Scientific Reference
VIP
Evidence profile: Predominantly preclinical
Vasoactive intestinal peptide was named for what its discoverers saw first, relaxation of blood vessels, after isolating it from gut tissue. It is a 28-residue amidated neuropeptide present in central and peripheral neurons and in the intestinal wall, a member of the secretin-glucagon family and a close relative of PACAP, with which it shares receptors. Today it is investigated as a neurotransmitter, a smooth-muscle signal and a link between nervous and immune systems. Most evidence comes from cells, tissues and animals. Small human studies of synthetic VIP exist, including for pulmonary (lung) conditions, though its removal from blood within minutes complicates them.
Mechanism of Action
Two class B GPCRs, VPAC1 and VPAC2, bind VIP with comparable affinity; the PACAP-preferring PAC1 receptor binds it far more weakly. VPAC receptors mostly signal through Gs, cyclic AMP and protein kinase A, although other G proteins have been reported. In cultured immune cells that signalling changes cytokine output and T-cell differentiation. Mouse work places VIP at VPAC2 in the suprachiasmatic nucleus as a synchroniser of clock neurons, and smooth-muscle preparations have treated it as a relaxing signal.
Molecular Information
- Type: Neuropeptide
- Molecular weight: 3326.8 g/mol
- Molecular formula: C147H237N43O43S