Structure et dynamique de la dynorphine et de son recepteur

International audienceDynorphin is a neuropeptide involved in pain, addiction and mood regulation. It exerts its activity by binding to the kappa opioid receptor (KOP) which belongs to the large family of G-protein coupled receptors. The dynorphin peptide was discovered in 1975, while its receptor was cloned in 1993. This review will describe: a) the activities and physiological functions of dynorphin and its receptor, b) early structure-activity relationship studies performed before cloning of the receptor (mostly pharmacological and biophysical studies of peptide analogues), c) structure-activity relationship studies performed after cloning of the receptor via receptor mutagenesis and the development of recombinant receptor expression systems, d) structural biology of the opiate receptors culminating in X-ray structures of the four opioid receptors in their inactive state and structures of MOP and KOP receptors in their active state. X-ray and EM structures are combined with NMR data, which gives complementary insight into receptor and peptide dynamics. Molecular modelling greatly benefited from the availability of atomic resolution 3D structures of receptor-ligand complexes and an example of the strategy used to model a dynorphin-KOP receptor complex using NMR data will be described. These achievements have led to a better understanding of the complex dynamics of KOP receptor activation and to the development of new ligands and drugs

OPA1-related dominant optic atrophy is not strongly influenced by mitochondrial DNA background

<p>Abstract</p> <p>Background</p> <p>Leber's hereditary optic neuropathy (LHON) and autosomal dominant optic atrophy (ADOA) are the most frequent forms of hereditary optic neuropathies. LHON is associated with mitochondrial DNA (mtDNA) mutations whereas ADOA is mainly due to mutations in the OPA1 gene that encodes a mitochondrial protein involved in the mitochondrial inner membrane remodeling. A striking influence of mtDNA haplogroup J on LHON expression has been demonstrated and it has been recently suggested that this haplogroup could also influence ADOA expression. In this study, we have tested the influence of mtDNA backgrounds on OPA1 mutations.</p> <p>Methods</p> <p>To define the relationships between OPA1 mutations and mtDNA backgrounds, we determined the haplogroup affiliation of 41 French patients affected by OPA1-related ADOA by control-region sequencing and RFLP survey of their mtDNAs.</p> <p>Results</p> <p>The comparison between patient and reference populations did not revealed any significant difference.</p> <p>Conclusion</p> <p>Our results argue against a strong influence of mtDNA background on ADOA expression. These data allow to conclude that OPA1 could be considered as a "severe mutation", directly responsible of the optic atrophy, whereas OPA1-negative ADOA and LHON mutations need an external factor(s) to express the pathology (i.e. synergistic interaction with mitochondrial background).</p

Three non-autonomous signals collaborate for nuclear targeting of CrMYC2, a Catharanthus roseus bHLH transcription factor

<p>Abstract</p> <p>Background</p> <p>CrMYC2 is an early jasmonate-responsive bHLH transcription factor involved in the regulation of the expression of the genes of the terpenic indole alkaloid biosynthesis pathway in <it>Catharanthus roseus</it>. In this paper, we identified the amino acid domains necessary for the nuclear targeting of CrMYC2.</p> <p>Findings</p> <p>We examined the intracellular localization of whole CrMYC2 and of various deletion mutants, all fused with GFP, using a transient expression assay in onion epidermal cells. Sequence analysis of this protein revealed the presence of four putative basic nuclear localization signals (NLS). Assays showed that none of the predicted NLS is active alone. Further functional dissection of CrMYC2 showed that the nuclear targeting of this transcription factor involves the cooperation of three domains located in the C-terminal region of the protein. The first two domains are located at amino acid residues 454-510 and 510-562 and contain basic classical monopartite NLSs; these regions are referred to as NLS3 (KRPRKR) and NLS4 (EAERQRREK), respectively. The third domain, between residues 617 and 652, is rich in basic amino acids that are well conserved in other phylogenetically related bHLH transcription factors. Our data revealed that these three domains are inactive when isolated but act cooperatively to target CrMYC2 to the nucleus.</p> <p>Conclusions</p> <p>This study identified three amino acid domains that act in cooperation to target the CrMYC2 transcription factor to the nucleus. Further fine structure/function analysis of these amino acid domains will allow the identification of new NLS domains and will allow the investigation of the related molecular mechanisms involved in the nuclear targeting of the CrMYC2 bHLH transcription factor.</p

Extracorporeal Membrane Oxygenation for Severe Acute Respiratory Distress Syndrome associated with COVID-19: An Emulated Target Trial Analysis.

