Acid suspends the circadian clock in hypoxia through inhibition of mTOR
Ontology highlight
ABSTRACT: Recent reports indicate hypoxia influences the clock through the transcriptional activities of hypoxia inducible factors (HIFs) at clock genes. Unexpectedly, we uncover a profound disruption of the circadian clock and diurnal transcriptome when hypoxic cells are permitted to acidify, recapitulating the tumor microenvironment. Buffering against acidification or inhibiting lactic acid production fully rescues circadian oscillation. Acidification of several human and murine cell lines, as well as primary murine T cells, suppresses mechanistic target of rapamycin complex 1 (mTORc1) signaling, a key regulator of translation in response to metabolic status. We find acid drives peripheral redistribution of normally perinuclear lysosomes, inhibiting lysosome-bound mTOR. Restoring mTORc1 signaling and the translation it governs rescues clock oscillation, revealing a model in which lactic acid produced during the cellular metabolic response to hypoxia suppresses the circadian clock through diminished translation of clock constituents.
Project description:The molecular circadian clock, which controls rhythmic 24-hour oscillation of genes, proteins, and metabolites, is disrupted across many human cancers. Deregulated expression of MYC oncoprotein has been shown to alter expression of molecular clock genes, leading to a disruption of molecular clock oscillation across cancer types. It remains unclear what benefit cancer cells gain from suppressing clock oscillation, and how this loss of molecular clock oscillation impacts global gene expression and metabolism in cancer. We hypothesized that MYC suppresses oscillation of gene expression and metabolism to instead upregulate pathways involved in biosynthesis in a static, non-oscillatory fashion. To test this, cells from distinct cancer types with inducible MYC or the closely related N-MYC were examined, using detailed time-series RNA-sequencing and metabolomics, to determine the extent to which MYC activation disrupts global oscillation of genes, gene expression, programs, and metabolites. We focused our analyses on genes, pathways, and metabolites that changed in common across multiple cancer cell line models. We report here that MYC disrupted over 85% of oscillating genes, while instead promoting enhanced ribosomal and mitochondrial biogenesis and suppressed cell attachment pathways. Notably, when MYC is activated, biosynthetic programs that were formerly circadian flipped to being upregulated in an oscillation-free manner. Further, activation of MYC ablates the oscillation of nutrient transporter proteins while greatly upregulating transporter expression, cell surface localization, and intracellular amino acid pools. Finally, we report that MYC disrupts metabolite oscillations and the temporal segregation of amino acid metabolism from nucleotide metabolism. Our results demonstrate that MYC disruption of the molecular circadian clock releases metabolic and biosynthetic processes from circadian control, which may provide a distinct advantage to cancer cells.
Project description:Translation initiation is a rate-limiting step in protein synthesis. The eukaryotic translation initiation factor 4E (eIF4E) plays an essential role in the translation initiation process. However, how eIF4E-dependent translation initiation regulates plant growth and development remains not fully understood. In this study, we have found that Arabidopsis eIF4E proteins distribute both in the nucleus and cytoplasm, and only cytoplasmic eIF4E is implicated in the control of flowering time. Results of profiling the genome-wide translation by Ribo-tag sequencing further reveal that eIF4E may regulate plant flowering by affecting homeostatic translation of flowering-time genes, including the Central Oscillator Genes (COGs). Consistent with the hypothesis that transcription-translation feedback loop is the core mechanism to drive the oscillation of circadian clock, we show that the eIF4E-dependent translation modulates the rhythmic oscillation of protein abundance of the clock-related genes (CCGs). Together, our study provides mechanistic insights into how the protein translation regulates multiple developmental processed in Arabidopsis including circadian clock and photoperiodic flowering.
Project description:The molecular circadian clock, which controls rhythmic 24-hour oscillation of genes, proteins, and metabolites, is disrupted across many human cancers. Deregulated expression of MYC oncoprotein has been shown to alter expression of molecular clock genes, leading to a disruption of molecular clock oscillation across cancer types. However, it remained unclear how this loss of molecular clock oscillation impacted global gene expression and metabolism in cancer, and what benefit cancer cells might gain from suppressing clock oscillation. We hypothesized that MYC suppresses oscillation of gene expression and metabolism to instead upregulate pathways involved in biosynthesis in a static, non-oscillatory fashion. To test this, we utilized cells from distinct cancer types with inducible MYC or the closely related N-MYC to determine, using detailed time-series RNA-sequencing and metabolomics, the extent to which MYC activation disrupts global oscillation of genes, gene expression, programs, and metabolites. We focused our analyses on genes, pathways, and metabolites that changed in common across multiple cancer cell line models. We report here that MYC disrupted over 85% of oscillating genes, while instead promoting enhanced ribosomal and mitochondrial biogenesis and suppressed cell attachment pathways. Notably, when MYC is activated, biosynthetic programs that were formerly circadian flipped to being upregulated in an oscillation-free manner. Further, activation of MYC ablates the oscillation of nutrient transporter glycosylation while greatly upregulating transporter expression, cell surface localization, and intracellular amino acid pools. Finally, we report that MYC disrupts metabolite oscillations and the temporal segregation of amino acid metabolism from nucleotide metabolism. Our results demonstrate that MYC disruption of the molecular circadian clock releases metabolic and biosynthetic processes from circadian control, which may provide a distinct advantage to cancer cells.
