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75 results on '"A Levoye"'

59. The CXCL12γ Chemokine Displays Unprecedented Structural and Functional Properties that Make It a Paradigm of Chemoattractant Proteins

Author

Rueda, Patricia, primary, Balabanian, Karl, additional, Lagane, Bernard, additional, Staropoli, Isabelle, additional, Chow, Ken, additional, Levoye, Angelique, additional, Laguri, Cedric, additional, Sadir, Rabia, additional, Delaunay, Thierry, additional, Izquierdo, Elena, additional, Pablos, Jose Luis, additional, Lendinez, Elena, additional, Caruz, Antonio, additional, Franco, Diego, additional, Baleux, Françoise, additional, Lortat-Jacob, Hugues, additional, and Arenzana-Seisdedos, Fernando, additional

Published
2008
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67. The orphan GPR50 receptor specifically inhibits MT1 melatonin receptor function through heterodimerization.

Author

Levoye, Angélique, Dam, Julie, Ayoub, Mohammed A., Guillaume, Jean-Luc, Couturier, Cyril, Delagrange, Philippe, and Jockers, Ralf

Subjects
CELL receptors, MELATONIN, G proteins, CELLULAR signal transduction, DIMERS, CHEMICAL inhibitors
Abstract

One-third of the ∼400 nonodorant G protein-coupled receptors (GPCRs) are still orphans. Although a considerable number of these receptors are likely to transduce cellular signals in response to ligands that remain to be identified, they may also have ligand-independent functions. Several members of the GPCR family have been shown to modulate the function of other receptors through heterodimerization. We show that GPR50, an orphan GPCR, heterodimerizes constitutively and specifically with MT1 and MT2 melatonin receptors, using biochemical and biophysical approaches in intact cells. Whereas the association between GPR50 and MT2 did not modify MT2 function, GPR50 abolished high-affinity agonist binding and G protein coupling to the MT1 protomer engaged in the heterodimer. Deletion of the large C-terminal tail of GPR50 suppressed the inhibitory effect of GPR50 on MT1 without affecting heterodimerization, indicating that this domain regulates the interaction of regulatory proteins to MT1. Pairing orphan GPCRs to potential heterodimerization partners might be of clinical importance and may become a general strategy to better understand the function of orphan GPCRs. [ABSTRACT FROM AUTHOR]

Published
2006
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70. Preferential Formation of MT1/MT2Melatonin Receptor Heterodimers with Distinct Ligand Interaction Properties Compared with MT2Homodimers▪

Author

Ayoub, Mohammed A., Levoye, Angélique, Delagrange, Philippe, and Jockers, Ralf

Abstract

Heterodimerization has been documented for several members of the G protein-coupled receptor (GPCR) superfamily, including the closely related MT1and MT2melatonin receptors. However, the relative abundance of hetero-versus homodimers and the specific properties, which can be attributed to each form, are difficult to determine. Using a bioluminescence resonance energy transfer (BRET) donor saturation assay, we show that half-maximal MT1/MT2heterodimer formation is reached for expression levels as low as ∼4000 receptors per cell. The relative propensity of MT1homodimer and MT1/MT2heterodimer formation are similar, whereas that for the MT2homodimer formation is 3- to 4-fold lower. These data indicate that both the relative expression level of each receptor isoform and the affinities between monomers may determine the actual proportion of homo- and heterodimers. The specific interaction of ligands with the MT1/MT2heterodimer was studied using a BRET-based assay as a readout for the conformational changes of the heterodimer. An MT1/MT2heterodimer-specific profile and ligands selective for the MT1/MT2heterodimer compared with the MT2homodimer could be identified. Classic radioligand binding and BRET studies suggest that heterodimers contain two functional ligand binding sites that maintain their respective selectivity for MT1and MT2ligands. Occupation of either binding site is sufficient to induce a conformational change within the heterodimer. Taken together, these results show that the probability of GPCR heterodimer formation may be equal to or even higher than that of the corresponding homodimers and that specific properties of heterodimers can be revealed using a BRET-based ligand/receptor interaction assay.

Published
2004
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71. Preferential formation of MT1/MT2 melatonin receptor heterodimers with distinct ligand interaction properties compared with MT2 homodimers.

Author

A, Ayoub Mohammed, Anglique, Levoye, Philippe, Delagrange, and Ralf, Jockers

Abstract

Heterodimerization has been documented for several members of the G protein-coupled receptor (GPCR) superfamily, including the closely related MT(1) and MT(2) melatonin receptors. However, the relative abundance of hetero-versus homodimers and the specific properties, which can be attributed to each form, are difficult to determine. Using a bioluminescence resonance energy transfer (BRET) donor saturation assay, we show that half-maximal MT(1)/MT(2) heterodimer formation is reached for expression levels as low as approximately 4000 receptors per cell. The relative propensity of MT(1) homodimer and MT(1)/MT(2) heterodimer formation are similar, whereas that for the MT(2) homodimer formation is 3- to 4-fold lower. These data indicate that both the relative expression level of each receptor isoform and the affinities between monomers may determine the actual proportion of homo- and heterodimers. The specific interaction of ligands with the MT(1)/MT(2) heterodimer was studied using a BRET-based assay as a readout for the conformational changes of the heterodimer. An MT(1)/MT(2) heterodimer-specific profile and ligands selective for the MT(1)/MT(2) heterodimer compared with the MT(2) homodimer could be identified. Classic radioligand binding and BRET studies suggest that heterodimers contain two functional ligand binding sites that maintain their respective selectivity for MT(1) and MT(2) ligands. Occupation of either binding site is sufficient to induce a conformational change within the heterodimer. Taken together, these results show that the probability of GPCR heterodimer formation may be equal to or even higher than that of the corresponding homodimers and that specific properties of heterodimers can be revealed using a BRET-based ligand/receptor interaction assay.

