adrenomedullin

Adrenomedullin consists of 52 amino acids and is a member of the adrenomedullin family. It s a a hypotensive peptide and has 1 intramolecular disulfide bond. It seems that adrenomedullin has a slight homology with the calcitonin gene-related peptide. Adrenomedullin has a highly expression in pheochromocytoma and adrenal medulla. It also can be detected in lung, ventricle and kidney tissues. Adrenomedullin and PAMP are potent hypotensive and vasodilatator agents. Numerous actions have been reported most related to the physiologic control of fluid and electrolyte homeostasis. In the kidney, adrenomedullin is diuretic and natriuretic, and both adrenomedullin and PAMP inhibit aldosterone secretion by direct adrenal actions. In pituitary gland, both peptides at physiologically relevant doses inhibit basal ACTH secretion. Both peptides appear to act in brain and pituitary gland to facilitate the loss of plasma volume, actions which complement their hypotensive effects in blood vessels. It is believed that adrenomedullin functions through combinations of the calcitonin receptor like receptor and receptor activity-modifying proteins complexes, as well as CGRP receptors.

RAMP3 belongs to the RAMP family. Members of this family are single-transmembrane-domain proteins, called receptor (calcitonin) activity modifying proteins (RAMPs). RAMPs have a wide biological distribution; high concentrations are found in the brain, lung, liver, heart and spleen with lower expression levels present in the testes, gastrointestinal tract and thyroid. RAMPs are type I transmembrane proteins with an extracellular N terminus and a cytoplasmic C terminus. They are required to transport calcitonin-receptor-like receptor (CRLR) to the plasma membrane. CRLR, a receptor with seven transmembrane domains, can function as either a calcitonin gene-related peptide (CGRP) receptor or an adrenomedullin receptor, depending on which members of the RAMP family are expressed. In the presence of RAMP3 protein, CRLR functions as an adrenomedullin receptor.