GPR18

GPR18 is a G protein-coupled receptor that is primarily expressed in the brain and immune cells. It belongs to the orphan receptor family, meaning its endogenous ligand has not yet been definitively identified. However, research has suggested that cannabinoids, particularly anandamide, may act as ligands for GPR18, though this remains a subject of ongoing investigation.

The receptor has been implicated in a variety of physiological processes. In the nervous system, GPR18 has been associated with pain modulation, neuroprotection, and the regulation of mood. Studies have also suggested a role for GPR18 in inflammatory responses and immune cell function, particularly in the context of cell migration and cytokine production.

The precise signaling pathways activated by GPR18 are still being elucidated, but it is known to couple to inhibitory G proteins (Gi/o), which can lead to downstream effects such as the inhibition of adenylyl cyclase and the activation of mitogen-activated protein kinase (MAPK) pathways.

Given its potential involvement in pain, inflammation, and neurological disorders, GPR18 has emerged as a target of interest for therapeutic development. However, the complexity of its signaling and the uncertainty surrounding its endogenous ligand present challenges in developing targeted interventions. Further research is needed to fully understand the physiological roles of GPR18 and its therapeutic potential.