Project description:Amino acid (AA) detection is fundamental for cellular function, balancing translation demands, biochemical pathways, and signaling networks. While the GCN2 and mTORC1 pathways are known to regulate AA sensing, the global cellular response to AA deprivation remains poorly understood, particularly in non-transformed cells, which may exhibit distinct adaptive strategies compared to cancer cells. Here we employed murine pluripotent embryonic stem (ES) cells as a model system to dissect cellular responses to AA stress. Using multi-omics analyses over an extended time course, we examined the effects of arginine (Arg) and leucine (Leu) deprivation, uncovering extensive yet non-lethal proteomic, phosphoproteomic, transcriptomic, and metabolomic adaptations, including increased lysosome production. We found that Arg or Leu starvation induces reversible cell cycle exit, promoting a quiescent state that enhances resistance to cytotoxic stressors. By contrast, cysteine (Cys) and threonine (Thr) deprivation led to cell death via distinct pathways: ferroptosis for Cys starvation, while Thr deprivation triggered a previously uncharacterized form of cell death, which could be entirely suppressed by methionine (Met) co-starvation, mTOR or translational inhibition. These findings suggest that ES cells implement specialized survival strategies in response to different AA limitations, highlighting their ability to reprogram cellular biochemistry under nutrient stress.
Project description:Mammalian cells respond to amino acid limitation by activating a coordinated response to preserve cell function and resources. Here we dissected amino acid stress sensing and adaptation and examined how prolonged arginine or leucine starvation alters cellular behavior of murine embryonic stem cells, that served as a model rapidly proliferating, non-transformed system. We used a temporal approach that combined proteomics, phosphoproteomics (EasyPhos), ubiqitinomics (TUBE-MS), and interaction proteomics (AP-MS) to provide a systematic investigation of the nutrient stress response and regulation networks of mTORC1 (with Castor1 and Sesn2 sensors) as well as cellular adaptation mechanisms.
Project description:Microorganisms can restructure their transcriptional output to adapt to environmental conditions by sensing endogenous metabolite pool. In this study, an Agilent customized microarray representing approximately 4,106 genes was used to study temporal transcript profiles of Bacillus subtilis in response to valine, glutamate and glutamine pulses. Amino-acid-regulated genes were identified having significantly changed expression at one or more time points in response to pulses of valine, glutamate, and glutamine, respectively, and Val-, Glu and Gln-specific genes were further distinguished from them. Different amino acid treatments were compared in terms of both the global temporal profiles and the 5-minute quick regulations, and between-experiment differential genes were identified. The highlighted genes were analyzed based on diverse sources of gene functions using a variety of computational tools, including T-profiler analysis, hierarchical clustering and enrichment of functional categories. The results revealed the common and distinct modes of action of these three amino acids, and should help to elucidate the specific signaling mechanism of each amino acid as an effector. Three amino acids (Glutamate, Glutamine, and Valine) were adopted to perturb the culture of subtilis. Four time-points were investigated for each perturbation. There are two replicates for the first time-point of Valine-treatment experiment.
Project description:Microorganisms can restructure their transcriptional output to adapt to environmental conditions by sensing endogenous metabolite pool. In this study, an Agilent customized microarray representing approximately 4,106 genes was used to study temporal transcript profiles of Bacillus subtilis in response to valine, glutamate and glutamine pulses. Amino-acid-regulated genes were identified having significantly changed expression at one or more time points in response to pulses of valine, glutamate, and glutamine, respectively, and Val-, Glu and Gln-specific genes were further distinguished from them. Different amino acid treatments were compared in terms of both the global temporal profiles and the 5-minute quick regulations, and between-experiment differential genes were identified. The highlighted genes were analyzed based on diverse sources of gene functions using a variety of computational tools, including T-profiler analysis, hierarchical clustering and enrichment of functional categories. The results revealed the common and distinct modes of action of these three amino acids, and should help to elucidate the specific signaling mechanism of each amino acid as an effector.
Project description:Limitation for amino acids is thought to regulate translation in mammalian cells primarily by signaling through the kinases mTORC1 and GCN2. We find that limitation for the amino acid arginine causes a selective loss of tRNA charging, which regulates translation through ribosome pausing at two of six arginine codons. Interestingly, limitation for leucine, an essential and abundant amino acid in protein, results in little or no ribosome pausing. Chemical and genetic perturbation of mTORC1 and GCN2 signaling revealed that their robust response to leucine limitation prevents ribosome pausing, while an insufficient response to arginine limitation led to loss of arginine tRNA charging and ribosome pausing. Codon-specific ribosome pausing decreased protein production and triggered premature ribosome termination without significantly reducing mRNA levels. Together, our results suggest that amino acids which are not optimally sensed by the mTORC1 and GCN2 pathways still regulate translation through an evolutionarily conserved mechanism based on synonymous codon usage.