Project description:Spinocerebellar ataxia type 2 (SCA2) is a neurodegenerative disorder, which is caused by an unstable CAG-repeat expansion in the SCA2 gene, that encodes a polyglutamine tract (polyQ-tract) expansion in ataxin-2 protein (ATXN2). The RNA-binding protein ATXN2 interacts with the poly(A)-binding protein PABPC1, localizing to ribosomes at the rough endoplasmic reticulum or to polysomes. Under cell stress ATXN2 and PABPC1 show redistribution to stress granules where mRNAs are kept away from translation and from degradation. It is unknown whether ATXN2 associates preferentially with specific mRNAs or how it modulates their processing. Here, we investigated Atxn2 knock-out (Atxn2-/-) mouse liver, cerebellum and midbrain regarding their RNA profile, employing oligonucleotide microarrays for screening and RNA deep sequencing for validation. Modest ~1.4-fold upregulations were observed for the level of many mRNAs encoding ribosomal proteins and other translation pathway factors. Quantitative reverse transcriptase PCR and immunoblots in liver tissue confirmed these effects and demonstrated an inverse correlation also with PABPC1 mRNA and protein. ATXN2 deficiency also enhanced phosphorylation of the ribosomal protein S6, while impairing the global protein synthesis rate, suggesting a block between the enhanced translation drive and the impaired execution. Furthermore, ATXN2 overexpression and deficiency retarded cell cycle progression. ATXN2 mRNA levels showed a delayed phasic twofold increase under amino acid and serum starvation, similar to ATXN3, but different from motor neuron disease genes MAPT and SQSTM1. ATXN2 mRNA levels depended particularly on mTOR signalling. Altogether the data implicate ATXN2 in the adaptation of mRNA translation and cell growth to nutrient availability and stress. Factorial design comparing ataxin-2 knock-out mice with wild type littermates in three different tissues (midbrain, cerebellum, liver) and 3 different ages.
Project description:Spinocerebellar ataxia type 2 (SCA2) is a neurodegenerative disorder, which is caused by an unstable CAG-repeat expansion in the SCA2 gene, that encodes a polyglutamine tract (polyQ-tract) expansion in ataxin-2 protein (ATXN2). The RNA-binding protein ATXN2 interacts with the poly(A)-binding protein PABPC1, localizing to ribosomes at the rough endoplasmic reticulum or to polysomes. Under cell stress ATXN2 and PABPC1 show redistribution to stress granules where mRNAs are kept away from translation and from degradation. It is unknown whether ATXN2 associates preferentially with specific mRNAs or how it modulates their processing. Here, we investigated Atxn2 knock-out (Atxn2-/-) mouse liver, cerebellum and midbrain regarding their RNA profile, employing oligonucleotide microarrays for screening and RNA deep sequencing for validation. Modest ~1.4-fold upregulations were observed for the level of many mRNAs encoding ribosomal proteins and other translation pathway factors. Quantitative reverse transcriptase PCR and immunoblots in liver tissue confirmed these effects and demonstrated an inverse correlation also with PABPC1 mRNA and protein. ATXN2 deficiency also enhanced phosphorylation of the ribosomal protein S6, while impairing the global protein synthesis rate, suggesting a block between the enhanced translation drive and the impaired execution. Furthermore, ATXN2 overexpression and deficiency retarded cell cycle progression. ATXN2 mRNA levels showed a delayed phasic twofold increase under amino acid and serum starvation, similar to ATXN3, but different from motor neuron disease genes MAPT and SQSTM1. ATXN2 mRNA levels depended particularly on mTOR signalling. Altogether the data implicate ATXN2 in the adaptation of mRNA translation and cell growth to nutrient availability and stress.
Project description:mTORC2 senses nutrients and coordinates substrate metabolism and macromolecule synthesis program with the availability of external nutrient availability. Knockdown of mTORC2 components and its chaperone partners impairs both nutrient sensing and downstrem metabolism/growth programs.
Project description:The median eminence (ME) of the hypothalamus is a structure that rapidly adapts to nutrient availability. We have used single-cell RNA sequencing to characterize the transcriptional profiles of cells specifically in the median eminence in the fasted and refed states. In our study, we focus on characterizing the oligodendrocyte population of the ME, and identifying how subpopulations respond to nutrient availability.
Project description:There is a fundamental gap in understanding the consequences of tau-ribosome interactions. Tau oligomers and filaments hinder protein synthesis in vitro, and they associate strongly with ribosomes in vivo. Here, we investigated the consequences of tau interactions with ribosomes in vivo and in human brain tissues to identify tau as a direct modulator of ribosomal selectivity. We performed microarrays and nascent proteomics to measure changes in protein synthesis using rTg4510 tau transgenic mice. We determined that tau expression differentially shifts the transcriptome and the proteome and that the synthesis of ribosomal proteins is reversibly dependent on tau levels. We further extended these results to human brains and show that tau pathologically interacts with ribosomal protein S6 (rpS6 or S6). Consequently, synthesis of ribosomal proteins coded by 5’TOP-mRNAs was reduced under tauopathic conditions in Alzheimer’s disease brains. Our data establish tau as a driver of RNA translation selectivity. Moreover, considering that regulation of protein synthesis is critical to learning and memory, aberrant tau-ribosome interactions in disease could explain the linkage between virtually every tauopathy and cognitive impairment and memory decline.
