A large new subset of TRIM genes highly diversified by duplication and positive selection in teleost fish

<p>Abstract</p> <p>Background</p> <p>In mammals, the members of the tripartite motif (TRIM) protein family are involved in various cellular processes including innate immunity against viral infection. Viruses exert strong selective pressures on the defense system. Accordingly, antiviral TRIMs have diversified highly through gene expansion, positive selection and alternative splicing. Characterizing immune TRIMs in other vertebrates may enlighten their complex evolution.</p> <p>Results</p> <p>We describe here a large new subfamily of TRIMs in teleosts, called finTRIMs, identified in rainbow trout as virus-induced transcripts. FinTRIMs are formed of nearly identical RING/B-box regions and C-termini of variable length; the long variants include a B30.2 domain. The zebrafish genome harbors a striking diversity of finTRIMs, with 84 genes distributed in clusters on different chromosomes. A phylogenetic analysis revealed different subsets suggesting lineage-specific diversification events. Accordingly, the number of <it>fintrim </it>genes varies greatly among fish species. Conserved syntenies were observed only for the oldest <it>fintrims</it>. The closest mammalian relatives are <it>trim16 </it>and <it>trim25</it>, but they are not true orthologs. The B30.2 domain of zebrafish finTRIMs evolved under strong positive selection. The positions under positive selection are remarkably congruent in finTRIMs and in mammalian antiviral TRIM5α, concentrated within a viral recognition motif in mammals. The B30.2 domains most closely related to finTRIM are found among NOD-like receptors (NLR), indicating that the evolution of TRIMs and NLRs was intertwined by exon shuffling.</p> <p>Conclusion</p> <p>The diversity, evolution, and features of finTRIMs suggest an important role in fish innate immunity; this would make them the first TRIMs involved in immunity identified outside mammals.</p

The epigenetic regulator RINF (CXXC5) maintains SMAD7 expression in human immature erythroid cells and sustains red blood cells expansion

The gene CXXC5, encoding a Retinoid-Inducible Nuclear Factor (RINF), is located within a region at 5q31.2 commonly deleted in myelodysplastic syndrome (MDS) and adult acute myeloid leukemia (AML). RINF may act as an epigenetic regulator and has been proposed as a tumor suppressor in hematopoietic malignancies. However, functional studies in normal hematopoiesis are lacking, and its mechanism of action is unknow. Here, we evaluated the consequences of RINF silencing on cytokineinduced erythroid differentiation of human primary CD34+ progenitors. We found that RINF is expressed in immature erythroid cells and that RINF-knockdown accelerated erythropoietin-driven maturation, leading to a significant reduction (~45%) in the number of red blood cells (RBCs), without affecting cell viability. The phenotype induced by RINF-silencing was TGFβ-dependent and mediated by SMAD7, a TGFβ- signaling inhibitor. RINF upregulates SMAD7 expression by direct binding to its promoter and we found a close correlation between RINF and SMAD7 mRNA levels both in CD34+ cells isolated from bone marrow of healthy donors and MDS patients with del(5q). Importantly, RINF knockdown attenuated SMAD7 expression in primary cells and ectopic SMAD7 expression was sufficient to prevent the RINF knockdowndependent erythroid phenotype. Finally, RINF silencing affects 5’-hydroxymethylation of human erythroblasts, in agreement with its recently described role as a Tet2- anchoring platform in mouse. Altogether, our data bring insight into how the epigenetic factor RINF, as a transcriptional regulator of SMAD7, may fine-tune cell sensitivity to TGFβ superfamily cytokines and thus play an important role in both normal and pathological erythropoiesis

Transfer of antioxidant message by microvesicles mediates antiapoptotic effects on human endothelial cells

