Evidence for the heterotetrameric structure of the adenosine A2A-dopamine D2 receptor complex (original) (raw)
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Allosteric mechanisms within the adenosine A2A–dopamine D2 receptor heterotetramer
Neuropharmacology, 2016
The structure constituted by a G protein coupled receptor (GPCR) homodimer and a G protein provides a main functional unit and oligomeric entities can be viewed as multiples of dimers. For GPCR heteromers, experimental evidence supports a tetrameric structure, comprised of two different homodimers, each able to signal with its preferred G protein. GPCR homomers and heteromers can act as the conduit of allosteric interactions between orthosteric ligands. The wellknown agonist/agonist allosteric interaction in the adenosine A 2A receptor (A 2A R)-dopamine D 2 receptor (D 2 R) heteromer, by which A 2A R agonists decrease the affinity of D 2 R agonists, gave the first rationale for the use of A 2A R antagonists in Parkinson's disease. We review new pharmacological findings that can be explained in the frame of a tetrameric structure of the A 2A R-D 2 R heteromer: first, ligand-independent allosteric modulations by the D 2 R that result in changes of the binding properties of A 2A R ligands; second, differential modulation of the intrinsic efficacy of D 2 R ligands for G protein-dependent and independent signaling; third, the canonical antagonistic Gs-Gi interaction within the frame of the heteromer; and fourth, the ability of A 2A R antagonists, including caffeine, to also exert the same allosteric modulations of D 2 R ligands than A 2A R agonists, while A 2A R agonists and antagonists counteract each other's effects. These findings can have important clinical implications when evaluating the use of A 2A R antagonists. They also call for the need of monitoring caffeine intake when evaluating the effect of D 2 R ligands, when used as therapeutic agents in neuropsychiatric disorders or as probes in imaging studies.
Adenosine A 2A and dopamine D 2 heteromeric receptor complexes and their function
Journal of Molecular Neuroscience, 2005
The existence of A2A-D2 heteromeric complexes is based on coimmunoprecipitation studies and on fluorescence resonance energy transfer and bioluminescence resonance energy transfer analyses. It has now become possible to show that A2A and D2 receptors also coimmunoprecipitate in striatal tissue, giving evidence for the existence of A2A-D2 heteromeric receptor complexes also in rat striatal tissue. The analysis gives evidence that these heteromers are constitutive, as they are observed in the absence of A2A and D2 agonists. The A2A-D2 heteromers could either be A2A-D2 heterodimers and/or higher-order A2A-D2 hetero-oligomers. In striatal neurons there are probably A2A-D2 heteromeric complexes, together with A2A-D2 homomeric complexes in the neuronal surface membrane. Their stoichiometry in various microdomains will have a major role in determining A2A and D2 signaling in the striatopallidal GABA neurons. Through the use of D2/D1 chimeras, evidence has been obtained that the fifth transmembrane (TM) domain and/or the 13 of the D2 receptor are part of the A2A-D2 receptor interface, where electrostatic epitope-epitope interactions involving the N-terminal part of 13 of the D2 receptor (arginine-rich epitope) play a major role, interacting with the carboxyl terminus of the A2A receptor. Computerized modeling of A2A-D2 heteromers are in line with these findings. It seems likely that A2A receptor-induced reduction of D2 receptor recognition, G protein coupling, and signaling, as well as the existence of A2A-D2 co-trafficking, are the consequence of the existence of an A2A-D2 receptor heteromer. The relevance of A2A-D2 heteromeric receptor complexes for Parkinson’s disease and schizophrenia is emphasized as well as for the treatment of these diseases. Finally, recent evidence for the existence of antagonistic A2A-D3 heteromeric receptor complexes in cotransfected cell lines has been summarized.
