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Lysosomal cystine export regulates mTORC1 signaling to guide kidney epithelial cell fate specialization (Microarray)

ABSTRACT: Differentiation is critical for epithelial cell fate decisions, but the signals involved remain unclear. The kidney proximal tubule (PT) cells reabsorb disulphide-rich proteins through endocytosis, generating cystine via lysosomal proteolysis. Here we report that defective cystine mobilization from lysosomes through cystinosin (CTNS), which is mutated in cystinosis, diverts PT cells towards growth and proliferation, disrupting their functions. Mechanistically, lysosomal cystine storage stimulates Ragulator-Rag GTPase-dependent recruitment of mechanistic target of Rapamycin complex 1 (mTORC1) and its constitutive activation. Re-introduction of CTNS restores nutrient-dependent regulation of mTORC1 in knockout cells, whereas cell-permeant analogues of L-cystine, accumulating within lysosomes, render wild-type cells resistant to nutrient withdrawal. Therapeutic mTORC1 inhibition corrects lysosome and differentiation downstream of cystine storage, and phenotypes in a zebrafish model of cystinosis. Thus, cystine serves as a lysosomal signal that tailors mTORC1 signaling and metabolism to direct epithelial cell fate decisions. These results identify mechanisms and therapeutic targets for dysregulated homeostasis in cystinosis.

ORGANISM(S): Mus musculus

PROVIDER: GSE226396 | GEO | 2023/03/08

REPOSITORIES: GEO

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Lysosomal cystine export regulates mTORC1 signaling to guide kidney epithelial cell fate specialization (RNA-Seq)

Project description:Differentiation is critical for epithelial cell fate decisions, but the signals involved remain unclear. The kidney proximal tubule (PT) cells reabsorb disulphide-rich proteins through endocytosis, generating cystine via lysosomal proteolysis. Here we report that defective cystine mobilization from lysosomes through cystinosin (CTNS), which is mutated in cystinosis, diverts PT cells towards growth and proliferation, disrupting their functions. Mechanistically, lysosomal cystine storage stimulates Ragulator-Rag GTPase-dependent recruitment of mechanistic target of Rapamycin complex 1 (mTORC1) and its constitutive activation. Re-introduction of CTNS restores nutrient-dependent regulation of mTORC1 in knockout cells, whereas cell-permeant analogues of L-cystine, accumulating within lysosomes, render wild-type cells resistant to nutrient withdrawal. Therapeutic mTORC1 inhibition corrects lysosome and differentiation downstream of cystine storage, and phenotypes in a zebrafish model of cystinosis. Thus, cystine serves as a lysosomal signal that tailors mTORC1 signaling and metabolism to direct epithelial cell fate decisions. These results identify mechanisms and therapeutic targets for dysregulated homeostasis in cystinosis.

2023-03-08 | GSE226397 | GEO

Proteomic analysis of Raptor-proximal proteins in U2OS cells

Project description:The mammalian target of rapamycin complex 1 (mTORC1) is a key nutrient-sensing hub and a master regulator of cellular growth and metabolism. Activation of mTORC1 by amino acids and growth factors requires its recruitment to the lysosomes. Furthermore, lysosomal distribution has been shown to be intimately involved in the control of mTORC1, where localisation of lysosomes near plasma membrane increases mTORC1 activity. However, the underlying mechanisms by which lysosomal positioning impacts on mTORC1 signalling are not well understood. To understand better the spatial associations of mTORC1, we analysed the proximal ‘interactome’ of the constitutive component of mTORC1, Raptor, using BioID2-based proximity labelling and MS-based proteomics.

