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Persistent hyperglycemia in type 1 diabetes triggers numerous signaling pathways, which may prove deleterious to the endothelium. As hyperglycemia damages the endothelial layer via multiple signaling pathways, including enhanced oxidative stress, downregulation of angiotensin-converting enzyme 2 signaling, and exacerbation of endoplasmic reticulum (ER) stress, it becomes difficult to prevent injury using monotherapy. Thus, the present study was conceived to evaluate the combined effect of ER stress inhibition along with angiotensin-converting enzyme 2 activation, two major contributors to hyperglycemia-induced endothelial dysfunction, in preventing endothelial dysfunction associated with type 1 diabetes. Streptozotocin-induced diabetic animals were treated with either diminazene aceturate (5 mg * [kg.sup.-1] per day, p.o.) or tauroursodeoxycholic acid, sodium salt (200 mg * [kg.sup.-1] per day i.p.), or both for 4 weeks. Endothelial dysfunction was evaluated using vasoreactivity assay, where acetylcholine-induced relaxation was assessed in phenylephrine pre-contracted rings. Combination therapy significantly improved vascular relaxation when compared with diabetic control as well as monotherapy. Restoration of nitrite levels along with prevention of collagen led to improved vasodilatation. Moreover, there was an overall reduction in aortic oxidative stress. We conclude that by simultaneously inhibiting ER stress and activating angiotensin converting enzyme 2 deleterious effects of hyperglycemia on endothelium were significantly alleviated. This could serve as a novel strategy for the prevention of endothelial dysfunction. Key words: endothelial dysfunction, endoplasmic reticulum stress, angiotensin-converting enzyme 2, type 1 diabetes. Dans le diabete de type 1, l'hyperglycemie persistante entraine le declenchement de nombreuses voies de signalisation, ce qui pourrait avoir des effets resolument deleteres sur l'endothelium. Puisque l'hyperglycemie entraine des dommages dans la couche endotheliale par l'intermediaire de nombreuses voies de signalisation, y compris l'augmentation du stress oxydatif, la regulation a la baisse de la signalisation par l'enzyme de conversion de l'angiotensine de type 2, de meme que l'exacerbation du stress du reticulum endoplasmique, etc., il devient difficile de prevenir la production de lesions a l'aide d'une monotherapie. Par consequent, nous avons concu la presente etude en vue d'evaluer l'effet combine de l'inhibition du stress du reticulum endoplasmique et de l'activation de l'enzyme de conversion de l'angiotensine de type 2, deux voies de signalisation contribuant de maniere tres importante au dysfonctionnement endothelial engendre par l'hyperglycemie, dans la prevention du dysfonctionnement endothelial associe avec le diabete de type 1. Pendant quatre semaines, nous avons administre de l'aceturate de diminazene (5 mg * [kg.sup.-1] par jour, p.o.) ou le sel de sodium de l'acide tauroursodeoxycholique (200 mg * [kg.sup.-1] par jour, i.p.), ou encore les deux chez des animaux devenus diabetiques par l'administration de streptozotocine. Nous avons evalue le dysfonctionnement endothelial a l'aide d'une epreuve de vasoreactivite, ou nous avons evalue la relaxation provoquee par l'acetylcholine dans des anneaux precontractes par la phenylephrine. Le traitement d'association permettait d'ameliorer la relaxation vasculaire par rapport aux temoins diabetiques, et la monotherapie aussi. La vasodilatation s'est amelioree avec le retablissement des taux de nitrite et la prevention du depot de collagene. En outre, nous avons observe une diminution globale du stress oxydatif aortique. Nous en arrivons a la conclusion qu'en inhibant simultanement le stress du reticulum endoplasmique et l'activation de l'enzyme de conversion de l'angiotensine de type 2, les effets deleteres de l'hyperglycemie sur l'endothelium s'attenuaient de facon marquee, ce qui pourrait servir de nouvelle strategie dans la prevention du dysfonctionnement endothelial. [Traduit par la Redaction] Mots-cles : dysfonctionnement endothelial, stress du reticulum endoplasmique, enzyme de conversion de l'angiotensine de type 2, diabete de type 1., Introduction Diabetes mellitus leads to different macrovascular complications, which are the major contributors to the morbidity and mortality associated with diabetes (Bjornstad et al. 2018; Varma et al. 2005). This [...]

