VPAC2 (VIPR2) is a receptor for vasoactive intestinal peptide, a small neuropeptide. Vasoactive intestinal peptide is involved in smooth muscle relaxation, exocrine and endocrine secretion, and water and ion flux in lung and intestinal epithelia. Its actions are effected through integral membrane receptors associated with a guanine nucleotide binding protein which activates adenylate cyclase. In immunohistochemistry, VPAC2 has membranous positivity in tissues throughout the body. It is also upregulated in gastric, thyroid, lung, pancreatic, and neuroendocrine tumors. References: Endocr Connect. 2015 Mar 1; 4(1): 18–26, PMID: 25504760