Functional Coupling of Human D₂, D₃, and D₄ Dopamine Receptors in HEK293 Cells

Abstract

The D2 dopamine receptor is known to be functionally coupled to the inhibition of adenylate cyclase when expressed in a number of mammalian cell lines. However, functional coupling of the recently discovered D3 and D4 dopamine receptor subtypes has been more difficult to demonstrate. In this study, human D2, D3 and D4 receptors were stably expressed separately in human embryonic kidney cells (HEK 293). In these cells, activation of D2, D3 or D4 receptors resulted in the inhibition of forskolin-stimulated adenylate cyclase activity in a dose responsive manner. This activation was prevented by pre-incubation of the cells expressing these receptors with the dopaminergic antagonist haloperidol. Radioligand binding studies using [3H]spiperone confirmed that the atypical neuroleptic clozapine has higher affinity for the human D4 receptor than the D3 or D4 receptors, although only 6-fold higher than the D2 receptor in this study. In addition, ribonuclease protection studies demonstrated the presence of D4 dopamine receptor mRNA in human brain regions.

Antagonism of the effects of (+)‐PD 128907 on midbrain dopamine neurones in rat brain slices by a selective D2 receptor antagonist L‐741,626

“…Although D3 receptors are more restricted in their distribution compared to their D2 counterparts, several studies have shown that these receptors can couple to G-proteins that link to similar effector mechanisms that include the regulation of calcium currents and inhibition of adenylate cyclase (Seabrook et al, 1994a;Chio et al, 1994;McAllister et al, 1995 (DeMattos et al, 1993). Furthermore, in functional assays this ligand is an agonist at cloned human D3 receptors (McAllister et al, 1995) and also modulates midbrain dopamine cell function (DeWald et al, 1990). Estimates of the binding selectivity of agonists for D3 over D2 receptors are influenced by whether one compares the high or low affinity states of the receptors (e.g.…”

“…to the D2 receptor subtype (Chio et al, 1994;Seabrook et al, 1994a,b;Tang et al, 1994;McAllister et al, 1995). Consequently this study was carried out to determine whether D3 dopamine receptors are functional autoreceptors in rat brain.…”

Increased Dopamine Receptor Signaling and Dopamine Receptor-G Protein Coupling in Denervated Striatum

“…A D 1 -like dopamine site, which couples to Gq/11 protein, has been linked to the modulation of phosphatidylinositol hydrolysis (Wang et al, 1995;Jin et al, 2001). On the other hand, D 2 -like dopamine receptors D 2 , D 3 , and D 4 are negatively coupled to adenylyl cyclase via Gi/o proteins (Onali et al, 1985;Potenza et al, 1994;Tang et al, 1994;McAllister et al, 1995). In addition, both D 1 and D 2 dopamine receptors have been shown to regulate calcium signaling (Missale et al, 1998) and to stimulate mitogen-activated protein kinase pathways (Zhen et al, 1998;Cai et al, 2000).…”

Effects of recent and reference antipsychotic agents at human dopamine D 2 and D 3 receptor signaling in Chinese hamster ovary cells

“…However, measuring signaling events of the D 3 receptor appeared problematic (Freedman et al 1994;Tang et al 1994;McAllister et al 1995). Recently, we succeeded in the generation of transfected Chinese hamster ovary (CHO) cells permanently expressing high levels of either hD 2S , hD 2L , or hD 3 receptors.…”