Adsorption des protéines sur les nanomatériaux. Biochimie et physico-chimie d'un nouveau stress

Les nanomatériaux posent de nouvelles questions en termes de toxicologie humaine et environnementale et représentent une nouvelle interface avec le milieu biologique aux propriétés spécifiques. De nombreuses inconnues demeurent, en particulier à l échelle moléculaire, pour permettre d expliquer certains mécanismes de toxicité. Lorsqu elles entrent en contact avec le milieu biologique, les nanoparticules se couvrent d une couche de protéines adsorbées. Celle-ci leur confère une nouvelle identité biologique qui contrôle la réponse cellulaire et leur devenir au sein de l organisme. Nous avons étudié l adsorption de protéines modèles sur la silice nanostructurée. Après avoir caractérisé la silice nanoporeuse et les nanoparticules de silice utilisées, l adsorption de la myoglobine, de l hémoglobine et des protéines d un extrait cellulaire de levure a été étudiée afin de déterminer les paramètres physico-chimiques et thermodynamiques de l adsorption des protéines sur la silice. Un enrichissement en résidus basiques, regroupés en clusters de charge, favorise l adsorption des protéines grâce à la formation d interactions électrostatiques avec la surface chargée de la silice, indépendamment de la charge globale de la protéine. A l inverse, un enrichissement en résidus aromatiques est défavorable à l adsorption car ces résidus forment des interactions p-p qui rigidifient la structure de la protéine. L identification des protéines adsorbées et non adsorbées à partir d un milieu complexe pourrait également être utilisée pour les études de toxicité cellulaire. A partir de l étude de la structure, de la dynamique et de l activité de la myoglobine et de l hémoglobine adsorbées sur les nanoparticules de silice, nous avons cherché à définir l état d une protéine adsorbée. L étude de la structure, réalisée par dichroïsme circulaire, spectroscopie UV-visible, d absorption X, infrarouge, fluorescence et microcalorimétrie, montre une perte partielle de structure importante des protéines adsorbées associée à une grande hétérogénéité de conformations, sans modification majeure de la structure de l hème. Deux sites potentiels d interaction entre myoglobine et nanoparticules de silice ont été identifiés à l aide d une technique de cartographie de surface par irradiation. L étude de la dynamique de la myoglobine adsorbée par diffusion élastique et inélastique de neutrons a permis de montrer que l adsorption s accompagnait d une diminution importante de la flexibilité de la protéine. Malgré la perte de structure, la metmyoglobine adsorbée conserve une activité de fixation de ligands très proche de celle de la protéine libre. L hémoglobine adsorbée présente de façon inattendue une augmentation de son affinité pour l oxygène et une diminution de sa coopérativité, sans dissociation du tétramère. Cet effet est reproductible lors de l adsorption de l hémoglobine humaine, de l hémoglobine pontée DCL et de l hémoglobine mutée S. Deux effecteurs permettent par ailleurs de moduler l affinité de l hémoglobine adsorbée. Aussi importantes soient-elles, les modifications de structure et d activité observées sont entièrement réversibles après désorption dans des conditions douces. L adsorption des hémoprotéines sur les nanoparticules de silice représente véritablement un nouveau type de stress avec résilience pour les protéines en termes de relations entre structure, dynamique et activité.Nanomaterials raise new questions in environmental and human toxicology and represent a novel interface with specific properties with the biological medium. Several unknown remain to explain all the mechanisms of toxicity, especially at the molecular lever. When they enter the biological medium, nanoparticles get covered by a protein corona. This corona yields to a new biological identity that controls the cellular response to nanoparticles and their fate in the organism. We studied the adsorption of model proteins on nanostructured silica. The first part is dedicated to the characterization of nanoporous silica and silica nanoparticles that we used. Then the adsorption of myoglobin, hemoglobin and protein mixture from yeast cells was studied to determine the thermodynamic and physical-chemical parameters of protein adsorption on silica. The enrichment of basic residues, gathered in charge clusters, favors the adsorption of proteins by the formation of electrostatic interactions with the charged surface of silica, independently of the global charge of the protein. On the contrary, the enrichment in aromatic residues is unfavorable to protein adsorption because they form p-p interactions that rigidify the protein structure. The identification of adsorbed and non-adsorbed proteins from a complex medium could also be used for cellular toxicity studies. From the study of the structure, the dynamics and the activity of myoglobin and hemoglobin adsorbed on silica nanoparticles, we tried to define the state of an adsorbed protein. The structural study, based on circular dichroism, fluorescence, infrared, X-ray and UV-visible spectroscopy and microcalorimetry, shows a substantial partial structure loss of adsorbed proteins together with a high conformational heterogeneity, without major modifications of the heme structure. Two potential interaction sites of myoglobin with silica nanoparticles have been identified by a footprinting technique. The study of adsorbed myoglobin dynamics by elastic and inelastic neutron scattering highlighted the important decrease of protein dynamics that occurs upon adsorption. However, despite the structure loss, adsorbed metmyoglobin retains almost all of its activity of ligand binding. Unexpectedly, adsorbed hemoglobin shows an increase of its oxygen affinity and a decrease of its cooperativity, without any dissociation of the tetramer. This effect can be reproduced on human hemoglobin, cross-linked DCL hemoglobin and variant S hemoglobin. Besides, two effectors allow modulating the affinity of adsorbed hemoglobin. Despite the extent of structural and activity changes, all these modifications are entirely reversible upon desorption in soft conditions. The adsorption of hemoproteins on silica nanoparticles depicts a new sort of stress with resilience for proteins in terms of structure, dynamics and activity relationship.PARIS11-SCD-Bib. électronique (914719901) / SudocSudocFranceF