Protein disulfide isomerases (PDIs) are pivotal protein folding catalysts in the endoplasmic reticulum (ER) through formation of disulfide bond, isomerization, and inhibition of misfolded protein aggregation. When protein folding capacity is overwhelmed by the demands during transitions between growth phases or under environmental changes, the accumulation of unfolded or misfolded proteins in the ER triggers ER stress. However, little is known about the PDI gene family in the model legume Medicago truncatula, especially the responses to ER stress. Therefore, we identified 17 putative PDI genes from the genome of M. truncatula and present their gene and protein structures, phylogenetic relationships, chromosomal distributions, and synteny analysis with the orthologs in four other eudicot species, including Arabidopsis thaliana, Glycine max, Brassica rapa, and Vitis vinifera. Moreover, expression profiles derived from transcriptome data showed distinct expression patterns of MtPDI genes among plant organs, while real-time quantitative PCR analysis and data from the proteome revealed the potential roles of MtPDI genes in response to ER stress. Our study provides a foundation for further investigations of the biological roles of PDI genes in Medicago, especially their roles in response to ER stress. Key words: protein disulfide isomerases, Medicago truncatula, endoplasmic reticulum stress, genome-wide characterization. Les disulfures isomerases proteiques (PDI) sont des catalyseurs cles du repliement des proteines dans le reticulum endoplasmique (ER) via la formation de ponts disulfures, leur isomerisation et l'inhibition de l'agregation de proteines mal repliees. Lorsque la capacite de repliement proteique est depassee, par exemple lors de transitions entre phases de croissance ou en reponse a des changements environnementaux, l'accumulation de proteines non-repliees ou mal repliees dans l'ER declenche un stress au sein de l'ER. Cependant, peu de choses sont connues au sujet de la famille de genes codant pour les PDI chez la legumineuse modele Medicago truncatula, particulierement en reponse au stress survenant dans l'ER. Les auteurs ont identifie17 PDI putatifs dans le genome du M. truncatula et en presentent les structures genique et proteique, les relations phylogenetiques, la distribution chromosomique et une analyse de syntenie avec les orthologues chez quatre autres especes de dicotyledones (Arabidopsis thaliana, Glycine max, Brassica rapa et Vitis vinifera). De plus, les profils d'expression derives a partir de donnees transcriptomiques montrent des expressions differentes des MtPDI au sein de differents organes vegetaux, tandis qu'une analyse PCR en temps reel et des donnees proteomiques ont revele des roles differents pour les MtPDI en reponseau stress del'ER. Cette etude fournit les assises pour de futures etudes sur les roles biologiques des PDI chez Medicago, particulierement en ce qui a trait a leurs roles en reponse aux stress affectant l'ER. [Traduit par la Redaction] Mots-cles : disulfures isomerases proteiques, Medicago truncatula, stress de l'ER, pangenomique., Introduction Newly produced secretory proteins must be folded and modified into their native structures within the endoplasmic reticulum (ER) prior to being distributed towards their final destinations within cells. Proper [...]

The apoptosis of bronchial and alveolar epithelial cells plays a key role in chronic obstructive pulmonary disease (COPD). The endoplasmic reticulum (ER) stress induced by cigarette smoke contributes to apoptosis. Previous studies demonstrated that melatonin prevented the development of COPD. In addition, silent information regulator 1 (SIRT1) had a protective effect against COPD. However, it remains unclear whether SIRT1 is involved in the protection of melatonin against COPD. In this study, 32 male Wistar rats were randomly assigned to 4 groups: Control, COPD, COPD + Mel, and COPD + Mel + EX527. Rats were challenged with cigarette smoke and lipopolysaccharide with or without melatonin or EX527 (a selective inhibitor of SIRT1). The lung histopathology, apoptotic index, as well as the protein expressions of cleaved caspase-3, SIRT1, C/EBP homologous protein, and caspase-12 in the lung tissues were measured. These results demonstrated that melatonin attenuated apoptosis and ER stress in the lung tissues of rats with COPD. In addition, melatonin increased SIRT1 expression in lung tissues of rats with COPD, while inhibition of SIRT1 by EX527 upregulated ER stress and abolished the protective effect of melatonin against apoptosis. In conclusion, these findings suggested that melatonin protected against COPD by attenuating apoptosis and ER stress via upregulating SIRT1 expression in rats. Key words: COPD, melatonin, apoptosis, endoplasmic reticulum stress, SIRT1. L'apoptose des cellules epitheliales bronchiques et alveolaires joue un role cle dans les maladies pulmonaires obstructives chroniques (MPOC). Par ailleurs, le stress du reticulum endoplasmique (RE) engendre par la fumee de cigarette contribue a l'apoptose. Des etudes anterieures ont montre que la melatonine (Mel) permet de prevenir l'apparition des MPOC. De plus, SIRT1 (pour<>) a un effet protecteur contre les MPOC. Cependant, il reste a clarifier si SIRT1 joue un role dans la protection que la Mel exerce contre les MPOC. Dans cette etude, nous avons reparti aleatoirement 32 rats Wistar males dans 4 groupes: temoin, MPOC, MPOC + Mel et MPOC + Mel + EX527. Nous avons expose les rats a des epreuves de provocation a la fumee de cigarette et a des lipopolysaccharydes avec ou sans Mel ou EX527 (un inhibiteur selectif de SIRT1). Nous avons etudie l'histopathologie du poumon, l'indice apoptotique, ainsi que mesure l'expression en proteines de la caspase 3 clivee, de SIRT1, de la proteine homologue a C/EBP et de la caspase 12 dans les tissus pulmonaires. Ces resultats ont montre que la Mel permettait d'attenuer l'apoptose et le stress du RE dans les tissus pulmonaires de rats atteints de MPOC. De plus, la Mel entrainait une augmentation de l'expression de SIRT1 dans les tissus pulmonaires de rats atteints de MPOC, tandis que l'inhibition de SIRT1 par l'EX527 entrainait une regulation a la hausse du stress du RE, avec une annihilation de l'effet protecteur qu'exerce la Mel contre l'apoptose. En conclusion, ces resultats ont laisse entendre que la Mel aurait exerce un effet protecteur contre les MPOC en attenuant l'apoptose et le stress du RE par l'intermediaire d'une regulation a la hausse de l'expression de SIRT1 chez le rat. [Traduit par la Redaction] Mots-cles: MPOC, melatonine, apoptose, stress du reticulum endoplasmique, SIRT1., Introduction Chronic obstructive pulmonary disease (COPD) is predicted to be the third-leading cause of death by 2020 and has become a major health problem worldwide (GBD 2015 Mortality and Causes [...]

