title: Dopamine D2 and 5-hydroxytryptamine 5-HT(₂A) receptors assemble into functionally interacting heteromers.
abstract: In view of the co-distribution of dopamine D(₂L)R and 5-hydroxytryptamine 5-HT(₂A) receptors (D(₂L)R and 5-HT(₂A)R, respectively) within inter alia regions of the dorsal and ventral striatum and their role as a target of antipsychotic drugs; in this study we assessed the potential existence of D(₂L)R-5-HT(₂A)R heteromers in living cells and the functional consequences of this interaction. Thus, by means of a proximity-based bioluminescence resonance energy transfer (BRET) approach we demonstrated that the D(₂L)R and the 5-HT(₂A)R form stable and specific heteromers when expressed in HEK293T mammalian cells. Furthermore, when the D(₂L)R-5-HT(₂A)R heteromeric signaling was analyzed we found that the 5-HT(₂A)R-mediated phospholipase C (PLC) activation was synergistically enhanced by the concomitant activation of the D(₂L)R as shown in a NFAT-luciferase reporter gene assay and a specific and significant rise of the intracellular calcium levels were observed when both receptors were simultaneously activated. Conversely, when the D(2L)R-mediated adenylyl cyclase (AC) inhibition was assayed we showed that costimulation of D(₂L)R and 5-HT(₂A)R within the heteromer led to inhibition of the D(₂L)R functioning, thus suggesting the existence of a 5-HT(₂A)R-mediated D(₂L)R trans-inhibition phenomenon. Finally, a bioinformatics study reveals that the triplet amino acid homologies LLT (Leu-Leu-Thr) and AIS (Ala-Ile-Ser) in TM1 and TM3, respectively of the D₂R-5-HT(₂A)R may be involved in the receptor interface. Overall, the presence of the D(₂L)R-5-HT(₂A)R heteromer in discrete brain regions is postulated based on the existence of D(₂L)R-5-HT(₂A) receptor-receptor interactions in living cells and their codistribution inter alia in striatal regions. Possible novel therapeutic strategies for treatment of schizophrenia should be explored by targeting this heteromer.
authors.affiliation: Department of Neuroscience, Karolinska Institutet, Retzius väg 8, 17177 Stockholm, Sweden.
authors.forename: Dasiel O
authors.initials: DO
authors.lastname: Borroto-Escuela
authors.forename: Wilber
authors.initials: W
authors.lastname: Romero-Fernandez
authors.forename: Alexander O
authors.initials: AO
authors.lastname: Tarakanov
authors.forename: Daniel
authors.initials: D
authors.lastname: Marcellino
authors.forename: Francisco
authors.initials: F
authors.lastname: Ciruela
authors.forename: Luigi F
authors.initials: LF
authors.lastname: Agnati
authors.forename: Kjell
authors.initials: K
authors.lastname: Fuxe
mesh_terms: D001921:Brain / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D017930:Genes, Reporter; D006801:Humans; D008156:Luciferases / Q000235:genetics; D055503:Protein Multimerization; D044402:Receptor, Serotonin, 5-HT2A / Q000235:genetics / Q000378:metabolism*; D017448:Receptors, Dopamine D2 / Q000235:genetics / Q000378:metabolism*; D014162:Transfection
chemical_list: D044402:Receptor, Serotonin, 5-HT2A; D017448:Receptors, Dopamine D2; C113776:dopamine D2L receptor; D008156:Luciferases; D002118:Calcium