Receptor for the glycosphingolipid psychosine (PSY) and several related glycosphingolipids (By similarity). Plays a role in immune response by maintaining lysosome function and supporting phagocytosis-mediated intracellular bacteria clearance (PubMed:27287411). May have a role in activation-induced cell death or differentiation of T-cells (PubMed:8599842). Detected in thymus and at low levels in spleen. By glucocorticoids, during apoptosis of immature thymocytes. Mutant mice are healthy with no signs of spontaneous colitis or inflammation, however are more susceptible to bacteria-induced colitis in comparison to the wild type. Belongs to the G-protein coupled receptor 1 family.