Apelin Receptor (APJ) 

Apelin receptor (APJ) is a member of the family A of G-protein-coupled receptors (GPCRs) and Apelin is an endogenous ligand for an APJ that was previously isolated from bovine stomachs. Apelin is a 77-amino acid precursor protein that is hydrolysed to produce active peptides of different lengths, such as Apelin-36, Apelin-31, Apelin-17, and Apelin13. The apelin/APJ system plays important roles in the physiology and pathophysiology of several organs, including regulation of fluid homeostasis, blood pressure, cardiac contractility, angiogenesis, metabolic balance, and cell proliferation, apoptosis, or inflammation. Additionally, the apelin/APJ system is widely expressed in the central nervous system, especially in neurons and oligodendrocytes. APJ is also involved in anxiety, and depression.