We aimed to investigate whether the cardioprotection of sevoflurane against ischemia-reperfusion (IR) injury is via inhibiting endoplasmic reticulum stress. The rat in vivo model of myocardial IR injury was induced by ligation of the left anterior descending coronary artery. Sevoflurane significantly ameliorated the reduced cardiac function, increased infarct size, and elevated troponin I level and lactate dehydrogenase activity in plasma induced by IR injury. Sevoflurane suppressed the IR-induced myocardial apoptosis. The increased protein levels of glucose-regulated protein 78 and C/EBP homologous protein (CHOP) after myocardial IR were significantly reduced by sevoflurane. The protein levels of phosphorylated protein kinase RNA-like endoplasmic reticulum kinase (PERK), phosphorylated eukaryotic initiation factor 2 (eIF2a), and activating transcription factor 4 (ATF4) were significantly increased in rats with IR and attenuated by sevoflurane treatment. The phosphorylation of Akt was further activated by sevoflurane. The cardioprotection of sevoflurane could be blocked by wortmannin, a PI3K/Akt inhibitor. Our results suggest that the cardioprotection of sevoflurane against IR injury might be mediated by suppressing PERK/eIF2a/ATF4/CHOP signaling via activating the Akt pathway, which helps in understanding the novel mechanism of the cardioprotection of sevoflurane. Key words: sevoflurane, cardioprotection, ischemia-reperfusion injury, endoplasmic reticulum stress, Akt. Nous avons vise a etudier si l'effet cardioprotecteur du sevoflurane contre les lesions d'ischemie/reperfusion (IR) est lie a l'inhibition du stress du reticulum endoplasmique. Nous avons obtenu un modele de lesions d'IR myocardique in vivo chez le rat par l'occlusion de l'artere coronaire interventriculaire anterieure. Le sevoflurane a nettement permis d'attenuer le dysfonctionnement cardiaque engendre par les lesions d'IR, ainsi que de faire diminuer le degre d'augmentation de la taille de l'infarctus, des taux de troponine I et de l'activite de la deshydrogenase lactique plasmatiques engendres par les lesions d'IR. Le sevoflurane a permis de faire disparaitre l'apoptose engendree par l'IR dans le myocarde. Le sevoflurane a nettement permis faire diminuer le degre d'augmentation des taux de la proteine 78 regulee par le glucose et de la proteine homologue de la C/EBP (pour << CCAAT/enhancer-binding protein >>) ou CHOP observes apres l'IR myocardique. L'administration de sevoflurane a permis de faire diminuer le degre d'augmentation des taux de proteine PERK (pour << protein kinase RNA-like endoplasmic reticulum kinase >>) phosphorylee, de facteur eIF2a (pour << eukaryotic initiation factor 2 >>) phosphoryle et d'ATF4 (pour << activating transcription factor 4 >>) observees de facon notable chez les rats soumis a l'IR. Le sevoflurane permettait d'activer davantage la phosphorylation de l'Akt. Il etait possible d'inhiber les effets cardioprotecteurs du sevoflurane par la wortmannine, un inhibiteur de la voie de signalisation PI3K/Akt. Nos resultats laissent entendre que les effets cardioprotecteurs du sevoflurane contre les lesions d'IR pourraient etre medies par l'inhibition de l'axe PERK/eIF2a/ATF4/CHOP par l'intermediaire de l'activation de la voie de signalisation de l'Akt, ce qui contribue a la comprehension du nouveau mode d'action des effets cardioprotecteurs du sevoflurane. [Traduit par la Redaction] Mots-cles: sevoflurane, cardioprotection, lesions d'ischemie-reperfusion, stress du reticulum endoplasmique, Akt., Introduction Ischemic heart disease is still one of the leading causes of mortality and morbidity worldwide (Ferdinandy et al. 2007; Xia et al. 2016). Despite the development and improvement of [...]

