Receptors for pituitary adenylate cyclase-activating polypeptide: comparison with vasoactive intestinal peptide receptors.
Pituitary adenylate cyclase-activating polypeptide (PACAP) is a new member of the secretin glucagon-vasoactive intestinal peptide (VIP) family of peptides, being most homologous to VIP. PACAP exists in two amidated forms with 38 residues (PACAP38) and 27 residues (PACAP27), respectively. PACAP38 is the major form in tissues. There are two types of high-affinity receptors for PACAP: type I, which specifically binds to both PACAPs, and type II, which is shared with VIP. Type I PACAP receptors appear to have two subtypes: type IA, which binds to both PACAP38 and PACAP27, with slight preference for the latter, and type IB, with greater preference for PACAP38. Distribution of the type I PACAP receptor is different from that of VIP, and it is found in high concentrations in brain, spinal cord, anterior pituitary, adrenal medulla, spermatogonia at certain stages, mature spermatozoa, and some cell lines. Type II PACAP receptors are found in lung, liver, intestine, and other tissues, and their distribution is similar to that of the VIP receptor. Type II PACAP receptor might be similar to or identical with the VIP receptor.
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Department of Medicine, Tulane University School of Medicine, New Orleans, LA 70012, USA.