2019-03-30 | GSE121264 | GEO
Project description:GCN2 Adapts Protein Synthesis to Scavenging-Dependent Growth
Project description:Skeletal muscle mass is an important determinant of whole-body glucose disposal. We here show that mice (M-PDK1KO mice) with skeletal muscle–specific deficiency of 3'-phosphoinositide–dependent kinase 1 (PDK1), a key component of the phosphatidylinositol 3-kinase (PI3K) signaling pathway, manifest a reduced skeletal muscle mass under the static condition as well as impairment of exercise load–induced muscle hypertrophy. Whereas exercise load-induced changes in gene expression were not affected, the phosphorylation of ribosomal protein S6 kinase (S6K) and S6 induced by exercise load was attenuated in skeletal muscle of M-PDK1KO mice, suggesting that PDK1 regulates muscle hypertrophy not through changes in gene expression but through stimulation of protein synthesis via the S6K-S6 axis.
Project description:<p>In pre-weaning calves, both leucine and threonine play important roles in growth and muscle metabolism. In this study, metabolomics, proteomics and clinical chemistry were used to assess the effects of leucine and threonine supplementation added to milk replacer on 14 newborn Holstein male calves: 7 were fed a control diet (Ctrl) and 7 were fed the Ctrl diet supplemented with 0.3% leucine and 0.3% threonine (LT) from 5.6 days of age to 53.6 days. At this time, blood and semitendinosus muscle biopsies were collected for analysis. Integrated metabolomics and proteomics showed that branched-chain amino acids (BCAA) degradation and mitochondrial oxidative metabolism (citrate cycle and respiratory chain) were the main activated pathways in muscle because of the supplementation. BCAA derivatives and metabolites related to lipid mobilization showed the major changes. The deleterious effects of activated oxidative phosphorylation were balanced by the upregulation of antioxidant proteins. An increase in protein synthesis was indicated by elevated aminoacyl-tRNA biosynthesis and increased S6 ribosomal protein phosphorylation in skeletal muscle. In conclusion, LT group showed greater BCAA availability and mitochondrial oxidative activity; as the muscle cells undergo greater aerobic metabolism, antioxidant defenses were activated to compensate for possible cell damage. Data are available via ProteomeXchange (PXD016098).</p><p><strong>SIGNIFICANCE:</strong> Leucine and threonine are essential amino acids for the pre-weaning calf, being of high importance for growth. In this study, we found that leucine and threonine supplementation of milk replacer to feed pre-weaning calves led to differences in the proteome, metabolome and clinical chemistry analytes in skeletal muscle and plasma, albeit no differences in productive performance were recorded. This study extends our understanding on the metabolism in dairy calves and helps optimizing their nutritional status.</p><p><br></p><p><strong>Data availability:</strong></p><p>The proteomics data have been deposited into the ProteomeXchange Consortium via the PRIDE partner repository with the data set identifier <a href='https://www.ebi.ac.uk/pride/archive/projects/PXD016098' rel='noopener noreferrer' target='_blank'>PXD016098</a>.</p>
Project description:The mechanistic target of rapamycin complex 1 (mTORC1) is involved in nutrient-induced signaling and is a master regulator of cell growth and metabolism. Amino acid-deficient conditions affect mTORC1 activity; however, its upstream regulators warrant further investigation. MicroRNAs are key regulators of nutrient-related responses; therefore, the present study aimed to assess the leucine starvation-induced microRNA profile and its impact on mTORC1 activity. Transcriptome analysis of human hepatocellular carcinoma cells (HepG2) under leucine deprivation revealed that hsa-miR-663a and hsa-miR-1469 were altered in a transcription factor 4-dependent manner. Overexpression of these microRNAs induced phosphorylation of the ribosomal protein S6 kinase beta-1, a mTORC1 downstream target. Furthermore, hsa-miR-663a downregulated proline-rich Akt1 substrate of 40 kDa (PRAS40), one of the mTORC1 components. In summary, this study provides new insights into the regulatory role of microRNAs in amino acid metabolism and demonstrate alterations in microRNA profile under leucine deprivation in human hepatocytes.
Project description:Glutathione peroxidase 4 (GPX4) utilizes glutathione (GSH) to detoxify lipid peroxidation and
plays an essential role in inhibiting ferroptosis. As a selenoprotein, GPX4 protein synthesis is
highly inefficient and energetically costly. How cells coordinate GPX4 synthesis with nutrient
availability remains unclear. In this study, integrated proteomic and functional analyses reveal
that SLC7A11-mediated cystine uptake promotes not only GSH synthesis but also GPX4 protein synthesis. Mechanistically, cyst(e)ine activates mechanistic/mammalian target of rapamycin complex 1 (mTORC1) and promotes GPX4 protein synthesis at least partly through the mTORC1-4E-BP signaling axis. Pharmacologic inhibition of mTORC1 decreases GPX4 protein levels, sensitizes cancer cells to ferroptosis, and synergizes with ferroptosis inducers (FINs) to suppress patient-derived xenograft tumor growth in vivo. Together, our results reveal a hitherto unrecognized regulatory mechanism to coordinate GPX4 protein synthesis with cyst(e)ine availability and suggest to use the combination of mTORC1 inhibitors and FINs in cancer treatment.