We show that cardiac sarco(endo)plasmic reticulum [Ca.sup.2+]-ATPase (SERCA) activity differs considerably among sockeye salmon (Oncorhynchus nerka) populations. Variability in SERCA activity was significantly correlated with elevation gain and temperature during migration, as well as maximum cardiac stroke volume. Furthermore, because SERCA activity was not lowered during the spawning migration, this aspect of the cardiac contraction machinery is apparently spared during the senescence of these semelparous salmon, likely because it is essential for these fish to complete spawning. Only when spawning had been completed was there a significant reduction in SERCA activity, which was detectable in males at a 25[degrees]C and in females at a 15[degrees]C assay temperature. Hence, we propose that migration conditions act as a strong selective force that has resulted in local adaptation of myocardial SERCA activity among sockeye salmon populations.Nous demontrons que l'activite cardiaque de la [Ca.sup.2+]-ATPase du reticulum sarco(endo)plasmique (SERCA) differe considerablement entre populations de saumons rouges (Oncorhynchus nerka). La variabilite de l'activite de la SERCA est significativement au gain d'elevation et a la temperature durant la migration, ainsi qu'au volume d'ejection systolique maximum. En outre, comme l'activite de la SERCA n'est pas reduite durant la migration de frai, cet aspect de la mecanique de la contraction cardiaque est apparemment epargne durant la senescence de ces saumons semelpares, vraisemblablement parce qu'il est necessaire a ces poisons pour completer leur frai. Une reduction significative de l'activite de la SERCA n'est observee qu'une fois le frai complete, cette reduction etant detectee, dans les essais, a une temperature de 25[degrees]C chez les males et de 15[degrees]C chez les femelles. Nous proposons donc que les conditions de migration constituent une importante force de selection qui s'est traduite par l'adaptation locale de l'activite de la SERCA dans le myocarde dans les populations de saumons sockeyes. [Traduit par la Redaction], IntroductionOrganisms facing environmental change may respond with emigration, acclimation, or adaptation. When acclimation processes are insufficient to meet the demands of the new conditions, a species' vulnerability to environmental change [...]

Tumours evade immune control by creating hostile microenvironments that perturb T cell metabolism and effector function.sup.1-4. However, it remains unclear how intra-tumoral T cells integrate and interpret metabolic stress signals. Here we report that ovarian cancer--an aggressive malignancy that is refractory to standard treatments and current immunotherapies.sup.5-8--induces endoplasmic reticulum stress and activates the IRE1[alpha]-XBP1 arm of the unfolded protein response.sup.9,10 in T cells to control their mitochondrial respiration and anti-tumour function. In T cells isolated from specimens collected from patients with ovarian cancer, upregulation of XBP1 was associated with decreased infiltration of T cells into tumours and with reduced IFNG mRNA expression. Malignant ascites fluid obtained from patients with ovarian cancer inhibited glucose uptake and caused N-linked protein glycosylation defects in T cells, which triggered IRE1[alpha]-XBP1 activation that suppressed mitochondrial activity and IFN[gamma] production. Mechanistically, induction of XBP1 regulated the abundance of glutamine carriers and thus limited the influx of glutamine that is necessary to sustain mitochondrial respiration in T cells under glucose-deprived conditions. Restoring N-linked protein glycosylation, abrogating IRE1[alpha]-XBP1 activation or enforcing expression of glutamine transporters enhanced mitochondrial respiration in human T cells exposed to ovarian cancer ascites. XBP1-deficient T cells in the metastatic ovarian cancer milieu exhibited global transcriptional reprogramming and improved effector capacity. Accordingly, mice that bear ovarian cancer and lack XBP1 selectively in T cells demonstrate superior anti-tumour immunity, delayed malignant progression and increased overall survival. Controlling endoplasmic reticulum stress or targeting IRE1[alpha]-XBP1 signalling may help to restore the metabolic fitness and anti-tumour capacity of T cells in cancer hosts.In human and mouse models of ovarian cancer, endoplasmic reticulum stress and the activation of the IRE1[alpha]-XBP1 pathway decreases the metabolic fitness of T cells and limits their anti-tumour functions., Author(s): Minkyung Song [sup.1] [sup.2] [sup.3] , Tito A. Sandoval [sup.2] [sup.3] , Chang-Suk Chae [sup.2] [sup.3] , Sahil Chopra [sup.1] [sup.2] [sup.3] , Chen Tan [sup.2] [sup.3] , Melanie [...]

