Dopamine receptor D2
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Location (UCSC) | Chr 11: 113.41 – 113.48 Mb | Chr 9: 49.25 – 49.32 Mb | |||||||
PubMed search | [3] | [4] |
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Dopamine receptor D2, also known as D2R, is a
Function
D2 receptors are coupled to Gi subtype of G protein. This G protein-coupled receptor inhibits adenylyl cyclase activity.[8]
In mice, regulation of D2R surface expression by the
In flies, activation of the D2 autoreceptor protected dopamine neurons from cell death induced by MPP+, a toxin mimicking Parkinson's disease pathology.[12]
While optimal dopamine levels favor D1R cognitive stabilization, it is the D2R that mediates the cognitive flexibility in humans.[13][14][15]
Isoforms
The long form (D2Lh) has the "canonical" sequence and functions as a classic post-synaptic receptor.[17] The short form (D2Sh) is pre-synaptic and functions as an autoreceptor that regulates the levels of dopamine in the synaptic cleft.[17] Agonism of D2sh receptors inhibits dopamine release; antagonism increases dopaminergic release.[17] A third D2(Longer) form differs from the canonical sequence where 270V is replaced by VVQ.[18]
Active and inactive forms
D2R conformers are equilibrated between two full active (D2HighR) and inactive (D2LowR) states, while in complex with an agonist and antagonist ligand, respectively.
The monomeric inactive conformer of D2R in binding with risperidone was reported in 2018 (PDB ID: 6CM4). However, the active form which is generally bound to an agonist, is not available yet and in most of the studies the homology modeling of the structure is implemented. The difference between the active and inactive of G protein-coupled receptor is mainly observed as conformational changes at the cytoplasmic half of the structure, particularly at the transmembrane domains (TM) 5 and 6. The conformational transitions occurred at the cytoplasmic ends are due to the coupling of G protein to the cytoplasmic loop between the TM 5 and 6.[19]
It was observed that either D2R agonist or antagonist ligands revealed better
In drug discovery studies in order to calculate the binding affinities of the D2R ligands inside the binding domain, it's important to work on which form of D2R. It's known that the full active and inactive states are recommended to be used for the agonist and antagonist studies, respectively.
Any disordering in equilibration of D2R states, which causes problems in signal transferring between the nervous systems, may lead to diverse serious disorders, such as
Allosteric pocket and orthosteric pocket
There is an orthosteric binding site (OBS), as well as a secondary binding pocket (SBP) on the dopamine 2 receptor, and interaction with the SBP is a requirement for allosteric pharmacology. The compound SB269652 is a negative allosteric modulator of the D2R.[21]
Oligomerization of D2R
It was observed that D2R exists in dimeric forms or higher order oligomers.[22] There are some experimental and molecular modeling evidences that demonstrated the D2R monomers cross link from their TM 4 and TM 5 to form dimeric conformers.[23][24]
Genetics
Allelic variants:
- A-241G
- C132T, G423A, T765C, C939T, C957T, and G1101A[25]
- Cys311Ser
- -141C insertion/deletion[26] The polymorphisms have been investigated with respect to association with schizophrenia.[27]
Some researchers have previously associated the polymorphism Taq 1A (rs1800497) to the DRD2 gene. However, the polymorphism resides in exon 8 of the ANKK1 gene.[28] DRD2 TaqIA polymorphism has been reported to be associated with an increased risk for developing motor fluctuations but not hallucinations in Parkinson's disease.[29][30] A splice variant in Dopamine receptor D2(rs1076560) was found to be associated with limb truncal Tardive dyskinesia and diminished expression factor of Positive and Negative Syndrome Scale (PANSS) in schizophrenia subjects.[31]
Ligands
Most of the older antipsychotic drugs such as chlorpromazine and haloperidol are antagonists for the dopamine D2 receptor, but are, in general, very unselective, at best selective only for the "D2-like family" receptors and so binding to D2, D3 and D4, and often also to many other receptors such as those for serotonin and histamine, resulting in a range of side-effects and making them poor agents for scientific research. In similar manner, older dopamine agonists used for Parkinson's disease such as bromocriptine and cabergoline are poorly selective for one dopamine receptor over another, and, although most of these agents do act as D2 agonists, they affect other subtypes as well. Several selective D2 ligands are, however, now available, and this number is likely to increase as further research progresses.
Agonists
- Bromocriptine – full agonist
- Cabergoline (Dostinex)
- N,N-Propyldihydrexidine – analogue of the D1/D5 agonist dihydrexidine; Selective for postsynaptic D2 receptor over the presynaptic D2 autoreceptor.
- α2–adrenergic antagonist
- Pramipexole – also D3, D4 receptor agonist
- Quinagolide (Norprolac)
- Quinelorane – affinity for D2 > D3
- Quinpirole – also D3 receptor agonist
- Ropinirole – full agonist
- Sumanirole – full agonist; highly selective
- Talipexole – selective for D2 over other dopamine receptors, but also acts as α2–adrenoceptor agonist and 5-HT3 antagonist.
