A molecular dissection of the glycoprotein hormone receptors

Vassart, Gilbert; Pardo, Leonardo; Costagliola, Sabine

doi:10.1007/3-540-34447-0_10

Cited by 94 publications

(133 citation statements)

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“…With an available crystal structure of hCG (Lapthorn et al, 1994;Wu et al, 1994;Tegoni et al, 1999), a reasonable working model of the LHR-ECD, coupled with considerable experimental structure-function data, primarily from site-directed mutagenesis, on both the hormone and receptor (Puett and Narayan, 2000;Zeng et al, 2001;Song et al, 2001a,b;Fanelli and Puett, 2002;Vischer et al, 2003a,b;Smits et al, 2003;Vassart et al, 2004), an attempt was made to generate plausible structures for the hCG-LHR-ECD complex. The 3D DOCK program (Gabb et al, 1997) was utilized for rigid-body docking; the structures were then ranked by an evaluation based on electrostatic interactions and geometrical fit, and finally the structures were filtered using several criteria for distance restraints, e.g.…”

Section: The Lhr-ecd: Structure and Hormone Bindingmentioning

confidence: 99%

A functional transmembrane complex: The luteinizing hormone receptor with bound ligand and G protein

Puett

DeMars

et al. 2007

Molecular and Cellular Endocrinology

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The luteinizing hormone receptor (LHR) is one of eight members in a cluster of the rhodopsin family of the large G protein-coupled receptor (GPCR) superfamily that contains some 800-900 genes in the human genome. LHR, along with its paralogons, follicle stimulating hormone receptor (FSHR) and thyroid stimulating hormone receptor, form one of the three classes in this cluster; the two other classes contain the relaxin-binding GPCRs and orphan GPCRs. These GPCRs are characterized by a relatively large ectodomain (ECD) containing leucine-rich-repeats (LRRs); in the class of glycoprotein hormone receptors, the LRR region is capped by N-terminal and C-terminal cysteinerich regions. Binding of human chorionic gonadotropin (hCG) or luteinizing hormone to the LHR-ECD triggers a conformational change of the transmembrane region of the receptor facilitating binding and activation of Gs, followed by effector enzyme activation and subsequent intracellular signaling. Viewing LHR as a transmembrane anchoring protein that sequentially binds hCG and Gs to give the hCG-LHR-Gs complex, numerous interactions and conformational changes must be considered. There is, unfortunately, a paucity of structural data on LHR, but crystal structures exist for hCG, the homologous FSH-FSHR-ECD (N-terminal fragment) complex, rhodopsin (in the inactive state), an active form of Gαs (transducin), and the βγ heterodimer. Using a combined experimental (site-directed mutagenesis followed by characterization in transfected cells) and computational (homology modeling and molecular dynamics simulations) approach, good working models are being developed for the protein-protein interaction faces and, in some cases, the ensuing conformational changes induced by complex formation. hCG binding to the LHR-ECD appears to involve several LRRs; LHR activation can be described in terms of disrupting a network of H-bonds in the cytosolic halves of helices 1-3, 6, and 7; and binding of LHR to Gs involves, in large part, intracellular loop 2 binding, presumably to Gsα at its C-terminus. Major gaps exist in our understanding at the molecular level of the six-polypeptide chain complex, hCG-LHR-Gs, but considerable progress has been made in the past few years.

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Section: The Lhr-ecd: Structure and Hormone Bindingmentioning

confidence: 99%

A functional transmembrane complex: The luteinizing hormone receptor with bound ligand and G protein

Puett

DeMars

et al. 2007

Molecular and Cellular Endocrinology

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“…© 2006 by The American Society for Cell Biology 2243 Vassart et al, 2004). The rLHR ectodomain splice variant differs from the full-length LHR mRNA by having a deletion of 266 base pairs, resulting from usage of an alternative splice site in exon 11 (Tsai-Morris et al, 1990;Aatsinki et al, 1992; Figure 1).…”

Section: Introductionmentioning

confidence: 99%

“…These results thus question the possibility that the variant could act as a soluble quencher of LH and hCG in the circulation and is therefore more likely to have a functional role in LH/hCG target cells by regulating the number of functional receptors. Thus it can be argued that the most prominent changes detected in transgenic mice overexpressing the variant (Apaja, Poutanen, Aatsinki, Petäjä-Repo, and Rajaniemi, unpublished results), namely alterations in pitu- itary-gonadal functions and steroidogenesis and morphological changes in the adrenals and kidneys, are likely to be caused by variant-mediated changes in the intracellular trafficking of the full-length receptor in the corresponding target cells.The LHRvariant contains all the amino acids that have been shown to be required for hormone binding (Ascoli et al, 2002;Vassart et al, 2004). Thus, it was not unexpected that it could be purified by hCG affinity chromatography when expressed in HEK293 cells.…”

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confidence: 99%

Luteinizing Hormone Receptor Ectodomain Splice Variant Misroutes the Full-Length Receptor into a Subcompartment of the Endoplasmic Reticulum

