vasoactive intestinal polypeptide (VIP) receptor 1, member of the class B family of seven-transmembrane G protein-coupled receptors
Vasoactive intestinal peptide (VIP) receptor 1 is a member of the group of G protein-coupled receptors for structurally similar peptide hormones that also include secretin, growth-hormone-releasing hormone (GHRH), and pituitary adenylate cyclase activating polypeptide (PACAP). These receptors are classified into the subfamily B1 of class B GRCRs that consists of the classical hormone receptors and have been identified in all the vertebrates, from fishes to mammals, but are not present in plants, fungi, or prokaryotes. For all class B receptors, the large N-terminal extracellular domain plays a critical role in peptide hormone recognition. VIP and PACAP exert their effects through three G protein-coupled receptors, PACAP-R1, VIP-R1 (vasoactive intestinal receptor type 1, also known as VPAC1) and VIP-R2 (or VPAC2). PACAP-R1 binds only PACAP with high affinity, whereas VIP-R1 and -R2 specifically bind and respond to both VIP and PACAP. VIP and PACAP and their receptors are widely expressed in the brain and periphery. They are upregulated in neurons and immune cells in responses to CNS injury and/or inflammation and exert potent anti-inflammatory effects, as well as play important roles in the control of circadian rhythms and stress responses, among many others. VIP-R1 is preferentially coupled to a stimulatory G(s) protein, which leads to the activation of adenylate cyclase and thereby increases in intracellular cAMP level. However, depending on its cellular location, VIP-R1 is also capable of coupling to additional G proteins such as G(q) protein, thus leading to the activation of phospholipase C and intracellular calcium influx.