Orphan receptor with constitutive G(s) signaling activity that activate cyclic AMP. Has a potential role in modulating a number of brain functions, including behavioral responses to stress (By similarity), amyloid-beta peptide generation in neurons and neurite outgrowth (By similarity). Maintains also meiotic arrest in oocytes (By similarity). Expressed predominantly in the central nervous system, and at low levels in the lung, kidney, testis, ovary and eye. Highly expressed in regions of the brain implicated in the Alzheimer disease. Overexpression stimulates amyloid-beta production. Belongs to the G-protein coupled receptor 1 family. Was originally (PubMed:12220620) thought to be a receptor for sphingosine 1-phosphate. PubMed:19286662 demonstrated that it is not the case.