scholarly journals Cis- and Trans-Activation of Hormone Receptors: the LH Receptor

2002 ◽  
Vol 16 (6) ◽  
pp. 1299-1308 ◽  
Author(s):  
Inhae Ji ◽  
ChangWoo Lee ◽  
YongSang Song ◽  
P. Michael Conn ◽  
Tae H. Ji
Keyword(s):  
Adenylyl Cyclase ◽  
Hormone Receptors ◽  
Transmembrane Domain ◽  
Wide Spectrum ◽  
Receptor Activation ◽  
Inherited Disorders ◽  
Glycoprotein Hormone ◽  
Lh Receptor ◽  
Amino Terminal ◽  
Gpcr Activation

Abstract G protein-coupled receptors (GPCRs) accommodate a wide spectrum of activators from ions to glycoprotein hormones. The mechanism of activation for this large and clinically important family of receptors is poorly understood. Although initially thought to function as monomers, there is a growing body of evidence that GPCR dimers form, and in some cases that these dimers are essential for signal transduction. Here we describe a novel mechanism of intermolecular GPCR activation, which we refer to as trans-activation, in the LH receptor, a GPCR that does not form stable dimers. The LH receptor consists of a 350-amino acid amino-terminal domain, which is responsible for high-affinity binding to human CG, followed by seven-transmembrane domains and connecting loops. This seven-transmembrane domain bundle transmits the signal from the extracellular amino terminus to intracellular G proteins and adenylyl cyclase. Here, we show that binding of hormone to one receptor can activate adenylyl cyclase through its transmembrane bundle, intramolecular activation (cis-activation), as well as trans-activation through the transmembrane bundle of an adjacent receptor, without forming a stable receptor dimer. Coexpression of a mutant receptor defective in hormone binding and another mutant defective in signal generation rescues hormone-activated cAMP production. Our observations provide new insights into the mechanism of receptor activation mechanisms and have implications for the treatment of inherited disorders of glycoprotein hormone receptors.

scholarly journals Trans-Activation of Mutant Follicle-Stimulating Hormone Receptors Selectively Generates Only One of Two Hormone Signals

2004 ◽  
Vol 18 (4) ◽  
pp. 968-978 ◽  
Author(s):  
Inhae Ji ◽  
ChangWoo Lee ◽  
MyoungKun Jeoung ◽  
YongBum Koo ◽  
Gail A. Sievert ◽  
...  
Keyword(s):  
Adenylyl Cyclase ◽  
G Protein ◽  
Hormone Receptors ◽  
Transmembrane Domain ◽  
Signal Generation ◽  
Lh Receptor ◽  
Glycosyl Phosphatidylinositol ◽  
Mutant Receptors ◽  
G Protein Coupled ◽  
Hormone Signals

Abstract Previously, we reported that a liganded LH receptor (LHR) is capable of activating itself (cis-activation) and other nonliganded LHRs to induce cAMP (trans-activation). Trans-activation of the LHR raises two crucial questions. Is trans-activation unique to LHR or common to other G protein-coupled receptors? Does trans-activation stimulate phospholipase Cβ as it does adenylyl cyclase? To address these questions, two types of novel FSH receptors (FSHRs) were constructed, one defective in hormone binding and the other defective in signal generation. The FSHR, a G protein-coupled receptor, comprises two major domains, the N-terminal extracellular exodomain that binds the hormone and the membrane-associated endodomain that generates the hormone signals. For signal defective receptors, the exodomain was attached to glycosyl phosphatidylinositol (ExoGPI) or the transmembrane domain of CD8 immune receptor (ExoCD). ExoGPI and ExoCD can trans-activate another nonliganded FSH. Surprisingly, the trans-activation generates a signal to activate either adenylyl cyclase or phospholipase Cβ, but not both. These results indicate that trans-activation in these mutant receptors is selective and limited in signal generation, thus providing new approaches to investigating the generation of different hormone signals and a novel means to selectively generate a particular hormone signal. Our data also suggest that the FSHR’s exodomain could not trans-activate LHR.

