2. Academic Validation
  3. A2A and A2B adenosine receptors: The extracellular loop 2 determines high (A2A) or low affinity (A2B) for adenosine

A2A and A2B adenosine receptors: The extracellular loop 2 determines high (A2A) or low affinity (A2B) for adenosine

  • Biochem Pharmacol. 2020 Feb:172:113718. doi: 10.1016/j.bcp.2019.113718.
Elisabetta De Filippo 1,  Sonja Hinz 1,  Veronica Pellizzari 2,  Giuseppe Deganutti 2,  Ali El-Tayeb 1,  Gemma Navarro 3,  Rafael Franco 4,  Stefano Moro 2,  Anke C Schiedel 1,  Christa E Müller 5
Affiliations

Affiliations

  • 1 PharmaCenter Bonn, Pharmaceutical Institute, Pharmaceutical & Medicinal Chemistry, University of Bonn, An der Immenburg 4, D-53121 Bonn, Germany.
  • 2 Molecular Modeling Section (MMS), Department of Pharmaceutical and Pharmacological Sciences, University of Padova, Via Marzolo 5, Padua, Italy.
  • 3 Dept. Biochemistry and Physiology, Faculty of Pharmacy and Food Science, University of Barcelona, Barcelona, Spain.
  • 4 Department of Biochemistry and Molecular Biomedicine, University of Barcelona, Avda Diagonal 643, 08028 Barcelona, Spain; Centro de Investigación en Red, Enfermedades Neurodegenerativas (CiberNed), Centro Nacional de Salud Carlos III. Madrid. Spain.
  • 5 PharmaCenter Bonn, Pharmaceutical Institute, Pharmaceutical & Medicinal Chemistry, University of Bonn, An der Immenburg 4, D-53121 Bonn, Germany. Electronic address: [email protected].
PMID: 31751537 DOI: 10.1016/j.bcp.2019.113718
Abstract

A2A and A2B adenosine receptors (ARs) are closely related G protein-coupled receptor subtypes, which represent important (potential) drug targets. Despite their almost identical binding sites for adenosine, A2AARs are activated by low (nanomolar) adenosine concentrations, while A2BARs require micromolar concentrations. In the present study, we exchanged the extracellular loop 2 (ECL2) of the human A2AAR for that of the A2BAR. The resulting chimeric A2A(ECL2-A2B)AR was investigated in radioligand binding and cAMP accumulation assays in comparison to the wildtype A2AAR. While the ribose-modified adenosine analog N-ethylcarboxamidoadenosine (NECA) and its 2-substituted derivative CGS-21680 did not exhibit significant changes, adenosine showed dramatically reduced potency and affinity for the A2A(ECL2-A2B)AR mutant displaying similarly low potency as for the wt A2BAR. Supervised molecular dynamics simulation studies predicted a meta-binding site with high affinity for adenosine, but not for NECA, which may contribute to the observed effects.

Keywords

Adenosine; Chimeric receptor; Extracellular loop; GPCR; Radioligand binding; cAMP.

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