The Experts below are selected from a list of 23699454 Experts worldwide ranked by ideXlab platform
Laure Gaufichon - One of the best experts on this subject based on the ideXlab platform.
-
ASN1-encoded asparagine synthetase in floral organs contributes to nitrogen filling in Arabidopsis seeds
Plant Journal, 2017Co-Authors: Laure Gaufichon, Sylvie Citerne, Takashi Hase, Anne Marmagne, Yukiko Sakakibara, Olivier Grandjean, Katia Belcram, Takayuki Yoneyama, Gilles Clément, Stéphanie Boutet-merceyAbstract:Despite a general view that asparagine synthetase generates asparagine as an amino acid for long-distance transport of nitrogen to sink organs, its role in nitrogen metabolic pathways in floral organs during seed nitrogen filling has remained undefined. We demonstrate that the onset of pollination in Arabidopsis induces selected genes for asparagine metabolism, namely ASN1 (At3g47340), GLN2 (At5g35630), GLU1 (At5g04140), AapAT2 (At5g19950), ASPGA1 (At5g08100) and ASPGB1 (At3g16150), particularly at the ovule stage (stage 0), accompanied by enhanced asparagine synthetase protein, asparagine and total amino acids. Immunolocalization confined asparagine synthetase to the vascular cells of the silique cell wall and septum, but also to the outer and inner seed integuments, demonstrating the post-phloem transport of asparagine in these cells to developing embryos. In the asn1 mutant, aberrant embryo cell divisions in upper suspensor cell layers from globular to heart stages assign a role for nitrogen in differentiating embryos within the ovary. Induction of asparagine metabolic genes by light/dark and nitrate supports fine shifts of nitrogen metabolic pathways. In transgenic Arabidopsis expressing promoter CaMV35S::ASN1 fusion, marked metabolomics changes at stage 0, including a several-fold increase in free asparagine, are correlated to enhanced seed nitrogen. However, specific promoter Napin2S::ASN1 expression during seed formation and a six-fold increase in asparagine toward the desiccation stage result in wild-type seed nitrogen, underlining that delayed accumulation of asparagine impairs the timing of its use by releasing amide and amino nitrogen. Transcript and metabolite profiles in floral organs match the carbon and nitrogen partitioning to generate energy via the tricarboxylic acid cycle, GABA shunt and phosphorylated serine synthetic pathway.
-
Asparagine metabolic pathways in arabidopsis
Plant and Cell Physiology, 2016Co-Authors: Laure Gaufichon, Steven J Rothstein, Akira SuzukiAbstract:Inorganic nitrogen in the form of ammonium is assimilated into asparagine via multiple steps involving glutamine synthetase (GS), glutamate synthase (GOGAT), aspartate aminotransferase (AspAT) and asparagine synthetase (AS) in Arabidopsis. The asparagine amide group is liberated by the reaction catalyzed by asparaginase (ASPG) and also the amino group of asparagine is released by asparagine aminotransferase (AsnAT) for use in the biosynthesis of amino acids. Asparagine plays a primary role in nitrogen recycling, storage and transport in developing and germinating seeds, as well as in vegetative and senescence organs. A small multigene family encodes isoenzymes of each step of asparagine metabolism in Arabidopsis, except for asparagine aminotransferase encoded by a single gene. The aim of this study is to highlight the structure of the genes and encoded enzyme proteins involved in asparagine metabolic pathways; the regulation and role of different isogenes; and kinetic and physiological properties of encoded enzymes in different tissues and developmental stages.
-
Arabidopsis thaliana ASN2 encoding asparagine synthetase is involved in the control of nitrogen assimilation and export during vegetative growth
Plant Cell and Environment, 2013Co-Authors: Laure Gaufichon, Yukiko Sakakibara, Michèle Cren-reisdorf, Olivier Grandjean, Gilles Clément, Celine Masclaux-daubresse, Guillaume Tcherkez, Toshiharu Hase, Jean-christophe Avice, Anne MarmagneAbstract:We investigated the function of ASN2, one of the three genes encoding asparagine synthetase (EC 6.3.5.4), which is the most highly expressed in vegetative leaves of Arabidopsis thaliana. Expression of ASN2 and parallel higher asparagine content in darkness suggest that leaf metabolism involves ASN2 for asparagine synthesis. In asn2-1 knockout and asn2-2 knockdown lines, ASN2 disruption caused a defective growth phenotype and ammonium accumulation. The asn2 mutant leaves displayed a depleted asparagine and an accumulation of alanine, GABA, pyruvate and fumarate, indicating an alanine formation from pyruvate through the GABA shunt to consume excess ammonium in the absence of asparagine synthesis. By contrast, asparagine did not contribute to photorespiratory nitrogen recycle as photosynthetic net CO2 assimilation was not significantly different between lines under both 21 and 2% O2. ASN2 was found in phloem companion cells by in situ hybridization and immunolocalization. Moreover, lack of asparagine in asn2 phloem sap and lowered 15N flux to sinks, accompanied by the delayed yellowing (senescence) of asn2 leaves, in the absence of asparagine support a specific role of asparagine in phloem loading and nitrogen reallocation. We conclude that ASN2 is essential for nitrogen assimilation, distribution and remobilization (via the phloem) within the plant.
