Project description:CD3-positive T cells were negatively isolated from 10 SLE patients and 9 healthy controls without SLE. All of the SLE samples and control samples were compared with one another to identify baseline differences in expression due to the disease. Next, T cell preparations from 4 of the control subjects were stimulated with either Nitric Oxide (NOC-18) 600 uM for 24hr or stimulated through CD3/CD28 for 24hr to determine which genes were responsive to these signaling mechanisms. Here, we show that activity of the mammalian target of rapamycin (mTOR), which is a sensor of the mitochondrial transmembrane potential, is increased in SLE T cells. Activation of mTOR was inducible by NO, a key trigger of MHP which in turn enhanced the expression of HRES-1/Rab4, a small GTPase that regulates recycling of surface receptors through early endosomes. Expression of HRES-1/Rab4 was increased in SLE T cells and, in accordance with its dominant impact on the endocytic recycling of CD4, it was inversely correlated with diminished CD4 expression. HRES-1/Rab4 over-expression was also inversely correlated with diminished TCRζ protein levels. Combined with follow up studies, these results suggest that activation of mTOR causes the loss of TCRζ in lupus T cells through HRES-1/Rab4-dependent lysosomal degradation. Experiment Overall Design: 10 replicate T cell samples from SLE (Lupus) patients Experiment Overall Design: 9 replicate T cell samples from healthy control (BC) subjects Experiment Overall Design: 4 replicate Nitric Oxide (NOC-18) stimulated T cell samples from 4 of the control subjects Experiment Overall Design: 4 replicate CD3/CD28 stimulated T cell samples from 4 of the control subjects
Project description:CD3-positive T cells were negatively isolated from 10 SLE patients and 9 healthy controls without SLE. All of the SLE samples and control samples were compared with one another to identify baseline differences in expression due to the disease. Next, T cell preparations from 4 of the control subjects were stimulated with either Nitric Oxide (NOC-18) 600 uM for 24hr or stimulated through CD3/CD28 for 24hr to determine which genes were responsive to these signaling mechanisms. Here, we show that activity of the mammalian target of rapamycin (mTOR), which is a sensor of the mitochondrial transmembrane potential, is increased in SLE T cells. Activation of mTOR was inducible by NO, a key trigger of MHP which in turn enhanced the expression of HRES-1/Rab4, a small GTPase that regulates recycling of surface receptors through early endosomes. Expression of HRES-1/Rab4 was increased in SLE T cells and, in accordance with its dominant impact on the endocytic recycling of CD4, it was inversely correlated with diminished CD4 expression. HRES-1/Rab4 over-expression was also inversely correlated with diminished TCRζ protein levels. Combined with follow up studies, these results suggest that activation of mTOR causes the loss of TCRζ in lupus T cells through HRES-1/Rab4-dependent lysosomal degradation.
Project description:The Ser/Thr protein kinase mTOR controls metabolic pathways, including the catabolic process of autophagy. Autophagy plays additional, catabolism-independent roles in homeostasis of cytoplasmic endomembranes and whole organelles. How signals from endomembrane damage are transmitted to mTOR to orchestrate autophagic responses is not known. Here we show that mTOR is inhibited by lysosomal damage. Lysosomal damage, recognized by galectins, leads to association of Gal8 with mTOR apparatus on the lysosome. Gal8 inhibits mTOR activity through its Ragulator-Rag signaling machinery. Thus, a novel galectin-based signal-transduction apparatus, termed here GALTOR, controls mTOR in response to lysosomal damage.
Project description:The PI3K-PKB/c-akt-FOXO signalling network provides a major intracellular hub for regulation of cell proliferation, survival and stress resistance1. Here we report a novel function for FOXO transcription factors in regulating autophagy through modulation of intracellular glutamine levels. To identify novel transcriptional targets of this module we performed an unbiased microarray analysis after conditional activation of the key components PI3K, PKB, FOXO3 and FOXO4. Utilising this global pathway approach we identified glutamine synthetase (GS) as being transcriptionally regulated by PI3K-PKB-FOXO signalling. FOXO-mediated increase in GS expression specifically induced glutamine production independently of cell type, and this was evolutionary conserved. FOXO activation resulted in mTOR inhibition by preventing the translocation of mTOR to lysosomal membranes, which was dependent on GS activity. Increased GS activity resulted in increased autophagosome turnover as measured by LC3 lipidation, p62 degradation, and confocal imaging of LC3, p62, WIPI-1, ULK2 and Atg12. Inhibition of FOXO3-mediated autophagy resulted in increased apoptosis, suggesting that the induction of autophagy by FOXO3-mediated upregulation of GS is important for cellular survival. These findings reveal a novel signalling network that can directly modulate autophagy through regulation of glutamine metabolism. conditional activation of pkb and pi3k were followed in a timeseries. Each timepoint consists of 4 independent replicates, labeled with either cy3 or cy5 and put on array against time0.
