''N''-Arachidonyl glycine receptor (NAGly receptor), also known as G protein-coupled receptor 18 (GPR18), is a

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...

that in humans is encoded by the ''GPR18''

gene In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a ba ...

. Along with the other previously "orphan" receptors

GPR55 G protein-coupled receptor 55 also known as GPR55 is a G protein-coupled receptor that in humans is encoded by the ''GPR55'' gene In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian unit ...

and

GPR119 G protein-coupled receptor 119 also known as GPR119 is a G protein-coupled receptor that in humans is encoded by the ''GPR119'' gene. GPR119, along with GPR55 and GPR18, have been implicated as novel cannabinoid receptors. Pharmacology GPR119 ...

, GPR18 has been found to be a receptor for endogenous lipid neurotransmitters, several of which also bind to

cannabinoid receptor Cannabinoid receptors, located throughout the body, are part of the endocannabinoid system a class of cell membrane receptors in the G protein-coupled receptor superfamily. As is typical of G protein-coupled receptors, the cannabinoid recepto ...

s. It has been found to be involved in the regulation of

intraocular pressure Intraocular pressure (IOP) is the fluid pressure inside the eye. Tonometry is the method eye care professionals use to determine this. IOP is an important aspect in the evaluation of patients at risk of glaucoma. Most tonometers are calibrated to ...

. Research supports the hypothesis that GPR18 is the

abnormal cannabidiol Abnormal cannabidiol (Abn-CBD) is a synthetic regioisomer of cannabidiol, which unlike most other cannabinoids produces vasodilator effects, lowers blood pressure, and induces cell migration, cell proliferation and mitogen-activated protein kinase ...

receptor and

N-arachidonoyl glycine ''N''-Arachidonylglycine (NAGly) is a carboxylic metabolite of the endocannabinoid anandamide (AEA). Since it was first synthesized in 1996, NAGly has been a primary focus of the relatively contemporary field of lipidomics due to its wide range ...

, the endogenous lipid metabolite of

anandamide Anandamide (ANA), also known as ''N''-arachidonoylethanolamine (AEA), is a fatty acid neurotransmitter. Anandamide was the first endocannabinoid to be discovered: it participates in the body's endocannabinoid system by binding to cannabinoid rec ...

, initiates directed

microglia Microglia are a type of neuroglia (glial cell) located throughout the brain and spinal cord. Microglia account for about 7% of cells found within the brain. As the resident macrophage cells, they act as the first and main form of active immune de ...

migration Migration, migratory, or migrate may refer to: Human migration * Human migration, physical movement by humans from one region to another ** International migration, when peoples cross state boundaries and stay in the host state for some minimum le ...

in the CNS through activation of GPR18, though recent evidence demonstrates that NAGly was not shown to be a GPR18 agonist in rat sympathetic neurons.

Resolvin D2 Resolvins are specialized pro-resolving mediators (SPMs) derived from omega-3 fatty acids, primarily eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), as well as docosapentaenoic acid (DPA) and clupanodonic acid. As autacoids similar ...

(RvD2), a member of the

specialized proresolving mediators Specialized pro-resolving mediators (SPM, also termed specialized proresolving mediators) are a large and growing class of cell signaling molecules formed in cells by the metabolism of polyunsaturated fatty acids (PUFA) by one or a combination of ...

(SPM) class of

polyunsaturated fatty acid Polyunsaturated fatty acids (PUFAs) are fatty acids that contain more than one double bond in their backbone. This class includes many important compounds, such as essential fatty acids and those that give drying oils their characteristic proper ...

metabolites, is an activating ligand for GPR18; RvD2 and its activation of GPR18 contribute to the resolution of inflammatory responses as well as inflammation-based and other diseases in animal models and are proposed to do so in humans. Furthermore, RvD2 is a metabolite of the

omega-3 fatty acid Omega−3 fatty acids, also called Omega-3 oils, ω−3 fatty acids or ''n''−3 fatty acids, are polyunsaturated fatty acids (PUFAs) characterized by the presence of a double bond, three atoms away from the terminal methyl group in their chem ...

docosahexaenoic acid Docosahexaenoic acid (DHA) is an omega-3 fatty acid that is a primary structural component of the human brain, cerebral cortex, skin, and retina. In physiological literature, it is given the name 22:6(n-3). It can be synthesized from alpha-lino ...

(DHA); the metabolism of DHA to RvD2 and RvD2's activation of GPR18 is proposed to one among many other mechanisms for the anti-inflammatory and other beneficial effects attributed to omega-3 fatty acid-rich diets

Ligands

;Agonists Ligands found to bind to GPR18 as agonists include: * ''N''-Arachidonoylglycine (NAGly) *

Abnormal cannabidiol Abnormal cannabidiol (Abn-CBD) is a synthetic regioisomer of cannabidiol, which unlike most other cannabinoids produces vasodilator effects, lowers blood pressure, and induces cell migration, cell proliferation and mitogen-activated protein kinase ...

(Abn-CBD) * AM-251 - partial agonist *

Cannabidiol Cannabidiol (CBD) is a phytocannabinoid discovered in 1940. It is one of 113 identified cannabinoids in cannabis plants, along with tetrahydrocannabinol (THC), and accounts for up to 40% of the plant's extract. , clinical research on CBD incl ...

- partial agonist * CBG-DMH *

O-1602 O-1602 is a synthetic compound most closely related to abnormal cannabidiol, and more distantly related in structure to cannabinoid drugs such as THC. O-1602 does not bind to the classical cannabinoid receptors CB1 or CB2 with any significant aff ...

* Δ⁹-Tetrahydrocannabinol (Δ⁹-THC) - THC is actually a more potent agonist at GPR18 than at CB₁ or CB₂, with Ki of 0.96nM at GPR18, 8.1nM at GPR55, 25.1nM at CB₁ and 35.2nM at CB₂. *

Anandamide Anandamide (ANA), also known as ''N''-arachidonoylethanolamine (AEA), is a fatty acid neurotransmitter. Anandamide was the first endocannabinoid to be discovered: it participates in the body's endocannabinoid system by binding to cannabinoid rec ...

(''N''-arachidonoyl ethanolamine, AEA) * Arachidonylcyclopropylamide (ACPA) *

(RvD2) ;Antagonists * Amauromine *

O-1918 O-1918 is a synthetic compound related to cannabidiol, which is an antagonist at two former orphan receptors GPR18 and GPR55, that appear to be related to the cannabinoid receptors. O-1918 is used in the study of these receptors, which have been ...

CID-85469571 PSB-CB5 (CID-85469571) is a compound which acts as an antagonist at the former orphan receptor GPR18, and is the first selective antagonist characterised for this receptor, with an IC50 of 279nM, and good selectivity over related receptors (over ...

Ligands

References

Further reading