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α2A-adrenoceptor

Family: Adrenoceptors

Contents:
Gene and Protein Information
Previous and Unofficial Names
Database Links
Agonists
Antagonists
Allosteric Regulators
Transduction Mechanisms
Tissue Distribution
Expression Datasets
Functional Assays
Physiological Functions
Physiological Consequences of Altering Gene Expression
Phenotypes, Alleles and Disease Models
General Comments
References
Gene and Protein Information
class A G protein-coupled receptor
Species TM AA Chromosomal Location Gene Symbol Gene Name Reference
Human 7 450 10q24-q26 ADRA2A adrenoceptor alpha 2A 17
Mouse 7 450 19 D2 Adra2a adrenergic receptor, alpha 2a 22
Rat 7 450 1 Adra2a adrenoceptor alpha 2A 19
Previous and Unofficial Names
α2-C10
RG20
α2D
ADRA2
ADRA2R
ADRAR
adrenergic, alpha-2A-, receptor
alpha-2AAR subtype C10
alpha-2A-adrenergic receptor
CA2-47
RATRG20
Adrenergic alpha 2A receptor
Adrenergic, alpha 2A, receptor
adrenergic receptor, alpha 2a
alpha-2A adrenergic receptor
alpha-2A adrenoceptor
alpha-2A adrenoreceptor
alpha-2AAR
alpha-2D adrenergic receptor
alpha2A
alpha2A-adrenergic receptor
Adra-2a
Adra-2
alpha2A-AR
alpha(2A)AR
AW122659
Database Links
ChEMBL Target
DrugBank Target
Ensembl
Entrez Gene
GeneCards
GenitoUrinary Development Molecular Anatomy Project
HomoloGene
Human Protein Reference Database
InterPro
KEGG Gene
OMIM
PharmGKB Gene
PhosphoSitePlus
Protein Ontology (PRO)
RefSeq Nucleotide
RefSeq Protein
TreeFam
UniGene Hs.
UniProt
Wikipedia
Search for 3D structures on the PDB
Search by keyword: Adrenoceptors α2A-adrenoceptor
Natural/Endogenous Ligand(s)
(-)-adrenaline
(-)-noradrenaline
Agonists
Key to terms and symbols View all chemical structures Click column headers to sort
Ligand Sp. Action Affinity Units Reference
dexmedetomidine Hs Partial agonist 7.6 – 9.6 pKi 14,29,31
clonidine Hs Partial agonist 7.2 – 9.2 pKi 14,29,31
oxymetazoline Hs Partial agonist 8.0 pKi 14,32
brimonidine Hs Full agonist 6.7 – 8.7 pKi 14,29,31
guanfacine Hs Partial agonist 7.3 pKi 14
pergolide Hs Partial agonist 7.3 pKi 24
(-)-noradrenaline Hs Full agonist 5.6 – 8.4 pKi 14,29,31
(-)-adrenaline Hs Full agonist 5.6 – 8.3 pKi 14,31
apomorphine Hs Partial agonist 6.9 pKi 24
xylazine Hs Partial agonist 5.7 pKi 14
Agonist Comments
[3H]UK4,304 binds to the α2A receptor of human platelet membranes with high and low affinity Kd values of 2.6 and 170 nM, respectively with 73% bound at the high affinity site [26]. The discrepancies between the two studies relate to buffer differences (and probably tissue source and membrane preparation methods).
[125I]p-iodoclonidine binds to the human α2A receptor with a Kd of 1.5 nM [27].
The species ortholog of the human α2A receptors (α2D) found in the rat, mouse and cow has significantly different antogonist pharmacology, but the agonist pharmacology appears to be similar.
Antagonists
Key to terms and symbols View all chemical structures Click column headers to sort
Ligand Sp. Action Affinity Units Reference
[3H]rauwolscine Hs Antagonist 9.5 pKd 4-5
[3H]RX821002 Hs Antagonist 8.8 – 9.5 pKd 5-6
[3H]MK-912 Hs Antagonist 8.9 pKd 32
lisuride Hs Antagonist 10.3 pKi 24
terguride Hs Antagonist 9.5 pKi 24
RX821002 Hs Antagonist 9.2 pKi 32
yohimbine Hs Antagonist 8.4 – 9.2 pKi 4,6,32
BRL 44408 Hs Antagonist 8.2 – 8.77 pKi 32,34
phentolamine Hs Antagonist 8.4 pKi 4,6
rauwolscine Hs Antagonist 8.4 pKi 32
WB 4101 Hs Antagonist 7.6 – 8.9 pKi 4,6,32
bromocriptine Hs Antagonist 8.0 pKi 24
cabergoline Hs Antagonist 7.9 pKi 24
spiroxatrine Hs Antagonist 7.3 pKi 32
piribedil Hs Antagonist 7.1 pKi 24
chlorpromazine Hs Antagonist 5.9 – 6.6 pKi 4,6
ARC-239 Hs Antagonist 5.5 – 6.8 pKi 4,6,32
prazosin Hs Antagonist 5.3 – 6.5 pKi 4,6,32
Antagonist Comments
The species orthologs of the human α2A receptors (α2D) found in the rat, mouse, cow and chicken have significantly different antagonist pharmacology.
For example, [3H]rauwolscine has a much lower affinity for the α2D as compared to the α2A, whereas [3H]RX821002 has higher affinity [5].
Other agents that have a five-fold or greater lower affinity for the α2D include WB 4101, oxymetazoline, SKF 104078, raubasine and chlorpromazine [27]).
In binding assays, affinities are dependent on buffer condidtions [5].
Allosteric Regulators
Key to terms and symbols View all chemical structures Click column headers to sort
Ligand Sp. Action Affinity Units Reference
HMA Hs Negative 2.5 pKd 20,33
5-(-N-ethyl-N-isopropyl)-amiloride Hs Positive 1.8 pKd 33

