Evolutionary changes in the Leishmania eIF4F complex involve variations in the eIF4E–eIF4G interactions

Translation initiation in eukaryotes is mediated by assembly of the eIF4F complex over the m7GTP cap structure at the 5′-end of mRNAs. This requires an interaction between eIF4E and eIF4G, two eIF4F subunits. The Leishmania orthologs of eIF4E are structurally diverged from their higher eukaryote counterparts, since they have evolved to bind the unique trypanosomatid cap-4 structure. Here, we characterize a key eIF4G candidate from Leishmania parasites (LeishIF4G-3) that contains a conserved MIF4G domain. LeishIF4G-3 was found to coelute with the parasite eIF4F subunits from an m7GTP-Sepharose column and to bind directly to LeishIF4E. In higher eukaryotes the eIF4E-eIF4G interaction is based on a conserved peptide signature [Y(X4)Lϕ], where X is any amino acid and Φ is a hydrophobic residue. A parallel eIF4E-binding peptide was identified in LeishIF4G-3 (20-YPGFSLDE-27). However, the binding motif varies extensively: in addition to Y20 and L25, binding strictly requires the presence of F23, whereas the hydrophobic amino acid (Φ) is dispensable. The LeishIF4E–LeishIF4G-3 interaction was also confirmed by nuclear magnetic resonance (NMR) studies. In view of these diversities, the characterization of the parasite eIF4E–eIF4G interaction may not only serve as a novel target for inhibiting Leishmaniasis but also provide important insight for future drug discovery

A novel 4E-interacting protein in Leishmania is involved in stage-specific translation pathways

In eukaryotes, exposure to stress conditions causes a shift from cap-dependent to cap-independent translation. In trypanosomatids, environmental switches are the driving force of a developmental program of gene expression, but it is yet unclear how their translation machinery copes with their constantly changing environment. Trypanosomatids have a unique cap structure (cap-4) and encode four highly diverged paralogs of the cap-binding protein, eIF4E; none were found to genetically complement a yeast mutant failing to express eIF4E. Here we show that in promastigotes, a typical cap-binding complex is anchored through LeishIF4E-4, which associates with components of the cap-binding pre-initiation complex. In axenic amastigotes, expression of LeishIF4E-4 decreases and the protein does not bind the cap, whereas LeishIF4E-1 maintains its expression level and associates with the cap structure and with translation initiation factors. However, LeishIF4E-1 does not interact with eIF4G-like proteins in both life stages, excluding its involvement in cap-dependent translation. Using pull-down assays and mass-spectrometry, we identified a novel, non-conserved 4E-Interacting Protein (Leish4E-IP), which binds to LeishIF4E-1 in promastigotes, but not in amastigotes. Yeast two-hybrid and NMR spectroscopy confirmed the specificity of this interaction. We propose that Leish4E-IP is a translation regulator that is involved in switching between cap-dependent and alternative translation pathways

Propriété littéraire et artistique

International audienceoctobre 2021 – décembre 202

Propriété littéraire et artistique

International audienceoctobre 2021 – décembre 202

The Juxtamembrane Domain of Butyrophilin BTN3A1 Controls Phosphoantigen-Mediated Activation of Human Vγ9Vδ2 T Cells

International audienceVγ9Vδ2 T lymphocytes are the major human peripheral γδ T cell subset, with broad reactivity against stressed human cells, including tumor cells. Vγ9Vδ2 T cells are specifically activated by small phosphorylated metabolites called phosphoantigens (PAg). Stress-induced changes in target cell PAg levels are specifically detected by butyrophilin (BTN)3A1, using its intracellular B30.2 domain. This leads to the activation of Vγ9Vδ2 T cells. In this study, we show that changes in the juxtamembrane domain of BTN3A1, but not its transmembrane domain, induce a markedly enhanced or reduced γδ T cell reactivity. There is thus a specific requirement for BTN3A1's juxtamembrane domain for correct γδ T cell-related function. This work identified, as being of particular importance, a juxtamembrane domain region of BTN3A molecules identified as a possible dimerization interface and that is located close to the start of the B30.2 domain

Subjective feeling of control during fNIRS-based neurofeedback targeting the DL-PFC is related to neural activation determined with short-channel correction

