Multidisciplinarité des sciences de la santé : naviguer dans les défis contemporains
Jour 2 - 18 Avril 2024
Karine BOQUET
Les enjeux d'une seule santé.
Résumé à venir
Enzo PETRACCO
Atomic resolution analysis of G protein-coupled receptors through NMR spectroscopy to unveil in situ mechanisms for green fragment-based drug design
G protein-coupled receptors (GPCRs) are major pharmacological targets, accounting for 35% of FDA approved drugs with still 56% of non-olfactory GPCR yet to be targeted.1 Structural biology techniques, such as x-ray crystallography and cryo-electron microscopy (Cryo-EM), have been fundamental in elucidating GPCR conformations upon ligand binding and complex formation with partner proteins.2 Complementary to these methods, Nuclear Magnetic Resonance (NMR) spectroscopy has provided for valuable information on GPCR conformational dynamics and ligand interactions timescales, enabling a comprehensive understanding of their activation mechanisms.3 In addition, NMR spectroscopy can be used as a highly versatile and powerful tool for fragment-based drug design, capable of detecting ligand binding with high precision.4 With the objective of making use of the aforementioned advantages of NMR spectroscopy, we developed an approach using High-Resolution Magic Angle Spinning (HRMAS) NMR to characterize the binding epitope of a variety of ligands on A2AAR in P. pastoris native membranes. By doing so, it was possible to get high resolution proton spectra of our mixed sample (both solid and liquid), auspicious for Saturation Transfer Difference (STD) experiments, a well characterized pulse sequence providing for an attenuation of the ligand’s signal upon weak binding (µM – mM range) onto the target. This methodology appeared to be not only useful to characterize the ligands’ motifs interacting with the target but also allows for a real analysis of the sample composition and thus on the overall state of the native membranes, insuring reproducibility. Even though the signal-to-noise ratio was good for some molecules, it was significantly lower for others with similar structures, which might highlight key differences in the binding mode or kinetic. Hence, the development of this method could pave the way for weak binder screening, orphan receptor screening or could be a base for further NMR analysis.
Delphine POLVE
Modulation of enteroendocrine cells by intestinal microbiota
Enteroendocrine cells (EECs) are key players in the intestinal epithelium due to their ability to produce and secrete intestinal hormones in response to changes in their environment. These hormones play a crucial role in energy metabolism, digestion and intestinal transit, functions which are impaired in many pathologies also associated with an imbalance of the intestinal microbiota. Different populations of EECs can be distinguished along the intestinal tract, linked to variations in the microbial environment. A strong link between gut microbiota and EECs is highlighted by the dysregulation of circulating levels of some gut hormones in axenic mice.
To understand the role of the microbiota in EECs regulation, mice with an unaltered microbiota were compared with mice treated with broad-spectrum antibiotics. The presence of microbiota led to a significant decrease in circulating GLP-1 levels, as well as changes in gene expression of certain gut hormones in specific intestinal regions. To distinguish the specific response of EECs, these cells were sorted using mice expressing a fluorescent protein in EECs. In addition to variations in the expression of genes encoding gut hormones, transcriptomic analysis revealed alterations in the energy metabolism of these cells, particularly in oxidative phosphorylation by the gut microbiota. These observations suggest that, beyond the known mechanisms, the intrinsic metabolic regulation of EECs could impact their functions, thus opening up new strategies to regulate EEC functions.
Lianet ABUIN DENIS
Receptor-mediated activation of tick microbiome-immune axis blocks Lyme transmission
Lyme disease, a prevalent tick-borne illness, poses substantial global health risks, with its incidence steadily increasing worldwide. Caused by spirochete bacteria of the Borrelia genus, transmitted by Ixodes spp. ticks, the disease necessitates effective control strategies. While synthetic acaricides are frequently employed to reduce vector populations, their adverse effects on animals and the environment, along with the development of resistance, highlight the need for safer and more environmentally friendly alternative methods without compromising efficacy. Tick microbiota modulation emerges as a friendly approach for tick control. Using a network approach, we studied microbial communities, revealing interaction patterns in response to pathogen infection. We demonstrate that tick microbiome manipulations reduce Borrelia afzelli colonization, nevertheless, the molecular mechanisms remain unclear. Our study elucidates an immune activation pathway involving a tick serotonin receptor that represses transcriptional expression of defensin gene and is sensitive to lysin inhibition. In vitro experiments demonstrate lysin-induced defensin activation and direct antimicrobial activity, suggesting a role in reducing Borrelia post-microbiota modulation. Future experiments aim to validate defensins' anti-borrelia efficacy post-microbiota modulation, advancing novel Lyme disease control strategies. These findings deepen our understanding of the molecular mechanisms involve in the immune systems of vector.
Soraya DINANT
Impact de l'infection grippale maternelle sur l'inflammation et le neurodéveloppement foetal
Les infections respiratoires virales constituent un problème de santé public majeur. Les virus influenza A (VIA) sont des virus zoonotiques figurant parmi les agents étiologiques responsables de ces pathologies.
Dans le but d’identifier des facteurs de restriction à même de lutter contre ces agents pathogènes, nous avons réalisé plusieurs analyses qui nous ont permis d’identifier les gènes de la famille prion comme facteur d’atténuation des symptômes grippaux en modèle souris. La famille Prion est composée des trois gènes : Prnp, Prnd et Sprn qui codent respectivement les protéines PrPC, Doppel et Shadoo. La PrPC a récemment été décrite pour ses capacités protectrices en réduisant la quantité de radicaux oxygénés dans les poumons et empêchant le stress oxydatif en contexte infectieux chez la souris. Dans ce projet, nous avons étendu nos recherches à toute la famille génique « prion ». Une expérience d’infection par un VIA sur souris invalidées (prnp-/-, prnd-/- et sprn-/-) a révélé une contribution de Doppel à la protection des animaux au même titre que la PrPC , tandis que Shadoo n’aurait aucun effet.
D’un point de vue fonctionnel, la PrPC jouant un rôle clé dans le développement embryonnaire et placentaire, et Doppel étant quant à lui, impliqué dans la morphogénèse et la maturation des vaisseaux sanguins, nous avons mis en place un modèle d’étude chez la femelle gestante afin de mieux mettre en évidence les fonctions anti-infectieuses de la PrPC et de Doppel. Une infection grippale durant la grossesse augmente le risque de pathologies du placenta telles que la prééclampsie et favorise des retards de croissance intra-utérin ainsi que des décès in utero, per- ou post-partum. De plus, une infection par un VIA durant la grossesse peut entrainer des troubles neurologiques importants du nouveau-né, notamment trouble du spectre autistique et schizophrénie. Néanmoins, aucune transmission verticale n’a été décrite.
L’emploi de souris transgéniques NF-kB-luciférase nous a permis de mettre en évidence une transmission de l’inflammation maternelle viro-induite à l’embryon en traversant la barrière placentaire visible au niveau du cerveau fœtal. Nous travaillons actuellement à quantifier l’impact de la PrPC et de Doppel dans ces processus inflammatoires. Nous avons également mis en place un protocole expérimental destiné à tester le comportement de la progéniture issue de mères infectées pendant la gestation. Collectivement, l’ensemble de nos travaux vont nous permettre de caractériser finement les fonctions protectrices des gènes de la famille prion dans le cadre d’une infection respiratoire.