Effect of glutamine on the degradation of glutamine synthetase in hepatoma tissue-culture cells.
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ABSTRACT:
SUBMITTER: Crook RB
PROVIDER: S-EPMC1186203 | biostudies-other | 1978 Oct
REPOSITORIES: biostudies-other
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Project description:Cereblon (CRBN), a substrate receptor for the cullin-RING ubiquitin ligase 4 (CRL4) complex, is a direct protein target for thalidomide teratogenicity and antitumor activity of immunomodulatory drugs (IMiDs). Here we report that glutamine synthetase (GS) is an endogenous substrate of CRL4(CRBN). Upon exposing cells to high glutamine concentration, GS is acetylated at lysines 11 and 14, yielding a degron that is necessary and sufficient for binding and ubiquitylation by CRL4(CRBN) and degradation by the proteasome. Binding of acetylated degron peptides to CRBN depends on an intact thalidomide-binding pocket but is not competitive with IMiDs. These findings reveal a feedback loop involving CRL4(CRBN) that adjusts GS protein levels in response to glutamine and uncover a new function for lysine acetylation.
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Project description:Rapid saltatory nerve conduction is facilitated by myelin structure, which is composed of Schwann cells in the peripheral nervous system. Schwann cells drastically change their phenotype following peripheral nerve injury. These phenotypic changes are required for efficient degeneration/regeneration. We previously identified ZNRF1 as an E3 ubiquitin ligase containing a RING finger motif, whose expression is upregulated in the Schwann cells following nerve injury. This suggested that posttranscriptional regulation of protein expression in Schwann cells may be involved in their phenotypic changes during nerve degeneration/regeneration. Here we report the identification of glutamine synthetase (GS), an enzyme that synthesizes glutamine using glutamate and ammonia, as a substrate for E3 activity of ZNRF1 in Schwann cells. GS is known to be highly expressed in differentiated Schwann cells, but its functional significance has remained unclear. We found that during nerve degeneration/regeneration, GS expression is controlled mostly by ZNRF1-dependent proteasomal degradation. We also found that Schwann cells increase oxidative stress upon initiation of nerve degeneration, which promotes carbonylation and subsequent degradation of GS. Surprisingly, we discovered that GS expression regulates Schwann cell differentiation; i.e., increased GS expression promotes myelination via its enzymatic activity. Among the substrates and products of GS, increased glutamate concentration inhibited myelination and yet promoted Schwann cell proliferation by activating metabotropic glutamate receptor signaling. This would suggest that GS may exert its effect on Schwann cell differentiation by regulating glutamate concentration. These results indicate that the ZNRF1-GS system may play an important role in correlating Schwann cell metabolism with its differentiation.
| S-EPMC6633780 | biostudies-literature
Project description:Glutamine synthetase (GS) plays an essential role in metabolism by catalyzing the synthesis of glutamine from glutamate and ammonia. Our recent study showed that CRBN, a direct protein target for the teratogenic and antitumor activities of immunomodulatory drugs such as thalidomide, lenalidomide, and pomalidomide, recognizes an acetyl degron of GS, resulting in ubiquitylation and degradation of GS in response to glutamine. Here, we report that valosin-containing protein (VCP)/p97 promotes the degradation of ubiquitylated GS, resulting in its accumulation in cells with compromised p97 function. Notably, p97 is also required for the degradation of all four known CRBN neo-substrates [Ikaros family zinc finger proteins 1 (IKZF1) and 3 (IKZF3), casein kinase 1? (CK1?), and the translation termination factor GSPT1] whose ubiquitylation is induced by immunomodulatory drugs. Together, these data point to an unexpectedly intimate relationship between the E3 ubiquitin ligase CRL4CRBN and p97 pathways.