Project description:The PI3K-PKB/c-akt-FOXO signalling network provides a major intracellular hub for regulation of cell proliferation, survival and stress resistance1. Here we report a novel function for FOXO transcription factors in regulating autophagy through modulation of intracellular glutamine levels. To identify novel transcriptional targets of this module we performed an unbiased microarray analysis after conditional activation of the key components PI3K, PKB, FOXO3 and FOXO4. Utilising this global pathway approach we identified glutamine synthetase (GS) as being transcriptionally regulated by PI3K-PKB-FOXO signalling. FOXO-mediated increase in GS expression specifically induced glutamine production independently of cell type, and this was evolutionary conserved. FOXO activation resulted in mTOR inhibition by preventing the translocation of mTOR to lysosomal membranes, which was dependent on GS activity. Increased GS activity resulted in increased autophagosome turnover as measured by LC3 lipidation, p62 degradation, and confocal imaging of LC3, p62, WIPI-1, ULK2 and Atg12. Inhibition of FOXO3-mediated autophagy resulted in increased apoptosis, suggesting that the induction of autophagy by FOXO3-mediated upregulation of GS is important for cellular survival. These findings reveal a novel signalling network that can directly modulate autophagy through regulation of glutamine metabolism. conditional activation of foxo3 and foxo4 were followed in a timeseries. Each timepoint consists of 4 independent replicates, labeled with either cy3 or cy5 and put on array against time0 as reference.
Project description:MiT/TFE transcriptional activity controls lysosomal biogenesis and is negatively regulated by the nutrient sensor mTORC1. Some tumors bypass this regulatory circuit via genetic alterations that drive MiT/TFE expression and activity; however, the mechanisms by which cells with intact or constitutive mTORC1 signaling maintain lysosomal catabolism remain to be elucidated. Using the murine epidermis as a model system, we find that epidermal Tsc1 deletion results in a wavy hair phenotype due to increased EGFR degradation. Unexpectedly, constitutive mTORC1 activation increases lysosomal content via up-regulated expression and activity of MiT/TFEs, while genetic or prolonged pharmacologic mTORC1 inactivation has the reverse effect. This paradoxical up-regulation of lysosomal biogenesis by mTORC1 is mediated by feedback inhibition of AKT, and a resulting suppression of AKT-induced MiT/TFE proteasomal degradation. These data suggest that oncogenic feedback loops work to restrain or maintain cellular lysosomal content during chronically inhibited or constitutively active mTORC1 signaling respectively, and reveal a mechanism by which mTORC1 regulates upstream receptor tyrosine kinase signaling.
Project description:The PI3K-PKB/c-akt-FOXO signalling network provides a major intracellular hub for regulation of cell proliferation, survival and stress resistance1. Here we report a novel function for FOXO transcription factors in regulating autophagy through modulation of intracellular glutamine levels. To identify novel transcriptional targets of this module we performed an unbiased microarray analysis after conditional activation of the key components PI3K, PKB, FOXO3 and FOXO4. Utilising this global pathway approach we identified glutamine synthetase (GS) as being transcriptionally regulated by PI3K-PKB-FOXO signalling. FOXO-mediated increase in GS expression specifically induced glutamine production independently of cell type, and this was evolutionary conserved. FOXO activation resulted in mTOR inhibition by preventing the translocation of mTOR to lysosomal membranes, which was dependent on GS activity. Increased GS activity resulted in increased autophagosome turnover as measured by LC3 lipidation, p62 degradation, and confocal imaging of LC3, p62, WIPI-1, ULK2 and Atg12. Inhibition of FOXO3-mediated autophagy resulted in increased apoptosis, suggesting that the induction of autophagy by FOXO3-mediated upregulation of GS is important for cellular survival. These findings reveal a novel signalling network that can directly modulate autophagy through regulation of glutamine metabolism.