scholarly journals The Nematode Leucine-Rich Repeat-Containing, G Protein-Coupled Receptor (LGR) Protein Homologous to Vertebrate Gonadotropin and Thyrotropin Receptors is Constitutively Activated in Mammalian Cells

2000 ◽  
Vol 14 (2) ◽  
pp. 272-284 ◽  
Author(s):  
Masataka Kudo ◽  
Thomas Chen ◽  
Koji Nakabayashi ◽  
Sheau Yu Hsu ◽  
Aaron J. W. Hsueh
Keyword(s):  
G Protein ◽  
Hormone Receptors ◽  
Receptor Activation ◽  
Leucine Rich Repeat ◽  
Camp Production ◽  
Glycoprotein Hormone ◽  
Lh Receptor ◽  
Glycoprotein Hormone Receptors ◽  
Leucine Rich Repeats ◽  
G Protein Coupled

Abstract The receptors for LH, FSH, and TSH belong to the large G protein-coupled, seven-transmembrane (TM) protein family and are unique in having a large N-terminal extracellular (ecto-) domain containing leucine-rich repeats important for interactions with the large glycoprotein hormone ligands. Recent studies indicated the evolution of an expanding family of homologous leucine-rich repeat-containing, G protein-coupled receptors (LGRs), including the three known glycoprotein hormone receptors; mammalian LGR4 and LGR5; and LGRs in sea anemone, fly, and snail. We isolated nematode LGR cDNA and characterized its gene from the Caenorhabditis elegans genome. This receptor cDNA encodes 929 amino acids consisting of a signal peptide for membrane insertion, an ectodomain with nine leucine-rich repeats, a seven-TM region, and a long C-terminal tail. The nematode LGR has five potential N-linked glycosylation sites in its ectodomain and multiple consensus phosphorylation sites for protein kinase A and C in the cytoplasmic loop and C tail. The nematode receptor gene has 13 exons; its TM region and C tail, unlike mammalian glycoprotein hormone receptors, are encoded by multiple exons. Sequence alignments showed that the TM region of the nematode receptor has 30% identity and 50% similarity to the same region in mammalian glycoprotein hormone receptors. Although human 293T cells expressing the nematode LGR protein do not respond to human glycoprotein hormones, these cells exhibited major increases in basal cAMP production in the absence of ligand stimulation, reaching levels comparable to those in cells expressing a constitutively activated mutant human LH receptor found in patients with familial male-limited precocious puberty. Analysis of cAMP production mediated by chimeric receptors further indicated that the ectodomain and TM region of the nematode LGR and human LH receptor are interchangeable and the TM region of the nematode LGR is responsible for constitutive receptor activation. Thus, the identification and characterization of the nematode receptor provides the basis for understanding the evolutionary relationship of diverse LGRs and for future analysis of mechanisms underlying the activation of glycoprotein hormone receptors and related LGRs.

scholarly journals Autoantibody and hormone activation of the thyrotropin G protein-coupled receptor

2022 ◽  
Author(s):  
Bryan Faust ◽  
Isha Singh ◽  
Kaihua Zhang ◽  
Nicholas Hoppe ◽  
Antonio F.M. Pinto ◽  
...  
Keyword(s):  
Thyroid Hormones ◽  
G Protein ◽  
Conformational Changes ◽  
Hormone Receptors ◽  
Transmembrane Domain ◽  
Extracellular Domain ◽  
Receptor Activation ◽  
Glycoprotein Hormone ◽  
Membrane Bilayer ◽  
G Protein Coupled