| S-EPMC5389304 | biostudies-literature
Project description:A mouse hepatoma cell line (Hepa1-6 cells, ATCC) was grown in T-25 tissue culture flasks (Corning) at 37ºC in 5% CO2 under two conditions. The first condition was the control, which contained DMEM medium (Gibco BRL) with 25 mM glucose, 4 mM glutamine, 1% penicillin-streptomycin (Sigma), and 10% CPSR-3 (Sigma). The second condition was identical to the first, however the glutamine concentration was altered periodically. Once the cells had grown to confluency, the experiment began at 9:30 PM by exchanging the medium in all flasks. The control flasks received the same medium, containing 4 mM glutamine, while the experimental flasks received identical medium with no glutamine. Twenty-four hours later, the medium was exchanged again, however this time all flasks received medium containing 4 mM glutamine. The first medium exchange was repeated at 48 hours into the experiment, while the second was repeated at 72 hours into the experiment. Hence the glutamine concentration of the experimental flasks oscillated between 0 mM and 4 mM glutamine over 96 hours, while the glutamine concentration of the control flasks remained constant at 4 mM glutamine. At regular intervals, the flasks were sampled. Total RNA was isolated, medium samples were retained, and isotopic measurements were performed from flasks fed different labelled compounds. All samples taken during the experiment were analyzed. The total RNA harvested was labeled and hybridized to DNA microarrays to measure the abundance of transcripts present. Total RNA control samples were labeled using Cy3 dCTP (Perkin-Elmer), and total RNA experimental samples were labeled using Cy5 dCTP (Perkin-Elmer) during reverse transcription. For reverse transcription 10 ug of total RNA was aliquoted into a 6 uL volume. If concentration of the RNA was necessary, this was conducted using a speed vacufuge (Eppendorf) at 60ºC for 10 minutes. The RNA sample was then mixed with 2 uL of 10X Cy-labeled dCTP, 2 uL of 100 mM DTT (Invitrogen), 4 uL of 5X First Strand Buffer (Invitrogen), 2 uL of a dNTP mixture containing 5 mM dGTP, dATP, dTTP and 2 mM dCTP (Invitrogen), 2 uL of 0.5 mg/ mL oligo-dT18-20 (Invitrogen), and 2 uL of Superscript II reverse transcriptase (Invitrogen). This reaction mixture was incubated at 42ºC for approximately two hours. Following the reverse transcription reaction, the RNA template was degraded by addition of 2 uL of 1 N NaOH and incubation at 65 ºC for 10 minutes. The alkaline conditions were then neutralized by addition of 2 uL of 1 N HCl. Samples from identical time points that were to be compared on DNA microarrays were then mixed. The combined sample was cleaned to remove extra primers and nucleotides using a QIAquick Nucleotide Removal kit as described by the manufacturer's instructions. Once cleaned, the sample was concentrated using a speed vacufuge (Eppendorf) for 20 minutes at 65ºC. Following concentration, the sample was resuspended in 32 uL of prewarmed hybridization buffer (Clontech Laboratories), 1 uL was removed for quantitation, and hybridized to prepared oligonucleotide microarrays. Hybridization occurred overnight at 55 ºC using Corning hybridization chambers. The following day the arrays were washed in Glass Hybridization Wash Solution (Clontech Laboratories), and then in 1X SSC, and finally 0.1X SSC. Each wash step was conducted for 20 minutes under high agitation. The arrays were dried by centrifugation and scanned using GenePix 4000B scanner (Axon Instruments). The resulting data was downloaded and formatted in Excel (Microsoft), and then analyzed using Matlab (The MathWorks, Inc.). The arrays used for hybridization were prepared using GAPS glass slides (Corning), and a Virtek arrayer (Bio-Rad). These arrays contained 17,280 features, printed from a synthesized oligonucleotide mouse library (Operon). Briefly, the library was resuspended in 3X SSC, centrifuged, and loaded into the arrayer. Arrays were printed using 32 pins (Telechem), at approximately 50% humidity. Once printed, the probes were crosslinked to the glass slides using a UV Stratalinker (Stratagene). The slides were then blocked for 15 minutes in a 250 mL mixture containing 15.7 g/ L succinic anhydride, 239 mL 1-methyl-2-pyrrolidinone, and 10.7 mL of 1 M boric acid, pH 8.0. They were cleaned by rinsing in 250 mL of milli-Q water (X2), followed by 250 mL of 95% ethanol. They were finally dried using filtered air and stored in the dark at room temperature. Keywords = mouse, liver, hepatoma, cell culture, glutamine, carbon metabolism Keywords: time-course
2003-04-16 | GSE404 | GEO
