Adenosine A 2A receptor ligand recognition and signaling is blocked by A 2B receptors

// Sonja Hinz 1 , Gemma Navarro 2, 4 , Dasiel Borroto-Escuela 3 , Benjamin F. Seibt 1 , York-Christoph Ammon 1 , Elisabetta de Filippo 1 , Azeem Danish 1 , Svenja K. Lacher 1 , Barbora Cervinkova 1 , Muhammad Rafehi 1 , Kjell Fuxe 3 , Anke C. Schiedel 1 , Rafael Franco 2, 4 and Christa E. Muller 1 1 PharmaCenter Bonn, Pharmaceutical Institute, Pharmaceutical Chemistry I, University of Bonn, Bonn, Germany 2 Department of Biochemistry and Molecular Biomedicine, Faculty of Biology, University of Barcelona, Barcelona, Spain 3 Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden 4 Centro de Investigacion en Red, Enfermedades Neurodegenerativas (CIBERNED), Instituto de Salud Carlos III, Madrid, Spain Correspondence to: Christa E. Muller, email: christa.mueller@uni-bonn.de Keywords: adenosine receptors (ARs); G protein-coupled receptor (GPCR); immuno-oncology; pharmacology; receptor heteromerization Received: November 08, 2017      Accepted: January 30, 2018      Published: February 06, 2018 ABSTRACT The adenosine receptor (AR) subtypes A 2A and A 2B are rhodopsin-like G s protein-coupled receptors whose expression is highly regulated under pathological, e.g. hypoxic, ischemic and inflammatory conditions. Both receptors play important roles in inflammatory and neurodegenerative diseases, are blocked by caffeine, and have now become major drug targets in immuno-oncology. By Forster resonance energy transfer (FRET), bioluminescence resonance energy transfer (BRET), bimolecular fluorescence complementation (BiFC) and proximity ligation assays (PLA) we demonstrated A 2A -A 2B AR heteromeric complex formation. Moreover we observed a dramatically altered pharmacology of the A 2A AR when co-expressed with the A 2B AR (A 2B ≥ A 2A ) in recombinant as well as in native cells. In the presence of A 2B ARs, A 2A -selective ligands lost high affinity binding to A 2A ARs and displayed strongly reduced potency in cAMP accumulation and dynamic mass redistribution (DMR) assays. These results have major implications for the use of A 2A AR ligands as drugs as they will fail to modulate the receptor in an A 2A -A 2B heteromer context. Accordingly, A 2A -A 2B AR heteromers represent novel pharmacological targets.