Neurofeedback (NF) training is a promising preventive and therapeutic approach for brain and behavioral impairments, the dorsolateral prefrontal cortex (DL-PFC) being a relevant region of interest. Functional near-infrared spectroscopy (NIRS) has recently been applied in NF training. However, this approach is highly sensitive to extra-cerebral vascularization, which could bias measurements of cortical activity. Here, we examined the feasibility of a NF training targeting the DL-PFC and its specificity by assessing the impact of physiological confounds on NF success via short-channel offline correction under different signal filtering conditions. We also explored whether the individual mental strategies affect the NF success. Thirty volunteers participated in a single 15-trial NF session in which they had to increase the oxy-hemoglobin (HbO2) level of their bilateral DL-PFC. We found that 0.01–0.09 Hz band-pass filtering was more suited than the 0.01–0.2 Hz band-pass filter to highlight brain activation restricted to the NF channels in the DL-PFC. Retaining the 10 out of 15 best trials, we found that 18 participants (60%) managed to control their DL-PFC. This number dropped to 13 (43%) with short-channel correction. Half of the participants reported a positive subjective feeling of control, and the “cheering” strategy appeared to be more effective in men (p<0.05). Our results showed successful DL-PFC fNIRS-NF in a single session and highlighted the value of accounting for extra cortical signals, which can profoundly affect the success and specificity of NF training

Structural basis for LeishIF4E-1 modulation by an interacting protein in the human parasite Leishmania major

Abstract Leishmania parasites are unicellular pathogens that are transmitted to humans through the bite of infected sandflies. Most of the regulation of their gene expression occurs post-transcriptionally, and the different patterns of gene expression required throughout the parasites’ life cycle are regulated at the level of translation. Here, we report the X-ray crystal structure of the Leishmania cap-binding isoform 1, LeishIF4E-1, bound to a protein fragment of previously unknown function, Leish4E-IP1, that binds tightly to LeishIF4E-1. The molecular structure, coupled to NMR spectroscopy experiments and in vitro cap-binding assays, reveal that Leish4E-IP1 allosterically destabilizes the binding of LeishIF4E-1 to the 5′ mRNA cap. We propose mechanisms through which Leish4E-IP1-mediated LeishIF4E-1 inhibition could regulate translation initiation in the human parasite

Conseil oecuménique des Eglises: analyse des archives audiovisuelles et propositions pour une exploitation et une gestion optimales du fonds

La bibliothèque et les archives du Conseil oecuménique des Eglises sont impliquées dans la création d’un Centre de Recherches oecuméniques. Elles possèdent un fonds relativement important d’archives audiovisuelles, «dormantes» jusqu’à présent, mais inestimable pour les chercheurs, les historiens et les étudiants du monde entier. Notre travail de diplôme, qui s’inscrit dans ce projet, a consisté essentiellement à analyser les fonds audiovisuels (en particulier le fonds sonore), afin de proposer des mesures pour la gestion de celui-ci. Notre étude de l’institution ainsi que l’application des fonctions archivistiques au fonds audiovisuel du COE, nous ont permis d’en analyser les ressources, d’élaborer des outils, de soulever les problèmes et de proposer des mesures et des solutions à ces derniers. Ce travail expose nos démarches et nos réalisations. Nous avons particulièrement développé nos réflexions relatives à l’évaluation ainsi qu’à la numérisation, solution principale retenue pour la conservation et l’accès. Diverses propositions ont été avancées dans ce sens afin de permettre des choix par rapport aux moyens, et offrir ainsi une plus grande flexibilité aux décideurs

Correlation between process and silica dispersion/distribution into composite: Impact on mechanical properties and Weibull statistical analysis

International audienceThe aim of this study is to propose a methodology for controlling and monitoring particle dispersion at each step of composite manufacturing. Composites with well and poor particle dispersion were manufactured and characterized by numerous methods to estimate the impact of different dispersion state on mechanical properties. An original: Weibull statistical analysis is suggested and shows the impact of this dispersion state on ultimate stress. For this purpose, a "model" matrix of PMMA was chosen. Well-dispersed silica enhanced Young's modulus by ∼9% and ultimate stress by ∼6%, while poorly-dispersed silica does not affect Young's modulus and ultimate stress. Moreover, a size effect is observed for well-dispersed composites; and not with poor particles dispersion