Project description:The molecular circadian clock, which controls rhythmic 24-hour oscillation of genes, proteins, and metabolites, is disrupted across many human cancers. Deregulated expression of MYC oncoprotein has been shown to alter expression of molecular clock genes, leading to a disruption of molecular clock oscillation across cancer types. However, it remained unclear how this loss of molecular clock oscillation impacted global gene expression and metabolism in cancer, and what benefit cancer cells might gain from suppressing clock oscillation. We hypothesized that MYC suppresses oscillation of gene expression and metabolism to instead upregulate pathways involved in biosynthesis in a static, non-oscillatory fashion. To test this, we utilized cells from distinct cancer types with inducible MYC or the closely related N-MYC to determine, using detailed time-series RNA-sequencing and metabolomics, the extent to which MYC activation disrupts global oscillation of genes, gene expression, programs, and metabolites. We focused our analyses on genes, pathways, and metabolites that changed in common across multiple cancer cell line models. We report here that MYC disrupted over 85% of oscillating genes, while instead promoting enhanced ribosomal and mitochondrial biogenesis and suppressed cell attachment pathways. Notably, when MYC is activated, biosynthetic programs that were formerly circadian flipped to being upregulated in an oscillation-free manner. Further, activation of MYC ablates the oscillation of nutrient transporter glycosylation while greatly upregulating transporter expression, cell surface localization, and intracellular amino acid pools. Finally, we report that MYC disrupts metabolite oscillations and the temporal segregation of amino acid metabolism from nucleotide metabolism. Our results demonstrate that MYC disruption of the molecular circadian clock releases metabolic and biosynthetic processes from circadian control, which may provide a distinct advantage to cancer cells.
Project description:The circadian clock, which regulates cellular physiology, such as energy metabolism, resides in each cell level throughout the body. Recently, it has been elucidated that the cellular circadian clock is closely linked with cellular differentiation. Moreover, the misregulation of cellular differentiation in mouse embryonic stem cells (ESCs) induced abnormally differentiated cells with impaired circadian clock oscillation, concomitant with the post-transcriptional suppression of CLOCK proteins. Here, we show that the circadian molecular oscillation is disrupted in dysdifferentiation-mediated mouse kidney tumors induced by partial in vivo reprogramming, resembling Wilms tumors. The expression of CLOCK protein was dramatically reduced in the tumor cells despite the Clock mRNA expression. We also showed that a similar loss of CLOCK was observed in human Wilms tumors, suggesting that the circadian molecular clockwork may be disrupted in dysdifferentiation-mediated embryonal tumors such as Wilms tumors, similar to the in vivo reprogramming induced mouse kidney tumors. These results support our previous reports and may provide a novel viewpoint for understanding the pathophysiological nature of cancers through the correlation between cellular differentiation and circadian clock.
Project description:Circadian clock is a highly conserved regulatory system which could coordinate many physiological processes with external stimuli, displaying oscillation with a periodicity of ~24 hour. Dysfunction of circadian clock has been involved in the pathogenesis of a broad spectrum of diseases such as metabolic diseases and chronic kidney disease. However the role of circadian clock in diabetic nephropathy remains largely unknown.
Project description:As a circadian organ, liver executes diverse functions in different phase of the circadian clock. This process is believed to be driven by a transcription program. Here, we present a TF DNA-binding activity centered multi-dimensional proteomics landscape, including DNA-binding activity of TFs, the phosphorylation pattern, ubiquitylation pattern, the nuclear sub-proteome, the whole proteome as well as the transcriptome, to portrait the hierarchical circadian clock network of mouse liver. The TF DNA-binding activity indicates diurnal oscillation in four major pathways, immune response, glucose metabolism, fatty acid metabolism, and the cell cycle. We also isolated the mouse liver Kupffer cells and measured their proteomes in the circadian clock to reveal cell type resolved circadian clock. These are the most comprehensive datasets for circadian clock in the mouse liver and provided the richest data resource for the understanding of mouse liver physiology around the circadian clock.
