The Mouse IAPE Endogenous Retrovirus Can Infect Cells through Any of the Five GPI-Anchored EphrinA Proteins

The IAPE (Intracisternal A-type Particles elements with an Envelope) family of murine endogenous retroelements is present at more than 200 copies in the mouse genome. We had previously identified a single copy that proved to be fully functional, i.e. which can generate viral particles budding out of the cell and infectious on a series of cells, including human cells. We also showed that IAPE are the progenitors of the highly reiterated IAP elements. The latter are now strictly intracellular retrotransposons, due to the loss of the envelope gene and re-localisation of the associated particles in the course of evolution. In the present study we searched for the cellular receptor of the IAPE elements, by using a lentiviral human cDNA library and a pseudotype assay on transduced cells. We identified Ephrin A4, a GPI-anchored molecule involved in several developmental processes, as a receptor for the IAPE pseudotypes. We also found that the other 4 members of the Ephrin A family –but not those of the closely related Ephrin B family- were also able to mediate IAPE cell entry, thus significantly increasing the amount of possible cell types susceptible to IAPE infection. We show that these include mouse germline cells, as illustrated by immunohistochemistry experiments, consistent with IAPE genomic amplification by successive re-infection. We propose that the uncovered properties of the identified receptors played a role in the accumulation of IAPE elements in the mouse genome, and in the survival of a functional copy

Effets des inhibiteurs de la protéase du VIH sur l'adipocyte en culture

Le syndrome lipodystrophique est aujourd'hui considéré comme un effet secondaire majeur des polythérapies du VIH (virus de l'immunodéficience humaine). Les polythérapies se composent de trois classes d'antiviraux : des inhibiteurs nucléosidiques (INTIs) et non nucléosidiques (INNTIs) de la transcriptase inverse du VIH et des inhibiteurs de la protéase du VIH (IPs). Le syndrome lipodystrophique se caractérise par des modifications des tissus adipeux (lipoatrophie des tissus adipeux sous cutanés et/ou lipohypertrophie au niveau de l'abdomen). De nombreuses pathologies sont associées à ce syndrome comme la résistance à l'insuline, l'hypertriglycéridémie et l'hypercholestérolémie. Les mécanismes mis en jeu dans le développement de ce syndrome étant encore inconnus, nous avons alors étudié les effets des IPs sur différents modèles adipocytaires. Dans un premier temps, nous avons analysé les effets des six IPs (APV, LPV, RTV, IDV, NFV, SQV) sur la différenciation adipocytaire de quatre modèles murins : 3T3-L1, 3T3-F442, Ob1771 et les cellules ES. Cette étude a pu montrer des effets inhibiteurs sur la différenciation adipocytaire suivant l'IP et le modèle cellulaire considérés. Par exemple, les cellules Ob1771 sont protégées de l'effet inhibiteur du ritonavir, alors que celui-ci réduit la différenciation adipocytaire des cellules 3T3-L1. Pour la première fois, cette étude a montré, in vitro, que les IPs du VIH entrent et s'accumulent dans l'adipocytes. Mais cette accumulation d'IP dans l'adipocyte n'est pas seule responsable des effets inhibiteurs du VIH car le RTV entre dans les cellules Ob1771 comme dans les cellules 3T3-L1. Nous avons aussi utilisé un modèle original de différenciation adipocytaire humaine, les cellules hMADS (" human multipotent adipose derived stem cell "). Ce modèle nous a permis d'étudier les effets des traitements chroniques des six IPs du VIH sur le développement des précurseurs et sur l'adipocyte mature. Nous avons pu montrer que les IPs s'accumulent dans l'adipocyte humain et que le RTV, SQV et LPV inhibent la différenciation adipocytaire des précurseurs. De plus, l'adipocyte sécrète des adipocytokines qui, pour la plupart, sont impliquées dans les pathologies associées au syndrome lipodystrophique comme la résistance à l'insuline. Nous avons pu montrer, par PCR quantitative en temps réel, que le RTV diminue l'expression d'adiponectine et augmente, in vitro, l'expression d'IL6, du TNFa et de la leptine. Ces adipocytes expriment le récepteur IL6 et les deux récepteurs du TNFa (TNFR1 et TNFR2). Ainsi, outre leur effet inhibiteur sur le développement des adipocytes, les IPs modifient l'expression des adipocytokines. Ces facteurs sécrétés peuvent alors avoir un effet autocrine/paracrine sur les adipocytes mais aussi endocrine et participer au développement de la résistance à l'insuline. Ainsi ces résultat sont en faveur d'un rôle direct des IPs du VIH sur les tissus adipeux et sur le développement du syndrome lipodystrophique mais aussi des pathologies observées chez les patients séropositifs sous polythérapies.NICE-BU Sciences (060882101) / SudocSudocFranceF

