Heteromerization between α2A adrenoceptors and different polymorphic variants of the dopamine D4 receptor determines pharmacological and functional differences. Implications for impulsive-control disorders

Polymorphic alleles of the human dopamine D(4) receptor gene (DRD4) have been consistently associated with individual differences in personality traits and neuropsychiatric disorders, particularly between the gene encoding dopamine D(4.7) receptor variant and attention deficit hyperactivity disorder (ADHD). The α(2A) adrenoceptor gene has also been associated with ADHD. In fact, drugs targeting the α(2A) adrenoceptor (α(2A)R), such as guanfacine, are commonly used in ADHD treatment. In view of the involvement of dopamine D(4) receptor (D(4)R) and α(2A)R in ADHD and impulsivity, their concurrent localization in cortical pyramidal neurons and the demonstrated ability of D(4)R to form functional heteromers with other G protein-coupled receptors, in this study we evaluate whether the α(2A)R forms functional heteromers with D(4)R and weather these heteromers show different properties depending on the D(4)R variant involved. Using cortical brain slices from hD(4.7)R knock-in and wild-type mice, here, we demonstrate that α(2A)R and D(4)R heteromerize and constitute a significant functional population of cortical α(2A)R and D(4)R. Moreover, in cortical slices from wild-type mice and in cells transfected with α(2A)R and D(4.4)R, we detect a negative crosstalk within the heteromer. This negative crosstalk is lost in cortex from hD(4.7)R knock-in mice and in cells expressing the D(4.7)R polymorphic variant. We also show a lack of efficacy of D(4)R ligands to promote G protein activation and signaling only within the α(2A)R-D(4.7)R heteromer. Taken together, our results suggest that α(2A)R-D(4)R heteromers play a pivotal role in catecholaminergic signaling in the brain cortex and are likely targets for ADHD pharmacotherapy.