"Cannabinoid Receptors"

Cannabinoid receptors, located throughout the body, are part of the endocannabinoid system of vertebrates– a class of cell membrane receptors in the G protein-coupled receptor superfamily. As is typical of G protein-coupled receptors, the cannabinoid receptors contain seven transmembrane spanning domains. Cannabinoid receptors are activated by three major groups of ligands:

• Endocannabinoids;
• Phytocannabinoids (plant-derived such as tetrahydrocannabinol (THC) produced by cannabis);
• Synthetic cannabinoids (such as HU-210).

cannabinoid receptor 1
Human cannabinoid receptor 1 (CB1) bound to tetrahydrocannabinol agonist AM11542 (black). PDB: 5XRA​
Identifiers
Symbol	CNR1
Alt. symbols	CNR
NCBI gene	1268
HGNC	2159
OMIM	114610
Orthologs	7273
RefSeq	NM_033181
UniProt	P21554
Other data
Locus	Chr. 6 q14-q15
Search for Structures Swiss-model Domains InterPro

cannabinoid receptor 2
Human cannabinoid receptor 2 (CB2) bound to agonist AM10257 (black). PDB: 5ZTY​
Identifiers
Symbol	CNR2
NCBI gene	1269
HGNC	2160
OMIM	605051
Orthologs	1389
RefSeq	NM_001841
UniProt	P34972
Other data
Locus	Chr. 1 p
Search for Structures Swiss-model Domains InterPro

All endocannabinoids and phytocannabinoids are lipophilic.

There are two known subtypes of cannabinoid receptors, termed CB₁ and CB₂. The CB₁ receptor is expressed mainly in the brain (central nervous system or "CNS"), but also in the lungs, liver and kidneys. The CB₂ receptor is expressed mainly in the immune system, in hematopoietic cells, and in parts of the brain.

The protein sequences of CB₁ and CB₂ receptors are about 44% similar. When only the transmembrane regions of the receptors are considered, amino acid similarity between the two receptor subtypes is approximately 68%. In addition, minor variations in each receptor have been identified. Cannabinoids bind reversibly and stereo-selectively to the cannabinoid receptors. Subtype selective cannabinoids have been developed which theoretically may have advantages for treatment of certain diseases such as obesity.

Enzymes involved in biosynthesis/inactivation of endocannabinoids and endocannabinoid signaling in general (involving targets other than CB1/2-type receptors) occur throughout the animal kingdom.