Adenosine A2A and Dopamine D2 Heteromeric Receptor Complexes and Their Function
Journal of Molecular Neuroscience, 2005
The existence of A 2A -D 2 heteromeric complexes is based on coimmunoprecipitation studies and on fluorescence resonance energy transfer and bioluminescence resonance energy transfer analyses. It has now become possible to show that A 2A and D 2 receptors also coimmunoprecipitate in striatal tissue, giving evidence for the existence of A 2A -D 2 heteromeric receptor complexes also in rat striatal tissue. The analysis gives evidence that these heteromers are constitutive, as they are observed in the absence of A 2A and D 2 agonists. The A 2A -D 2 heteromers could either be A 2A -D 2 heterodimers and/or higher-order A 2A -D 2 hetero-oligomers. In striatal neurons there are probably A 2A -D 2 heteromeric complexes, together with A 2A -D 2 homomeric complexes in the neuronal surface membrane. Their stoichiometry in various microdomains will have a major role in determining A 2A and D 2 signaling in the striatopallidal GABA neurons. Through the use of D 2 /D 1 chimeras, evidence has been obtained that the fifth transmembrane (TM) domain and/or the I3 of the D 2 receptor are part of the A 2A -D 2 receptor interface, where electrostatic epitope-epitope interactions involving the N-terminal part of I3 of the D 2 receptor (arginine-rich epitope) play a major role, interacting with the carboxyl terminus of the A 2A receptor. Computerized modeling of A 2A -D 2 heteromers are in line with these findings. It seems likely that A 2A receptor-induced reduction of D 2 receptor recognition, G protein coupling, and signaling, as well as the existence of A 2A -D 2 co-trafficking, are the consequence of the existence of an A 2A -D 2 receptor heteromer. The relevance of A 2A -D 2 heteromeric receptor complexes for Parkinson's disease and schizophrenia is emphasized as well as for the treatment of these diseases. Finally, recent evidence for the existence of antagonistic A 2A -D 3 heteromeric receptor complexes in cotransfected cell lines has been summarized.
Journal of Neural Transmission, 2007
Summary. The molecular basis for the known intramembrane receptor–receptor interactions among heptahelical receptors (G protein coupled receptors, GPCR) was postulated to be heteromerization based on receptor subtype specific interactions between different types of homomers of GPCR. Adenosine and dopamine receptors in the basal ganglia have been fundamental to demonstrate the existence of receptor heteromers and the functional consequences of such molecular
D2/D3 Dopamine Receptor Heterodimers Exhibit Unique Functional Properties
Journal of Biological Chemistry, 2001
Evidence for heterodimerization has recently been provided for dopamine D 1 and adenosine A 1 receptors as well as for dopamine D 2 and somatostatin SSTR 5 receptors. In this paper, we have studied the possibility that D 2 and D 3 receptors interact functionally by forming receptor heterodimers. Initially, we split the two receptors at the level of the third cytoplasmic loop into two fragments. The first, containing transmembrane domains (TM) I to V and the N-terminal part of the third cytoplasmic loop, was named D 2trunk or D 3trunk , and the second, containing the C-terminal part of the third cytoplasmic loop, TMVI and TMVII, and the C-terminal tail, was named D 2tail or D 3tail . Then we defined the pharmacological profiles of the homologous (D 2trunk / D 2tail and D 3trunk /D 3tail ) as well as of the heterologous (D 2trunk /D 3tail and D 3trunk /D 2tail ) cotransfected receptor fragments. The pharmacological profile of the cross-cotransfected fragments was different from that of the native D 2 or D 3 receptors. In most cases, the D 3trunk /D 2tail was the one with the highest affinity for most agonists and antagonists. Moreover, we observed that all of these receptor fragments reduced the expression of the wild type dopamine D 2 and D 3 receptors, suggesting that D 2 and D 3 receptors can form complexes with these fragments and that these complexes bind [ 3 H]nemonapride less efficiently or are not correctly targeted to the membrane. In a second set of experiments, we tested the ability of the split and the wild type receptors to inhibit adenylyl cyclase (AC) types V and VI. All of the native and split receptors inhibited AC-V and AC-VI, with the exception of D 3 , which was unable to inhibit AC-VI. We therefore studied the ability of D 2 and D 3 to interact functionally with one another to inhibit AC-VI. We found that with D 2 alone, R-(؉)-7-hydroxydypropylaminotetralin hydrobromide inhibited AC-VI with an IC 50 of 2.05 ؎ 0.15 nM, while in the presence of D 2 and D 3 it inhibited AC-VI with an IC 50 of 0.083 ؎ 0.011 nM. Similar results were obtained with a chimeric cyclase made from AC-V and AC-VI. Coimmunoprecipitation experiments indicate that D 2 and D 3 receptors are capable of physical interaction.