Explore drug-target interactions for this set of compounds using iPHACE

Primary Transduction Mechanisms
Transducer Effector/Response
Gi/Go family Adenylate cyclase inhibition
Potassium channel
Calcium channel
Phospholipase A2 stimulation
References:  3,15,21
Secondary Transduction Mechanisms
Transducer Effector/Response
Gs family Adenylate cyclase stimulation
Comments:  The physiological significance of this mechanism is unknown.
References:  9
Tissue Distribution
Brain > spleen > kidney > aorta = lung = skeletal muscle > heart = liver.
Species:  Human
Technique:  RNAse protection of mRNA.
References:  8,30
Brain > spleen = kidney = aorta > lung = skeletal muscle.
Absent in heart and liver.
Species:  Rat
Technique:  RNAse protection of mRNA.
References:  2,10
Expression Datasets

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Log average relative transcript abundance in mouse tissues measured by qPCR from Regard, J.B., Sato, I.T., and Coughlin, S.R. (2008). Anatomical profiling of G protein-coupled receptor expression. Cell, 135(3): 561-71. [PMID:18984166] [Raw data: website]

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Functional Assays
Measurement of the inhibition of adenylate cyclase activity using intact cell preparations (either native or transfected) using the [3H]adenine prelabeling technique to measure cAMP accumulation.
Species:  Human
Tissue:  HT29 cells.
Response measured:  Inhibition of cAMP accumulation.
References:  3
Segments of saphenous vein are incubated with [3H]noradrenaline and subsequently superfused with physiological salt solution containing uptake 1 and uptake 2 blockers. The antagonists potencies in facilitating the electrically (2 Hz) evoked tritium overflow is determined.
Species:  Human
Tissue:  Saphenous vein.
Response measured:  Electrically evoked tritium overflow.
References:  7,25
Physiological Functions
Hypotension.
Species:  Mouse
Tissue:  CNS.
References:  16,23
Sedation.
Species:  Mouse
Tissue:  CNS.
References:  13,16,18
Analgesia.
Species:  Mouse
Tissue:  Brain.
References:  13,16,18
Hypothermia.
Species:  Mouse
Tissue:  CNS.
References:  13,16
Anesthetic-sparing effect.
Species:  Mouse
Tissue:  CNS.
References:  16,18
Presynaptic inhibition of noradrenaline release.
Species:  Mouse
Tissue:  Vasa deferens, heart.
References:  1,11,16
Physiological Consequences of Altering Gene Expression
The α2A-adrenoceptor knock-out mice show an increase in sympathetic activity, resting tachycardia, depletion of cardiac tissue noradrenaline concentration and down-regulation of cardiac β-adrenoceptors.
Species:  Mouse
Tissue: 
Technique:  Gene targeting in embryonic stem cells.
References:  1
α2A-adrenoceptor knockout mice exhibit disruption of presynaptic inhibition of noradrenaline release at high stimulation frequencies. This study showed that the α2A receptor is the principal autoreceptor in the presynaptic feedback loop regulating noradrenaline release. However, another α2 autoreceptor is also present.
Species:  Mouse
Tissue: 
Technique:  Gene targeting in embryonic stem cells.
References:  11
α2A-adrenoceptor knockout mice exhibit no amitriptyline-induced (a tricyclic antidepressant) or clonidine-induced analgesia. This study shows that the α2A-adrenoceptors are involved in the sedative effects of these drugs.
Species:  Mouse
Tissue: 
Technique:  Transgenesis.
References:  28
The hypotensive effects of α2A agonists are abolished in α2A-adrenoceptor knockout mice.
Species:  Mouse
Tissue: 
Technique:  Transgenesis.
References:  12
Phenotypes, Alleles and Disease Models Mouse data from MGI