International audienceMicrovesicles (MVs) are small membrane-derived fragments shed from various cell types during activation and/or apoptosis and represent a new class of biological information mediators. MVs generated from T lymphocytes undergoing activation and apoptosis exert a beneficial potential effect on the cardiovascular system through their dual capacity to increase nitric oxide and reduce reactive oxygen species production. This study investigated the effect of MVs on the apoptosis of human umbilical vein endothelial cells triggered by actinomycin D (Act D). The effect of Act D treatment on reactive oxygen species (ROS) production was biphasic. Indeed, ROS levels significantly increased during the early phase of apoptosis (2 h) and after 10 h of treatment, but not at 4, 8 and 24 h. MVs significantly attenuated the increase in ROS production induced by Act D at 2 h, but not at 10 h, indicating that they normalize ROS production during the early phase of apoptosis by acting directly as ROS scavengers, owing to their ability to carry active antioxidant enzymes such as catalase and the three isoforms of the superoxide dismutase. Furthermore, the effects of MVs on the late phases of apoptosis were associated with the ability of these vesicles to increase the expression of manganese-superoxide dismutase, probably by the transfer of its mRNA, in endothelial cells, through internalization process. These findings illustrate new mechanisms by which MVs from T lymphocytes exert their vasculo-protective effects by improving endothelial function under pathological conditions in which apoptosis and oxidative stress are enhanced.</p

Internalization and induction of antioxidant messages by microvesicles contribute to the antiapoptotic effects on human endothelial cells

International audienceMicrovesicles are plasma membrane-derived fragments released from various cell types during activation and/or apoptosis and posses the ability to deliver biological information between cells. Microvesicles generated from T lymphocytes undergoing activation and apoptosis bear the morphogen Sonic Hedgehog, and exert a beneficial potential effect on the cardiovascular system through their dual capacity to increase nitric oxide and reduce reactive oxygen species production. This study investigated the effect of microvesicles on the apoptosis of human umbilical vein endothelial cells triggered by actinomycin D. Microvesicles prevented apoptosis induced by actinomycin D by modulating reactive oxygen species production: during the early phase of apoptosis, microvesicles might act directly as reactive oxygen species scavengers, owing to their ability to carry active antioxidant enzymes, catalase, and isoforms of the superoxide dismutase. Furthermore, their effects were associated with the ability to increase the expression of manganese-superoxide dismutase in endothelial cells, through the internalization process. Interestingly, microvesicles bearing Sonic Hedgehog induced cytoprotection in endothelial cells through the activation of the Sonic Hedgehog pathway. These findings provide additional evidence that microvesicles from T lymphocytes exert their vasculoprotective effects by promoting internalization and induction of antioxidant messages to the endothelial monolayer.</p

Estrogen receptor alpha as a key target of organochlorines to promote angiogenesis

International audienceEpidemiological studies report that exposure to pesticides like chlordecone and lindane increases risk of cancer. They may act as endocrine disruptors via the activation of estrogen receptor α (ERα). Carcinogenesis involved angiogenesis and no available data regarding these organochlorines have been reported. The present study aimed at investigating the effects of lindane and chlordecone on cellular processes leading to angiogenesis through an involvement of ERα. Angiogenesis has been analyzed both in vitro, on human endothelial cells, and in vivo by quantifying neovascularization with the use of ECMgel® plug in mice. Both pesticides increased endothelial cell proliferation, migration and MMP2 activity. These toxics potentiated cell adhesion by enhancing FAK phosphorylation and stress fibers. The two organochlorines increased nitric oxide production via an enhancement of eNOS activity without modification of oxidative stress. Evidence has been provided that the two toxins increased in vivo neovascularization. Most interestingly, all the above processes were either partially or completely prevented after silencing of ERα. Altogether, these data highlight that organochlorines modulate cellular angiogenic processes through activation of ERα. This study further reinforces the harmful effects of these pesticides in carcinogenesis, particularly in the modulation of angiogenesis, a critical step in tumor promotion, through ERα.</p

