Dopamine GPCR Assays
Background of Dopamine Receptors
Dopamine acts as an important neurotransmitter in the central nervous system (CNS), which is the predominant catecholamine released by neurons to transmit signals to other nerve cells. Dopamine interacts with a family of G protein-coupled receptors, including D1, D2, D3, D4, and D5 receptors, which play different roles in different physiological effects, including attention, motivation, cognitive functions, and hormonal regulation, as well as cardiovascular, renal, and gastrointestinal functions. Dysfunction of the dopamine system may cause several diseases related to the nervous system, such as Parkinson's disease, schizophrenia, and attention deficit hyperactivity disorder (ADHD). Dopamine antagonists could be used as drugs for anti-nausea agents and schizophrenia. Low doses of dopamine could be used to treat ADHD, heart failure, and shock.
Fig.1. Structure of the human D4 Dopamine receptor in complex with Nemonapride. (Beaulieu, 2019)
Distribution and Function of Dopamine Receptors
Five G protein-coupled receptor subtypes of dopamine act in distinct roles reflected in their different capability of cAMP formation, which offer an opportunity for subtype-selective drug development for dopaminergic dysfunctions. D2 receptors are expressed principally in the caudate putamen, nucleus accumbens, and olfactory tubercle, which are responsible for locomotion activation, memory and learning regulation. D3 receptors are primarily distributed in the nucleus accumbens, the island of Calleja, and the olfactory tubercle, participating in locomotion activation and regulation of cognition and emotion. D4 receptors are found in the frontal cortex, midbrain, amygdala, and the cardiovascular system, which are possibly involved in cognition and emotion. D1 and D5 receptors are highly homologous and distributed throughout the brain.
Subtypes and Mechanism of Dopamine Receptors
The family of dopamine receptors contains five subtypes of receptors. D1 and D5 receptors promote signal transduction through Gs proteins, while D2, D3, and D4 receptors couple Gi/Go proteins.
| Receptor | Gene | Mechanism | Agonists | Antagonists |
| D1 receptor | DRD1 |
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| D2 receptor | DRD2 |
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| D3 receptor | DRD3 |
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| D4 receptor | DRD4 |
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| D5 receptor | DRD5 |
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Assay List of Dopamine Receptors
Creative Biolabs can provide a range of assays of dopamine receptors. You can choose the assay in the list or contact us for more information:
| Assay No. | Assay Name | Host Cell | Assay Type | Datasheet |
|---|---|---|---|---|
| cAMP Assay | ||||
| S01YF-0722-KX99 | Magic™ Human DRD1 In Vitro cAMP Assay & Binding Assay, HEK293 | HEK293 | cAMP Assay; Binding Assay | |
| Assay No. | Assay Name | Host Cell | Assay Type | Datasheet |
|---|---|---|---|---|
| Calcium Flux Assay | ||||
| S01YF-0722-KX102 | Magic™ Human DRD3 In Vitro Calcium Assay & Binding Assay, HEK293-Ga15 | HEK293-Ga15 | Calcium Assay; Binding Assay | |
Published Data
| Paper Title | Characterizing fucoxanthin as a selective dopamine D3/D4 receptor agonist: Relevance to Parkinson's disease |
| Journal | Chemico-Biological Interactions |
| Published | 2019 |
| Abstract | Dopamine is one of the major neurotransmitters playing a role in many functions including motor coordination, emotions, memory, reward, and neuroendocrine regulation. Abnormalities in the dopaminergic system and its receptors in the basal ganglia structures are the basis of multiple neurodegenerative disorders, including Parkinson's disease, Huntington's disease, Alzheimer's disease, etc. The study aimed to investigate the role of fucoxanthin and fucosterol in the aminergic system and as a prime treatment approach for multifactorial neurodegenerative diseases. They used in vitro human monoamine oxidase (hMAO) inhibition to underline the effect of fucosterol on monoamine oxidase enzyme activity. Cell-based functional G-protein coupled receptor (GPCR) assays were used to determine the modulatory effect of fucoxanthin and fucosterol in GPCRs. They used in silico molecular docking studies to underline possible mechanisms of action on D3/D4 GPCRs. |
| Result |
With IC50 values of 197.41 ± 2.20 and 211.12 ± 1.17 μM for the two isoenzymes hMAO-A and hMAO-B, respectively, fucoxanthin showed modest inhibitive effect. Fucosterol was inactive up to 500 μM. Fucoxanthin demonstrated a concentration-dependent agonist activity on dopamine D3/D4 receptors in the functional assay. For dopamine D3/D4 receptors, the half maximal effective concentration (EC50) of fucoxanthin was 16.87 ± 3.41 and 81.87 ± 6.11 μM, respectively. The reference agonist EC50 values for D3/D4 receptors were 3.7 and 24 nM, respectively. No tested receptors for agonist action by fucosterol were found. Fucoxanthin similarly had a modest antagonistic action on the dopamine D1 and tachykinin (NK1) receptors, inhibiting the response to the control agonist by about 40% at 100 μM. Mild antagonist effects of fucosterol were shown on D1/D4 receptors. Fucoxanthin may bind to dopamine receptors to show its agonist effects through low binding energy interactions with Ser196 and Thr115 at the D3 receptor and Ser196 and Asp115 at the D4 receptor, according to in silico assay. Collectively, the findings pointed to fucoxanthin as a possible D3/D4 agonist for treating neurodegenerative disorders like Parkinson's disease.
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Fig.2. Concentration-dependent percentage of control agonist effect of fucoxanthin and fucosterol on dopamine D3 (A) and D4 (B) receptors. (Paudel, 2019)
References
- Beaulieu, J. M.; et al. Dopamine receptors (version 2019.4) in the IUPHAR/BPS Guide to Pharmacology Database. IUPHAR/BPS Guide to Pharmacology CITE. 2019, 2019(4).
- Paudel, P.; et al. Characterizing fucoxanthin as a selective dopamine D3/D4 receptor agonist: Relevance to Parkinson's disease. Chemico-Biological Interactions. 2019, 310: 108757.
