Apelin (APLN)

Apelin is a secreted peptide hormone produced as a 77-amino acid precursor (pre-proapelin) and processed into several active isoforms—including apelin-36, apelin-17, and apelin-13—that act as endogenous ligands for the G protein-coupled apelin receptor (APLNR, also called APJ)[1][3][4][5]. Apelin is widely expressed across mammalian tissues and modulates diverse physiological processes including cardiovascular homeostasis, regulation of fluid balance, angiogenesis, cellular proliferation, and neuroprotection[1][2][3]. Its signaling involves multiple G protein-mediated pathways and downstream effectors such as ERK, Akt, and intracellular calcium mobilization. The apelinergic system is implicated in the pathophysiology of cardiovascular disease, neurodegeneration, cancer, diabetes, and metabolic disorders[1][2][3][4][5]. Synthetic apelin analogs and receptor modulators are under preclinical development. Apelin (primarily Apelin-13 and Apelin-17) in plasma may have biomarker potential in cardiovascular and infectious diseases, but the short in vivo half-life and wide systemic effects pose therapeutic challenges[1].

Other names

Apelin-36Apelin-31Apelin-28Apelin-13APJ endogenous ligandAPELAGTRL1 ligandPre-proapelin

Binding to the apelin receptor (APLNR/APJ), activating G protein-coupled signaling (typically Gi/o, sometimes Gq, leading to downstream effects on cAMP, ERK1/2, Akt, intracellular calcium)[1][3] Regulation of angiogenesis via APJ pathway[2]