Homodimerization of adenosine A₁ receptors in brain cortex explains the biphasic effects of caffeine

Eduard Gracia, Estefania Moreno, Antoni Cortés, Carme Lluís, Josefa Mallol, Peter J McCormick, Enric I Canela, Vicent Casadó

Research output: Contribution to journalArticlepeer-review

27 Citations (Scopus)


Using bioluminescence resonance energy transfer and proximity ligation assays, we obtained the first direct evidence that adenosine A₁ receptors (A₁Rs) form homomers not only in cell cultures but also in brain cortex. By radioligand binding experiments in the absence or in the presence of the A₁Rs allosteric modulator, adenosine deaminase, and by using the two-state dimer receptor model to fit binding data, we demonstrated that the protomer-protomer interactions in the A₁R homomers account for some of the pharmacological characteristics of agonist and antagonist binding to A₁Rs. These pharmacological properties include the appearance of cooperativity in agonist binding, the change from a biphasic saturation curve to a monophasic curve in self-competition experiments and the molecular cross-talk detected when two different specific molecules bind to the receptor. In this last case, we discovered that caffeine binding to one protomer increases the agonist affinity for the other protomer in the A₁R homomer, a pharmacological characteristic that correlates with the low caffeine concentrations-induced activation of agonist-promoted A₁R signaling. This pharmacological property can explain the biphasic effects reported at low and high concentration of caffeine on locomotor activity.
Original languageEnglish
Pages (from-to)56-69
Number of pages14
Publication statusPublished - Aug 2013


  • Adenosine A1 Receptor Agonists
  • Adenosine A1 Receptor Antagonists
  • Adenosine Deaminase
  • Allosteric Site
  • Animals
  • Bacterial Proteins
  • Caffeine
  • Cattle
  • Cell Membrane
  • Central Nervous System Stimulants
  • Cerebral Cortex
  • Dimerization
  • HEK293 Cells
  • Humans
  • Kinetics
  • Luminescent Proteins
  • Models, Biological
  • Nerve Tissue Proteins
  • Neurons
  • Receptor, Adenosine A1
  • Recombinant Fusion Proteins

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