The Protein Complex Ragulator is the Substrate-specific Scaffold for mTORC1 to Regulate Transcription Factor EB
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ABSTRACT:
PROVIDER: PRJNA719171 | ENA |
REPOSITORIES: ENA
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Project description:Mechanistic target of rapamycin complex 1 (mTORC1) signaling pathway is activated by nutrition sufficiency signals and extracellular growth signals. mTORC1 acts the hub that integrates these inputs to orchestrate number of cellular responses such as translation, nucleotide synthesis, lipid synthesis, and lysosome biogenesis. However, the scaffold protein which specifically regulates any single downstream signaling molecule has not been identified to date. Here we show the heteropentamer protein complex Ragulator is critically required to regulate nuclear translocation of transcription factor EB (TFEB). We established a unique RAW264.7 clone that lacks Ragulator but maintained total mTORC1 activity. The clone showed a markedly enhanced nuclear translocation of TFEB even in nutrition-sufficient state, despite the full mTORC1 activity. As a cellular phenotype, the number of lysosomes were increased by 10 times in the Ragulator-deficient clone. These findings suggest that mTORC1 essentially requires the scaffold Ragulator to regulate the subcellular location of TFEB. Our finding implicates that mTORC1 has other scaffold proteins that regulate downstream molecules specifically.
2021-08-08 | GSE171357 | GEO
Project description:The mammalian target of rapamycin complex 1 (mTORC1) signaling pathway is activated by intracellular nutritional sufficiency and extracellular growth signals. It has been reported that mTORC1 acts as a hub that integrates these inputs to orchestrate a number of cellular responses, including translation, nucleotide synthesis, lipid synthesis, and lysosome biogenesis. However, little is known about specific control of mTORC1 signaling downstream of this complex. Here, we demonstrate that Ragulator, a heteropentameric protein complex required for mTORC1 activation in response to amino acids, is critical for inhibiting the nuclear translocation of transcription factor EB (TFEB). We established a unique RAW264.7 clone that lacked Ragulator but retained total mTORC1 activity. In a nutrition-sufficient state, the nuclear translocation of TFEB was markedly enhanced in the clone despite total mTORC1 kinase activity. In addition, as a cellular phenotype, the number of lysosomes was increased by tenfold in the Ragulator-deficient clone compared with that of control cells. These findings indicate that mTORC1 essentially requires the Ragulator complex for regulating the subcellular distribution of TFEB. Our findings also suggest that other scaffold proteins may be associated with mTORC1 for the specific regulation of downstream signaling.
| S-EPMC8920921 | biostudies-literature
Project description:The process of pyroptosis is mediated by inflammasomes and a downstream effector known as gasdermin D (GSDMD). Upon cleavage by inflammasome-associated caspases, the N-terminal domain of GSDMD forms membrane pores that promote cytolysis. Numerous proteins promote GSDMD cleavage, but none are known to be required for pore formation after GSDMD cleavage. Herein, we report a forward genetic screen that identified the Ragulator-Rag complex as being necessary for GSDMD pore formation and pyroptosis in macrophages. Mechanistic analysis revealed that Ragulator-Rag is not required for GSDMD cleavage upon inflammasome activation, but rather promotes GSDMD oligomerization in the plasma membrane. Defects in GSDMD oligomerization and pore formation can be rescued by mitochondrial poisons that stimulate reactive oxygen species (ROS) production, and ROS modulation impacts the ability of inflammasome pathways to promote pore formation downstream of GSDMD cleavage. These findings reveal an unexpected link between key regulators of immunity (inflammasome-GSDMD) and metabolism (Ragulator-Rag).