Molecular pharmacology, 2014
The dopamine D1 receptor-D3 receptor (D1R-D3R) heteromer is being considered as a potential therapeutic target for neuropsychiatric disorders. Previous studies suggested that this heteromer could be involved in the ability of D3R agonists to potentiate locomotor activation induced by D1R agonists. It has also been postulated that its overexpression plays a role in L-dopa-induced dyskinesia and in drug addiction. However, little is known about its biochemical properties. By combining bioluminescence resonance energy transfer, bimolecular complementation techniques, and cell-signaling experiments in transfected cells, evidence was obtained for a tetrameric stoichiometry of the D1R-D3R heteromer, constituted by two interacting D1R and D3R homodimers coupled to Gs and Gi proteins, respectively. Coactivation of both receptors led to the canonical negative interaction at the level of adenylyl cyclase signaling, to a strong recruitment of β-arrestin-1, and to a positive cross talk of D1R a...
Frontiers in pharmacology, 2018
The A adenosine (AR) and D dopamine (DR) receptors form oligomers in the cell membrane and allosteric interactions across the AR-DR heteromer represent a target for development of drugs against central nervous system disorders. However, understanding of the molecular determinants of AR-DR heteromerization and the allosteric antagonistic interactions between the receptor protomers is still limited. In this work, a structural model of the AR-DR heterodimer was generated using a combined experimental and computational approach. Regions involved in the heteromer interface were modeled based on the effects of peptides derived from the transmembrane (TM) helices on AR-DR receptor-receptor interactions in bioluminescence resonance energy transfer (BRET) and proximity ligation assays. Peptides corresponding to TM-IV and TM-V of the AR blocked heterodimer interactions and disrupted the allosteric effect of AR activation on DR agonist binding. Protein-protein docking was used to construct a m...
Proceedings of the National Academy of Sciences, 2015
Adenosine A2A receptor (A2AR)-dopamine D2 receptor (D2R) heteromers are key modulators of striatal neuronal function. It has been suggested that the psychostimulant effects of caffeine depend on its ability to block an allosteric modulation within the A2AR-D2R heteromer, by which adenosine decreases the affinity and intrinsic efficacy of dopamine at the D2R. We describe novel unsuspected allosteric mechanisms within the heteromer by which not only A2AR agonists, but also A2AR antagonists, decrease the affinity and intrinsic efficacy of D2R agonists and the affinity of D2R antagonists. Strikingly, these allosteric modulations disappear on agonist and antagonist coadministration. This can be explained by a model that considers A2AR-D2R heteromers as heterotetramers, constituted by A2AR and D2R homodimers, as demonstrated by experiments with bioluminescence resonance energy transfer and bimolecular fluorescence and bioluminescence complementation. As predicted by the model, high concen...
Neurochemistry International, 2013
The molecular interaction between adenosine A 2A and dopamine D 2 receptors (A 2A Rs and D 2 Rs, respectively) within an oligomeric complex has been postulated to play a pivotal role in the adenosine-dopamine interplay in the central nervous system, in both normal and pathological conditions (e.g. Parkinson's disease). While the effects of A 2A R challenge on D 2 R functioning have been largely studied, the reverse condition is still unexplored, a fact that might have impact in therapeutics. Here, we aimed to examine in a real-time mode the D 2 R-mediated allosteric modulation of A 2A R binding when an A 2A R/D 2 R oligomer is established. Thus, we synthesized fluorescent A 2A R agonists and evaluated, by means of a flow cytometry homogeneous no-wash assay and a real-time fluorescence resonance energy transfer (FRET)-based approach, the effects on A 2A R binding of distinct antiparkinsonian drugs in current clinical use (i.e. pramipexole, rotigotine and apomorphine). Our results provided evidence for the existence of a differential D 2 R-mediated negative allosteric modulation on A 2A R agonist binding that was oligomerformation dependent, and with apomorphine being the best antiparkinsonian drug attenuating A 2A R agonist binding. Overall, the here-developed methods were found valid to prospect the ability of drugs acting on D 2 Rs to modulate A 2A R binding, thus featuring as possible helpful tools for the preliminary selection of D 2 R-like candidate drugs in the management of Parkinson's disease.