Interactions foeto-maternelles chez la souris (échanges cellulaires et influence maternelle sur le développement des lymphocytes foetaux)

PARIS7-Bibliothèque centrale (751132105) / SudocSudocFranceF

Differentiation of embryonic stem cells for pharmacological studies on adipose cells.

International audienceThe ongoing global explosion in the incidence of obesity has focused attention on the development of adipose cells. Severe obesity is the result of an increase in fat cell size in combination with increased fat cell number. New fat cells arise from a pre-existing pool of adipose stem cells that are present irrespective of age. The development of established preadipocyte cell lines has facilitated the study of different steps leading to terminal differentiation. However, these systems are limited for studying early events of differentiation as they represent cells which are already determined for the adipogenic lineage. In vitro differentiation of mouse embryonic stem (ES) cells towards the adipogenic lineage provides an alternative source of adipocytes for study in tissue culture and offers the possibility to investigate regulation of the first steps of adipose cell development. In this review, we describe the sequential requirement of retinoic acid and PPARgamma during adipogenesis in ES cells. Stimulation of ES cells with synthetic retinoids which are selective ligands of the retinoic acid receptor isotypes allowed the investigation of the contribution of the different retinoic receptors on the RA-dependent differentiation. The effects of thiazolidinediones, a new class of pharmacological agents used for the treatment of type 2 diabetes, and of statins, drugs used in therapy for lowering cholesterol, on the differentiation of ES cells into adipocytes or osteoblasts are described. Finally, we propose a model in which PPARgamma plays a key role in the decision of stem cells to undergo differentiation into adipocytes or osteoblasts, two closely related lineages

Affinity-Dependent Alterations of Mouse B Cell Development by Noninherited Maternal Antigen.

We have examined the passage of maternal cells into the fetus during the gestation and postpartum in mice. Using enhanced green fluorescent protein (EGFP)-transgenic females, we showed that maternal cells frequently gain access to the fetus, mostly in syngeneic pregnancies, but also in allogeneic and outbred crosses. EGFP-transgenic cells, including B, T, and natural killer cells, can persist until adulthood, primarily in bone marrow and thymus. We then asked whether maternal cells, bearing antigens not inherited by the fetus, influence the development of fetal and neonatal B lymphocytes. We have used the B cell receptor 3-83 µ/{delta} transgenic mouse model, whose B cells recognize the major histocompatibility complex class I molecules H-2Kk and H-2Kb, with a high or moderate affinity, respectively. The fate of transgenic B cells in animals exposed to noninherited H-2Kk or H-2Kb maternal antigens (NIMA) during gestation and lactation was compared with those of nonexposed controls. In H-2Kk-exposed fetuses, NIMA-specific transgenic B cells are partially deleted during late gestation. Nondeleted cells have downmodulated their B cell receptor. In contrast, in NIMA H-2Kb-exposed neonates, transgenic B cells present an activated phenotype, including proliferation, upregulation of surface CD69, and preferential localization in the T cell zone of splenic follicles. This state of activation is still clearly detectable up to 3 wk of age. Thus, we show that fetal and neonatal B cell development is affected by maternal cells bearing antigens noninherited by the fetus and that this phenomenon is highly dependent on the affinity of the B cell receptor for the NIMA