Apelin Receptors
The Apelin (APJ) receptor is a G-protein-coupled receptor for which Apelin-36, apelin-13 and [Pyr1]-apelin-13 are the predominant endogenous ligands. Elabela (ELA; also known as Toddler) has been proposed as another endogenous ligand for this receptor. The APJ receptor mediates cardiovascular function, fluid homeostasis and adipocyte endocrine secretion.
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Apelin Receptor Agonists |
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|---|---|
| Cat. No. | Product Name / Activity |
| 2420 | [Pyr1]-Apelin-13 |
| Potent peptide apelin agonist | |
| 2426 | Apelin-36 (human) |
| Endogenous apelin agonist | |
| 5966 | ML 233 |
| Non-peptide apelin agonist | |
Apelin Receptor Antagonists |
|
| Cat. No. | Product Name / Activity |
| 4748 | ML 221 |
| Apelin antagonist | |
| 5992 | MM 54 |
| Potent apelin antagonist | |
The apelin receptor comprises 380 amino acids and exhibits homology with the angiotensin II type 1 receptor (AT1), although it does not bind angiotensin. No apelin receptor subtypes have been discovered to date. In humans, APJ receptors are expressed in endothelial cells and cardiomyocytes, and throughout the brain and spinal cord. In the periphery the highest expression levels are seen in the spleen and placenta, while lower levels of expression are seen in other tissues. APJ receptors are also present in neonatal tissues.
Apelin is initially expressed as the 77-amino acid peptide pre-pro-apelin. Following secretion, the peptide is cleaved to produce three main apelin fragments: apelin 36, apelin-17 and apelin-16. Apelin is thought to signal primarily through Gαi, although there is evidence that the receptor may also couple to Gαq. Elabela is a 54-amino acid peptide that is cleaved to produce a 32-amino acid secreted peptide. ELA peptides display some bias toward the G protein pathway versus the β-arrestin signaling pathway, although both Apelin and ELA probably have different signaling profiles in different tissues and organs.
Apelin has a significant role in the cardiovascular system, causing vasodilation and having a positive inotropic effect. It regulates fluid homeostasis via the hypothalamic-pituitary-adrenal axis and modulates cardiovascular function via the forebrain and brain stem. Increased apelin expression is associated with certain cancers, inducing endothelial cell migration and proliferation, and promoting neoangiogenesis. In addition, apelin inhibits insulin secretion, decreases glucose levels, regulates gut glucose absorption, and has a role in the pathogenesis of diabetes-related complications.
ELA is important in development, particularly of the cardiovascular system, and promotes self-renewal of human embryonic stem cells.