Project description:Salmonella Typhimurium (S. Typhimurium) is an enteric bacterium capable of invading a wide range of host cell types and adopting different intracellular lifestyles for survival. Host endocytic trafficking and autophagy have been implied to regulate the S. Typhimurium subcellular localization and survival. To reveal alternative host regulators on S. Typhimurium lifestyle, we combined a novel fluorescent reporter, Salmonella Intracellular Analyzer (SINA) with haploid forward genetic screening. This identified transcription factor c-MYC as a negative regulator of S. Typhimurium cytosolic lifestyle via stabilizing the Salmonella-containing vacuole (SCV). We further confirmed that c-MYC downstream regulated LC3 acts to maintain SCV stability and limits S. Typhimurium cytosolic lifestyle. We demonstrated that LC3 is recruited to the SCV prior to the endomembrane damage marker Galectin 3, and it regulates SCV stability independent of the autophagosome adaptor NDP52. The LC3 processing enzymes ATG3 and ATG4 reciprocally act on SCV stability, where the loss of LC3-PE conjugation in the absence of ATG3 limits SCV damages. We further identified the dosage-dependent function of the S. Typhimurium effector SopF in mediating SCV stability by actively avoiding LC3 recruitment to the proximity of the SCV to reduce its catastrophic rupture and host cell death. Altogether, we offer insights on the significance of cellular transcription profile in the determination of S. Typhimurium pathophysiology as well as the underlying host-evasion strategy of S. Typhimurium.
Project description:Macroautophagy (hereafter autophagy) is the major pathway by which macromolecules and organelles are degraded. Autophagy is regulated by the mTOR signaling pathway, which is the focal point for integration of metabolic information, with mTORC1 playing a central role in balancing biosynthesis and catabolism. Of the various inputs to mTORC1, the amino acid sensing pathway is among the most potent. Based upon transcriptome analysis of neurons subjected to nutrient deprivation, we identified let-7 as a microRNA capable of promoting neuronal autophagy. We found that let-7 activates autophagy by coordinately down-regulating the amino acid sensing pathway to prevent mTORC1 activation. Let-7 induced autophagy in the brain and greatly reduced protein aggregates in a lentivirus model of polyglutamine disease, establishing the physiological relevance of let-7 for in vivo autophagy modulation. Moreover, peripheral delivery of let-7 anti-miR repressed autophagy in muscle and white fat, suggesting that let-7 autophagy regulation extends beyond the CNS. Hence, let-7 plays a central role in nutrient homeostasis and proteostasis regulation in higher organisms. Using sets of wild-type C57BL/6J mice, we established primary cortical neuron cultures from P0 littermates, and cultured these neurons (n = 3 / set) in CM or NLM for 4 hrs.
Project description:Under defined differentiation conditions human embryonic stem cells (hESCs) can be directed toward a mesendodermal (ME) or neuroectoderm (NE) fate, the first decision during hESC differentiation. Coupled with G1 lengthening a divergent ciliation pattern emerged within the first 24 hours of induced lineage specification and these changes heralded a neuroectoderm decision before any neural precursor markers were expressed. By day 2, increased ciliation in NE precursors induced autophagy that resulted in the inactivation of Nrf2. Nrf2 binds directly to upstream regions of the OCT4 and NANOG genes to promote their expression and represses NE derivation. Nrf2 suppression was sufficient to rescue poorly neurogenic iPSC lines. Only after these events have been initiated do neural precursor markers get expressed at day 4. Thus we have identified a primary cilium-autophagy-Nrf2 (PAN) axis coupled to cell cycle progression that directs hESCs toward NE. Transcriptome analysis of hESC-derived neuroectoderm and mesendoderm cells
Project description:Macroautophagy (hereafter autophagy) is the major pathway by which macromolecules and organelles are degraded. Autophagy is regulated by the mTOR signaling pathway, which is the focal point for integration of metabolic information, with mTORC1 playing a central role in balancing biosynthesis and catabolism. Of the various inputs to mTORC1, the amino acid sensing pathway is among the most potent. Based upon transcriptome analysis of neurons subjected to nutrient deprivation, we identified let-7 as a microRNA capable of promoting neuronal autophagy. We found that let-7 activates autophagy by coordinately down-regulating the amino acid sensing pathway to prevent mTORC1 activation. Let-7 induced autophagy in the brain and greatly reduced protein aggregates in a lentivirus model of polyglutamine disease, establishing the physiological relevance of let-7 for in vivo autophagy modulation. Moreover, peripheral delivery of let-7 anti-miR repressed autophagy in muscle and white fat, suggesting that let-7 autophagy regulation extends beyond the CNS. Hence, let-7 plays a central role in nutrient homeostasis and proteostasis regulation in higher organisms.
Project description:Macroautophagy (hereafter autophagy) is the major pathway by which macromolecules and organelles are degraded. Autophagy is regulated by the mTOR signaling pathway, which is the focal point for integration of metabolic information, with mTORC1 playing a central role in balancing biosynthesis and catabolism. Of the various inputs to mTORC1, the amino acid sensing pathway is among the most potent. Based upon transcriptome analysis of neurons subjected to nutrient deprivation, we identified let-7 as a microRNA capable of promoting neuronal autophagy. We found that let-7 activates autophagy by coordinately down-regulating the amino acid sensing pathway to prevent mTORC1 activation. Let-7 induced autophagy in the brain and greatly reduced protein aggregates in a lentivirus model of polyglutamine disease, establishing the physiological relevance of let-7 for in vivo autophagy modulation. Moreover, peripheral delivery of let-7 anti-miR repressed autophagy in muscle and white fat, suggesting that let-7 autophagy regulation extends beyond the CNS. Hence, let-7 plays a central role in nutrient homeostasis and proteostasis regulation in higher organisms.
Project description:Autophagy selectively degrades aggregation-prone misfolded proteins caused by defective cellular proteostasis. However, the complexity of autophagy may prevent the full appreciation of how its modulation could be used as a therapeutic strategy in disease management. Here we define a molecular pathway through which recombinant interleukin-1 receptor antagonist (IL-1Ra, anakinra) affects cellular proteostasis independently from the IL-1 receptor (IL-1R1). Anakinra promoted H2O2-driven autophagy through a xenobiotic sensing pathway involving the aryl hydrocarbon receptor that, activated through the indoleamine 2,3-dioxygenase 1-kynurenine pathway, transcriptionally activates NADPH Oxidase 4 independent of the IL-1R1. By coupling the mitochondrial redox balance to autophagy, anakinra improved the dysregulated proteostasis network in murine and human cystic fibrosis. We anticipate that anakinra may represent a therapeutic option in addition to its IL-1R1 dependent anti-inflammatory properties by acting at the intersection of mitochondrial oxidative stress and autophagy with the capacity to restore conditions in which defective proteostasis leads to human disease.