Thyroid hormones are vital to growth and metabolism. Thyroid hormone synthesis is controlled by thyrotropin (TSH), which acts at the thyrotropin receptor (TSHR). Autoantibodies that activate the TSHR pathologically increase thyroid hormones in Graves' disease. How autoantibodies mimic TSH function remains unclear. We determined cryogenic-electron microscopy structures of active and inactive TSHR. In inactive TSHR, the extracellular domain lies close to the membrane bilayer. TSH selects an upright conformation of the extracellular domain due to steric clashes between a conserved hormone glycan and the membrane bilayer. An activating autoantibody selects a similar upright conformation of the extracellular domain. Conformational changes in the extracellular domain are transduced to the seven transmembrane domain via a conserved hinge domain, a tethered peptide agonist, and a phospholipid that binds within the seven transmembrane domain. Rotation of the TSHR ECD relative to the membrane bilayer is sufficient for receptor activation, revealing a shared mechanism for other glycoprotein hormone receptors that may also extend to G protein-coupled receptors with large extracellular domains.

scholarly journals Actions of the Small Molecule Ligands SW106 and AH-3960 on the Type-1 Parathyroid Hormone Receptor

2015 ◽  
Vol 29 (2) ◽  
pp. 307-321 ◽  
Author(s):  
Percy H. Carter ◽  
Thomas Dean ◽  
Brijesh Bhayana ◽  
Ashok Khatri ◽  
Raj Rajur ◽  
...  
Keyword(s):  
Parathyroid Hormone ◽  
Small Molecule ◽  
Hormone Receptor ◽  
Transmembrane Domain ◽  
Receptor Activation ◽  
Blood Calcium ◽  
Parathyroid Hormone Receptor ◽  
Peptide Analog ◽  
Amino Terminal ◽  
Small Molecule Ligands

Abstract The parathyroid hormone receptor-1 (PTHR1) plays critical roles in regulating blood calcium levels and bone metabolism and is thus of interest for small-molecule ligand development. Of the few small-molecule ligands reported for the PTHR1, most are of low affinity, and none has a well-defined mechanism of action. Here, we show that SW106 and AH-3960, compounds previously identified to act as an antagonist and agonist, respectively, on the PTHR1, each bind to PTHR1-delNT, a PTHR1 construct that lacks the large amino-terminal extracellular domain used for binding endogenous PTH peptide ligands, with the same micromolar affinity with which it binds to the intact PTHR1. SW106 antagonized PTHR1-mediated cAMP signaling induced by the peptide analog, M-PTH(1–11), as well as by the native PTH(1–9) sequence, as tethered to the extracellular end of transmembrane domain (TMD) helix-1 of the receptor. SW106, however, did not function as an inverse agonist on either PTHR1-H223R or PTHR1-T410P, which have activating mutations at the cytoplasmic ends of TMD helices 2 and 6, respectively. The overall data indicate that SW106 and AH-3960 each bind to the PTHR1 TMD region and likely to within an extracellularly exposed area that is occupied by the N-terminal residues of PTH peptides. Additionally, they suggest that the inhibitory effects of SW106 are limited to the extracellular portions of the TMD region that mediate interactions with agonist ligands but do not extend to receptor-activation determinants situated more deeply in the helical bundle. The study helps to elucidate potential mechanisms of small-molecule binding at the PTHR1.

scholarly journals Modulation of PTH1R signaling by an ECD binding antibody results in inhibition of β-arrestin 2 coupling

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Kaushik Sarkar ◽  
Lisa Joedicke ◽  
Marta Westwood ◽  
Rebecca Burnley ◽  
Michael Wright ◽  
...  
Keyword(s):  
Parathyroid Hormone ◽  
Conformational Changes ◽  
Transmembrane Domain ◽  
Receptor Activation ◽  
Parathyroid Hormone Receptor ◽  
Exchange Mass Spectrometry ◽  
Gpcr Activation ◽  
Hydrogen Deuterium ◽  
Binding Antibody ◽  
Hdx Ms