Partial agonists
- Aplindore
- Aripiprazole[32]
- Armodafinil – although primarily thought to be a weak DAT inhibitor, armodafinil is also a D2 partial agonist.[33]
- Modafinil - The (R)-(−)-enantiomer, known as Armodafinil in its pure form[33]
- Brexpiprazole
- Cariprazine
- Cannabidiol
- GSK-789,472 – Also D3 antagonist, with good selectivity over other receptors[34]
- Ketamine (also NMDA antagonist)
- 2-Phenethylamine– (also a TAAR1 agonist and GABAb antagonist with effects at AMPA receptors)
- LSD – in vitro, LSD was found to be a partial agonist and potentiates dopamine-mediated prolactin secretion in lactotrophs.[35] LSD is also a 5-HT2A agonist.
- OSU-6162 – also 5-HT2A partial agonist, acts as "dopamine stabilizer"
- Roxindole (only at the D2 autoreceptors)
- RP5063)
- Salvinorin A – also κ-opioid agonist.
Antagonists
- Atypical antipsychotics(except aripiprazole, brexpiprazole, and any other D2 receptor partial agonists)
- Cinnarizine
- Chloroethylnorapomorphine
- Desmethoxyfallypride
- Domperidone – D2 and D3 antagonist; does not cross the blood-brain barrier
- Metoclopramide – Antiemetic, crosses blood-brain barrier. Causes drug-induced Parkinsonism.
- Eticlopride
- Fallypride
- Hydroxyzine (Vistaril, Atarax)
- Itopride
- L-741,626 – highly selective D2 antagonist
- 11C-radiolabeled Raclopride – commonly employed in positron emission tomography studies[38]
- Typical antipsychotics
- SV 293[39]
- Yohimbine
- Buspirone – D2 presynaptic autoreceptors (low dose) and postsynaptic D2 receptors (at higher doses) antagonist[40]
- D2sh selective (presynaptic autoreceptors)
- Amisulpride (low doses)
- UH-232
- Quetiapine
Allosteric modulators
- Homocysteine – negative allosteric modulator[41]
- PAOPA[42]
- SB-269,652[43][44][45][46]
Heterobivalent ligands
- 1-(6-(((R,S)-7-Hydroxychroman-2-yl)methylamino]hexyl)-3-((S)-1-methylpyrrolidin-2-yl)pyridinium bromide (compound 2, D2R agonist and nAChR antagonist)[47]
Dual D2AR/ A2AAR ligands
Functionally selective ligands
- UNC9994[49]
Protein–protein interactions
The dopamine receptor D2 has been shown to
Receptor oligomers
The D2 receptor forms
- D1–D2 dopamine receptor heteromer
- D2–adenosine A2A
- D2–ghrelin receptor
- D2sh–TAAR1[note 1]
The D2 receptor has been shown to form hetorodimers
See also
Explanatory notes
References
- ^ a b c GRCh38: Ensembl release 89: ENSG00000149295 - Ensembl, May 2017
- ^ a b c GRCm38: Ensembl release 89: ENSMUSG00000032259 - Ensembl, May 2017
- ^ "Human PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
- ^ "Mouse PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
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- ^ "NIMH » Molecular Secrets Revealed: Antipsychotic Docked in its Receptor". www.nimh.nih.gov. 29 January 2018. Retrieved 26 November 2018.
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- ^ "Entrez Gene: DRD2 dopamine receptor D2".
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- ^ Universal protein resource accession number P14416 for "D(2) dopamine receptor" at UniProt.
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This original observation of TAAR1 and DA D2R interaction has subsequently been confirmed and expanded upon with observations that both receptors can heterodimerize with each other under certain conditions ... Additional DA D2R/TAAR1 interactions with functional consequences are revealed by the results of experiments demonstrating that in addition to the cAMP/PKA pathway (Panas et al., 2012) stimulation of TAAR1-mediated signaling is linked to activation of the Ca++/PKC/NFAT pathway (Panas et al.,2012) and the DA D2R-coupled, G protein-independent AKT/GSK3 signaling pathway (Espinoza et al., 2015; Harmeier et al., 2015), such that concurrent TAAR1 and DA DR2R activation could result in diminished signaling in one pathway (e.g. cAMP/PKA) but retention of signaling through another (e.g., Ca++/PKC/NFA)
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Interaction of TAAR1 with D2R altered the subcellular localization of TAAR1 and increased D2R agonist binding affinity.
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External links
- Receptors,+Dopamine+D2 at the U.S. National Library of Medicine Medical Subject Headings (MeSH)
- Pappas S (17 January 2011). "Study: Genes Influence Who Your Friends Are". Imaginova Corp. LiveScience. Retrieved 20 January 2011.
This article incorporates text from the United States National Library of Medicine, which is in the public domain.