Constitutively active homo-oligomeric angiotensin II type 2 receptor induces cell signaling independent of receptor conformation and ligand stimulation

Abstract

Members of the G-protein-coupled receptor superfamily (GPCRs) undergo homo- and/or hetero-oligomerization to induce cell signaling. Although some of these show constitutive activation, it is not clear how such GPCRs undergo homo-oligomerization with transmembrane helix movement. We previously reported that angiotensin II (Ang II) type 2 (AT2) receptor, a GPCR, showed constitutive activation and induced apoptosis independent of its ligand, Ang II. In the present study, we analyzed the translocation and oligomerization of the AT2 receptor with transmembrane movement when the receptor induces cell signaling. Constitutively active homo-oligomerization, which was due to disulfide bonding between Cys35 in one AT2 receptor and Cys290 in another AT2 receptor, was localized in the cell membrane without Ang II stimulation and induced apoptosis without changes in receptor conformation. These results provide the direct evidence that the constitutively active homo-oligomeric GPCRs by intermolecular interaction in two extracellular loops is translocated to the cell membrane and induces cell signaling independent of receptor conformation and ligand stimulation. © 2005 by The American Society for Biochemistry and Molecular Biology, Inc.