Project description:The PI3K-PKB/c-akt-FOXO signalling network provides a major intracellular hub for regulation of cell proliferation, survival and stress resistance1. Here we report a novel function for FOXO transcription factors in regulating autophagy through modulation of intracellular glutamine levels. To identify novel transcriptional targets of this module we performed an unbiased microarray analysis after conditional activation of the key components PI3K, PKB, FOXO3 and FOXO4. Utilising this global pathway approach we identified glutamine synthetase (GS) as being transcriptionally regulated by PI3K-PKB-FOXO signalling. FOXO-mediated increase in GS expression specifically induced glutamine production independently of cell type, and this was evolutionary conserved. FOXO activation resulted in mTOR inhibition by preventing the translocation of mTOR to lysosomal membranes, which was dependent on GS activity. Increased GS activity resulted in increased autophagosome turnover as measured by LC3 lipidation, p62 degradation, and confocal imaging of LC3, p62, WIPI-1, ULK2 and Atg12. Inhibition of FOXO3-mediated autophagy resulted in increased apoptosis, suggesting that the induction of autophagy by FOXO3-mediated upregulation of GS is important for cellular survival. These findings reveal a novel signalling network that can directly modulate autophagy through regulation of glutamine metabolism.
Project description:Hyperactive TLR7 signaling has long been appreciated as a driver of autoimmune disease in mouse models by breaking tolerance to self-nucleic acids1-5. Recently, the first monogenic mutations within TLR7 or its associated regulator Unc93b16,7 have been identified as causative agents of human lupus. The unifying feature of these mutations is TLR7 gain-of-function resulting from increased ligand binding. TLR7 is an intracellular transmembrane receptor, localized to late endosomes, that senses RNA breakdown products within these hydrolytic compartments8,9. Hence, its function depends on a complex interplay between specialized organelles, transport mechanisms and membrane interactions. Whether perturbations of any of these endosome-related processes can give rise to TLR7 gain-of-function and facilitate self-reactivity has not been investigated. Here we show that a dysregulated endosomal compartment can result in TLR7 gain-of-function and lupus disease in humans. Mechanistically, the late endosomal protein complex BORC-Arl8b controls TLR7 protein levels by mediating the receptor's final sorting step towards lysosomal degradation. A direct interaction between Arl8b and Unc93b1 is required to regulate the turnover of TLR7. We identified an amino acid insertion in Unc93b1 in a patient with childhood-onset lupus, which results in loss of interaction with the BORC-Arl8b complex and an accumulation of functional TLR7. Our results highlight the importance of an intact endomembrane system to prevent autoimmune disease. Disrupting the proper progression of TLR7 through its endocytic life cycle is sufficient to break immunological tolerance to nucleic acids. Our work expands the repertoire of cellular mechanisms important to restrict pathological TLR7 activity. Identifying and stratifying lupus patients based on a TLR7-driven pathology opens the way for precision medicine specifically targeting TLR7.
Project description:Hyperactive TLR7 signaling has long been appreciated as a driver of autoimmune disease in mouse models by breaking tolerance to self-nucleic acids1-5. Recently, the first monogenic mutations within TLR7 or its associated regulator Unc93b16,7 have been identified as causative agents of human lupus. The unifying feature of these mutations is TLR7 gain-of-function resulting from increased ligand binding. TLR7 is an intracellular transmembrane receptor, localized to late endosomes, that senses RNA breakdown products within these hydrolytic compartments8,9. Hence, its function depends on a complex interplay between specialized organelles, transport mechanisms and membrane interactions. Whether perturbations of any of these endosome-related processes can give rise to TLR7 gain-of-function and facilitate self-reactivity has not been investigated. Here we show that a dysregulated endosomal compartment can result in TLR7 gain-of-function and lupus disease in humans. Mechanistically, the late endosomal protein complex BORC-Arl8b controls TLR7 protein levels by mediating the receptor's final sorting step towards lysosomal degradation. A direct interaction between Arl8b and Unc93b1 is required to regulate the turnover of TLR7. We identified an amino acid insertion in Unc93b1 in a patient with childhood-onset lupus, which results in loss of interaction with the BORC-Arl8b complex and an accumulation of functional TLR7. Our results highlight the importance of an intact endomembrane system to prevent autoimmune disease. Disrupting the proper progression of TLR7 through its endocytic life cycle is sufficient to break immunological tolerance to nucleic acids. Our work expands the repertoire of cellular mechanisms important to restrict pathological TLR7 activity. Identifying and stratifying lupus patients based on a TLR7-driven pathology opens the way for precision medicine specifically targeting TLR7.