glycoprotein hormone receptors and leucine-rich repeats containing G protein-coupled receptors, member of the class A family of seven-transmembrane G protein-coupled receptors
This subfamily includes the glycoprotein hormone receptors (GPHRs), vertebrate receptors containing 17 leucine-rich repeats (LGR4-6), and the relaxin family peptide receptors (also known as LGR7 and LGR8). They are seven transmembrane domain receptors with a very large extracellular N-terminal domain containing many leucine-rich repeats responsible for hormone recognition and binding. The glycoprotein hormone receptor family contains receptors for the pituitary hormones, thyrotropin (thyroid-stimulating hormone receptor), follitropin (follicle-stimulating hormone receptor), and lutropin (luteinizing hormone receptor). Glycoprotein hormone receptors couple primarily to the G(s)-protein and promotes cAMP production, but also to the G(i)- or G(q)-protein. Two orphan GPCRs, LGR7 and LGR8, have been recently identified as receptors for the relaxin peptide hormones.