carboxy terminal domain) could also interact with the AT2 receptor in a y east Two-Hybrid protein-protein interaction assay. Studies using mutated an d chimeric AT2 receptors showed that replacing the third intracellular loop (ICL) of the AT2 receptor with that of the AT1 abolishes the interaction b etween the ErbB3 and the AT2 in yeast Two-Hybrid protein-protein interactio n assay. Thus the interaction between the AT2 receptor and the ErbB3 recept or seems to require the region spanning the third ICL and carboxy terminus of the AT2 receptor. Since the third ICL of the AT2 receptor is essential f or exerting its inhibitory effects on cell growth, possible involvement of this region in the interaction with the cytoplasmic domain of the ErbB3 rec eptor suggests a novel signaling mechanism for the AT2 receptor mediated in hibition of cell growth. Furthermore, since both the AT2 and the ErbB3 rece ptors are expressed during fetal development, we propose that the existence of direct interaction between these two receptors may play a role in the r egulation of growth during the initial stages of development. (C) 2000 Else vier Science B.V. All rights reserved.