-
Biological functions of asparagine synthetase in plants
Plant Science, 2010Co-Authors: Laure Gaufichon, Michèle Cren-reisdorf, Fabien Chardon, Steven J Rothstein, Akira SuzukiAbstract:Ammonium is a form of inorganic nitrogen derived from several metabolic pathways, and is assimilated into glutamine, glutamate, asparagine and carbamoylphosphate. These molecules play important roles in nitrogen assimilation, recycling, transport and storage in plants. Ammonium assimilation into asparagine is catalyzed by ammonia-dependent asparagine synthetase encoded by asnA (EC 6.3.1.1) or glutamine-dependent asparagine synthetase encoded by asnB (EC 6.3.5.4) in prokaryotes and eukaryotes. These organisms display a distinct distribution of these two forms of asparagine synthetase. Gene and primary protein structure for asparagine synthetase-A and -B from prokaryotes and eukaryotes is examined. Using nucleotide sequences, we constructed a phylogenetic tree that distinguished two major classes (classes I and II) for ASN genes from a range of organisms. Only the glutamine-dependent asparagine synthetases-B have been identified, and are encoded by a small multigene family in plants. The isoenzyme encoded by each member of the gene family provides asparagine at specific phases of development. These include the nitrogen mobilization in germinating seeds, nitrogen recycling in vegetative organs in response to stress, and nitrogen remobilization during seed embryogenesis. The expression of genes for asparagine synthetase is regulated by light and metabolites. Genetic and molecular data using mutants and transgenic plants have provided insights into the light perception by the photoreceptors, carbon and nitrogen sensing and signal transduction mechanism in the asn regulation. Global analysis of carbon and nitrogen metabolites supports the impact of asn regulation in the synthesis and transport of asparagine in plants.
Akira Suzuki - One of the best experts on this subject based on the ideXlab platform.
-
Asparagine metabolic pathways in arabidopsis
Plant and Cell Physiology, 2016Co-Authors: Laure Gaufichon, Steven J Rothstein, Akira SuzukiAbstract:Inorganic nitrogen in the form of ammonium is assimilated into asparagine via multiple steps involving glutamine synthetase (GS), glutamate synthase (GOGAT), aspartate aminotransferase (AspAT) and asparagine synthetase (AS) in Arabidopsis. The asparagine amide group is liberated by the reaction catalyzed by asparaginase (ASPG) and also the amino group of asparagine is released by asparagine aminotransferase (AsnAT) for use in the biosynthesis of amino acids. Asparagine plays a primary role in nitrogen recycling, storage and transport in developing and germinating seeds, as well as in vegetative and senescence organs. A small multigene family encodes isoenzymes of each step of asparagine metabolism in Arabidopsis, except for asparagine aminotransferase encoded by a single gene. The aim of this study is to highlight the structure of the genes and encoded enzyme proteins involved in asparagine metabolic pathways; the regulation and role of different isogenes; and kinetic and physiological properties of encoded enzymes in different tissues and developmental stages.
-
Biological functions of asparagine synthetase in plants
Plant Science, 2010Co-Authors: Laure Gaufichon, Michèle Cren-reisdorf, Fabien Chardon, Steven J Rothstein, Akira SuzukiAbstract:Ammonium is a form of inorganic nitrogen derived from several metabolic pathways, and is assimilated into glutamine, glutamate, asparagine and carbamoylphosphate. These molecules play important roles in nitrogen assimilation, recycling, transport and storage in plants. Ammonium assimilation into asparagine is catalyzed by ammonia-dependent asparagine synthetase encoded by asnA (EC 6.3.1.1) or glutamine-dependent asparagine synthetase encoded by asnB (EC 6.3.5.4) in prokaryotes and eukaryotes. These organisms display a distinct distribution of these two forms of asparagine synthetase. Gene and primary protein structure for asparagine synthetase-A and -B from prokaryotes and eukaryotes is examined. Using nucleotide sequences, we constructed a phylogenetic tree that distinguished two major classes (classes I and II) for ASN genes from a range of organisms. Only the glutamine-dependent asparagine synthetases-B have been identified, and are encoded by a small multigene family in plants. The isoenzyme encoded by each member of the gene family provides asparagine at specific phases of development. These include the nitrogen mobilization in germinating seeds, nitrogen recycling in vegetative organs in response to stress, and nitrogen remobilization during seed embryogenesis. The expression of genes for asparagine synthetase is regulated by light and metabolites. Genetic and molecular data using mutants and transgenic plants have provided insights into the light perception by the photoreceptors, carbon and nitrogen sensing and signal transduction mechanism in the asn regulation. Global analysis of carbon and nitrogen metabolites supports the impact of asn regulation in the synthesis and transport of asparagine in plants.