Microparticles Carrying Peroxisome Proliferator-Activated Receptor Alpha Restore the Reduced Differentiation and Functionality of Bone Marrow-Derived Cells Induced by High-Fat Diet

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Microparticles from activated/apoptotic lymphocytes preserve endothelial cell integrity

International audienceMicroparticles (MPs), small membrane-derived fragments shed from various cell types during activation and/or apoptosis, represent a new class of biological information mediators. MPs generated from T lymphocytes undergoing activation and apoptosis exert a beneficial potential effect on the cardiovascular system through their dual capacity to increase nitric oxide and reduce reactive oxygen species production. This study investigated the effect of MPs on both the angiogenesis and apoptosis of human umbilical vein endothelial cells. MPs induced the formation of capillary-like structures in an in vitro model, by regulating cell proliferation. Both cell adhesion and expression of proteins involved in this process, such as Rho A, and phosphorylation of focal-activated kinase were increased by MPs, via a ROCK inhibitor-sensitive pathway. MPs increased mRNA and protein levels of pro-angiogenic factors as measured by qRT-PCR and western blot. MPs significantly attenuated the increase in reactive oxygen species (ROS) associated with Act D-induced apoptosis at early phase of apoptosis (2 h), by acting directly as ROS scavengers, owing to their ability to carry active antioxidant enzymes such as catalase and the 3 isoforms of the superoxide dismutase. Furthermore, the effects of MPs on the late phases of apoptosis were associated with the ability of these vesicles to increase the expression of manganese-superoxide dismutase through internalisation process. Interestingly, the effects induced by MPs on the formation of capillary-like structures, expression of adhesion molecules and pro-angiogenic factors and on apoptosis were reversed when Sonic Hedgehog signalling was pharmacologically inhibited with cyclopamine. These findings illustrate new mechanisms by which MPs from T lymphocytes exert their vasculo-protective effects by improving endothelial function under pathological conditions in which cell integrity is impaired.</p

Modulation of progenitor cell phenotypes in high-fat diet mice: role of PPAR-alpha

National audienc

Mitochondrial Antiviral Signaling Protein Plays a Major Role in Induction of the Fish Innate Immune Response against RNA and DNA Viruses▿ †

Viral infection triggers host innate immune responses through cellular sensor molecules which activate multiple signaling cascades that induce the production of interferons (IFN) and other cytokines. The recent identification of mammalian cytoplasmic viral RNA sensors, such as retinoic acid-inducible gene I (RIG-I)-like receptors (RLRs) and their mitochondrial adaptor, the mitochondrial antiviral signaling protein (MAVS), also called IPS-1, VISA, and Cardif, highlights the significance of these molecules in the induction of IFN. Teleost fish also possess a strong IFN system, but nothing is known concerning the RLRs and their downstream adaptor. In this study, we cloned MAVS cDNAs from several fish species (including salmon and zebrafish) and showed that they were orthologs of mammalian MAVS. We demonstrated that overexpression of these mitochondrial proteins in fish cells led to a constitutive induction of IFN and IFN-stimulated genes (ISGs). MAVS-overexpressing cells were almost fully protected against RNA virus infection, with a strong inhibition of both DNA and RNA virus replication (1,000- and 10,000-fold decreases, respectively). Analyses of MAVS deletion mutants showed that both the N-terminal CARD-like and C-terminal transmembrane domains, but not the central proline-rich region, were indispensable for MAVS signaling function. In addition, we cloned the cDNAs encoding a RIG-I-like molecule from salmonid and cyprinid cell lines. Like the case with MAVS, overexpression of RIG-I CARDs in fish cells led to a strong induction of both IFN and ISGs, conferring on fish cells full protection against RNA virus infection. This report provides the first demonstration that teleost fish possess a functional RLR pathway in which MAVS may play a central role in the induction of the innate immune response

MAVS joue un rôle majeur dans l'induction de la réponse immunitaire innée contre les virus ARN et ADN chez le poisson

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