relaxin family peptide receptors, member of the class A family of seven-transmembrane G protein-coupled receptors
This group includes relaxin/insulin-like family peptide receptor 1 (RXFP1 or LGR7) and 2 (RXFP2 or LGR8), which contain a very large extracellular N-terminal domain with numerous leucine-rich repeats responsible for hormone recognition and binding. Relaxin is a member of the insulin superfamily that has diverse actions in both reproductive and non-reproductive tissues. The relaxin-like peptide family includes relaxin-1, relaxin-2, and the insulin-like (INSL) peptides such as INSL3, INSL4, INSL5 and INSL6. The relaxin family peptides share high structural but low sequence similarity, and exert their physiological functions by activating a group of four GPCRs, RXFP1-4. Relaxin and INSL3 are the endogenous ligands for RXFP1 and RXFP2, respectively. Upon receptor binding, relaxin activates a variety of signaling pathways to produce second messengers such as cAMP.