Trans-Activation of Mutant Follicle-Stimulating Hormone Receptors Selectively Generates Only One of Two 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.

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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

Molecular Endocrinology ◽

10.1210/mend.14.2.0422 ◽

2000 ◽

Vol 14 (2) ◽

pp. 272-284 ◽

Cited By ~ 35

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.

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

10.1101/2022.01.06.475289 ◽

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.

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

Molecular Endocrinology ◽

10.1210/mend.16.6.0852 ◽

2002 ◽

Vol 16 (6) ◽

pp. 1299-1308 ◽

Cited By ~ 43

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.

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Characterization of Two Fly LGR (Leucine-Rich Repeat-Containing, G Protein-Coupled Receptor) Proteins Homologous to Vertebrate Glycoprotein Hormone Receptors: Constitutive Activation of Wild-Type Fly LGR1 But Not LGR2 in Transfected Mammalian Cells**This study was supported by NIH Grant HD-23273. The GenBank submission number for fly LGR2 is AF274591.

Endocrinology ◽

10.1210/endo.141.11.7744 ◽

2000 ◽

Vol 141 (11) ◽

pp. 4081-4090 ◽

Cited By ~ 28

Author(s):

Shinya Nishi ◽

Sheau Yu Hsu ◽

Karen Zell ◽

Aaron J. W. Hsueh

Keyword(s):

G Protein ◽

Hormone Receptors ◽

Coupling Mechanism ◽

Leucine Rich Repeat ◽

G Protein Coupled Receptor ◽

Glycoprotein Hormone ◽

Glycoprotein Hormone Receptors ◽

Signaling Mechanisms ◽

G Protein Coupled

Abstract The receptors for lutropin (LH), FSH, and TSH belong to the large G protein-coupled receptor (GPCR) superfamily and are unique in having a large N-terminal extracellular (ecto-) domain important for interactions with the large glycoprotein hormone ligands. Recent studies indicated the evolution of a large family of the leucine-rich repeat-containing, G protein-coupled receptors (LGRs) with at least seven members in mammals. Based on the sequences of mammalian glycoprotein hormone receptors, we have identified a new LGR in Drosophila melanogaster and named it as fly LGR2 to distinguish it from the previously reported fly LH/FSH/TSH receptor (renamed as fly LGR1). Genomic analysis indicated the presence of 10 exons in fly LGR2 as compared with 16 exons in fly LGR1. The deduced fly LGR2 complementary DNA (cDNA) showed 43 and 64% similarity to the fly LGR1 in the ectodomain and transmembrane region, respectively. Comparison of 12 LGRs from diverse species indicated that these proteins can be divided into three subfamilies and fly LGR1 and LGR2 belong to different subfamilies. Potential signaling mechanisms were tested in human 293T cells overexpressing the fly receptors. Of interest, fly LGR1, but not LGR2, showed constitutive activity as reflected by elevated basal cAMP production in transfected cells. The basal activity of fly LGR1 was further augmented following point mutations of key residues in the intracellular loop 3 or transmembrane VI, similar to those found in patients with familial male precocious puberty. The present study reports the cloning of fly LGR2 and indicates that the G protein-coupling mechanism is conserved in fly LGR1 as compared with the mammalian glycoprotein hormone receptors. The characterization of fly receptors with features similar to mammalian glycoprotein hormone receptors allows a better understanding of the evolution of this unique group of GPCRs and future elucidation of their ligand signaling mechanisms.

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Rescue of defective G protein–coupled receptor function in vivo by intermolecular cooperation

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.0906695106 ◽

2010 ◽

Vol 107 (5) ◽

pp. 2319-2324 ◽

Cited By ~ 141

Author(s):

Adolfo Rivero-Müller ◽

Yen-Yin Chou ◽

Inhae Ji ◽

Svetlana Lajic ◽

Aylin C. Hanyaloglu ◽

...