Previous studies have found decreased functional capacity of the sodium pump ([Na.sup.+]-[K.sup.+]-ATPase) alpha and beta subunits and recovery of [Na.sup.+]-[K.sup.+]-ATPase activity significantly decreased myocyte apoptosis in myocardial ischemia- reperfusion (I/R) injury. However, the potential role of the [Na.sup.+]-[K.sup.+]-ATPase [alpha]-2 subunit (ATP1A2) in cardiomyocyte anoxia- reoxygenation (A/R) injury has not been elucidated. Rat myocardial cells were subjected to siRNA transfection followed by A/R injury. Apoptosis and expression of endoplasmic reticulum (ER) stress proteins CHOP, GRP78, and caspase-12 were detected in 4 groups of cells: ATP1A2 siRNA + A/R, control siRNA+A/R, control, and A/R injury model. We found that apoptosis was significantly elevated in the ATP1A2 siRNA + A/R group as compared with control siRNA + A/R, control, and A/R injury model groups (p < 0.05, p < 0.01, and p < 0.05). Furthermore, expression of CHOP, GRP78, and caspase-12 were significantly elevated in the ATP1A2 siRNA + A/R group as compared with control siRNA + A/R, control, and A/R injury model groups (p Key words: sodium pump, apoptosis, endoplasmic reticulum stress, myocardial ischemia-reperfusion injury. Des etudes anterieures ont montre que la diminution de la capacite fonctionnelle des sous-unites alpha et beta de la pompe au sodium ([Na.sup.+]-[K.sup.+]-ATPase), ainsi que le retablissement de l'activite de la [Na.sup.+]-[K.sup.+]- ATPase entrainaient une diminution notable de l'apoptose des myocytes dans les lesions d'ischemie-reperfusion (I/R) myocardiques. Cependant, le role potentiel de la sous-unite [alpha]-2 de la [Na.sup.+]-[K.sup.+]-ATPase (ATP1A2) dans les lesions d'anoxie-reoxygenation (A/R) des cardiomyocytes n'a pas ete elucide. Nous avons soumis des cellules myocardiques de rat a une transfection d'ARN interferent (siRNA), suivie de lesions d'A/R. Nous avons decele de l'apoptose et l'expression de proteines de stress CHOP, GRP78 et caspase-12 dans le reticulum endoplasmique (RE) dans quatre groupes de cellules : siRNA d'ATP1A2+A/R, siRNA temoin+A/R, temoin, modele d'A/R. Nous avons observe que l'apoptose augmentait nettement plus dans le groupe siRNA d'ATP1A2 + A/R que dans les groupes siRNA temoin + A/R, temoin et modele d'A/R (p < 0,05, p < 0,01 et p Mots-cles : pompe au sodium, apoptose, stress du reticulum endoplasmique, lesions d'ischemie-reperfusion myocardiques., Introduction Advancements in medical technology have resulted in an increase in coronary artery recanalization after acute myocardial infarction (AMI). Consequently, post-surgical myocardial ischemia-reperfusion (I/R) injury occurs due to artificial ischemia [...]

Author(s): Stefan Schoebel [1]; Wei Mi [2]; Alexander Stein [3]; Sergey Ovchinnikov [4]; Ryan Pavlovicz [4]; Frank DiMaio [4]; David Baker [4]; Melissa G. Chambers [2]; Huayou Su [5]; Dongsheng [...]

Author(s): Naama Aviram [1]; Tslil Ast (corresponding author) [1]; Elizabeth A. Costa [2]; Eric C. Arakel [3]; Silvia G. Chuartzman [1]; Calvin H. Jan [2]; Sarah Hadenteufel [4]; Johanna Dudek [...]

