E-Poster 63rd Endocrine Society of Australia Annual Scientific Meeting 2020

Heteromerisation of the angiotensin II type 1 and type 2 receptor (#48)

Elizabeth KM Johnstone 1 2 3 , Kevin DG Pfleger 1 2 3 4
  1. Harry Perkins Institute of Medical Research, Nedlands, WA, Australia
  2. Centre for Medical Research, The University of Western Australia, Crawley, WA, Australia
  3. Australian Research Council Centre for Personalised Therapeutics Technologies, Australia
  4. Dimerix Limited, Nedlands, WA, Australia

Angiotensin II (AngII) is a vital hormone that is involved in the regulation of many physiological processes, including the maintenance of blood pressure, inflammation and proliferation. AngII exerts its actions via two G protein-coupled receptors (GPCRs), the AT1 and the AT2 receptor. The AT1 receptor mediates most of the well-established actions of AngII, such as vasoconstriction and inflammation. In contrast, the AT2 receptor often exerts countervailing effects, such as vasodilation and anti-inflammation. In addition, it is also well established that the AT2 receptor is able to antagonize the functions of the AT1 receptor, with one suggested mechanism for this being heteromerisation of the receptors. This phenomenon was first described by AbdAlla et al (1), who demonstrated the proximity between the two receptors and showed that the AT2 receptor inhibited AT1 receptor signaling. In our studies, we have previously uncovered a potential mechanism for the antagonism of the AT1 receptor by the AT2 receptor, showing that although the heteromer recruits the regulatory protein β-arrestin, it is unable to subsequently internalise (2).

            We have further investigated the pharmacology of the AT1-AT2 heteromer using novel bioluminescence resonance energy transfer (BRET) assays. Firstly, we adapted our BRET ligand binding assay (3), enabling us to confirm the close proximity of the receptors. Additionally, this assay revealed no evidence for binding cooperativity between the two receptors in this system. We also used our BRET trafficking assay (4) to thoroughly investigate the cellular trafficking of the heteromer following agonist stimulation. In accordance with our earlier study (2), we found no evidence for AngII-induced internalization of the heteromer. However, some AngII-induced trafficking was observed, such as an increase in surface expression and movement out of various intracellular compartments. Overall, these results provide further evidence of the existence of the AT1-AT2 heteromer and reveal more of its novel pharmacology.

  1. AbdAlla et al. (2001) Journal of Biological. Chemistry 276(43), 39721–39726.
  2. Porrello et al. (2011) Cellular Signalling 23(11): 1767-1776.
  3. Stoddart et al. (2015) Nature Methods 12(7): 661 663.
  4. Tiulpakov et al. (2016) Molecular Endocrinology 30(8): 889 904.