RXFP4 is a receptor with high affinity for INSL5. It also binds RLN3/relaxin-3, bradykinin and kallidin. Binding of ligands to RXFP4 results in an inhibition of adenylate cyclase. It may play an important role in autocrine and paracrine signaling and the regulation of insulin secretion and ß-cell homeostasis in the normal colon and also in neuroendocrine tumors. In immunohistochemistry, RXFP4 has moderate membranous positivity throughout the central nervous system, and in peripheral tissues is found on neuroendocrine cells, in adrenal tissue, smooth muscle, and on epithelial cells in various tissues including the colon, pancreas, breast, prostate and endometrium. References: Br J Pharmacol. 2007 Mar; 150(6): 677–691, PMID: 17293890; Oncol Rep. 2013 Jan;29(1):149-54, PMID: 23128569