Rescue of expression and signaling of human luteinizing hormone G protein-coupled receptor mutants with an allosterically binding small-molecule agonist

• Published in: Proceedings of the National Academy of Sciences - PNAS 2011-04, Vol.108 (17), p.7172-7176
• Main Authors: Newton, Claire L, Whay, Adele M, McArdle, Craig A, Zhang, Meilin, van Koppen, Chris J, van de Lagemaat, Ruud, Segaloff, Deborah L, Millar, Robert P
• Format: Article
• Language: English
• Subjects: Agonists; Allosteric Regulation - drug effects; Allosteric Regulation - genetics; Amino Acid Substitution; Binding sites; Biochemistry; Biological Sciences; Cell Membrane - genetics; Cell Membrane - metabolism; Cell membranes; Cell surface receptors; cytoplasm; Female; Fertility Agents - pharmacology; Gene expression; Gene Expression Regulation - drug effects; Gene Expression Regulation - genetics; Genetic mutation; glycosylation; Glycosylation - drug effects; HEK293 Cells; Hormones; Humans; Infertility - drug therapy; Infertility - genetics; Infertility - metabolism; Leydig cells; LH receptors; Ligands; luteinizing hormone; Luteinizing Hormone - pharmacology; luteinizing hormone receptors; Male; Medical treatment; Molecular chemistry; Mutants; Mutation; Mutation, Missense; pathogenesis; patients; Pharmacology; plasma membrane; Protein folding; Protein Transport - drug effects; Protein Transport - genetics; Proteins; Receptors; Receptors, LH - agonists; Receptors, LH - biosynthesis; Receptors, LH - genetics
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1015723108

Naturally occurring mutations of G protein-coupled receptors (GPCRs) causing misfolding and failure to traffic to the cell surface can result in disease states. Some small-molecule orthosteric ligands can rescue such misfolded receptors, presumably by facilitating their correct folding and shuttling to the plasma membrane. Here we show that a cell-permeant, allosterically binding small-molecule agonist (Org 42599) rescues the folding and cell surface expression, and therefore target cell signaling, of mutant human luteinizing hormone (LH) receptors (A593P and S616Y) that cause Leydig cell hypoplasia in man. Both mutant receptors were retained in the cytoplasm whereas WT receptor localized at the cell membrane, and binding of LH to cells expressing the mutant receptors was markedly lower than to those expressing the WT receptor. Incubation with Org 42599 increased mutant receptor expression, cell surface localization, and the proportion of mutant receptor in the mature glycosylated form. Importantly, although LH stimulated little (S616Y) or no (A593P) activation of cells expressing mutant receptors, incubation of cells with Org 42599 facilitated rescue of expression and stimulation by the native ligand, LH. Although Org 42599 could activate these receptors, it could not displace ¹²⁵I-labeled human LH binding to the WT receptor, indicating that it acts in an allosteric manner. Here we demonstrate a small-molecule GPCR allosteric agonist that functionally rescues intracellularly retained mutant LH receptors by facilitating their cell surface expression. This approach may have application for treatment of infertile patients bearing such mutations and, more broadly, for other misfolded GPCR mutants resulting in human pathologic processes.