2021-09-08 | PXD012795 | Pride

Lysosomal cystine governs ferroptosis sensitivity in cancer via nuclear cysteine response

Project description:The amino acid cysteine and its oxidized dimeric form cystine are commonly believed to be synonymous in metabolic functions. Cyst(e)ine depletion not only induces amino acid response, but also triggers ferroptosis, a non-apoptotic cell death. Here we report that, unlike general amino acid starvation, cyst(e)ine deprivation triggers ATF4 induction at the transcriptional level. Unexpectedly, it is the shortage of lysosomal cystine, but not the cytosolic cysteine, that elicits the adaptative ATF4 response. The lysosome-nucleus signaling pathway involves the aryl hydrocarbon receptor (AhR) that senses lysosomal cystine via the kynurenine pathway. A blockade of lysosomal cystine efflux attenuates ATF4 induction and sensitizes ferroptosis. To potentiate ferroptosis in cancer, we develop a synthetic mRNA reagent CysRx that converts cytosolic cysteine to lysosomal cystine. CysRx maximizes cancer cell ferroptosis and effectively suppresses tumor growth in vivo. Thus, intracellular nutrient reprogramming has the potential to induce selective ferroptosis in cancer without systematic perturbation.

2023-08-30 | GSE237928 | GEO

Lysosomes mediate the mitochondrial UPR via mTORC1-dependent ATF4 phosphorylation

Project description:Lysosomes are central platforms for not only the degradation of macromolecules but also the integration of multiple signaling pathways. However, whether and how lysosomes mediate the mitochondrial stress response (MSR) remain largely unknown. Here, we demonstrate that lysosomal acidification via the vacuolar H+-ATPase (v-ATPase) is essential for the transcriptional activation of the mitochondrial unfolded protein response (UPRmt). Mitochondrial stress stimulates v-ATPase-mediated lysosomal activation of the mechanistic target of rapamycin complex 1 (mTORC1), which then directly phosphorylates the MSR transcription factor, activating transcription factor 4 (ATF4). Disruption of mTORC1-dependent ATF4 phosphorylation blocks the UPRmt, but not other similar stress responses, such as the UPRER. Finally, ATF4 phosphorylation downstream of the v-ATPase/mTORC1 signaling is indispensable for sustaining mitochondrial redox homeostasis and protecting cells from reactive oxygen species (ROS)-associated cell death upon mitochondrial stress. Thus, v-ATPase/mTORC1-mediated ATF4 phosphorylation via lysosomes links mitochondrial stress to UPRmt activation and mitochondrial function resilience.

2023-06-19 | GSE179510 | GEO

Next Generation Sequencing Facilitates Quantitative Analysis of Cystine-regulated Transcriptomes

Project description:Purpose: To identify differentially expressed genes regulated by cystine. Methods: HCT116 or RKO cells were cultured for 48 hours in cystine-free or 25μM cystine-containing conditional media, and three independent samples were collected by Trizol reagent and subjected to mRNA-sequencing by the LC Bio (Zhejiang, China) and data analysis Results: we identified cystine upregulated 145 genes and downregulated 169 genes in both HCT116 and RKO cells. GO enrichment analysis revealed that cystine regulated biological functions of G1/S transition of mitotic cell cycle and regulation of DNA replication biosynthetic process.In addition, KEGG enrichment analysis showed that mammalian target of rapamycin (mTOR) signaling pathway, a well-known nutrient sensor, was regulated by cystine. Furthermore,we noticed that SESN2 was one of the most significantly downregulated genes by cystine in both cell lines, and confirmed that cystine activates mTORC1 via the GCN2-ATF4-SESN2 axis in colon cancer cells. Conclusions: Our study established that cystine activates mTORC1 through GCN2-ATF4-SESN2 axis.