Project description:As a circadian organ, liver executes diverse functions in different phase of the circadian clock. This process is believed to be driven by a transcription program. Here, we present a TF DNA-binding activity centered multi-dimensional proteomics landscape, including DNA-binding activity of TFs, the phosphorylation pattern, ubiquitylation pattern, the nuclear sub-proteome, the whole proteome as well as the transcriptome, to portrait the hierarchical circadian clock network of mouse liver. The TF DNA-binding activity indicates diurnal oscillation in four major pathways, immune response, glucose metabolism, fatty acid metabolism, and the cell cycle. We also isolated the mouse liver Kupffer cells and measured their proteomes in the circadian clock to reveal cell type resolved circadian clock. These are the most comprehensive datasets for circadian clock in the mouse liver and provided the richest data resource for the understanding of mouse liver physiology around the circadian clock.
Project description:Circadian rhythms are daily physiological and behavioral changes governed by an internal molecular clock, and dysfunctions in circadian rhythms have long been associated with various neurodegenerative diseases. Abnormal sleep-wake cycle often precedes the onset of cognitive and motor symptoms in patients, while the pathological changes may further exacerbate the disturbance in circadian cycle. It is unclear whether dysregulated circadian rhythm is a consequence of, or a contributing factor for, neurodegeneration. In addition, the evidence directly connecting the neurodegeneration-associated proteins to core circadian clock gene expression remains sparse. Here we show that FUS, a RNA-binding protein implicated in the pathogenesis of ALS and frontotemporal dementia, exhibits a bi-directional regulation with circadian rhythm. Our meta-analysis of RNAseq datasets and subsequent biochemical analysis revealed FUS as a gene regulated by circadian oscillation. Furthermore, NR1D1 binds the FUS promoter and regulates the amplitude of FUS oscillation. Meanwhile, FUS is recruited by transcriptional co-repressor PSF, and is found in the same complex as Bmal-Clock to repress Per2 expression. More strikingly, in cells and brain tissues from homozygous knock-in rats, the pathogenic R521C mutant FUS significantly alters the oscillation patterns of core circadian genes even at young age. Therefore, our results have revealed a novel bi-directional mechanism whereby dysregulated circadian clock and FUS expression may exacerbate neurodegeneration via mutual influence.
Project description:Circadian rhythms are daily oscillations in metabolism and physiology and are generated by the circadian clock. In fruit fly Drosophila, the circadian clock is generated by a transcription-translation feedback loop in which the positive arm components Clock and Cycle activate the expression of the Period and Timeless genes of negative arm, as well as other circadian clock-regulated genes. After being retained in the cytoplasm, the Period and Timeless proteins then migrate to the nucleus to inhibit the Clock/Cycle transactivity by protein-protein interactions (PPIs). The endogenous circadian clock is synchronized with the geological (solar) clock via photoreceptors. Drosophila Cryptochrome protein functions as a circadian photoreceptor. In the early morning, exposure of Cryptochrome to light causes a conformational change in it which results in the formation of new PPIs. Light-activated Cryptochrome interacts with the core clock protein Timeless and the E3 ubiquitin ligase-substrate adaptor protein Jetlag, which results in the ubiquitylation of Timeless by Jetlag-E3 ligase complex and then degradation of Timeless within minutes by proteasome system. Rapid degradation of Timeless and then its partner protein Period, because of its instability in the absence of Timeless, relieves the inhibition on the Clock/Cycle transcription factors suddenly. Therefore, Clock/Cycle-driven expression of circadian clock-regulated genes are induced again, which is the restart of the circadian oscillation or the resetting of the clock. Following Timeless degradation, Cryptochrome is also degraded so the photoreceptor mechanism does not start a new resetting signal until all the required factors are re-synthesized in a circadian manner. Light-dependent degradation of Drosophila Cryptochrome can be observed in Drosophila S2 cell line in culture. In this project, we aimed at finding the interactome of Cryptochrome protein in Drosophila S2 cell line under light and in the dark using proximity labeling method. Because of the fast kinetics of Cryptochrome degradation, we chose the enzymes that can saturate in less than one hour. TurboID (TID) and APEX2 enzymes label proteins with biotin in the proximity even though they work with different mechanisms. They were fused to Cryptochrome protein, and proximity labeling was performed in the dark or under light. We have identified novel light-dependent or -independent interactors of Drosophila Cryptochrome and confirmed some of them using classical coimmunoprecipitation technique.