Published
2004

72. High-Density Lipoprotein Therapy in Stroke: Evaluation of Endothelial SR-BI-Dependent Neuroprotective Effects.

Author

Tran-Dinh, Alexy, Levoye, Angélique, Couret, David, Galle-Treger, Lauriane, Moreau, Martine, Delbosc, Sandrine, Hoteit, Camille, Montravers, Philippe, Amarenco, Pierre, Huby, Thierry, and Meilhac, Olivier

Subjects
*HIGH density lipoproteins, *NEUROPROTECTIVE agents, *ISCHEMIC preconditioning, *STROKE, *SALINE injections, *ENDOTHELIAL cells, *GLYCOCALYX
Abstract

High-density lipoproteins (HDLs) display endothelial protective effects. We tested the role of SR-BI, an HDL receptor expressed by endothelial cells, in the neuroprotective effects of HDLs using an experimental model of acute ischemic stroke. After transient intraluminal middle cerebral artery occlusion (tMCAO), control and endothelial SR-BI deficient mice were intravenously injected by HDLs or saline. Infarct volume and blood-brain barrier (BBB) breakdown were assessed 24 h post tMCAO. The potential of HDLs and the role of SR-BI to maintain the BBB integrity was assessed by using a human cellular model of BBB (hCMEC/D3 cell line) subjected to oxygen-glucose deprivation (OGD). HDL therapy limited the infarct volume and the BBB leakage in control mice relative to saline injection. Interestingly, these neuroprotective effects were thwarted by the deletion of SR-BI in endothelial cells and preserved in mice deficient for SR-BI in myeloid cells. In vitro studies revealed that HDLs can preserve the integrity of the BBB in OGD conditions, and that this effect was reduced by the SR-BI inhibitor, BLT-1. The protection of BBB integrity plays a pivotal role in HDL therapy of acute ischemic stroke. Our results show that this effect is partially mediated by the HDL receptor, SR-BI expressed by endothelial cells. [ABSTRACT FROM AUTHOR]

Published
2021
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73. Characterization of the first non-insect invertebrate functional angiotensin-converting enzyme (ACE): leech TtACE resembles the N-domain of mammalian ACE

Author

Franck Vandenbulcke, Pierre Corvol, Annie Michaud, Michel Salzet, Guillaume Riviere, Laurence A.M. Deloffre, Christophe Breton, Didier Vieau, and Angélique Levoye

Subjects
Homolog, Molecular Sequence Data, Leech, Polymerase chain-reaction, Angiotensin-Converting Enzyme Inhibitors, In situ hybridization, CHO Cells, Carboxypeptidase, Peptidyl-Dipeptidase A, Biochemistry, Gene, Cell Line, Terminal active site, Complementary DNA, Cricetinae, Leeches, Animals, Drosophila Proteins, Humans, Amino Acid Sequence, RNA, Messenger, Cloning, Molecular, Caenorhabditis elegans, Caenorhabditis elegans Proteins, Molecular Biology, chemistry.chemical_classification, Metalloproteinase, biology, Sequence Homology, Amino Acid, Inhibitors, Crystal structure, Active site, Angiotensin-converting enzyme, Cell Biology, Messenger-Rna expression, Angiotensin II, Recombinant Proteins, Protein Structure, Tertiary, Neobellieria bullata, Enzyme, Drosophila melanogaster, chemistry, In-Vitro, biology.protein, Peptides, Research Article
Abstract

Angiotensin-converting enzyme (ACE) is a zinc metallopeptidase that plays a major role in blood homoeostasis and reproduction in mammals. In vertebrates, both transmembrane and soluble ACE, containing one or two homologous active sites, have been characterized. So far, several ACEs from invertebrates have been cloned, but only in insects. They are soluble and display a single active site. Using biochemical procedures, an ACE-like activity was detected in our model, the leech, Theromyzon tessulatum. Annelida is the most distant phylum in which an ACE activity has been observed. To gain more insight into the leech enzyme, we have developed a PCR approach to characterize its mRNA. The approx. 2 kb cDNA has been predicted to encode a 616-amino-acid soluble enzyme containing a single active site, named TtACE (T. tessulatum ACE). Surprisingly, its primary sequence shows greater similarity to vertebrates than to invertebrates. Stable in vitro expression of TtACE in transfected Chinese-hamster ovary cells revealed that the leech enzyme is a functional metalloprotease. As in mammals, this 79 kDa glycosylated enzyme functions as a dipeptidyl carboxypeptidase capable of hydrolysing angiotensin I to angiotensin II. However, a weak chloride inhibitory effect and acetylated N-acetyl-SDKP (Ac SDAcKP) hydrolysis reveal that TtACE activity resembles that of the N-domain of mammalian ACE. In situ hybridization shows that its cellular distribution is restricted to epithelial midgut cells. Although the precise roles and endogenous substrates of TtACE remain to be identified, characterization of this ancestral peptidase will help to clarify its physiological roles in non-insect invertebrate species.

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