title: Diversity and Bias through Receptor-Receptor Interactions in GPCR Heteroreceptor Complexes. Focus on Examples from Dopamine D2 Receptor Heteromerization.
abstract: Allosteric receptor-receptor interactions in GPCR heteromers appeared to introduce an intermolecular allosteric mechanism contributing to the diversity and bias in the protomers. Examples of dopamine D2R heteromerization are given to show how such allosteric mechanisms significantly change the receptor protomer repertoire leading to diversity and biased recognition and signaling. In 1980s and 1990s, it was shown that neurotensin (NT) through selective antagonistic NTR-D2 like receptor interactions increased the diversity of DA signaling by reducing D2R-mediated dopamine signaling over D1R-mediated dopamine signaling. Furthermore, D2R protomer appeared to bias the specificity of the NTR orthosteric binding site toward neuromedin N vs. NT in the heteroreceptor complex. Complex CCK2R-D1R-D2R interactions in possible heteroreceptor complexes were also demonstrated further increasing receptor diversity. In D2R-5-HT2AR heteroreceptor complexes, the hallucinogenic 5-HT2AR agonists LSD and DOI were recently found to exert a biased agonist action on the orthosteric site of the 5-HT2AR protomer leading to the development of an active conformational state different from the one produced by 5-HT. Furthermore, as recently demonstrated allosteric A2A-D2R receptor-receptor interaction brought about not only a reduced affinity of the D2R agonist binding site but also a biased modulation of the D2R protomer signaling in A2A-D2R heteroreceptor complexes. A conformational state of the D2R was induced, which moved away from Gi/o signaling and instead favored β-arrestin2-mediated signaling. These examples on allosteric receptor-receptor interactions obtained over several decades serve to illustrate the significant increase in diversity and biased recognition and signaling that develop through such mechanisms.
authors.affiliation: Department of Neuroscience, Karolinska Institutet , Stockholm , Sweden.
authors.forename: Kjell
authors.initials: K
authors.lastname: Fuxe
authors.affiliation: St. Petersburg Institute for Informatics and Automation, Russian Academy of Sciences , Saint Petersburg , Russia.
authors.forename: Alexander
authors.initials: A
authors.lastname: Tarakanov
authors.affiliation: Department of Neuroscience, Karolinska Institutet , Stockholm , Sweden.
authors.forename: Wilber
authors.initials: W
authors.lastname: Romero Fernandez
authors.affiliation: Pharmacology Section, Department of Clinical and Experimental Medicine, University of Ferrara , Ferrara , Italy.
authors.forename: Luca
authors.initials: L
authors.lastname: Ferraro
authors.affiliation: Pharmacology Section, Department of Clinical and Experimental Medicine, University of Ferrara , Ferrara , Italy.
authors.forename: Sergio
authors.initials: S
authors.lastname: Tanganelli
authors.affiliation: Laboratory of Drug Addiction Pharmacology, Department of Pharmacology, Institute of Pharmacology, Polish Academy of Sciences , Kraków , Poland.
authors.forename: Malgorzata
authors.initials: M
authors.lastname: Filip
authors.affiliation: Istituto di Ricovero e Cura a Carattere Scientifico , Venice Lido , Italy.
authors.forename: Luigi F
authors.initials: LF
authors.lastname: Agnati
authors.affiliation: Departament d'Enginyeria Química, Universitat Politècnica de Catalunya , Barcelona , Spain.
authors.forename: Pere
authors.initials: P
authors.lastname: Garriga
authors.affiliation: Department of Physiology, School of Medicine, University of Málaga , Málaga , Spain.
authors.forename: Zaida
authors.initials: Z
authors.lastname: Diaz-Cabiale
authors.affiliation: Department of Neuroscience, Karolinska Institutet , Stockholm , Sweden.
authors.forename: Dasiel O
authors.initials: DO
authors.lastname: Borroto-Escuela
keywords: G protein-coupled receptor; allosteric modulation; biased recognition; biased signaling; heterodimerization; receptor diversity; receptor heterodimers; receptor–receptor interactions