Michael Bidinosti - One of the best experts on this subject based on the ideXlab platform.
-
Repair of isoaspartate formation modulates the interaction of deamidated 4E-BP2 with mTORC1 in brain.
The Journal of biological chemistry, 2010Co-Authors: Michael Bidinosti, Yvan Martineau, Filipp Frank, Nahum SonenbergAbstract:In eukaryotes, a rate-limiting step of translation initiation is recognition of the mRNA 5′ m7GpppN cap structure by the eukaryotic initiation factor 4F (eIF4F), a heterotrimeric complex consisting of the cap-binding protein, eIF4E, along with eIF4G, and eIF4A. The eIF4E-binding proteins (4E-BPs) repress translation by disrupting eIF4F formation, thereby preventing ribosome recruitment to the mRNA. Of the three 4E-BPs, 4E-BP2 is the predominant paralog expressed in the mammalian brain and plays an important role in synaptic plasticity and learning and memory. 4E-BP2 undergoes asparagine deamidation, solely in the brain, during early postnatal development. Deamidation spontaneously converts asparagines into a mixture of aspartates or isoaspartates, the latter of which may be destabilizing to proteins. The enzyme protein l-isoaspartyl methyltransferase (PIMT) prevents isoaspartate accumulation by catalyzing the conversion of isoaspartates to aspartates. PIMT exhibits high activity in the brain, relative to other tissues. We report here that 4E-BP2 is a substrate for PIMT. In vitro deamidated 4E-BP2 accrues isoapartyl residues and is methylated by recombinant PIMT. Using an antibody that recognizes 4E-BP2, which harbors isoaspartates at the deamidation sites, Asn99 and Asn102, we demonstrate that 4E-BP2 in PIMT−/− brain lysates contains isoaspartate residues. Further, we show that 4E-BP2 containing isoaspartates lacks the augmented association with raptor that is a feature of deamidated 4E-BP2.
-
postnatal deamidation of 4e bp2 in brain enhances its association with raptor and alters kinetics of excitatory synaptic transmission
Molecular Cell, 2010Co-Authors: Michael Bidinosti, Maria Del Rayo Sanchezcarbente, Yvan Martineau, Christos G Gkogkas, Mauro Costamattioli, Anne-claude Gingras, Wayne S Sossin, Brian Raught, Clive R Bramham, Luc DesgroseillersAbstract:Summary The eIF4E-binding proteins (4E-BPs) repress translation initiation by preventing eIF4F complex formation. Of the three mammalian 4E-BPs, only 4E-BP2 is enriched in the mammalian brain and plays an important role in synaptic plasticity and learning and memory formation. Here we describe asparagine deamidation as a brain-specific posttranslational modification of 4E-BP2. Deamidation is the spontaneous conversion of asparagines to aspartates. Two deamidation sites were mapped to an asparagine-rich sequence unique to 4E-BP2. Deamidated 4E-BP2 exhibits increased binding to the mammalian target of rapamycin (mTOR)-binding protein raptor, which effects its reduced association with eIF4E. 4E-BP2 deamidation occurs during postnatal development, concomitant with the attenuation of the activity of the PI3K-Akt-mTOR signaling pathway. Expression of deamidated 4E-BP2 in 4E-BP2 −/− neurons yielded mEPSCs exhibiting increased charge transfer with slower rise and decay kinetics relative to the wild-type form. 4E-BP2 deamidation may represent a compensatory mechanism for the developmental reduction of PI3K-Akt-mTOR signaling.
Nahum Sonenberg - One of the best experts on this subject based on the ideXlab platform.
-
Repair of isoaspartate formation modulates the interaction of deamidated 4E-BP2 with mTORC1 in brain.
