Receptor for ATP and UTP coupled to G-proteins that activate a phosphatidylinositol-calcium second messenger system. Not activated by ADP or UDP. Widely expressed at low levels. In brain, higher expression in the pineal gland and ventricular system. Phosphorylation of Ser-329 and Ser-330 is a key step in agonist-dependent desensitization and loss of surface P2RY4. This phosphorylation does not involve PKC, nor other calcium-activated kinases (By similarity). Belongs to the G-protein coupled receptor 1 family.