Vasoactive intestinal peptide (VIP) is a 28 amino acid peptide (human, chr 6q26-q27). It is expressed and secreted by neurons innervating primary and secondary immune organs such as lymph nodes with a mol. wt of 20kD. VIP is a potent neurotrophic factor causes vasodilation, lowers arterial blood pressure, and relaxes the smooth muscle of trachea, stomach and gall bladder. VIP also modulates several T-lymphocyte activities including motility, cytokine production, proliferation and apoptosis, VIP exerts its biological activity by binding to two closely related class II G-protein-coupled receptors VPAC-1 and VPAC-2 beside this VIP has its own receptors VIPR1&2 (Vasoactive Intestinal Polypeptide Receptor 1&2) and VIPRRP (VIP receptor-gene repressor protein). VIP shows similarities to glucagon, secretin and gastric inhibitory peptide (GIP) as such it has been considered a member of the glucagon-secretin family. The VIP is 100% conserved in mouse, rat and human. VIP is considered to be a viable candidate for the development of treatments for rheumatoid arthritis, since treatment with VIP significantly reduced incidence of severity of arthritis, the therapeutic effect of VIP was associated with down regulation of both inflammatory and autoimmune components of the disease.

The VIP receptor, VIPR mediated by G-proteins activates Adenylyl cyclase, it is an integral membrane protein mainly expressed in lung, liver, kidney, heart and placenta and belongs to the family 2 of G-protein coupled receptors, the other receptor VIPRRP demonstrates the transcriptional repressor of vasoactive intestinal peptide receptor (VIPR) gene constitutes a 42-base pair core element that is the binding site for a nuclear protein. This element was able to confer transcriptional repression to a heterologous promoter and that deletion or point mutations with in this element resulted in loss of transcriptional repression. Thus the expression of VIPR is regulated by multiple transcription factors including VIPRRP.

VIPR1 is a 457aa (chr. 3p22) glycosylated receptor in human (459aa in rat, 459aa in mouse) has a signal peptide sequence with several transmembrane domains. The VIP receptor 1 is also termed as type II PACAP receptor, RCD1. It is predominantly expressed in cholinergic presynaptic neurons of the central nervous system and in peripheral peptidergic neurons innervating diverse tissues. The Highly conserved aspartate 68, tryptophan 73 and glycine 109 in the N-terminal extracellular domain of the human VIP receptor are essential for its ability to bind VIP. VIPR1 appears in two isoforms, a long form/ hIVR5 and a short form/ hIVR8 formed after alternative splicing.

VIPR2, a 438aa (chr.7q36.3) protein in human (437aa in rat and mouse). The VIP receptor2 is also termed as type III PACAP receptor, mainly expressed in neural tissues. This is a receptor for VIP as well as PACAP 38 and 27, the activity of this receptor is mediated by G proteins, which activates adenyly cyclase and can be coupled to phospholipase C. It shows 86% sequence homology with rat VIPR2.

VIPRRP is a novel transcriptional repressor protein (656aa, rat) that regulates VIPR expression; it encodes a 72kD novel protein that interacts specifically with VIPR repressor element. Expression of VIPRRP led to transcriptional repression, thus indicating, positive and negative factors interact with VIPR promoter to regulate its expression. The VIPRRP is 78% identical to a previously characterized protein, differentiation-specific element binding protein, which is a member of a family of proteins including components of DNA replication factor C complex.

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a bioactive peptide (human 176aa, 175 each in mouse and rat) that was originally isolated from ovine hypothalamus on the basis of its ability to stimulate adenylate cyclase and functions as a neurotransmitter and neuromodulator The N-terminal amino acid sequence of PACAP shows 68% identity with VIP and more limited similarity with growth hormone-releasing hormone.

PRP (PACAP Related Peptide), a 29 amino-acid region of the PACAP precursor protein, has been synthesized in quantities sufficient for biological and structural studies. PRP has a distinct biological activity on the gallbladder that is similar to PACAP, but opposite to that of VIP and its related peptide, PHM.

PHM (Peptide Histidine-Methionine) is a 27aa peptide (Chr 6q26-q27) in human with a mol. wt of 20kD, belongs to the Glucagon family causes vasodilation. Expressed in gastrointestinal tissues and neural tissue, possibly as neurotransmitter.

Rb=rabbit; m=mouse; r=rat; h=human; s=sheep; b=bovine; c=chicken; d=dog; ~CT or ~NT=near C or N-terminus. EC=Extracellular; CL=Cytoplasmic loop;

* Expected antibody crossreactivity information is mostly based upon high (>70%) sequence conservation of antigenic/control peptides in various species. When antibody crossreactivity has actually been experimentally confirmed in various species, it will be mentioned in the appropriate data sheets.

"Neat Antisera or antisera" are the unpurified antiserum and it is suitable for ELISA and Western.
"Affinity pure" IgG may be more suitable for immunohistochemical (IHC) applications and to reduce background in most immunological applications including ELISA and Western.
"Control peptides" can not be used for Western as they are very short peptides. They are intended for ELISA or antibody blocking studies to establish antibody specificity.
Western blot +ve protein controls, where available, are semi-pure, pure or recombinant proteins that are formulated in SDS-PAGE sample buffer. They are recommended to be used for Western (load 10 ul/lane) for visualization with antibodies.