The proteome of cytosolic lipid droplets isolated from differentiated Caco-2/TC7 enterocytes reveals cell-specific characteristics

Background information. Intestinal absorption of alimentary lipids is a complex process ensured by enterocytes and leading to TRL [TAG (triacylglycerol)-rich lipoprotein] assembly and secretion. The accumulation of circulating intestine-derived TRL is associated with atherosclerosis, stressing the importance of the control of postprandial hypertriglyceridaemia. During the postprandial period, TAGs are also transiently stored as CLDs (cytosolic lipid droplets) in enterocytes. As a first step for determining whether CLDs could play a role in the control of enterocyte TRL secretion, we analysed the protein endowment of CLDs isolated by sucrose-gradient centrifugation from differentiated Caco-2/TC7 enterocytes, the only human model able to secrete TRL in culture and to store transiently TAGs as CLDs when supplied with lipids. Cells were analysed after a 24 h incubation with lipid micelles and thus in a state of CLD-associated TAG mobilization

Sensing of Dietary Lipids by Enterocytes: A New Role for SR-BI/CLA-1

BACKGROUND: The intestine is responsible for absorbing dietary lipids and delivering them to the organism as triglyceride-rich lipoproteins (TRL). It is important to determine how this process is regulated in enterocytes, the absorptive cells of the intestine, as prolonged postprandial hypertriglyceridemia is a known risk factor for atherosclerosis. During the postprandial period, dietary lipids, mostly triglycerides (TG) hydrolyzed by pancreatic enzymes, are combined with bile products and reach the apical membrane of enterocytes as postprandial micelles (PPM). Our aim was to determine whether these micelles induce, in enterocytes, specific early cell signaling events that could control the processes leading to TRL secretion. METHODOLOGY/PRINCIPAL FINDINGS: The effects of supplying PPM to the apex of Caco-2/TC7 enterocytes were analyzed. Micelles devoid of TG hydrolysis products, like those present in the intestinal lumen in the interprandial period, were used as controls. The apical delivery of PPM specifically induced a number of cellular events that are not induced by interprandial micelles. These early events included the trafficking of apolipoprotein B, a structural component of TRL, from apical towards secretory domains, and the rapid, dose-dependent activation of ERK and p38MAPK. PPM supply induced the scavenger receptor SR-BI/CLA-1 to cluster at the apical brush border membrane and to move from non-raft to raft domains. Competition, inhibition or knockdown of SR-BI/CLA-1 impaired the PPM-dependent apoB trafficking and ERK activation. CONCLUSIONS/SIGNIFICANCE: These results are the first evidence that enterocytes specifically sense postprandial dietary lipid-containing micelles. SR-BI/CLA-1 is involved in this process and could be a target for further study with a view to modifying intestinal TRL secretion early in the control pathway

Voice knowledge acquisition system for the management of cultural heritage.

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Approche interdisciplinaire du management des connaissances en patrimoine culturel

National audienceCet article présente un travail de recherche appliquée répondant à un réel besoin d'amélioration de recueil, d'indexation et de recherche de connaissances dans le domaine du patrimoine culturel. Conçu, modélisé et expérimenté en environnement réel par Stephan du Chateau, Danielle Boulanger, Eunika Mercier-Laurent, le système Simplicius présenté dans cet article permet d'automatiser le cycle de vie d'informations et connaissances pour une recherche future. Il est composé de plusieurs modules permettant le recueil d'informations orales, leur "traduction" automatique vers un fichier texte, l'analyse linguistique et l'extraction d'informations et, enfin, le peuplement semi-automatique d'une ontologie de domaine selon un modèle conceptuel prédéfini

Domain Knowledge: Application to Cultural Patrimony

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Managing the domain knowledge: Application to Cultural Patrimony

International audienceThis article presents applied research work that addresses a real need for improvement of the collection, indexing and retrieval of knowledge of cultural heritage. To facilitate the task of fieldwork and to improve the access to knowledge, we designed, prototyped and tested in a real environment a system for automating the cycle of collecting and storing information and knowledge for future processing. It contains several modules, allowing the knowledge acquisition cycle to be completed: registering artwork description using a voice interface, automatic 'translation' of the audio files to text files, linguistic analysis and extraction of information for the Inventory Descriptive System and, finally, automatic construction of a domain ontology according to a predefined conceptual model. This hybrid system combines the techniques of signal and natural language processing and of knowledge modelling. After introducing the process of the acquisition and management of information gathered in the field, we describe the nature of knowledge, the models used, the architecture and the various treatments performed by our system. Finally, we provide some perspectives on future development

Advanced System for Acquisition and Knowledge Management in Cultural Heritage

International audienceIn this paper we present our research work on the system of acquisition and knowledge management in cultural heritage. This is a hybrid system because it uses several techniques, signal and natural language processing and knowledge modelling to effectively help a researcher in cultural patrimony in collecting, recording and finding the relevant knowledge. The signal processing is used for the oral description of the cultural heritage and for transcription from voice to text. The linguistic analysis is used for search and extraction of information. Modelling of knowledge is used for the creation of a partial ontology of domain according to a model predefines. After introducing the problem of on field information collecting and managing, we describe the specific work of a researcher in the field of cultural heritage and main difficulties. Furthermore we explain our choice of the architecture of this hybrid system, our experiments and the results. Finally we give some perspective on extending this system to the other domains

Modélisation des connaissances et technologies du Web sémantique: deux applications au patrimoine culturel

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Lipid-dependent Bidirectional Traffic of Apolipoprotein B in Polarized Enterocytes

Enterocytes are highly polarized cells that transfer nutrients across the intestinal epithelium from the apical to the basolateral pole. Apolipoprotein B (apoB) is a secretory protein that plays a key role in the transepithelial transport of dietary fatty acids as triacylglycerol. The evaluation of the control of apoB traffic by lipids is therefore of particular interest. To get a dynamic insight into this process, we used the enterocytic Caco-2 cells cultured on microporous filters, a system in which the apical and basal compartments can be delimited. Combining biochemical and morphological approaches, our results showed that, besides their role in protection from degradation, lipids control the intracellular traffic of apoB in enterocytes. A supply of fatty acids and cholesterol is sufficient for the export of apoB from the endoplasmic reticulum and its post-Golgi traffic up to the apical brush-border domain, where it remains until an apical supply of complex lipid micelles signals its chase down to the basolateral secretory domain. This downward traffic of apoB involves a microtubule-dependent process. Our results demonstrate an enterocyte-specific bidirectional process for the lipid-dependent traffic of a secretory protein

Détection luminale des micelles lipidiques

Post-prandial hypertriglyceridemia is a risk factor for metabolic diseases. The intestine, through its role in alimentary lipid absorption, participates in the secretion of lipoprotein rich-triglycerides (TRL) and contributes to the increase in plasma triglyceride levels during the postprandial state. Understanding the molecular mechanisms involved in the secretion of intestinal TRL would allow the identification of new drug targets for treatment of metabolic diseases. The sensing of lipids by intestinal cells represents a promising mechanism allowing the modulation of TRL secretion. While many studies show the importance of enteroendocrine cells in the detection of alimentary lipids, several evidence suggest also the implication of enterocytes, the absorptive intestinal cells, in this process. Recent experimental results on the role of the scavenger receptor SR-BI in the detection of dietary lipids, supplied in their physiological form of postprandial lipid micelles, are reviewed