Abstract Parathyroid hormone receptor 1 (PTH1R) belongs to the secretin class of G protein coupled receptors (GPCRs) and natively binds parathyroid hormone (PTH) and parathyroid hormone related peptide (PTHrP). Ligand binding to PTH1R involves binding to the large extracellular domain (ECD) and the orthosteric pocket, inducing conformational changes in the transmembrane domain and receptor activation. PTH1R regulates bone metabolism, signaling mainly through Gs and Gq/11 G-proteins. Here, we used phage display to generate PTH1R ECD-specific antibodies with the aim of modulating receptor functionality. We identified ECD-scFvhFc, which exhibited high affinity binding to both the isolated ECD and to the full-length receptor in styrene-maleic acid (SMA) lipid particles. Epitope mapping using hydrogen-deuterium exchange mass spectrometry (HDX-MS) indicates that the α1 helix of the ECD is ECD-scFvhFc’s epitope which may partially overlap with the known PTH (1–34) binding site. However, PTH (1–34)-mediated Gs activation is Undisturbed by ECD-scFvhFc binding. In contrast, ECD-scFvhFc potently inhibits β-arrestin-2 recruitment after PTH (1–34)-driven receptor activation and thus represents the first monoclonal antibody to selectively inhibit distinct PTH1R signaling pathways. Given the complexity of PTH1R signaling and the emerging importance of biased GPCR activation in drug development, ECD-scFvhFc could be a valuable tool to study PTH1R signaling bias.

Intervention Strategies into Glycoprotein Hormone Receptors for Modulating (Mal–)function, with Special Emphasis on the TSH Receptor

2018 ◽  
Vol 50 (12) ◽  
pp. 894-907 ◽  
Author(s):  
Gerd Krause ◽  
Patrick Marcinkowski
Keyword(s):  
Small Molecule ◽  
Hormone Receptors ◽  
Transmembrane Domain ◽  
Current Knowledge ◽  
Special Focus ◽  
Glycoprotein Hormone ◽  
Autoimmune Thyroid ◽  
Glycoprotein Hormone Receptors ◽  
Lack Of Information ◽  
Blocking Antibodies

AbstractThe thyrotropin receptor (TSHR), the lutropin- (LHR), and the follicotropin receptor (FSHR) belong to glycoprotein hormone receptors (GPHR), a subgroup of the class A G-protein coupled receptors. In this review, the unique features of GPHR have been taken into account for their pharmacological interventions: i) The respective hormone and stimulating or blocking antibodies are binding on the large ectodomain that is ii) via a hinge region, containing iii) an internal tethered agonist linked to the transmembrane domain. iv) Multimerization and mechanisms for negative or positive cooperativity of GPHR upon ligand binding and v) dimer- and oligomeric arrangements enabling trans-activation on GPHR signaling are considered. Available knowledge concerning the modulation of the GPHR (mal)-function and associated structural aspects by diverse entities such as antibodies, chaperones, peptides, small molecule agonists, inverse agonists, and antagonists is summarized. The TSHR is important with respect to autoimmune [Graves’ disease (GD), Graves’ orbitopathy (GO)] or non-autoimmune thyroid dysfunctions and cancer-development. To date there is neither an agonist nor antagonist modulator of pathogenic such as TSHR signaling in the clinics. However, several different ligands monoclonal stimulating and inhibiting antibodies and small molecule drug-like ligands have been reported in the last decade. In special focus are the most recent findings regarding the development and use of small molecule TSHR ligands. Finally, limitations of current knowledge and lack of information are discussed highlighting the need for intensified efforts towards understanding the interplay of TSHR multimers, especially their interaction with drug-like ligands. Important in this context is the biased ligand development.

scholarly journals Revisiting and Questioning Functional Rescue between Dimerized LH Receptor Mutants