Mapping orangutan habitat and agricultural areas using Landsat OLI imagery augmented with unmanned aircraft system aerial photography

Conservation of the Sumatran orangutans’ (Pongo abelii) habitat is threatened by change in land use/land cover (LULCC), due to the logging of its native primary forest habitat, and the primary forest conversion to oil palm, rubber tree, and coffee plantations. Frequent LULCC monitoring is vital to rapid conservation interventions. Due to the costs of high-resolution satellite imagery, researchers are forced to rely on cost-free sources (e.g. Landsat), those, however, provide images at a moderate-to-low resolution (e.g. 15–250 m), permitting identification only general LULC classes, and limit the detection of small-scale deforestation or degradation. Here, we combine Landsat imagery with very high-resolution imagery obtained from an unmanned aircraft system (UAS). ​The UAS imagery was used as ‘drone truthing’ data to train image classification algorithms. Our results show that UAS data can successfully be used to help discriminate similar land-cover/use classes (oil palm plantation vs. reforestation vs. logged forest) with consistently high identification of over 75% on the generated thematic map, where the oil palm detection rate was as high as 89%. Because UAS is employed increasingly in conservation projects, this approach can be used in a large variety of them to improve land-cover classification or aid-specific mapping needs

Targeting LOXL2 for cardiac interstitial fibrosis and heart failure treatment

Interstitial fibrosis plays a key role in the development and progression of heart failure. Here, we show that an enzyme that crosslinks collagen-Lysyl oxidase-like 2 (Loxl2)-is essential for interstitial fibrosis and mechanical dysfunction of pathologically stressed hearts. In mice, cardiac stress activates fibroblasts to express and secrete Loxl2 into the interstitium, triggering fibrosis, systolic and diastolic dysfunction of stressed hearts. Antibody-mediated inhibition or genetic disruption of Loxl2 greatly reduces stress-induced cardiac fibrosis and chamber dilatation, improving systolic and diastolic functions. Loxl2 stimulates cardiac fibroblasts through PI3K/AKT to produce TGF-β2, promoting fibroblast-to-myofibroblast transformation; Loxl2 also acts downstream of TGF-β2 to stimulate myofibroblast migration. In diseased human hearts, LOXL2 is upregulated in cardiac interstitium; its levels correlate with collagen crosslinking and cardiac dysfunction. LOXL2 is also elevated in the serum of heart failure (HF) patients, correlating with other HF biomarkers, suggesting a conserved LOXL2-mediated mechanism of human HF

Prognostic value of the expression of C-Chemokine Receptor 6 and 7 and their ligands in non-metastatic breast cancer

<p>Abstract</p> <p>Background</p> <p>Chemokines and chemokine receptors are major actors of leukocytes trafficking and some have been shown to play an important role in cancer metastasis. Chemokines CCL19, CCL20 and CCL21 and their receptors CCR6 and CCR7, were assessed as potential biomarkers of metastatic dissemination in primary breast cancer.</p> <p>Methods</p> <p>Biomarker expression levels were evaluated using immunohistochemistry on paraffin-embedded tissue sections of breast cancer (n = 207).</p> <p>Results</p> <p>CCR6 was expressed by tumor cells in 35% of cases. CCR7 was expressed by spindle shaped stromal cells in 43% of cases but not by tumor cells in this series. CCL19 was the only chemokine found expressed in a significant number of breast cancers and was expressed by both tumor cells and dendritic cells (DC). CCR6, CCL19 and CCR7 expression correlated with histologic features of aggressive disease. CCR6 expression was associated with shorter relapse-free survival (RFS) in univariate and but not in multivariate analysis (p = 0.0316 and 0.055 respectively), and was not associated with shorter overall survival (OS). Expression of CCR7 was not significantly associated with shorter RFS or OS. The presence of CCL19-expressing DC was associated with shorter RFS in univariate and multivariate analysis (p = 0.042 and 0.020 respectively) but not with shorter OS.</p> <p>Conclusion</p> <p>These results suggest a contribution of CCR6 expression on tumor cells and CCL19-expressing DC in breast cancer dissemination. In our series, unlike what was previously published, CCR7 was exclusively expressed on stromal cells and was not associated with survival.</p

X-linked primary ciliary dyskinesia due to mutations in the cytoplasmic axonemal dynein assembly factor PIH1D3

