Structure
The CB2 receptor is encoded by the CNR2 gene. Approximately 360 amino acids comprise the human CB2 receptor, making it somewhat shorter than the 473-amino-acid-long CB1 receptor.
As is commonly seen in G protein-coupled receptors, the CB2 receptor has seven transmembrane spanning domains, a glycosylated N-terminus, and an intracellular C-terminus. The C-terminus of CB2 receptors appears to play a critical role in the regulation of ligand-induced receptor desensitization and downregulation following repeated agonist application, perhaps causing the receptor to become less responsive to particular ligands.
The human CB1 and the CB2 receptors possess approximately 44% amino acid similarity. When only the transmembrane regions of the receptors are considered, however, the amino acid similarity between the two receptor subtypes is approximately 68%. The amino acid sequence of the CB2 receptor is less highly conserved across human and rodent species as compared to the amino acid sequence of the CB1 receptor. Based on computer modeling, ligand interactions with CB2 receptor residues S3.31 and F5.46 appears to determine differences between CB1 and CB2 receptor selectivity. In CB2 receptors, lipophilic groups interact with the F5.46 residue, allowing them to form a hydrogen bond with the S3.31 residue. These interactions induce a conformational change in the receptor structure, which triggers the activation of various intracellular signaling pathways. Further research is needed to determine the exact molecular mechanisms of signaling pathway activation.
Read more about this topic: Cannabinoid Receptor Type 2
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