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Allele Composition & genetic background Accession Phenotype Id Phenotype Reference
Adra2atm1Bkk Adra2atm1Bkk/Adra2atm1Bkk
involves: 129S1/Sv * 129X1/SvJ
MGI:87934  MP:0002078 abnormal glucose homeostasis PMID: 17992256 
Adra2atm1Bkk|Adra2btm1Gsb|Adra2ctm1Gsb Adra2atm1Bkk/Adra2atm1Bkk,Adra2btm1Gsb/Adra2btm1Gsb,Adra2ctm1Gsb/Adra2ctm1Gsb
involves: 129S1/Sv * 129X1/SvJ * C57BL/6 * DBA/2J
MGI:87934  MGI:87935  MGI:87936  MP:0001712 abnormal placenta development PMID: 12068299 
Adra2atm1Bkk Adra2atm1Bkk/Adra2atm1Bkk
involves: 129S1/Sv * 129X1/SvJ * C57BL/6
MGI:87934  MP:0005447 abnormal synaptic norepinephrine release PMID: 10647009 
Adra2atm1Bkk|Adra2ctm1Gsb Adra2atm1Bkk/Adra2atm1Bkk,Adra2ctm1Gsb/Adra2ctm1Gsb
involves: 129S1/Sv * 129X1/SvJ * C57BL/6 * DBA/2J
MGI:87934  MGI:87936  MP:0005447 abnormal synaptic norepinephrine release PMID: 10647009 
Adra2atm1Bkk Adra2atm1Bkk/Adra2atm1Bkk
involves: 129S1/Sv * 129X1/SvJ * C57BL/6
MGI:87934  MP:0000230 abnormal systemic arterial blood pressure PMID: 10385696 
Adra2atm1Lel Adra2atm1Lel/Adra2atm1Lel
involves: 129S2/SvPas * C57BL/6
MGI:87934  MP:0000230 abnormal systemic arterial blood pressure PMID: 8670421 
Adra2atm1Bkk|Adra2btm1Gsb|Adra2ctm1Gsb Adra2atm1Bkk/Adra2atm1Bkk,Adra2btm1Gsb/Adra2btm1Gsb,Adra2ctm1Gsb/Adra2ctm1Gsb
involves: 129S1/Sv * 129X1/SvJ * C57BL/6 * DBA/2J
MGI:87934  MGI:87935  MGI:87936  MP:0001718 abnormal yolk sac morphology PMID: 12068299 
Adra2atm1Bkk|Adra2ctm1Gsb Adra2atm1Bkk/Adra2atm1Bkk,Adra2ctm1Gsb/Adra2ctm1Gsb
involves: 129S1/Sv * 129X1/SvJ * C57BL/6 * DBA/2J
MGI:87934  MGI:87936  MP:0001625 cardiac hypertrophy PMID: 10647009 
Adra2atm1Bkk|Adra2btm1Gsb|Adra2ctm1Gsb Adra2atm1Bkk/Adra2atm1Bkk,Adra2btm1Gsb/Adra2btm1Gsb,Adra2ctm1Gsb/Adra2ctm1Gsb
involves: 129S1/Sv * 129X1/SvJ * C57BL/6 * DBA/2J
MGI:87934  MGI:87935  MGI:87936  MP:0005333 decreased heart rate PMID: 12068299 
Adra2atm1Bkk|Adra2btm1Gsb|Adra2ctm1Gsb Adra2atm1Bkk/Adra2atm1Bkk,Adra2btm1Gsb/Adra2btm1Gsb,Adra2ctm1Gsb/Adra2ctm1Gsb
involves: 129S1/Sv * 129X1/SvJ * C57BL/6 * DBA/2J
MGI:87934  MGI:87935  MGI:87936  MP:0006207 embryonic lethality during organogenesis PMID: 12068299 
Adra2atm1Bkk Adra2atm1Bkk/Adra2atm1Bkk
involves: 129S1/Sv * 129X1/SvJ
MGI:87934  MP:0000189 hypoglycemia PMID: 17992256 
Adra2atm1Bkk Adra2atm1Bkk/Adra2atm1Bkk
involves: 129S1/Sv * 129X1/SvJ * C57BL/6
MGI:87934  MP:0002626 increased heart rate PMID: 10385696 
Adra2atm1Qiwa Adra2atm1Qiwa/Adra2atm1Qiwa
B6.129-Adra2a
MGI:87934  MP:0002169 no abnormal phenotype detected PMID: 19276088 
General Comments
Receptors designated as α2A and α2D are species orthologues. Although these receptors are highly homologous, they have sufficiently different pharmacology to have been designated as separate subtypes in the literature. The α2A subtype is found in the human, pig and rabbit, whereas the α2D is found in the rat, mouse and cow.

REFERENCES

To cite this database page, please use the following:

Richard A. Bond, David B. Bylund, Douglas C. Eikenburg, J. Paul Hieble, Rebecca Hills, Kenneth P. Minneman, Sergio Parra.
Adrenoceptors: α2A-adrenoceptor. Last modified on 27/11/2012. Accessed on 22/05/2013. IUPHAR database (IUPHAR-DB), http://www.iuphar-db.org/DATABASE/ObjectDisplayForward?objectId=25.


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