2021-04-16 | GSE157894 | GEO

Enhanced and selective translation expands the lysosome size and promotes antigen presentation during phagocyte activation

Project description:The mechanisms that govern organelle remodeling remain poorly defined. Lysosomes degrade cargo from various routes including endocytosis, phagocytosis and autophagy. For phagocytes, lysosomes are a kingpin organelle since they are essential to kill pathogens and process and present antigens. During phagocyte activation, lysosomes undergo a striking reorganization, changing from dozens of globular structures to a tubular network, in a process that requires the phosphatidylinositol-3-kinase-AKT-mTOR signalling pathway. Here, we show that lysosomes undergo a remarkable expansion in volume and holding capacity during phagocyte activation within 2 h of LPS stimulation. Lysosome expansion was paralleled by an increase in lysosomal protein levels, but this was unexpectedly independent of TFEB and TFE3 transcription factors, known to scale up lysosome biogenesis. Instead, we demonstrate a hitherto unappreciated mechanism of acute organelle expansion via mTORC1-dependent increase in translation of mRNAs encoding key lysosomal proteins. Importantly, mTORC1-dependent increase in translation activity was necessary for efficient and rapid antigen presentation by dendritic cells. Collectively, we identified a previously unknown and functionally relevant mechanism for lysosome expansion that relies on mTORC1-dependent enhanced translation of mRNAs to boost protein synthesis and lysosome biogenesis in response to an infection signal.

2020-01-07 | GSE136470 | GEO

Identification and characterization of a ribosome receptor for starvation-induced ribophagy

Project description:The lysosome degrades and recycles macromolecules, signals to the master growth regulator mTORC1, and is associated with human disease. Here, we performed quantitative proteomic analyses of lysosomes rapidly isolated using the LysoIP method and find that nutrient levels and mTOR dynamically modulate the lysosomal proteome. We focus on NUFIP1, a protein that upon mTORC1 inhibition redistributes from the nucleus to autophagosomes and lysosomes. Upon these conditions, NUFIP1 interacts with ribosomes and delivers them to autophagosomes by directly binding to LC3B. The starvation-induced degradation of ribosomes via autophagy (ribophagy) depends on the capacity of NUFIP1 to bind LC3B and promotes cell survival. We conclude that NUFIP1 is a receptor for the selective autophagy of ribosomes.

2018-06-21 | PXD009084 | Pride

mTORC1 feedback to AKT modulates MiT/TFE-driven lysosomal biogenesis and EGFR degradation

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.

2020-04-14 | GSE124754 | GEO

Lysosome Lipid Signaling from the Periphery to Neurons Regulates Longevity

Project description:<p>Lysosomes are key cellular organelles that metabolize extra- and intra-cellular substrates. Alterations in lysosomal metabolism are implicated in aging-associated metabolic and neurodegenerative diseases. However, how lysosomal metabolism actively coordinates the metabolic and nervous systems to regulate aging remains unclear. Here, we report a fat-to-neuron lipid signaling pathway induced by lysosomal metabolism and its longevity promoting role in <em>Caenorhabditis elegans</em>. We discovered that induced lysosomal lipolysis in peripheral fat storage tissue up-regulates the neuropeptide signaling pathway in the nervous system to promote longevity. This cell-non-autonomous regulation is mediated by a 47 specific polyunsaturated fatty acid, dihomo-gamma-linolenic acid (DGLA) and LBP-3 lipid chaperone protein transporting from the fat storage tissue to neurons. LBP-3 binds to DGLA, and acts through NHR-49 nuclear receptor and NLP-11 neuropeptide in neurons to extend lifespan. These results reveal lysosomes as a signaling hub to coordinate metabolism and aging, and lysosomal signaling mediated inter-tissue communication in promoting longevity.</p>

2022-05-06 | MTBLS4654 | MetaboLights

Lysosomal Dynamics Orchestrate Neurogenesis [RIP-Seq]

Project description:Lysosomes are cellular recycling stations and metabolic signaling hubs. Whether lysosome dynamics regulate mammalian brain development is unknown. We found that radial glia cells possess a large number of endolysosomes and that asymmetric inheritance of lysosomes in daughters of radial glia cells can predict fate and cell cycle length. To determine the lysosomal regulation of translation initiation by mTORC1/eIF4E axis, we performed RNA immunoprecipitation sequencing (RIP-seq) with antibody against eIF4E in E13.5 neocortex.

2022-08-31 | GSE205683 | GEO

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