Receptor for apelin receptor early endogenous ligand (APELA) and apelin (APLN) hormones coupled to G proteins that inhibit adenylate cyclase activity (PubMed:11359874). Plays a key role in early development such as gastrulation, blood vessels formation and heart morphogenesis by acting as a receptor for APELA hormone. May promote angioblast migration toward the embryonic midline, i.e. the position of the future vessel formation, during vasculogenesis. Promotes sinus venosus (SV)-derived endothelial cells migration into the developing heart to promote coronary blood vessel development. Also plays a role in various processes in adults such as regulation of blood vessel formation, blood pressure, heart contractility and heart failure (By similarity). After exposure to apelin (APLN), internalized from the cell surface into an endosomal recycling compartment, from where it is recycled to the cell membrane (PubMed:11359874). After exposure to apelin receptor early endogenous ligand (APELA), internalized from the cell surface into an endosomal recycling compartment, from where it is recycled to the cell membrane (By similarity). Widely expressed. Highest expression in the lung, lower in the heart, placenta, ovary, skeletal muscle, mammary gland, kidney and several structures in the brain as the hypothalamus (supraoptic and periventricular nuclei), pituitary, olfactory bulb and pineal gland. Higher expression in neonates than in adult. Belongs to the G-protein coupled receptor 1 family.