The sarco(endo)plasmic reticulum calcium ATPase (SERCA) is responsible for transporting calcium ([Ca.sup.2+]) from the cytosol into the lumen of the sarcoplasmic reticulum (SR) following muscular contraction. The [Ca.sup.2+] sequestering activity of SERCA facilitates muscular relaxation in both cardiac and skeletal muscle. There are more than 10 distinct isoforms of SERCA expressed in different tissues. SERCA2a is the primary isoform expressed in cardiac tissue, whereas SERCA1a is the predominant isoform expressed in fast-twitch skeletal muscle. The [Ca.sup.2+] sequestering activity of SERCA is regulated at the level of protein content and is further modified by the endogenous proteins phospholamban (PLN) and sarcolipin (SLN). Additionally, several novel mechanisms, including post-translational modifications and microRNAs (miRNAs) are emerging as integral regulators of [Ca.sup.2+] transport activity. These regulatory mechanisms are clinically relevant, as dysregulated SERCA function has been implicated in the pathology of several disease states, including heart failure. Currently, several clinical trials are underway that utilize novel therapeutic approaches to restore SERCA2a activity in humans. The purpose of this review is to examine the regulatory mechanisms of the SERCA pump, with a particular emphasis on the influence of exercise in preventing the pathological conditions associated with impaired SERCA function. Key words: calcium ([Ca.sup.2+]), cardiac muscle, skeletal muscle, phospholamban (PLN), sarcolipin (SLN), exercise, post-translational modifications, heart failure. L'ATPase SERCA (<>) est responsable du transport du calcium ([Ca.sup.2+]) du cytosol a la lumiere du reticulum sarcoplasmique (RS) a la suite de la contraction musculaire. L'activite de sequestration de [Ca.sup.2+] de SERCA facilite la relaxation musculaire tant dans le muscle cardiaque que dans le muscle squelettique. Il existe plus de 10 formes distinctes de SERCA exprimees dans differents tissus. SERCA2a est la principale isoforme exprimee dans le tissu cardiaque alors que SERCAla est l'isoforme predominante du muscle squelettique a contraction rapide. L'activite de sequestration de [Ca.sup.2+] de SERCA est regulee au niveau du contenu en proteine, et elle est modifiee en plus par deux proteines endogenes, le phospholamban (PLN) et la sarcolipine (SLN). En outre, plusieurs mecanismes nouveaux, dont les modifications posttraductionnelles et les microARN (miARN) emergent maintenant en tant que regulateurs integraux de l'activite de transport du [Ca.sup.2+]. Ces mecanismes regulateurs sont pertinents sur le plan clinique, car la deregulation de la fonction de SERCA a ete impliquee dans plusieurs pathologies incluant l'insuffisance cardiaque. Actuellement, plusieurs essais cliniques en cours utilisent de nouvelles approches therapeutiques afin de retablir l'activite de SERCA2a chez l'humain. Le but de cet article de revue est d'examiner les mecanismes regulateurs de la pompe SERCA, en mettant l'emphase sur l'influence de l'exercice dans la prevention des conditions pathologiques associees a une deficience de la fonction de SERCA. [Traduit par la Redaction] Mots-cles: calcium ([Ca.sup.2+]), muscle cardiaque, muscle squelettique, phospholamban (PLN), sarcolipine (SLN), exercice, modifications post-traductionnelles, insuffisance cardiaque., Introduction The role of calcium in regulating muscular contraction Calcium ([Ca.sup.2+]) plays an integral role in regulating the process of excitation-contraction coupling (ECC) in both cardiac and skeletal muscle tissues. [...]

The main organelles of the secretory and endocytic pathways--the endoplasmic reticulum (ER) and endosomes, respectively--are connected through contact sites whose numbers increase as endosomes mature (1-3.) One function of such sites is to enable dephosphorylation of the cytosolic tails of endosomal signalling receptors by an ER-associated phosphatase (4), whereas others serve to negatively control the association of endosomes with the minus-end-directed microtubule motor dynein (5) or mediate endosome fission (6). Cholesterol transfer and [Ca.sup.2+] exchange have been proposed as additional functions of such sites (2,3). However, the compositions, activities and regulations of ER-endosome contact sites remain incompletely understood. Here we show in human and rat cell lines that protrudin, an ER protein that promotes protrusion and neurite outgrowth (7), forms contact sites with late endosomes (LEs) via coincident detection of the small GTPase RAB7 and phosphatidylinositol 3-phosphate (PtdIns(3)P). These contact sites mediate transfer of the microtubule motor kinesin 1 from protrudin to the motor adaptor FYCO1 on LEs. Repeated LE-ER contacts promote microtubule-dependent translocation of LEs to the cell periphery and subsequent synaptotagmin-VII-dependent fusion with the plasma membrane. Such fusion induces outgrowth of protrusions and neurites, which requires the abilities of protrudin and FYCO1 to interact with LEs and kinesin 1. Thus, protrudin-containing ER-LE contact sites are platforms for kinesin-1 loading onto LEs, and kinesin-1-mediated translocation of LEs to the plasma membrane, fuelled by repeated ER contacts, promotes protrusion and neurite outgrowth., The unusual presence of a PtdIns(3)P-binding FYVE domain in the ER protein protrudin (7-10) begged the question as to whether this protein interacts with endosomes, the major PtdIns(3)P-containing organelles in [...]

Airway inflammation is a key aspect of diseases such as asthma. Several inflammatory cytokines (e.g., TNFα and IL-13) increase cytosolic [Ca.sup.2+] ([[[Ca.sup.2+]].sub.cyt]) responses to agonist stimulation and [Ca.sup.2+] sensitivity of force generation, thereby enhancing airway smooth muscle (ASM) contractility (hyper-reactive state). Inflammation also induces ASM proliferation and remodeling (synthetic state). In normal ASM, the transient elevation of [[[Ca.sup.2+]].sub.cyt] induced by agonists leads to a transient increase in mitochondrial [Ca.sup.2+] ([[[Ca.sup.2+]].sub.mito]) that may be important in matching ATP production with ATP consumption. In human ASM (hASM) exposed to TNFα and IL-13, the transient increase in [[[Ca.sup.2+]].sub.mito] is blunted despite enhanced [[[Ca.sup.2+]].sub.cyt] responses. We also found that TNFα and IL-13 induce reactive oxidant species (ROS) formation and endoplasmic/sarcoplasmic reticulum (ER/SR) stress (unfolded protein response) in hASM. ER/SR stress in hASM is associated with disruption of mitochondrial coupling with the ER/SR membrane, which relates to reduced mitofusin 2 (Mfn2) expression. Thus, in hASM it appears that TNFα and IL-13 result in ROS formation leading to ER/SR stress, reduced Mfn2 expression, disruption of mitochondrion-ER/SR coupling, decreased mitochondrial [Ca.sup.2+] buffering, mitochondrial fragmentation, and increased cell proliferation. Key words: inflammation, ER/SR stress, airway, asthma, unfolded protein response. L'inflammation de voies respiratoires est un aspect cle de maladies comme l'asthme. Plusieurs cytokines inflammatoires (ex. TNFα et IL-13) augmentent le [Ca.sup.2+] cytosolique ([[[Ca.sup.2+]].sub.cyt]) en reponse a une stimulation par un agoniste et la sensibilite de la generation de forces au calcium, augmentant ainsi la contractilite du muscle lisse respiratoire (MLR) (etat d'hyperreactivite). L'inflammation induit aussi la proliferation et le remodelage des cellules du MLR (etat de synthese). Chez le MLR, l'elevation transitoire de [[[Ca.sup.2+]].sub.cyt] induite par un agoniste mene a une augmentation transitoire du [Ca.sup.2+] mitochondrial ([[[Ca.sup.2+]].sub.mito]) qui peut etre importante pour arrimer la production d'ATP a sa consommation. Chez les cellules de MLR humain (hMLR) exposees au TNFα et a l'IL-13, l'augmentation transitoire de [[[Ca.sup.2+]].sub.mito] est attenuee malgre l'augmentation de [[[Ca.sup.2+]].sub.cyt]. Les auteurs trouvent aussi que le TNFα et l'IL-13 induisent la formation d'especes reactives d'oxygene (ERO) et un stress du reticulum endoplasmique/ sarcoplasmique (RE/RS) (reponse aux proteines depliees) chez les hMLR. Le stress RE/RS chez les hMLR est associe au decouplage de la mitochondrie a la membrane du RE/RS, phenomene relie a la reduction de l'expression de la mitofusine 2 (Mfn2). Ainsi, chez les hMLR, il semble que le TNFα et l'IL-13 induisent la formation d'ERO conduisant a un stress du RE/RS, a la reduction de l'expression de Mfn2, au decouplage de la mitochondrie au RE/RS, a la diminution du tamponnage du [Ca.sup.2+] mitochondrial, a la fragmentation mitochondriale et a l'augmentation de la proliferation cellulaire. [Traduit par la Redaction] Mots-cles: inflammation, stress du RE/RS, voies respiratoires, asthme, reponse aux proteines depliees., Introduction Asthma affects more than 20 million people in the USA (~10% of the population), and more than 300 million people world-wide (GINA 2012). It is now recognized that inflammation [...]

The blood system is sustained by a pool of haematopoietic stem cells (HSCs) that are long-lived due to their capacity for self-renewal. A consequence of longevity is exposure to stress stimuli including reactive oxygen species (ROS), nutrient fluctuation and DNA damage (1,2). Damage that occurs within stressed HSCs must be tightly controlled to prevent either loss of function or the clonal persistence of oncogenic mutations that increase the risk of leukaemogenesis (3,4). Despite the importance of maintaining cell integrity throughout life, how the HSC pool achieves this and how individual HSCs respond to stress remain poorly understood. Many sources of stress cause misfolded protein accumulation in the endoplasmic reticulum (ER), and subsequent activation of the unfolded protein response (UPR) enables the cell to either resolve stress or initiate apoptosis (5,6). Here we show that human HSCs are predisposed to apoptosis through strong activation of the PERK branch of the UPR after ER stress, whereas closely related progenitors exhibit an adaptive response leading to their survival. Enhanced ER protein folding by overexpression of the cochaperone ERDJ4 (also called DNAJB9) increases HSC repopulation capacity in xenograft assays, linking the UPR to HSC function. Because the UPR is a focal point where different sources of stress converge, our study provides a framework for understanding how stress signalling is coordinated within tissue hierarchies and integrated with stemness. Broadly, these findings reveal that the HSC pool maintains clonal integrity by clearance of individual HSCs after stress to prevent propagation of damaged stem cells., The human haematopoietic hierarchy has recently been delineated at the single-cell level, enabling precise isolation of HSCs and progenitor cells (7-9) (Extended Data Table 1). Pathway analysis using gene expression [...]

Administration of glucocorticoids induces ocular hypertension in some patients. If untreated, these patients can develop a secondary glaucoma that resembles primary open-angle glaucoma (POAG). The underlying pathology of glucocorticoid-induced glaucoma is not fully understood, due in part to lack of an appropriate animal model. Here, we developed a murine model of glucocorticoid-induced glaucoma that exhibits glaucoma features that are observed in patients. Treatment of WT mice with topical ocular 0.1% dexamethasone led to elevation of intraocular pressure (IOP), functional and structural loss of retinal ganglion cells, and axonal degeneration, resembling glucocorticoid-induced glaucoma in human patients. Furthermore, dexamethasone-induced ocular hypertension was associated with chronic ER stress of the trabecular meshwork (TM). Similar to patients, withdrawal of dexamethasone treatment reduced elevated IOP and ER stress in this animal model. Dexamethasone induced the transcriptional factor CHOP, a marker for chronic ER stress, in the anterior segment tissues, and Chop deletion reduced ER stress in these tissues and prevented dexamethasone-induced ocular hypertension. Furthermore, reduction of ER stress in the TM with sodium 4-phenylbutyrate prevented dexamethasone-induced ocular hypertension in WT mice. Our data indicate that ER stress contributes to glucocorticoid-induced ocular hypertension and suggest that reducing ER stress has potential as a therapeutic strategy for treating glucocorticoid-induced glaucoma., Introduction Glaucoma is the second leading cause of visual impairment and blindness worldwide, affecting about 70 million people, and is the leading cause of blindness among African-Americans in the United [...]

Axonopathies are a group of clinically diverse disorders characterized by the progressive degeneration of the axons of specific neurons. In hereditary spastic paraplegia (HSP), the axons of cortical motor neurons [...]

Although endoplasmic reticulum (ER) stress is a pathologic mechanism in a variety of chronic diseases, it is unclear what role it plays in chronic hypertension (HTN). Dysregulation of brain mechanisms controlling arterial pressure is strongly implicated in HTN, particularly in models involving angiotensin II (Ang II). We tested the hypothesis that ER stress in the brain is causally linked to Ang II-dependent HTN. Chronic systemic infusion of low-dose Ang II in C57BL/6 mice induced slowly developing HTN, which was abolished by co-infusion of the ER stress inhibitor tauroursodeoxycholic acid (TUDCA) into the lateral cerebroventricle. Investigations of the brain regions involved revealed robust increases in ER stress biomarkers and profound ER morphological abnormalities in the circumventricular subfornical organ (SFO), a region outside the blood-brain barrier and replete with Ang II receptors. Ang II-induced HTN could be prevented in this model by selective genetic supplementation of the ER chaperone 78-kDa glucose-regulated protein (GRP78) in the SFO. These data demonstrate that Ang II-dependent HTN is mediated by ER stress in the brain, particularly the SFO. To our knowledge, this is the first report that ER stress, notably brain ER stress, plays a key role in chronic HTN. Taken together, these findings may have broad implications for the pathophysiology of this disease., Introduction ER stress has emerged as a major pathophysiological mecha-nism of various chronic diseases. The ER, the cellular organelle responsible for protein synthesis, folding, and trafficking, is also recognized as [...]

The endoplasmic reticulum (ER) is the main site of protein and lipid synthesis, membrane biogenesis, xenobiotic detoxification and cellular calcium storage, and perturbation of ER homeostasis leads to stress and the activation of the unfolded protein response (1). Chronic activation of ER stress has been shown to have an important role in the development of insulin resistance and diabetes in obesity (2). However, the mechanisms that lead to chronic ER stress in a metabolic context in general, and in obesity in particular, are not understood. Here we comparatively examined the proteomic and lipidomic landscape of hepatic ER purified from lean and obese mice to explore the mechanisms of chronic ER stress in obesity. We found suppression of protein but stimulation of lipid synthesis in the obese ER without significant alterations in chaperone content. Alterations in ER fatty acid and lipid composition result in the inhibition of sarco/endoplasmic reticulum calcium ATPase (SERCA) activity and ER stress. Correcting the obesity-induced alteration of ER phospholipid composition or hepatic Serca over-expression in vivo both reduced chronic ER stress and improved glucose homeostasis. Hence, we established that abnormal lipid and calcium metabolism are important contributors to hepatic ER stress in obesity., It has been generally accepted that a surplus of nutrients and energy stimulates synthetic pathways and may lead to client overloading in the ER. However, it has not been demonstrated [...]