The Journal of biological chemistry, 2010Co-Authors: Michael Bidinosti, Yvan Martineau, Filipp Frank, Nahum SonenbergAbstract:In eukaryotes, a rate-limiting step of translation initiation is recognition of the mRNA 5′ m7GpppN cap structure by the eukaryotic initiation factor 4F (eIF4F), a heterotrimeric complex consisting of the cap-binding protein, eIF4E, along with eIF4G, and eIF4A. The eIF4E-binding proteins (4E-BPs) repress translation by disrupting eIF4F formation, thereby preventing ribosome recruitment to the mRNA. Of the three 4E-BPs, 4E-BP2 is the predominant paralog expressed in the mammalian brain and plays an important role in synaptic plasticity and learning and memory. 4E-BP2 undergoes asparagine deamidation, solely in the brain, during early postnatal development. Deamidation spontaneously converts asparagines into a mixture of aspartates or isoaspartates, the latter of which may be destabilizing to proteins. The enzyme protein l-isoaspartyl methyltransferase (PIMT) prevents isoaspartate accumulation by catalyzing the conversion of isoaspartates to aspartates. PIMT exhibits high activity in the brain, relative to other tissues. We report here that 4E-BP2 is a substrate for PIMT. In vitro deamidated 4E-BP2 accrues isoapartyl residues and is methylated by recombinant PIMT. Using an antibody that recognizes 4E-BP2, which harbors isoaspartates at the deamidation sites, Asn99 and Asn102, we demonstrate that 4E-BP2 in PIMT−/− brain lysates contains isoaspartate residues. Further, we show that 4E-BP2 containing isoaspartates lacks the augmented association with raptor that is a feature of deamidated 4E-BP2.
Yvan Martineau - One of the best experts on this subject based on the ideXlab platform.
-
Repair of isoaspartate formation modulates the interaction of deamidated 4E-BP2 with mTORC1 in brain.
The Journal of biological chemistry, 2010Co-Authors: Michael Bidinosti, Yvan Martineau, Filipp Frank, Nahum SonenbergAbstract:In eukaryotes, a rate-limiting step of translation initiation is recognition of the mRNA 5′ m7GpppN cap structure by the eukaryotic initiation factor 4F (eIF4F), a heterotrimeric complex consisting of the cap-binding protein, eIF4E, along with eIF4G, and eIF4A. The eIF4E-binding proteins (4E-BPs) repress translation by disrupting eIF4F formation, thereby preventing ribosome recruitment to the mRNA. Of the three 4E-BPs, 4E-BP2 is the predominant paralog expressed in the mammalian brain and plays an important role in synaptic plasticity and learning and memory. 4E-BP2 undergoes asparagine deamidation, solely in the brain, during early postnatal development. Deamidation spontaneously converts asparagines into a mixture of aspartates or isoaspartates, the latter of which may be destabilizing to proteins. The enzyme protein l-isoaspartyl methyltransferase (PIMT) prevents isoaspartate accumulation by catalyzing the conversion of isoaspartates to aspartates. PIMT exhibits high activity in the brain, relative to other tissues. We report here that 4E-BP2 is a substrate for PIMT. In vitro deamidated 4E-BP2 accrues isoapartyl residues and is methylated by recombinant PIMT. Using an antibody that recognizes 4E-BP2, which harbors isoaspartates at the deamidation sites, Asn99 and Asn102, we demonstrate that 4E-BP2 in PIMT−/− brain lysates contains isoaspartate residues. Further, we show that 4E-BP2 containing isoaspartates lacks the augmented association with raptor that is a feature of deamidated 4E-BP2.
-
postnatal deamidation of 4e bp2 in brain enhances its association with raptor and alters kinetics of excitatory synaptic transmission
Molecular Cell, 2010Co-Authors: Michael Bidinosti, Maria Del Rayo Sanchezcarbente, Yvan Martineau, Christos G Gkogkas, Mauro Costamattioli, Anne-claude Gingras, Wayne S Sossin, Brian Raught, Clive R Bramham, Luc DesgroseillersAbstract:Summary The eIF4E-binding proteins (4E-BPs) repress translation initiation by preventing eIF4F complex formation. Of the three mammalian 4E-BPs, only 4E-BP2 is enriched in the mammalian brain and plays an important role in synaptic plasticity and learning and memory formation. Here we describe asparagine deamidation as a brain-specific posttranslational modification of 4E-BP2. Deamidation is the spontaneous conversion of asparagines to aspartates. Two deamidation sites were mapped to an asparagine-rich sequence unique to 4E-BP2. Deamidated 4E-BP2 exhibits increased binding to the mammalian target of rapamycin (mTOR)-binding protein raptor, which effects its reduced association with eIF4E. 4E-BP2 deamidation occurs during postnatal development, concomitant with the attenuation of the activity of the PI3K-Akt-mTOR signaling pathway. Expression of deamidated 4E-BP2 in 4E-BP2 −/− neurons yielded mEPSCs exhibiting increased charge transfer with slower rise and decay kinetics relative to the wild-type form. 4E-BP2 deamidation may represent a compensatory mechanism for the developmental reduction of PI3K-Akt-mTOR signaling.