Project description:A mouse hepatoma cell line (Hepa1-6 cells, ATCC) was grown in T-25 tissue culture flasks (Corning) at 37ºC in 5% CO2 under two conditions. The first condition was the control, which contained DMEM medium (Gibco BRL) with 25 mM glucose, 4 mM glutamine, 1% penicillin-streptomycin (Sigma), and 10% CPSR-3 (Sigma). The second condition was identical to the first, however the glutamine concentration was altered periodically. Once the cells had grown to confluency, the experiment began at 9:30 PM by exchanging the medium in all flasks. The control flasks received the same medium, containing 4 mM glutamine, while the experimental flasks received identical medium with no glutamine. Twenty-four hours later, the medium was exchanged again, however this time all flasks received medium containing 4 mM glutamine. The first medium exchange was repeated at 48 hours into the experiment, while the second was repeated at 72 hours into the experiment. Hence the glutamine concentration of the experimental flasks oscillated between 0 mM and 4 mM glutamine over 96 hours, while the glutamine concentration of the control flasks remained constant at 4 mM glutamine. At regular intervals, the flasks were sampled. Total RNA was isolated, medium samples were retained, and isotopic measurements were performed from flasks fed different labelled compounds. All samples taken during the experiment were analyzed. The total RNA harvested was labeled and hybridized to DNA microarrays to measure the abundance of transcripts present. Total RNA control samples were labeled using Cy3 dCTP (Perkin-Elmer), and total RNA experimental samples were labeled using Cy5 dCTP (Perkin-Elmer) during reverse transcription. For reverse transcription 10 ug of total RNA was aliquoted into a 6 uL volume. If concentration of the RNA was necessary, this was conducted using a speed vacufuge (Eppendorf) at 60ºC for 10 minutes. The RNA sample was then mixed with 2 uL of 10X Cy-labeled dCTP, 2 uL of 100 mM DTT (Invitrogen), 4 uL of 5X First Strand Buffer (Invitrogen), 2 uL of a dNTP mixture containing 5 mM dGTP, dATP, dTTP and 2 mM dCTP (Invitrogen), 2 uL of 0.5 mg/ mL oligo-dT18-20 (Invitrogen), and 2 uL of Superscript II reverse transcriptase (Invitrogen). This reaction mixture was incubated at 42ºC for approximately two hours. Following the reverse transcription reaction, the RNA template was degraded by addition of 2 uL of 1 N NaOH and incubation at 65 ºC for 10 minutes. The alkaline conditions were then neutralized by addition of 2 uL of 1 N HCl. Samples from identical time points that were to be compared on DNA microarrays were then mixed. The combined sample was cleaned to remove extra primers and nucleotides using a QIAquick Nucleotide Removal kit as described by the manufacturer's instructions. Once cleaned, the sample was concentrated using a speed vacufuge (Eppendorf) for 20 minutes at 65ºC. Following concentration, the sample was resuspended in 32 uL of prewarmed hybridization buffer (Clontech Laboratories), 1 uL was removed for quantitation, and hybridized to prepared oligonucleotide microarrays. Hybridization occurred overnight at 55 ºC using Corning hybridization chambers. The following day the arrays were washed in Glass Hybridization Wash Solution (Clontech Laboratories), and then in 1X SSC, and finally 0.1X SSC. Each wash step was conducted for 20 minutes under high agitation. The arrays were dried by centrifugation and scanned using GenePix 4000B scanner (Axon Instruments). The resulting data was downloaded and formatted in Excel (Microsoft), and then analyzed using Matlab (The MathWorks, Inc.). The arrays used for hybridization were prepared using GAPS glass slides (Corning), and a Virtek arrayer (Bio-Rad). These arrays contained 17,280 features, printed from a synthesized oligonucleotide mouse library (Operon). Briefly, the library was resuspended in 3X SSC, centrifuged, and loaded into the arrayer. Arrays were printed using 32 pins (Telechem), at approximately 50% humidity. Once printed, the probes were crosslinked to the glass slides using a UV Stratalinker (Stratagene). The slides were then blocked for 15 minutes in a 250 mL mixture containing 15.7 g/ L succinic anhydride, 239 mL 1-methyl-2-pyrrolidinone, and 10.7 mL of 1 M boric acid, pH 8.0. They were cleaned by rinsing in 250 mL of milli-Q water (X2), followed by 250 mL of 95% ethanol. They were finally dried using filtered air and stored in the dark at room temperature. Keywords = mouse, liver, hepatoma, cell culture, glutamine, carbon metabolism
2010-06-05 | E-GEOD-404 | biostudies-arrayexpress
Project description:BACKGROUND:Many neuroprotective approaches targeting neurons in animal models fail to provide benefits for the treatment of ischemic stroke in clinic and glial cells have become the targets in some basic studies. Baicalin has neuroprotective effects but the mechanisms related to glial cells are not revealed. This study investigated whether and how baicalin can combat excitotoxicity via protecting the functions of astrocytes in early stage of ischemia/reperfusion (I/R) insult by focusing on glutamine synthetase (GS). EXPERIMENTAL APPROACH:The role of baicalin was explored in primary astrocytes exposed to oxygen-glucose deprivation/reperfusion (OGD/R) and rats subjected to middle cerebral artery occlusion/reperfusion (MCAO/R). KEY RESULTS:Mitochondrial succinate dehydrogenase (SDH) activation led to an excessive production of reactive oxygen species (ROS) via reverse electron transport (RET) under conditions of OGD/R or I/R, which increased the carbonylation and proteasomal degradation of GS in astrocytes. Treatment of baicalin decreased the oxidative stress mediated by SDH and reduced the subsequent loss of GS. This effect increased the glutamate disposal by astrocytes and protected neurons from excitotoxicity in response to I/R insults. CONCLUSIONS AND IMPLICATIONS:Baicalin inactivated SDH to suppress ROS production and protected GS protein stability against oxidative stress, contributing to the improvement of the glutamate disposal and decrease in excitotoxicity. These results suggest that protection of GS stability in astrocytes might be an effective strategy to prevent neuronal injury in acute ischemic stroke.
