apelin

Description

Apelin (APLN) is secreted from various tissues in the cardiovascular, digestive, urinary, and CNS, and regulates a wide range of physiological/pathophysiological functions, including cardiovascular function, blood pressure, angiogenesis, and drinking behavior. In 1998, APLN was isolated and characterized from bovine stomach extracts as an endogenous ligand for an orphan GPCR, APJ (putative receptor protein related to the angiotensin receptor, AT1). The peptide sequences of bovine APLN and bovine cDNA encoding preproAPLN were used to identify human APLN.

Clinical Use

The down regulation of APJ is suggested to be a possible cause for the development of heart failure. APLN is indicated to present a future drug target for the treatment of hypertension and heart failure. APJ agonists are expected to be blockers of HIV infection.

Structure and conformation

The human APLN gene encodes a preproprotein of 77 aa residues, containing a signal peptide of 22 aa residues. After cleavage of the signal peptide, the proprotein of 55 aa residues generates several active fragments, including APLN-36 (aa 42–77), APLN-17 (aa 61–77), and APLN-13 (aa 65–77). The APLN-13 is highly active and responsible for the APJ binding and biological activities of mature APLN. So far, 46 different APLN peptides ranging from APLN-55 to APLN-12 have been identified in the bovine colostrum, including C-terminal truncated isoforms. APLN has been identified in mammals, birds, reptiles, amphibians, and teleosts. Mr 8569 (Human preproAPLN), 4195.87 (Human APLN-36), 1550.84 (Human APLN-13). The mature APLN, APLN-13, contains no cysteine or N-glycosylation site. It is soluble in water and physiological saline solution. APLN is a specific substrate of angiotensinconverting enzyme 2 (ACE2).