Genome-wide CRISPR screening reveals nucleotide synthesis negatively regulates autophagy
Ontology highlight
ABSTRACT:
PROVIDER: PRJNA691936 | ENA |
REPOSITORIES: ENA
Dataset's files
| Action | DRS | |||
|---|---|---|---|---|
| SRR13430514_1.fastq.gz | Fastqsanger.gz | |||
| SRR13430514_2.fastq.gz | Fastqsanger.gz | |||
| SRR13430515_1.fastq.gz | Fastqsanger.gz | |||
| SRR13430515_2.fastq.gz | Fastqsanger.gz | |||
| SRR13430516_1.fastq.gz | Fastqsanger.gz |
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Project description:Macroautophagy (hereafter, autophagy) is a process that directs the degradation of cytoplasmic material in lysosomes. In addition to its homeostatic roles, autophagy undergoes dynamic positive and negative regulation in response to multiple forms of cellular stress, thus enabling the survival of cells. However, the precise mechanisms of autophagy regulation are not fully understood. To identify potential negative regulators of autophagy, we performed a genome-wide CRISPR screen using the quantitative autophagic flux reporter GFP-LC3-RFP. We identified phosphoribosylformylglycinamidine synthase (PFAS), a component of the de novo purine synthesis pathway, as one such negative regulator of autophagy. Autophagy was activated in cells lacking PFAS or phosphoribosyl pyrophosphate amidotransferase (PPAT), another de novo purine synthesis enzyme, or treated with methotrexate when exogenous levels of purines were insufficient. Purine starvation-induced autophagy activation was concomitant with mTORC1 suppression, and was profoundly suppressed in cells deficient for TSC2, which negatively regulates mTORC1 through inhibition of RHEB, suggesting that purines regulate autophagy through the TSC-RHEB-mTORC1 signaling axis. Moreover, depletion of the pyrimidine synthesis enzymes carbamoyl-phosphate synthetase 2, aspartate transcarbamylase, and dihydroorotase (CAD) and dihydroorotate dehydrogenase (DHODH) activated autophagy as well, although mTORC1 activity was not altered by pyrimidine shortage. These results suggest a different mechanism of autophagy induction between purine and pyrimidine starvation. These findings provide novel insights into the regulation of autophagy by nucleotides and possibly the role of autophagy in nucleotide metabolism, leading to further developing anticancer strategies involving nucleotide synthesis and autophagy.
2021-05-11 | GSE164778 | GEO
Project description:Macroautophagy (hereafter, autophagy) is a process that directs the degradation of cytoplasmic material in lysosomes. In addition to its homeostatic roles, autophagy undergoes dynamic positive and negative regulation in response to multiple forms of cellular stress, thus enabling the survival of cells. However, the precise mechanisms of autophagy regulation are not fully understood. To identify potential negative regulators of autophagy, we performed a genome-wide CRISPR screen using the quantitative autophagic flux reporter GFP-LC3-RFP. We identified phosphoribosylformylglycinamidine synthase, a component of the de novo purine synthesis pathway, as one such negative regulator of autophagy. Autophagy was activated in cells lacking phosphoribosylformylglycinamidine synthase or phosphoribosyl pyrophosphate amidotransferase, another de novo purine synthesis enzyme, or treated with methotrexate when exogenous levels of purines were insufficient. Purine starvation-induced autophagy activation was concomitant with mammalian target of rapamycin complex 1 (mTORC1) suppression and was profoundly suppressed in cells deficient for tuberous sclerosis complex 2, which negatively regulates mTORC1 through inhibition of Ras homolog enriched in brain, suggesting that purines regulate autophagy through the tuberous sclerosis complex-Ras homolog enriched in brain-mTORC1 signaling axis. Moreover, depletion of the pyrimidine synthesis enzymes carbamoyl-phosphate synthetase 2, aspartate transcarbamylase, and dihydroorotase and dihydroorotate dehydrogenase activated autophagy as well, although mTORC1 activity was not altered by pyrimidine shortage. These results suggest a different mechanism of autophagy induction between purine and pyrimidine starvation. These findings provide novel insights into the regulation of autophagy by nucleotides and possibly the role of autophagy in nucleotide metabolism, leading to further developing anticancer strategies involving nucleotide synthesis and autophagy.