2012 ◽  
Vol 26 (4) ◽  
pp. 655-668 ◽  
Author(s):  
Meilin Zhang ◽  
Rongbin Guan ◽  
Deborah L. Segaloff
Keyword(s):  
Chorionic Gonadotropin ◽  
Human Chorionic Gonadotropin ◽  
Hormone Receptors ◽  
Resonance Energy ◽  
Extracellular Domain ◽  
Glycoprotein Hormone ◽  
Lh Receptor ◽  
Defective Mutant

Abstract The glycoprotein hormone receptors are G protein-coupled receptors containing a large extracellular domain fused to a prototypical serpentine domain. cis-activation occurs when binding of hormone to the extracellular domain stabilizes the serpentine domain in an active conformation. Studies by others suggested that these receptors can also signal by trans-activation, where hormone binding to one receptor protomer activates the serpentine domain of an associated protomer, as documented by the partial rescue of hormone-dependent signaling when a binding defective mutant is coexpressed with a signaling defective mutant. However, our characterizations of several LH receptor (LHR) mutants used in previous studies differ markedly from those originally reported. Also, when examining a pair of LHR mutants previously shown to functionally rescue in vitro as well as in vivo, in addition to finding that the properties of the individual mutants differ significantly from those originally described, we determined that when this pair of mutants was coexpressed in vitro, quantitative analyses did not indicate functional rescue. Additional data are presented that provide a plausible alternate explanation for the apparent in vivo trans-activation that was reported. Finally, using LHR mutants that we have documented to be expressed at the cell surface but to lack human chorionic gonadotropin binding activity or to be severely impaired in their ability to activate Gs, we did not observe functional rescue of human chorionic gonadotropin-stimulated cAMP when the mutants were coexpressed, even though bioluminescence resonance energy transfer analyses confirmed that the coexpressed mutants formed dimers. Taken altogether, our data substantively question the concept of functional rescue between LHR mutants.

scholarly journals Role of the Third Intracellular Loop for the Activation of Gonadotropin Receptors

1999 ◽  
Vol 13 (2) ◽  
pp. 181-190 ◽  
Author(s):  
Angela Schulz ◽  
Torsten Schöneberg ◽  
Ralf Paschke ◽  
Günter Schultz ◽  
Thomas Gudermann
Keyword(s):  
Amino Acid ◽  
Receptor Activation ◽  
Receptor Activity ◽  
Tsh Receptor ◽  
Activation Mechanism ◽  
Glycoprotein Hormone ◽  
Gonadotropin Receptors ◽  
Lh Receptor ◽  
Deletion Mutations ◽  
The Third

Abstract Hyperfunctional endocrine thyroid and testicular disorders can frequently be traced back to gain-of-function mutations in glycoprotein hormone receptor genes. Deletion mutations in the third intracellular (i3) loop of the TSH receptor have recently been identified as a cause of constitutive receptor activity. To examine whether the underlying mechanism of receptor activation applies to all glycoprotein hormone receptors, we created deletion mutations in the LH and FSH receptors. In analogy to the situation with the TSH receptor, a deletion of nine amino acids resulted in constitutive activity irrespective of the location of deletions within the i3 loop of the LH receptor. In contrast, only one (Δ563–566) of four different 4-amino acid deletion mutants displayed agonist-independent activity. Systematic examination of the structural requirements for this effect in the Δ563–566 mutant revealed that only deletions including D564 resulted in constitutive receptor activity. Replacement of D564 by G, K, and N led to agonist-independent cAMP formation while introduction of a negatively charged E silenced constitutive receptor activity, indicating that an anionic amino acid at this position may be required to maintain an inactive receptor conformation. Insertion of A residues up- and downstream of D564 did not perturb receptor quiescence, showing that a certain degree of spatial freedom of the negatively charged amino acid within the context of the i3 loop is well tolerated. In contrast to the results obtained with the LH receptor, deletion of the corresponding D567 from the i3 loop of the FSH receptor did not cause constitutive receptor activation, highlighting significant differences in the activation mechanism of gonadotropin receptors.

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