Glutamine synthetase regulates the alternative metabolism of γ-aminobutyrate in oral squamous cell carcinoma
Ontology highlight
ABSTRACT: More than 90% of cancer cases in head and neck region are oral squamous cell carcinoma. Recent studies identified several tumor-specific metabolites for the screening or diagnosis of OSCC patients. However, the metabolic reprogramming of OSCC is not well understood. Here, we compared the metabolites between cancerous and paracancerous tissues of OSCC patients and investigated the metabolism of γ-aminobutyrate in OSCC derived cells. Our data revealed that the increase of γ-aminobutyrate was promoted by the synthesis of glutamate beyond the mitochondria, which was regulated by glutamine synthetase. This study is not only benefit for understanding the pathological mechanisms of OSCC, but also has application prospects for the diagnosis and therapy of OSCC.
Project description:Goal of the study is to characterize distinct function(s) of two cytosolic glutamine synthetase (GS) in rice plants. We grew rice lacking GS1;1 and GS1;2 under the ammonium sufficient condition. We harvested roots from the two mutants as well as those of the corresponding control.
Project description:Rice grown in paddy fields prefers to use ammonium ions as a major source of inorganic nitrogen. Glutamine synthetase (GS) catalyzes the conversion of ammonium ions to glutamine. In three cytosolic GS in rice, OsGS1;1 has the critical role for normal growth and grain filling. To understand a role of GS1;1, we performed transcriptional profiling of wild type Nipponbare and GS1;1 mutant plants in seedling using the Agilent Rice Oligo Microarray.
Project description:Goal of the study is to characterize specific function(s) of the cytosolic glutamine synthetase (GS) 1;2 for apical meristem induction in rice plants. To address the issue, we conducted transcript profiling toward basal parts of the knockout mutant lacking GS1;2. We used microarrays conduct transcript profiling of gs1;2 plants. Wild-type samples were used as control.
Project description:During protein synthesis, charged tRNAs deliver amino acids to translating ribosomes, and are then re-charged by tRNA synthetases (aaRS). In humans, mutant aaRS cause a diversity of neurological disorders, but their molecular aetiologies are incompletely characterised. To understand system responses to aaRS depletion, the yeast glutamine aaRS gene (GLN4) was transcriptionally regulated using doxycycline by tet-off control. Depletion of Gln4p inhibited growth, and induced a transcriptional GCN4 amino acid starvation response, indicative of uncharged tRNA accumulation and Gcn2 kinase activation. The GCN4 response was confirmed using SILAC proteomics, using heavy isotope labelling to identify changes in protein expression during glutamine tRNA synthetase depletion.
Project description:We investigated the effect of methionine sulfoximine (MetSox), a potent inhibitor of glutamine synthetase, on Mycobacterium tuberculosis. M. tuberculosis encodes four glutamine synthetases, of which MetSox targets the type I enzyme encoded by glnA1. Trancriptional profiling revealed that glutamate synthetase (gltB) and a type II glutamine synthetase (glnA3) were induced after exposure to MetSox. In addition, we observed a high rate (10(-5)) of spontaneous resistance to MetSox. All resistant strains had a single-nucleotide deletion in the 5' region of glnA1, and Western analysis revealed that GlnA1 expression was increased in resistant as compared with sensitive strains. These data show that M. tuberculosis can respond to the effect of MetSox inhibition either by up-regulation of GlnA3 or by GlnA1. The high frequency of resistance suggests that MetSox and other compounds specifically targeting GlnA1 are not likely to become successful anti-mycobacterial agents. Data is also available from http://bugs.sgul.ac.uk/E-BUGS-112
Project description:The aim of the project was to understand the mechanisms that underlie the oxidative inactivation of human glutamine synthetase (HsGS). For that purpose, we expressed and purified recombinant HsGS, exposed it in phosphate buffer to peroxynitrite (ONOO-) and assessed the functional and structural consequences. To characterize the oxidative post-translational modifications induced by ONOO-, several approaches were carried out (e.g. SDS-PAGE, western-blot, amino acid quantification by LC, etc). The most detailed characterization was performed through LC-MS/MS analysis after trypsin digestion of the ONOO--treated protein, which allowed us to identify the amino acid residues that are modified and to estimate the extent of such modifications.
Project description:We used single-cell RNA sequencing (sc-RNAseq) to examine the diversity and potential function of CD45+ immune cells from URI and glutamine synthetase knockout mouse livers along with their littermate controls.
Project description:Glutamine synthetase (GS), a key enzyme in biological nitrogen assimilation, is regulated in multiple ways in response to varying nitrogen sources and levels. Here we show a small regulatory RNA, NsiR4 (nitrogen stress induced RNA 4), which plays an important role in the regulation of GS in cyanobacteria. NsiR4 expression in the unicellular Synechocystis sp. PCC 6803 and in the filamentous, nitrogen-fixing Anabaena sp. PCC 7120 is stimulated through nitrogen-limitation via NtcA, the global transcriptional regulator of genes involved in nitrogen metabolism. NsiR4 is widely conserved throughout the cyanobacterial phylum, suggesting a conserved function. In silico target prediction, transcriptome profiling upon pulse overexpression and site-directed mutagenesis experiments using a heterologous reporter system showed that NsiR4 interacts with the 5’UTR of gifA mRNA, which encodes glutamine synthetase inactivating factor IF7. In Synechocystis, we observed an inverse relationship between the levels of NsiR4 and the accumulation of IF7 in vivo. This NsiR4-dependent modulation of gifA (IF7) mRNA accumulation influenced the glutamine pool and thus NH4+ assimilation via glutamine synthetase. As a second target, we identified ssr1528, a hitherto uncharacterized nitrogen-regulated gene. Competition experiments between wild type and an NsiR4 knock-out mutant showed that the lack of NsiR4 led to decreased acclimation capabilities of Synechocystis towards oscillating nitrogen levels. These results suggest a role for NsiR4 in the regulation of nitrogen metabolism in cyanobacteria, especially for the adaptation to rapid changes in available nitrogen sources and concentrations. NsiR4 is the first identified bacterial sRNA regulating the primary assimilation of a macronutrient.
Project description:Glutamine synthetases (GS) play central roles in cellular nitrogen assimilation. Although GS active-site formation requires the oligomerization of just two GS subunits, all GS form large, multi-oligomeric machines. Here we describe a structural dissection of the archaeal Methanosarcina mazei (Mm) GS and its regulation. We show that Mm GS forms unstable dodecamers. Strikingly, we show this Mm GS oligomerization property is leveraged for a unique mode of regulation whereby labile Mm GS hexamers are stabilized by binding the nitrogen regulatory protein, GlnK1. Our GS-GlnK1 structure shows that GlnK1 functions as molecular glue to affix GS hexamers together, stabilizing formation of GS active-sites. These data, therefore, reveal the structural basis for a unique form of enzyme regulation by oligomer modulation.