Apaja

Tuusa

Pietilä

et al. 2006

MBoC

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The luteinizing hormone receptor (LHR) is a G protein-coupled receptor that is expressed in multiple RNA messenger forms. The common rat ectodomain splice variant is expressed concomitantly with the full-length LHR in tissues and is a truncated transcript corresponding to the partial ectodomain with a unique C-terminal end. Here we demonstrate that the variant alters the behavior of the full-length receptor by misrouting it away from the normal secretory pathway in human embryonic kidney 293 cells. The variant was expressed as two soluble forms of M r 52,000 and M r 54,000, but although the protein contains a cleavable signal sequence, no secretion to the medium was observed. Only a very small fraction of the protein was able to gain hormone-binding ability, suggesting that it is retained in the endoplasmic reticulum (ER) by its quality control due to misfolding. This was supported by the finding that the variant was found to interact with calnexin and calreticulin and accumulated together with these ER chaperones in a specialized juxtanuclear subcompartment of the ER. Only proteasomal blockade with lactacystin led to accumulation of the variant in the cytosol. Importantly, coexpression of the variant with the full-length LHR resulted in reduction in the number of receptors that were capable of hormone binding and were expressed at the cell surface and in targeting of immature receptors to the juxtanuclear ER subcompartment. Thus, the variant mediated misrouting of the newly synthesized full-length LHRs may provide a way to regulate the number of cell surface receptors. INTRODUCTIONNewly synthesized proteins destined for the secretory pathway enter the endoplasmic reticulum (ER) and after correct folding and assembly are either secreted from the cell or transported to their site of action in other cellular compartments. Folding of the nascent proteins is constantly monitored by the ER quality control apparatus. It has an important task in maintaining the cellular homeostasis by preventing premature export of incompletely folded and assembled proteins and removing misfolded and unassembled ones via the ER-associated degradation (ERAD) pathway, presumably by recognizing structural signals that are enriched in incompletely folded proteins (Ellgaard and Helenius, 2003;Helenius and Aebi, 2004). Recent evidence suggests that the ER quality control does not only target permanently misfolded proteins to ERAD but may also dispose some folding competent ones, possibly due to their slow folding kinetics. This applies also to several polytopic membrane proteins, including G protein-coupled receptors (GPCRs; Petäjä-Repo et al., 2000;Imai et al., 2001;Lu et al., 2003;Wü ller et al., 2004;Pietilä et al., 2005). Thus, export from the ER is the limiting step in their expression and probably provides a mean to regulate the number of functional receptors at the cell surface. This is supported by our recent finding that final maturation of the rat luteinizing hormone receptor (rLHR) was found to be developmentally regulated in targ...

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“…Glycoprotein hormone receptors (GpHrs) constitute a subfamily of rhodopsin-like GPCRs responsible for signal transduction by thyrotropin (TSH), lutropin or chorionic gonadotropin (LH/CG), and follitropin (FSH) 2,3 . Because cells express several GPCR subtypes, signal transduction is both temporally and spatially integrated to generate the appropriate cellular response on activation of several receptors.…”

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confidence: 99%

“…Whereas direct interaction between the agonist and different regions of the TMD takes place for the majority of GPCRs, a favoured current model holds that GpHr activation involves switching of the ECD from an inverse agonist into a tethered agonist of the TMD, on binding of the hormone 3,15 . This model provides a rational explanation to the observation that the TSHr can be activated by binding of ligands with little, if any sequence identity (TSH, thyrostimulin, autoantibodies) as well as by point mutation in a specific residue of the ECD 3,16,17 .…”

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confidence: 99%

Evidence for activity-regulated hormone-binding cooperativity across glycoprotein hormone receptor homomers

et al. 2012

Self Cite

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Glycoprotein hormone receptors show strong negative cooperativity. As a consequence, at physiological hormone concentrations, a single agonist binds to a receptor dimer. Here we present evidence that constitutively active receptors lose cooperative allosteric regulation in direct relation with their basal activity. The most constitutive mutants lost nearly all cooperativity and showed an increase of initial tracer binding, reflecting the ability of each protomer to bind with equal affinity. Allosteric interaction between the protomers takes place at the transmembrane domain. The allosteric message resulting from hormone binding to the ectodomain of one protomer travels 'downward' to its transmembrane domain, before affecting the transmembrane domain of the other protomer. This results in transmission of an 'upward' message lowering the binding affinity of the ectodomain of the second protomer. our results demonstrate a direct relation between the conformational changes associated with activation of the transmembrane domain and the allosteric behaviour of glycoprotein hormone receptors dimers.

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A molecular dissection of the glycoprotein hormone receptors

Cited by 94 publications

References 58 publications

A functional transmembrane complex: The luteinizing hormone receptor with bound ligand and G protein

A functional transmembrane complex: The luteinizing hormone receptor with bound ligand and G protein

Luteinizing Hormone Receptor Ectodomain Splice Variant Misroutes the Full-Length Receptor into a Subcompartment of the Endoplasmic Reticulum

Evidence for activity-regulated hormone-binding cooperativity across glycoprotein hormone receptor homomers

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