Keyword(s):

G Protein ◽

G Protein Coupled Receptors ◽

Luteinizing Hormone Receptor ◽

Wild Type ◽

Gpcr Signaling ◽

Physiological Relevance ◽

Biosynthesis Activation ◽

Mutant Receptors ◽

G Protein Coupled

G protein–coupled receptors (GPCRs) are ubiquitous mediators of signaling of hormones, neurotransmitters, and sensing. The old dogma is that a one ligand/one receptor complex constitutes the functional unit of GPCR signaling. However, there is mounting evidence that some GPCRs form dimers or oligomers during their biosynthesis, activation, inactivation, and/or internalization. This evidence has been obtained exclusively from cell culture experiments, and proof for the physiological significance of GPCR di/oligomerization in vivo is still missing. Using the mouse luteinizing hormone receptor (LHR) as a model GPCR, we demonstrate that transgenic mice coexpressing binding-deficient and signaling-deficient forms of LHR can reestablish normal LH actions through intermolecular functional complementation of the mutant receptors in the absence of functional wild-type receptors. These results provide compelling in vivo evidence for the physiological relevance of intermolecular cooperation in GPCR signaling.

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FoldGPCR: Structure prediction protocol for the transmembrane domain of G protein-coupled receptors from class A

Proteins Structure Function and Bioinformatics ◽

10.1002/prot.22731 ◽

2010 ◽

Vol 78 (10) ◽

pp. 2189-2201 ◽

Cited By ~ 26

Author(s):

Mayako Michino ◽

Jianhan Chen ◽

Raymond C. Stevens ◽

Charles L. Brooks

Keyword(s):

G Protein ◽

Structure Prediction ◽

Transmembrane Domain ◽

G Protein Coupled Receptors ◽

Class A ◽

G Protein Coupled

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Regulation of G Protein–Coupled Receptor–Adenylyl Cyclase Responsiveness in Human Airway Smooth Muscle by Exogenous and Autocrine Adenosine

American Journal of Respiratory Cell and Molecular Biology ◽

10.1165/ajrcmb.24.2.4243 ◽

2001 ◽

Vol 24 (2) ◽

pp. 155-163 ◽

Cited By ~ 29

Author(s):

Stuart J. Mundell ◽

Mark E. Olah ◽

Reynold A. Panettieri ◽

Jeffrey L. Benovic ◽

Raymond B. Penn

Keyword(s):

Smooth Muscle ◽

Adenylyl Cyclase ◽

G Protein ◽

Airway Smooth Muscle ◽

G Protein Coupled Receptor ◽

Human Airway Smooth Muscle ◽

Human Airway ◽

G Protein Coupled

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Overview of Bile Acids Signaling and Perspective on the Signal of Ursodeoxycholic Acid, the Most Hydrophilic Bile Acid, in the Heart

Biomolecules ◽

10.3390/biom8040159 ◽

2018 ◽

Vol 8 (4) ◽

pp. 159 ◽

Cited By ~ 14

Author(s):

Noorul Izzati Hanafi ◽

Anis Syamimi Mohamed ◽

Siti Hamimah Sheikh Abdul Kadir ◽

Mohd Hafiz Dzarfan Othman

Keyword(s):

Heart Failure ◽

Bile Acid ◽

Chronic Heart Failure ◽

Ursodeoxycholic Acid ◽

Bile Acids ◽

G Protein ◽

Hormone Receptors ◽

Nuclear Hormone Receptors ◽

Heart Failure Patients ◽

G Protein Coupled

Bile acids (BA) are classically known as an important agent in lipid absorption and cholesterol metabolism. Nowadays, their role in glucose regulation and energy homeostasis are widely reported. BAs are involved in various cellular signaling pathways, such as protein kinase cascades, cyclic AMP (cAMP) synthesis, and calcium mobilization. They are ligands for several nuclear hormone receptors, including farnesoid X-receptor (FXR). Recently, BAs have been shown to bind to muscarinic receptor and Takeda G-protein-coupled receptor 5 (TGR5), both G-protein-coupled receptor (GPCR), independent of the nuclear hormone receptors. Moreover, BA signals have also been elucidated in other nonclassical BA pathways, such as sphingosine-1-posphate and BK (large conductance calcium- and voltage activated potassium) channels. Hydrophobic BAs have been proven to affect heart rate and its contraction. Elevated BAs are associated with arrhythmias in adults and fetal heart, and altered ratios of primary and secondary bile acid are reported in chronic heart failure patients. Meanwhile, in patients with liver cirrhosis, cardiac dysfunction has been strongly linked to the increase in serum bile acid concentrations. In contrast, the most hydrophilic BA, known as ursodeoxycholic acid (UDCA), has been found to be beneficial in improving peripheral blood flow in chronic heart failure patients and in protecting the heart against reperfusion injury. This review provides an overview of BA signaling, with the main emphasis on past and present perspectives on UDCA signals in the heart.

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