Identification of G protein-coupled receptors and their specific function in a given neuron becomes essential to better understand the variety of signal transduction mechanisms associated with neurotransmission. We hypothesized that angiotensin II type 1 (AT1) and dopamine D2 receptors form heteromers in the central nervous system, specifically in striatum. Using bioluminescence resonance energy transfer, a direct interaction was demonstrated in cells transfected with the cDNA for the human version of the receptors. Heteromerization did not affect cAMP signaling via D2 receptors but attenuated the coupling of AT1 receptors to Gq. A common feature of heteromers, namely cross-antagonism, i.e. the blockade of the signaling of one receptor by the blockade of the partner receptor, was tested in co-transfected cells. Candesartan, the selective AT1 receptor antagonist, was able to block D2-receptor mediated effects on cAMP levels, MAP kinase activation and β-arrestin recruitment. This effect of candesartan, which constitutes a property for the dopamine-angiotensin receptor heteromer, was similarly occurring in primary cultures of neurons and rat striatal slices. The expression of heteromers in striatum was confirmed by robust labeling using in situ proximity ligation assays. The results indicate that AT1 receptors are expressed in striatum and form heteromers with dopamine D2 receptors that enable drugs selective for the AT1 receptor to alter the functional response of D2 receptors.
Keywords: BRET; Basal ganglia; Calcium release; GPCR heteromerization; cAMP.
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