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

Elisabetta De Filippo, Sonja Hinz, Veronica Pellizzari, Giuseppe Deganutti, Ali El-Tayeb, Gemma Navarro, Rafael Franco, Stefano Moro, Anke C. Schiedel, Christa E. Müller

Research output: Contribution to journalArticlepeer-review

16 Citations (Scopus)


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.
Original languageEnglish
Article number113718
JournalBiochemical Pharmacology
Early online date18 Nov 2019
Publication statusPublished - Feb 2020
Externally publishedYes


  • Adenosine
  • Chimeric receptor
  • Extracellular loop
  • GPCR
  • Radioligand binding
  • cAMP

ASJC Scopus subject areas

  • Biochemistry
  • Pharmacology


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