By moving essential body fluids and molecules, motile cilia and flagella govern respiratory mucociliary clearance, laterality determination and the transport of gametes and cerebrospinal fluid. Primary ciliary dyskinesia (PCD) is an autosomal recessive disorder frequently caused by non-assembly of dynein arm motors into cilia and flagella axonemes. Before their import into cilia and flagella, multi-subunit axonemal dynein arms are thought to be stabilized and pre-assembled in the cytoplasm through a DNAAF2–DNAAF4–HSP90 complex akin to the HSP90 co-chaperone R2TP complex. Here, we demonstrate that large genomic deletions as well as point mutations involving PIH1D3 are responsible for an X-linked form of PCD causing disruption of early axonemal dynein assembly. We propose that PIH1D3, a protein that emerges as a new player of the cytoplasmic pre-assembly pathway, is part of a complementary conserved R2TP-like HSP90 co-chaperone complex, the loss of which affects assembly of a subset of inner arm dyneins

Identifying Where REDD+ Financially Out Competes Oil Palm in Floodplain Landscapes Using a Fine-Scale Approach

Reducing Emissions from Deforestation and forest Degradation (REDD+) aims to avoid forest conversion to alternative land-uses through financial incentives. Oil-palm has high opportunity costs, which according to current literature questions the financial competitiveness of REDD+ in tropical lowlands. To understand this more, we undertook regional finescale and coarse-scale analyses (through carbon mapping and economic modelling) to assess the financial viability of REDD+ in safeguarding unprotected forest (30,173 ha) in the Lower Kinabatangan floodplain in Malaysian Borneo. Results estimate 4.7 million metric tons of carbon (MgC) in unprotected forest, with 64% allocated for oil-palm cultivations. Through fine-scale mapping and carbon accounting, we demonstrated that REDD+ can outcompete oil-palm in regions with low suitability, with low carbon prices and low carbon stock. In areas with medium oil-palm suitability, REDD+ could outcompete oil palm in areas with: very high carbon and lower carbon price; medium carbon price and average carbon stock; or, low carbon stock and high carbon price. Areas with high oil palm suitability, REDD + could only outcompete with higher carbon price and higher carbon stock. In the coarse-scale model, oil-palm outcompeted REDD+ in all cases. For the fine-scale models at the landscape level, low carbon offset prices (US $3 MgCO2e) would enable REDD+ to outcompete oil-palm in 55$27 million to secure these areas for 25 years. Higher carbon offset price (US $30 MgCO2e) would increase the competitiveness of REDD+ within the landscape but would still only capture between 69$380–416 million in carbon financing. REDD+ has been identified as a strategy to mitigate climate change by many countries (including Malaysia). Although REDD+ in certain scenarios cannot outcompete oil palm, this research contributes to the global REDD+ debate by: highlighting REDD+ competitiveness in tropical floodplain landscapes; and, providing a robust approach for identifying and targeting limited REDD+ funds

Retrospective evaluation of whole exome and genome mutation calls in 746 cancer samples

Funder: NCI U24CA211006Abstract: The Cancer Genome Atlas (TCGA) and International Cancer Genome Consortium (ICGC) curated consensus somatic mutation calls using whole exome sequencing (WES) and whole genome sequencing (WGS), respectively. Here, as part of the ICGC/TCGA Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium, which aggregated whole genome sequencing data from 2,658 cancers across 38 tumour types, we compare WES and WGS side-by-side from 746 TCGA samples, finding that ~80% of mutations overlap in covered exonic regions. We estimate that low variant allele fraction (VAF < 15%) and clonal heterogeneity contribute up to 68% of private WGS mutations and 71% of private WES mutations. We observe that ~30% of private WGS mutations trace to mutations identified by a single variant caller in WES consensus efforts. WGS captures both ~50% more variation in exonic regions and un-observed mutations in loci with variable GC-content. Together, our analysis highlights technological divergences between two reproducible somatic variant detection efforts

(SIC [IS [STIC]]) OR (STIC [IS [SIC]])

Le but de cet article est de présenter quelques éléments de compréhension qui font le lien entre les Sciences et Technologies de l’Information et la Communication (STIC), les Sciences de l’Information et la Communication (SIC) et l’Information Stratégique (IS) utile à la prise de décision. Bien sûr, l’analyse proposée est essentiellement orientée par les Sciences Humaines et Sociales (SHS) et particulièrement par le point de vue des SIC. Nous présentons comment les SIC bornent un territoire, ..

β-lactoglobulin under high pressure studied by small-angle neutron scattering

International audienceWe used small-angle neutron scattering to study the effects of the high hydrostatic pressure on the structure of β-lactoglobulin. Experiments were carried out at pH 7 on the dimeric form of the protein in a pressure range going from 50 MPa to 300 MPa. These measurements allow the protein size and the interactions between macromolecules to be studied during the application of pressure. Increasing pressure up to 150 MPa leads to a swollen state of the protein that gives rise to an increase of the radius of gyration by about 7%. Within this pressure range, we also show that the interaction between macromolecules weakens although it remains repulsive. The measurements show an aggregation process occurring above 150 MPa. From the spectra analysis, it appears that the aggregation occurs mainly by association of the dimeric units