2021-06-29 | GSE179089 | GEO
Project description:The type I interferon (IFN) response is a pivotal transcription program in the host innate immunity against infectious viruses that induces a multitude of interferon-stimulated genes (ISGs) to antagonize every stage of viral replication. Aberrant IFN response often leads to enhanced viral susceptibility or autoimmune conditions. Accordingly, type I IFN induction is tightly regulated from viral recognition to signaling propagation and transcriptional activation to cytokine production. Lysosomes, which are essential organelles for cellular homeostasis and metabolic signaling, play an evolutionarily conserved role in viral clearance. Through their degradative capacity and recycling function, lysosomes facilitate the containment and destruction of viral particles or debris delivered via endocytic, autophagic, and phagocytic routes. Despite the central role of lysosomes in virus-host interactions, it remains unclear whether type I IFN induction requires direct lysosomal input. Here, we identified the lysosomal scaffold Ragulator as crucial for IFN-β transcriptional activation through an antiviral screen using a GFP-expressing Influenza A virus as a readout. Independent of their known roles in mTORC1 regulation, the Ragulator-dependent antiviral response requires downstream heterodimeric Rag GTPases that alter their nucleotide-loading states to establish the IFN-I gene signature. Depleting Ragulator or Rag GTPases causes exhaustion of a regulatory pool of interferon-regulator factors (IRFs), leading to abrogated Ifnb1 transcription, IFN-β secretion, and ISG response, thereby enhancing susceptibility to viral infections both in cells and in vivo. Thus, our findings reveal a new role for lysosomes in the nuclear transcription of antiviral innate immunity.
2025-12-31 | GSE240632 | GEO
Project description:The type I interferon (IFN) response is a pivotal transcription program in the host innate immunity against infectious viruses that induces a multitude of interferon-stimulated genes (ISGs) to antagonize every stage of viral replication. Aberrant IFN response often leads to enhanced viral susceptibility or autoimmune conditions. Accordingly, type I IFN induction is tightly regulated from viral recognition to signaling propagation and transcriptional activation to cytokine production. Lysosomes, which are essential organelles for cellular homeostasis and metabolic signaling, play an evolutionarily conserved role in viral clearance. Through their degradative capacity and recycling function, lysosomes facilitate the containment and destruction of viral particles or debris delivered via endocytic, autophagic, and phagocytic routes. Despite the central role of lysosomes in virus-host interactions, it remains unclear whether type I IFN induction requires direct lysosomal input. Here, we identified the lysosomal scaffold Ragulator as crucial for IFN-β transcriptional activation through an antiviral screen using a GFP-expressing Influenza A virus as a readout. Independent of their known roles in mTORC1 regulation, the Ragulator-dependent antiviral response requires downstream heterodimeric Rag GTPases that alter their nucleotide-loading states to establish the IFN-I gene signature. Depleting Ragulator or Rag GTPases causes exhaustion of a regulatory pool of interferon-regulator factors (IRFs), leading to abrogated Ifnb1 transcription, IFN-β secretion, and ISG response, thereby enhancing susceptibility to viral infections both in cells and in vivo. Thus, our findings reveal a new role for lysosomes in the nuclear transcription of antiviral innate immunity.
2025-12-31 | GSE240633 | GEO
Project description:Control of gasdermin D oligomerization and pyroptosis by the Ragulator-Rag-mTORC1 pathway
| PRJNA742124 | ENA
Project description:Phosphatidylinositol-5-phosphate 4-kinases (PIP4ks) are a family of lipid kinases that specifically use PI-5-P as a substrate to synthesize PI-4,5-P2. Suppression of PIP4k function in Drosophila results in smaller cells and reduced target of rapamycin complex 1 (TORC1) signaling. We showed that the γ isoform of PIP4k stimulated signaling through mammalian TORC1 (mTORC1). Knockdown of PIP4kγ reduced cell mass in cells in which mTORC1 is constitutively activated by Tsc2 deficiency. In Tsc2 null cells mTORC1 activation was partially independent of amino acids or glucose and glutamine. PIP4kγ knockdown inhibited the nutrient-independent activation of mTORC1 in Tsc2 knockdown cells and reduced basal mTORC1 signaling in wild-type cells. PIP4kγ was phosphorylated by mTORC1 and associated with the complex. Phosphorylated PIP4kγ was enriched in light microsomal vesicles, whereas the unphosphorylated form was enriched in heavy microsomal vesicles associated with the Golgi. Furthermore, basal mTORC1 signaling was enhanced by overexpression of an unphosphorylated wild-type PIP4kγ and phosphorylation-defective mutant and decreased by overexpression of a phosphorylation mimetic mutant. Together these results demonstrate that PIP4kγ and mTORC1 interact in a self-regulated feedback loop to maintain low and tightly regulated mTORC1 activation during starvation.