RATIONALE: Whether COVID patients may benefit from extracorporeal membrane oxygenation (ECMO) compared with conventional invasive mechanical ventilation (IMV) remains unknown. OBJECTIVES: To estimate the effect of ECMO on 90-Day mortality vs IMV only Methods: Among 4,244 critically ill adult patients with COVID-19 included in a multicenter cohort study, we emulated a target trial comparing the treatment strategies of initiating ECMO vs. no ECMO within 7 days of IMV in patients with severe acute respiratory distress syndrome (PaO2/FiO2 <80 or PaCO2 ≥60 mmHg). We controlled for confounding using a multivariable Cox model based on predefined variables. MAIN RESULTS: 1,235 patients met the full eligibility criteria for the emulated trial, among whom 164 patients initiated ECMO. The ECMO strategy had a higher survival probability at Day-7 from the onset of eligibility criteria (87% vs 83%, risk difference: 4%, 95% CI 0;9%) which decreased during follow-up (survival at Day-90: 63% vs 65%, risk difference: -2%, 95% CI -10;5%). However, ECMO was associated with higher survival when performed in high-volume ECMO centers or in regions where a specific ECMO network organization was set up to handle high demand, and when initiated within the first 4 days of MV and in profoundly hypoxemic patients. CONCLUSIONS: In an emulated trial based on a nationwide COVID-19 cohort, we found differential survival over time of an ECMO compared with a no-ECMO strategy. However, ECMO was consistently associated with better outcomes when performed in high-volume centers and in regions with ECMO capacities specifically organized to handle high demand. This article is open access and distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives License 4.0 (http://creativecommons.org/licenses/by-nc-nd/4.0/)

L’obésité : aspects physiologiques, cellulaires et moléculaires

L’obésité est devenu un problème majeur de santé publique avec une prévalence qui dépasse les 30 % dans certaines sociétés occidentales. L’obésité est un reflet du développement excessif du tissu adipeux lié à un stockage massif de lipides sous forme de triglycérides (hypertrophie et hyperplasie adipocytaires) et due à un déséquilibre de la balance énergétique (apport\\dépenses caloriques). Pour perdre du poids, il faut alors augmenter les dépenses ou diminuer les apports énergétiques. Bien qu’il existe des mécanismes de régulation de la prise alimentaire, leur efficacité dans le sens du stockage est bien plus grande que dans le sens du déstockage. Chez l’homme une régulation de la dépense énergétique qui permettrait de brûler les calories en excès ne semble pas développée. En résumé, nous sommes programmés pour stocker et non pour dépenser, ce qui aurait pu représenter un avantage évolutif important en cas de périodes de famines, seuls survivant alors les plus « gras ». A l’heure actuelle, il n’existe pas de traitement pharmacologique efficace de l’obésité et il paraît donc plus raisonnable d’essayer de prévenir que de guérir

REGULATION TRANSCRIPTIONNELLE DU GENE DE LA SYNTHASE DES ACIDES GRAS DANS LE TISSU ADIPEUX (ROLE DE L'OBESITE ET DES FACTEURS DE TRANSCRIPTION SREBPS (STEROL REGULATORY ELEMENT BINDING PROTEINS) ET IDS (INHIBITORS OF DNA BINDING))

PARIS-BIUSJ-Physique recherche (751052113) / SudocCentre Technique Livre Ens. Sup. (774682301) / SudocSudocFranceF

Etude de la régulation du facteur de transcription SREBP-1c au cours du développement hépatique

PARIS-BIUSJ-Thèses (751052125) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF