Coordination by the circadian clock of rhythmic activation of the unfolded protein response and translation in mouse liver

En premier lieu, l'horloge circadienne des mammifères joue un rôle fondamental dans le foie en régulant le métabolisme des acides gras, du glucose et des xénobiotiques. L'altération de ce rythme a été montrée comme menant à diverses pathologies incluant le syndrome métabolique. Il est supposé que l'horloge circadienne régule principalement le métabolisme en régulant l'expression des enzymes hépatiques au niveau transcriptionnel. Nous montrons que l'horloge circadienne contrôle au ssi le métabolisme hépatique en synchronisant un rythme secondaire d'une période de 12 heures caractérisé par l'activation rythmique de la voie IRE1a dans le RE. L'absence d'horloge circadienne perturbe cette horloge secondaire et provoque une dérégulation des enzymes localisées dans le RE. Cela mène à une altération du métabolisme lipidique, résultant en une activation aberrante du facteur de transcription SREBP. Cette altération dans le métabolisme lipidique circadien chez les souris sans horloge pourrait être impliquée dans l'apparition du syndrome métabolique. D'autre part, la croissance cellulaire animale est principalement régulée par la détection des nutriments et est principalement médiée par la voie TOR. Chez la souris, un gène est identifié pour la kinase TOR et son association en complexe avec d'autres protéines permet de discriminer TORC1 et TORC2. TORC1 est la forme majeure sensible à la rapamycine et est le premier médiateur de la détection d'énergie et d'acides aminés pour le contrôle de la croissance. Ce contrôle consiste en la régulation de la traduction par la phosphorylation de S6 Kinase et 4E-BP et le contrôle de la biogenèse des ribosomes. Nous sommes intéressés de montrer si l'horloge circadienne régule la traduction régulée par TOR dans le foie de souris.In one hand, The mammalian circadian clock plays a fundamental role in the liver by regulating fatty acid, glucose, and xenobiotic metabolism. Impairment of this rhythm has been shown to lead to diverse pathologies, including metabolic syndrome. Currently, it is supposed that the circadian clock regulates metabolism mostly by regulating expression of liver enzymes at the transcriptional level. We show that the circadian clock also controls hepatic metabolism by synchronizing a secondary 12 hr period rhythm characterized by rhythmic activation of the IRE1a pathway in the endoplasmic reticulum. The absence of circadian clock perturbs this secondary clock and provokes deregulation of endoplasmic reticulum localized enzymes. This leads to impaired lipid metabolism, resulting in aberrant activation of the sterol-regulated SREBP transcription factors. The resulting aberrant circadian lipid metabolism in mice devoid of the circadian clock could be inv olved in the appearance of the associated metabolic syndrome.In a second hand, the tissue growth in animals is principally regulated by nutrient sensing and principally by the protein kinase TOR. In mice one gene is identified as TOR kinase and the association of Tor protein associated with 2 different complex of protein (TORC1 and TORC2). TORC1 is the major rapamycin sensitive form and is the primary mediator of energy and amino acid sensing for growth control. This control consists in the regulation of translation through the phosphorylation of S6 Kinase (ribosomal S6 kinase) and 4E-BP (Eif4E binding protein) and the control of ribosome biogenesis. We are interested to show if the circadian clock regulate TOR translation regulation in mice liver

Coordination by the circadian clock of rhythmic activation of the unfolded protein response and translation in mouse liver

En premier lieu, l'horloge circadienne des mammifères joue un rôle fondamental dans le foie en régulant le métabolisme des acides gras, du glucose et des xénobiotiques. L'altération de ce rythme a été montrée comme menant à diverses pathologies incluant le syndrome métabolique. Il est supposé que l'horloge circadienne régule principalement le métabolisme en régulant l'expression des enzymes hépatiques au niveau transcriptionnel. Nous montrons que l'horloge circadienne contrôle au ssi le métabolisme hépatique en synchronisant un rythme secondaire d'une période de 12 heures caractérisé par l'activation rythmique de la voie IRE1a dans le RE. L'absence d'horloge circadienne perturbe cette horloge secondaire et provoque une dérégulation des enzymes localisées dans le RE. Cela mène à une altération du métabolisme lipidique, résultant en une activation aberrante du facteur de transcription SREBP. Cette altération dans le métabolisme lipidique circadien chez les souris sans horloge pourrait être impliquée dans l'apparition du syndrome métabolique. D'autre part, la croissance cellulaire animale est principalement régulée par la détection des nutriments et est principalement médiée par la voie TOR. Chez la souris, un gène est identifié pour la kinase TOR et son association en complexe avec d'autres protéines permet de discriminer TORC1 et TORC2. TORC1 est la forme majeure sensible à la rapamycine et est le premier médiateur de la détection d'énergie et d'acides aminés pour le contrôle de la croissance. Ce contrôle consiste en la régulation de la traduction par la phosphorylation de S6 Kinase et 4E-BP et le contrôle de la biogenèse des ribosomes. Nous sommes intéressés de montrer si l'horloge circadienne régule la traduction régulée par TOR dans le foie de souris.In one hand, The mammalian circadian clock plays a fundamental role in the liver by regulating fatty acid, glucose, and xenobiotic metabolism. Impairment of this rhythm has been shown to lead to diverse pathologies, including metabolic syndrome. Currently, it is supposed that the circadian clock regulates metabolism mostly by regulating expression of liver enzymes at the transcriptional level. We show that the circadian clock also controls hepatic metabolism by synchronizing a secondary 12 hr period rhythm characterized by rhythmic activation of the IRE1a pathway in the endoplasmic reticulum. The absence of circadian clock perturbs this secondary clock and provokes deregulation of endoplasmic reticulum localized enzymes. This leads to impaired lipid metabolism, resulting in aberrant activation of the sterol-regulated SREBP transcription factors. The resulting aberrant circadian lipid metabolism in mice devoid of the circadian clock could be inv olved in the appearance of the associated metabolic syndrome.In a second hand, the tissue growth in animals is principally regulated by nutrient sensing and principally by the protein kinase TOR. In mice one gene is identified as TOR kinase and the association of Tor protein associated with 2 different complex of protein (TORC1 and TORC2). TORC1 is the major rapamycin sensitive form and is the primary mediator of energy and amino acid sensing for growth control. This control consists in the regulation of translation through the phosphorylation of S6 Kinase (ribosomal S6 kinase) and 4E-BP (Eif4E binding protein) and the control of ribosome biogenesis. We are interested to show if the circadian clock regulate TOR translation regulation in mice liver.MONTPELLIER-BU Sciences (341722106) / SudocSudocFranceF

Combined ibrutinib and venetoclax treatment vs single agents in the TCL1 mouse model of chronic lymphocytic leukemia

The covalent inhibitor of Bruton’s tyrosine kinase ibrutinib and the specific Bcl-2 inhibitor venetoclax are both highly efficacious single-agent drugs in the treatment of chronic lymphocytic leukemia (CLL). Based on their complementary modes of action, ibrutinib and venetoclax are hypothesized to act in a synergistic fashion. Currently, it is unclear whether combined treatment is indeed superior to continuous single-agent treatment and what mechanisms underlie the resistance to combination treatment. In addition, the effects of such treatment on the skewed T-cell compartment characteristic of CLL are as yet unknown. In the murine Em-TCL1 adoptive transfer model resembling aggressive CLL, we found that combined treatment resulted in the deepest responses, with the longest duration related to a combination of decreased proliferation and increased induction of apoptosis. In addition, alterations in T-cell subsets were most prominent after combination treatment, with increased naive cells and reduced effector memory cells. Remarkably, effects of single agents but also combination treatment were eventually interrupted by relapse, and we found downregulation of BIM expression as a plausible cause of acquired drug resistance. Nevertheless, in this murine model, the combination of venetoclax and ibrutinib has increased efficacy over single agents, accompanied by a restoration of the T-cell compartment

Resveratrol stimulates the metabolic reprogramming of human CD4 + T cells to enhance effector function

International audienceThe polyphenol resveratrol activates the deacetylase Sirt1, resulting in various antioxidant, chemoprotectant, neuroprotective, cardioprotective, and anti-inflammatory properties. We found that at high concentrations of resveratrol, human CD4+ T cells showed defective antigen receptor signaling and arrest at the G1 stage of the cell cycle, whereas at low concentrations, cells were readily activated and exhibited enhanced Sirt1 deacetylase activity. Nevertheless, low-dose resveratrol rapidly stimulated genotoxic stress in the T cells, which resulted in engagement of a DNA damage response pathway that depended on the kinase ATR [ataxia telangiectasia–mutated (ATM) and Rad3-related], but not ATM, and subsequently in premitotic cell cycle arrest. The concomitant activation of p53 was coupled to the expression of gene products that regulate cell metabolism, leading to a metabolic reprogramming that was characterized by decreased glycolysis, increased glutamine consumption, and a shift to oxidative phosphorylation. These alterations in the bioenergetic homeostasis of CD4+ T cells resulted in enhanced effector function, with both naïve and memory CD4+ T cells secreting increased amounts of the inflammatory cytokine interferon-γ. Thus, our data highlight the wide range of metabolic adaptations that CD4+ T lymphocytes undergo in response to genomic stress

Rhythmic RNA expression of factors involved in ribosomes biogenesis is disrupted in arrhythmic <i>Cry1</i>/<i>Cry2</i> and <i>Bmal1</i> KO mice.

<p>Temporal expression of factors involved in ribosomes biogenesis in <i>Cry1</i>/<i>Cry2</i> (A) and <i>Bmal1</i> (B) KO mice and their control littermates. Temporal real-time RT-PCR expression profile of 45S rRNA precursor, <i>Rpl23</i> pre-mRNA, and translation initiation factors expression in mouse liver. Black line corresponds to the WT animals and red line to the KO. For each time point, data are mean ± SEM obtained from three (A) and two (B) independent animals. The zeitgeber times (ZT) at which the animals were sacrificed are indicated on each panel.</p

Rhythmic transcription of RP mRNA and rRNA through circadian clock regulated expression of UBF1.

<p>(A) Temporal real-time RT-PCR profile of RP pre-mRNA and 45S rRNA precursor expression in mouse liver. For each time point, data are mean ± standard error of the mean (SEM) obtained from four independent animals. (B) Temporal <i>Ubf1</i> mRNA (upper panel) and protein (lower panel) expression in mouse liver. mRNA were measured by real-time RT-PCR and, for each time point, data are mean ± SEM obtained from four independent animals. UBF1 protein expression was measured by Western blot on nuclear extracts during two consecutive days. The lines through gels indicate where the images have been cropped. (C–D) Temporal <i>Ubf1</i> expression in mice devoid of a functional circadian clock. <i>Ubf1</i> expression was measured by real-time RT-PCR with liver RNAs obtained from arrhythmic <i>Cry1</i>/<i>Cry2</i> (C) and <i>Bmal1</i> (D) KO mice and their control littermates (upper panel). Data are mean ± SEM obtained from three and two animals, respectively. Black line corresponds to the WT animals and red line to the KO. Protein levels (lower panel) were measured by Western blot on nuclear extracts. The zeitgeber times (ZT) at which the animals were sacrificed are indicated on each panel. Naphtol blue black staining of the membranes was used as a loading control.</p

Temporal activation of signaling pathways controlling translation initiation.

<p>(A) Temporal expression and phosphorylation of representative proteins of key signaling pathways regulating translation initiation in mouse liver during two consecutive days. Western blots were performed on total liver extracts. Naphtol blue black staining of the membranes was used as a loading control. (B) Temporal binding of EIF4E and 4E-BP1 to 7-methyl-GTP-sepharose during two consecutive days. Total liver extracts were incubated with 7-methyl-GTP beads mimicking the mRNA cap structure. After washing of the beads, bound proteins were analyzed by Western blotting. The zeitgeber times (ZT), with ZT0, lights on; ZT12, lights off, at which the animals were sacrificed, are indicated on each panel. The lines through gels indicate where the images have been cropped.</p

Model describing the coordination of ribosome biogenesis by the circadian clock.

<p>The molecular oscillator in the master circadian pacemaker localized in the SCN of the hypothalamus synchronizes peripheral clocks, including liver clock, and, in parallel, regulates feeding behavior, which itself influences peripheral oscillator. The liver circadian clock controls expression of translation initiation factors, and rRNA, and conceivably RP mRNA, through regulation of UBF1. In addition, in association with signals from nutrients, the molecular clock, via the TORC1 pathway, coordinates the rhythmic activation of signaling pathways controlling translation of RP and, in turn, ribosome biogenesis. This succession of events coordinated by the circadian clock finally leads to a subtle rhythmic change of general translation in mouse liver.</p