| S-EPMC7260594 | biostudies-literature
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.
| S-EPMC10651883 | biostudies-literature
Project description:BackgroundCisplatin (CDDP) significantly prolongs survival in various cancers, but many patients also develop resistance that results in treatment failure. Thus, this study aimed to elucidate the underlying mechanisms by which ovarian cancer cells acquire CDDP resistance.MethodsWe evaluated the metabolic profiles in CDDP-sensitive ovarian cancer A2780 cells and CDDP-resistant A2780cis cells using capillary electrophoresis-time-of-flight mass spectrometry (CE-TOFMS). We further examined the expression of glutamine metabolism enzymes using real-time PCR and Western blot analyses. Cell viability was accessed using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay.ResultsThe results showed that levels of glutamine, glutamate, and glutathione (GSH), a key drug resistance mediator synthesized from glutamate, were significantly elevated in A2780cis cells than those in A2780 cells. Furthermore, glutamine starvation decreased the GSH levels and CDDP resistance in A2780cis cells. Interestingly, the expression of glutamine synthetase (GS/GLUL), which synthesizes glutamine from glutamate and thereby negatively regulates GSH production, was almost completely suppressed in resistant A2780cis cells. In addition, treatment of A2780cis cells with 5-aza-2'-deoxycytidine, a DNA-demethylating agent, restored GS expression and reduced CDDP resistance. In contrast, GS knockdown in CDDP-sensitive A2780 cells induced CDDP resistance.ConclusionsThe results indicate that upregulation of GSH synthesis from glutamine via DNA methylation-mediated silencing of GS causes CDDP resistance in A2780cis cells. Therefore, glutamine metabolism could be a novel therapeutic target against CDDP resistance.
| S-EPMC7891143 | biostudies-literature
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.
2019-04-01 | E-MTAB-6303 | biostudies-arrayexpress
Project description:Effect of [6]-gingerol, a major pungent component in ginger, on the proliferation of a rat ascites hepatoma AH109A cells was investigated by measuring [(3)H]thymidine incorporation into acid-insoluble fraction of the cultured cells and that on the invasion by co-culturing the hepatoma cells with rat mesentery-derived mesothelial cells. [6]-Gingerol inhibited both the proliferation and invasion of hepatoma cells in a dose-dependent manner at concentrations of 6.25-200 muM (proliferation) and 50-200 muM (invasion). [6]-Gingerol accumulated cells in S phase and elongated doubling time of hepatoma cells, and increased the rate of apoptosis. Hepatoma cells previously cultured with hypoxanthine (HX) and xanthine oxidase (XO) or with hydrogen peroxide showed increased invasive activities. [6]-Gingerol suppressed the reactive oxygen species-potentiated invasive capacity by simultaneously treating AH109A cells with [6]-gingerol, HX and XO or with [6]-gingerol and hydrogen peroxide. Furthermore, [6]-gingerol reduced the intracellular peroxide levels in AH109A cells. These results suggest that the suppression of hepatoma cell proliferation by [6]-gingerol may be due to cell cycle arrest and apoptosis induction. They also suggest that the anti-oxidative property of [6]-gingerol may be involved in its anti-invasive activity of hepatoma cells.
| S-EPMC2553670 | biostudies-other