2016-05-04 | PXD001340 | Pride
Project description:Galectin-3 is a carbohydrate binding protein implicated in cell-cell interaction and cell growth. Interestingly, recent studies suggest that galectin-3 is involved in cell metabolism and linked to diabetes and cancer. How galectin-3 might act as a diabetogenic and tumorogenic factor remains to be investigated. Here we report that intracellular galectin-3 is physically associated with Rag GTPases and Ragulator of the mTORC1 signaling machinery on lysosomes. We show that galectin-3 senses lipopolysaccharide (LPS) to facilitate the interaction of Rag GTPases and Ragulator, leading to activation of Rag GTPases thus lysosomal loading of mTOR and activation of mTORC1. Integrative genomics and transcriptomics analyses reveal that the LPS/galectin-3-Rag GTPases/Ragulator-mTORC1 axis regulates a cohort of genes including GLUT1 (glucose transporter member 1) that functions in glucose uptake and glycolysis and HK2 (hexokinase 2) and PKM2 (pyruvate kinase M2) that catalyze the first and last step of glycolysis, respectively. Indeed, galectin-3 deficiency severely compromises LPS-promoted glycolysis. Importantly, in diabetes patients, the expression of HK2 was significantly reduced, and in hepatocellular carcinoma (HCC), thyroid cancer, and prostate cancer, galectin-3 is highly expressed, and its level of expression is positively correlated with that of HK2 and PKM2 and negatively correlated with the prognosis of HCC patients. Our study unravels that galectin-3 is a sensor of LPS, an important modulator of the mTORC1 signaling, and a critical regulator of glucose metabolism, adding to the understanding of diabetogenesis and tumorigenesis.
2022-10-25 | GSE211784 | GEO
Project description:Mammalian target of rapamycin (mTOR) complex 1 (mTORC1) is a critical regulator of cell growth by integrating multiple signals (nutrients, growth factors, energy and stress) and is frequently deregulated in many types of cancer. We used a robust experimental paradigm involving the combination of two interventions, one genetic and one pharmacologic to identify genes regulated transcriptionally by mTORC1. In Tsc2+/+, but not Tsc2-/- immortalized mouse embryo fibroblasts (MEFs), serum deprivation downregulates mTORC1 activity. In Tsc2-/- cells, abnormal mTORC1 activity can be downregulated by treatment with rapamycin (sirolimus). By contrast, rapamycin has little effect on mTORC1 in Tsc2+/+ cells in which mTORC1 is already inhibited by low serum. Thus, under serum deprived conditions, mTORC1 activity is low in Tsc2+/+ cells (untreated or rapamycin treated), high in Tsc2-/- cells, but lowered by rapamycin; a pattern referred to as a M-bM-^@M-^\low/low/high/lowM-bM-^@M-^] or M-bM-^@M-^\LLHLM-bM-^@M-^]. We found that mTORC1 regulated the expression of, among other lysosomal genes, V-ATPases through the transcription factor EB (TFEB, Tcfeb in the mouse). The knockdown of Tfeb resulted in the 'flattening' of the LLHL pattern and allowed the identification of genes regulated by mTORC1 through Tfeb Mouse embryo fibroblasts (MEFs) wild type or deficient in Tsc2 expressing a Tfeb shRNA or scrambled shRNA vector were treated with 25 nM rapamycin or vehicle (methanol) for 24 h under low serum conditions (0.1% FBS)
2011-08-02 | E-GEOD-28021 | biostudies-arrayexpress
Project description:A key step in nutrient sensing is activation of the master growth regulator, mTORC1 kinase, on the lysosomal membrane. Nutrients enable mTORC1 scaffolding by a complex composed of the Rag GTPases (Rags) and Ragulator, but the underlying mechanism of mTORC1 capture is poorly understood. Combining dynamic imaging in cells and reconstituted systems, we uncover an affinity switch that controls mTORC1 lifetime and activation at the lysosome. Nutrients destabilize the Rag-Ragulator interface, causing cycling of the Rags between lysosome-bound Ragulator and the cytoplasm, and rendering mTORC1 capture contingent on simultaneous engagement of two Rag-binding interfaces. Rag GTPase domains trigger cycling by coordinately weakening binding of the C-terminal domains to Ragulator in a nucleotide-controlled manner. Cancer-specific Rag mutants override release from Ragulator and enhance mTORC1 recruitment and signalling output. Cycling in the active state sets the Rags apart from most signalling GTPases, and provides a mechanism to attenuate mTORC1 signalling.
| S-EPMC6279252 | biostudies-literature