Dataset Information

Protein kinase A controls the hexosamine pathway by tuning feedback inhibition of GFAT-1

ABSTRACT: The hexosamine pathway (HP) is a key anabolic pathway whose product uridine 5’-diphospho-N-acetyl-D-glucosamine (UDP-GlcNAc) is an essential precursor for all glycosylation processes in mammals. It modulates the ER stress response, is implicated in cancer and diabetes, and HP activation extends lifespan in Caenorhabditis elegans. The highly conserved glutamine fructose-6-phosphate amidotransferase 1 (GFAT 1) is the first and rate-limiting HP enzyme. GFAT 1 activity is modulated through UDP-GlcNAc feedback inhibition and by kinase signaling, including Ser205 phosphorylation by protein kinase A (PKA). The consequence and molecular mechanism of GFAT 1 PKA phosphorylation, however, remains poorly understood. Here, we identify the GFAT 1 R203H substitution that elevates UDP-GlcNAc levels in C. elegans, leading to ER stress resistance. In human GFAT-1, the R203H substitution interfered with UDP-GlcNAc inhibition and with PKA-mediated Ser205 phosphorylation. Of note, Ser205 phosphorylation had two discernible effects: It lowered baseline GFAT 1 activity while abolishing UDP-GlcNAc feedback inhibition. Thus, GFAT-1 phosphorylation by PKA uncoupled the feedback loop of the HP and depending on UDP-GlcNAc availability, phosphorylation by PKA lowers or enhances GFAT 1 activity in vivo. Mechanistically, our data indicate that the relative positioning of the two GFAT 1 domains might be affected by phosphorylation and we propose a model how Ser205 phosphorylation modulates the activity and feedback inhibition of GFAT 1.

INSTRUMENT(S): Orbitrap Fusion

ORGANISM(S): Homo Sapiens (human)

SUBMITTER: Ilian Atanassov

LAB HEAD: Martin S. Denzel

PROVIDER: PXD020451 | Pride | 2020-07-23

REPOSITORIES: Pride

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Protein kinase A controls the hexosamine pathway by tuning the feedback inhibition of GFAT-1.

Ruegenberg Sabine S Mayr Felix A M C FAMC Atanassov Ilian I Baumann Ulrich U Denzel Martin S MS

Nature communications 20210412 1

The hexosamine pathway (HP) is a key anabolic pathway whose product uridine 5'-diphospho-N-acetyl-D-glucosamine (UDP-GlcNAc) is an essential precursor for glycosylation processes in mammals. It modulates the ER stress response and HP activation extends lifespan in Caenorhabditis elegans. The highly conserved glutamine fructose-6-phosphate amidotransferase 1 (GFAT-1) is the rate-limiting HP enzyme. GFAT-1 activity is modulated by UDP-GlcNAc feedback inhibition and via phosphorylation by protein k ...[more]

PMID: 33846315

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Project description:Over the past decades, protein O-GlcNAcylation has been found to play a fundamental role in cell cycle control, metabolism, transcriptional regulation, and cellular signaling. Nevertheless, quantitative approaches to determine in vivo GlcNAc dynamics at a large-scale are still not readily available. Here, we have developed an approach to isotopically label O-GlcNAc modifications on proteins by producing 13C-labeled UDP-GlcNAc from 13C6-glucose via the hexosamine biosynthetic pathway. This metabolic labeling was combined with quantitative mass spectrometry-based proteomics to determine site-specific protein O-GlcNAcylation turnover rates. First, an efficient enrichment method for O-GlcNAc peptides was developed with the use of phenylboronic acid solid-phase extraction and anhydrous DMSO. The near stoichiometry reaction between the diol of GlcNAc and boronic acid dramatically improved the enrichment efficiency. Additionally, our kinetic model for turnover rates integrates both metabolomic and proteomic data, which increase the accuracy of the turnover rate estimation. Other advantages of this metabolic labeling method include in vivo application, direct labeling of the O-GlcNAc sites and higher confidence for site identification. Concentrating only on nuclear localized GlcNAc modified proteins, we are able to identify 159 O-GlcNAc sites on 74 proteins and determine turnover rates of 24 O-GlcNAc peptides from 21 proteins extracted from HeLa nuclei. In general, we found O-GlcNAcylation turnover rates are slower than those published for phosphorylation or acetylation. Nevertheless, the rates widely varied depending on both the protein and the residue modified. We believe this methodology can be broadly applied to reveal turnovers/dynamics of protein O-GlcNAcylation from different biological states and will provide more information on the significance of site-specific O-GlcNAcylation, enabling us to study the temporal dynamics of this critical modification in a site-specific manner for the first time.

Project description:Drosophila development is a complex and dynamic process regulated, in part, by members of the Polycomb (Pc), Trithorax (Trx) and Compass chromatin modifier complexes. O-GlcNAc Transferase (OGT/SXC) is essential for Pc repression suggesting that the O-GlcNAcylation of proteins plays a key role in regulating development. OGT transfers N-acetyl-D-glucosamine (GlcNAc) onto hydroxyl groups of serine or threonine residues of key transcriptional regulators using the nutrient-derived UDP-GlcNAc as a substrate, which is dynamically removed by O-GlcNAcase (OGA). We performed ChIP-chip and microarray analysis after OGT or OGA RNAi knockdown in Drosophila S2 cells and found that O-GlcNAc was elevated genome wide particularly at genes related to mitosis and cell cycle in OGA RNAi cells, but not at sites co-occupied by Pc member Pleiohomeotic (Pho), such as the Hox and NK homeobox gene clusters. Microarray analysis suggested that altered O-GlcNAc cycling perturbed the expression of genes associated with morphogenesis and cell cycle regulation. To examine the in vivo consequences of disturbed O-GlcNAc cycling in the whole animal, we produced a null allele of oga (ogadel.1) in Drosophila. Epigenetic activators including Trx group members Trithorax (Trx), Absent small or homeotic discs 1 (Ash1) and Compass member Set1 histone methyltransferases are O-GlcNAc modified in ogadel.1 mutants. ogadel.1 mutants displayed altered expression of a distinct set of cell cycle related genes in ovaries. Our results suggest that the loss of OGA could affect epigenetic machinery by accumulating O-GlcNAc on numerous chromatin factors including Trx, Ash1 and Set1 in Drosophila. We performed affymetrix tilingarray analysis after OGT or OGA RNAi knockdown in Drosophila S2 cells to find if that O-GlcNAc was elevated genome wide particularly at genes related to mitosis and cell cycle in OGA RNAi cells, but not at sites co-occupied by Pc member Pleiohomeotic (Pho), ------------------------------- This represents the gene expression component only

Dataset Information

Protein kinase A controls the hexosamine pathway by tuning feedback inhibition of GFAT-1

Publications

Protein kinase A controls the hexosamine pathway by tuning the feedback inhibition of GFAT-1.

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