title: Activation of the luteinizing hormone receptor in the extracellular domain.
abstract: Glycoprotein hormone receptors have ligand-binding ectodomains consisting of leucine-rich repeats, followed by a conserved cysteine-rich hinge region to the seven transmembrane (TM) region. Based on constitutively active mutations at Ser-281 in the hinge region of the thyroid-stimulating hormone receptor, we mutated the conserved serine in the luteinizing hormone (LH) receptor (S277I) and observed increased basal cAMP production and ligand affinity by mutant receptor. Conversion of Ser-277 to all natural amino acids led to varying degrees of receptor activation. Hydropathy index analysis indicated that substitution of neutral serine with selective nonpolar hydrophobic residues (Leu>Val>Met>Ile) confers constitutive receptor activation. Furthermore, mutation of the angular proline near Ser-273 to flexible Gly also led to receptor activation. The findings suggest the ectodomain of LH receptor constrains the TM region. Point mutations in the hinge region or ligand binding could cause conformational changes in the TM region that result in Gs activation.
authors.affiliation: Division of Reproductive Biology, Department of Gynecology and Obstetrics, Stanford University School of Medicine, Stanford, CA, USA. nakabayashi@japan.com
authors.forename: Koji
authors.initials: K
authors.lastname: Nakabayashi
authors.forename: Masataka
authors.initials: M
authors.lastname: Kudo
authors.forename: Aaron J W
authors.initials: AJ
authors.lastname: Hsueh
authors.forename: Takeshi
authors.initials: T
authors.lastname: Maruo
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D017124:Conserved Sequence; D000242:Cyclic AMP / Q000096:biosynthesis; D019205:GTP-Binding Protein alpha Subunits, Gs / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D008024:Ligands; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D011974:Receptors, LH / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction
chemical_list: D008024:Ligands; D011974:Receptors, LH; D000242:Cyclic AMP; D019205:GTP-Binding Protein alpha Subunits, Gs