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Project description:Yap regulates glucose utilization and sustains nucleotide synthesis to enable organ growth
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Project description:Mitochondrial oxidative phosphorylation (OXPHOS) generates ATP and is required for pyrimidine nucleotide synthesis during proliferation. In contrast, the role of OXPHOS in post-mitotic cells, beyond its contribution to ATP production, is less understood. Here, we show that in non-proliferating cells, OXPHOS ensures protection against oxidative stress by sustaining autophagy. Autophagy is suppressed and oxidative stress resistance is compromised in OXPHOS-deficient non-proliferating cells in vitro and in TFAM knockout mice in vivo, while attenuation of autophagy in OXPHOS-functional cells phenocopies the effects of OXPHOS deficiency. Mechanistically, the regulation of the autophagy / stress response by OXPHOS does not require changes in gene expression, AMPK/mTOR1/ULK1 signaling or NADH levels. Instead, OXPHOS maintains ROS levels to prevent activation of ATG4, a ROS-activated inhibitor of autophagy. We propose that protection against oxidative stress via the ROS-ATG4 axis is a novel function of mitochondrial respiration in non-proliferating cells that may have consequences for cancer therapy and beyond.
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2015-11-10 | E-MTAB-3085 | biostudies-arrayexpress
Project description:In response to starvation, cells undergo a metabolic shift to ensure their survival by shutting down protein synthesis and activating catabolic processes, including autophagy, to degrade proteins and recycle nutrients. These processes, however, do require protein synthesis. We asked how this fundamental conflict is resolved. Upon starvation, cells activate the Integrated Stress Response (ISR) and inhibit mammalian target of rapamycin complex 1 (mTORC1). The ISR inhibits protein translation through the phosphorylation of the alpha subunit of eukaryotic translation initiation factor 2 (eIF2), whereas mTORC1 inhibition induces activation of the transcription factors TFEB/TFE3. We discovered that PPP1R15A (aka GADD34), a member of the protein phosphatase 1 complex (PP1) is a direct and early target of TFEB. GADD34 recruits PP1 to dephosphorylate eIF2 and thus fine-tunes protein synthesis to enable translation of the transcriptional program induced by starvation leading to a sustained autophagic flux.
2020-09-30 | PXD016149 | Pride
Project description:The nucleotide messenger (p)ppGpp allows bacteria to adapt to fluctuating environments by reprogramming the transcriptome. Despite its well-recognized role in gene regulation, (p)ppGpp is only known to directly affect transcription in Proteobacteria by binding to the RNA polymerase. Here we reveal a different mechanism of gene regulation by (p)ppGpp in Firmicutes from soil bacteria to pathogens: (p)ppGpp directly binds to the transcription factor PurR to downregulate purine biosynthesis. We identified PurR as a receptor of (p)ppGpp in Bacillus anthracis and revealed that (p)ppGpp strongly enhances PurR binding to its regulon in the Bacillus subtilis genome. A co-structure reveals that (p)ppGpp binds to a PurR pocket reminiscent of the active site of PRT enzymes that has been repurposed to serve a purely regulatory role, where the effectors (p)ppGpp and PRPP compete to allosterically control transcription. PRPP inhibits PurR DNA binding to induce transcription of purine synthesis genes, whereas (p)ppGpp antagonizes PRPP to enhance PurR DNA binding and repress transcription. A (p)ppGpp-refractory purR mutant fails to downregulate purine synthesis genes upon starvation. Our work establishes the precedent of (p)ppGpp as a classical effector of transcription repressors and reveals the key function of (p)ppGpp in regulating nucleotide synthesis through gene regulation, from the human intestinal tract to host-pathogen interfaces.
2021-12-10 | GSE185164 | GEO
Project description:Autophagy is an intracellular degradation mechanism in response to nutrient starvation. Via autophagy, some non-essential cellular constituents are degraded in a lysosome-dependent manner to generate biomolecules that can be utilized for maintaining the metabolic homeostasis. Although it is known that under starvation, the global protein synthesis is significantly reduced mainly due to suppression of mechanistic target of rapamycin (MTOR), there is emerging evidence demonstrating that de novo protein synthesis is involved in the autophagic process. However, characterizing these de novo proteins has been an issue with current techniques. Here, we developed a novel method to identify newly synthesized proteins during starvation-mediated autophagy by combining bio-orthogonal non-canonical amino acid tagging (BONCAT) and isobaric tags for relative and absolute quantitation (iTRAQ). Using bio-orthogonal metabolic tagging, L-azidohomoalanine (AHA) was incorporated into newly synthesized proteins which were then enriched with avidin beads after a click reaction between alkyne bearing biotin and AHA’s bio-orthogonal azide moiety. The enriched proteins were subjected to iTRAQ labeling for protein identification and quantification using liquid chromatography-tandem mass spectrometry (LC-MS/MS). A total of 711 proteins were identified. The characterized functional profiles of these newly synthesized proteins by bioinformatics analysis suggest their roles in ensuring the pro-survival outcome of autophagy. Finally, we performed validation assays for some selected proteins and found that knockdown of some genes has a significant impact on starvation-induced autophagy and cell death. Thus, the BONCAT-iTRAQ approach is effective in the identification of newly synthesized proteins and provides useful insights to the molecular mechanisms and biological functions of autophagy.
2016-10-18 | PXD003546 | Pride
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