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1.
Cell ; 156(6): 1179-1192, 2014 Mar 13.
Artículo en Inglés | MEDLINE | ID: mdl-24630721

RESUMEN

The hexosamine biosynthetic pathway (HBP) generates uridine diphosphate N-acetylglucosamine (UDP-GlcNAc) for glycan synthesis and O-linked GlcNAc (O-GlcNAc) protein modifications. Despite the established role of the HBP in metabolism and multiple diseases, regulation of the HBP remains largely undefined. Here, we show that spliced X-box binding protein 1 (Xbp1s), the most conserved signal transducer of the unfolded protein response (UPR), is a direct transcriptional activator of the HBP. We demonstrate that the UPR triggers HBP activation via Xbp1s-dependent transcription of genes coding for key, rate-limiting enzymes. We further establish that this previously unrecognized UPR-HBP axis is triggered in a variety of stress conditions. Finally, we demonstrate a physiologic role for the UPR-HBP axis by showing that acute stimulation of Xbp1s in heart by ischemia/reperfusion confers robust cardioprotection in part through induction of the HBP. Collectively, these studies reveal that Xbp1s couples the UPR to the HBP to protect cells under stress.


Asunto(s)
Vías Biosintéticas , Proteínas de Unión al ADN/metabolismo , Hexosaminas/metabolismo , Factores de Transcripción/metabolismo , Respuesta de Proteína Desplegada , Animales , Glutamina-Fructosa-6-Fosfato Transaminasa (Isomerizadora) , Humanos , Masculino , Ratones , Ratones Transgénicos , Isquemia Miocárdica/metabolismo , Daño por Reperfusión Miocárdica/metabolismo , Miocitos Cardíacos/metabolismo , Transferasas de Grupos Nitrogenados/genética , Factores de Transcripción del Factor Regulador X , Proteína 1 de Unión a la X-Box
2.
Immunity ; 43(3): 463-74, 2015 Sep 15.
Artículo en Inglés | MEDLINE | ID: mdl-26320659

RESUMEN

TREX1 is an endoplasmic reticulum (ER)-associated negative regulator of innate immunity. TREX1 mutations are associated with autoimmune and autoinflammatory diseases. Biallelic mutations abrogating DNase activity cause autoimmunity by allowing immunogenic self-DNA to accumulate, but it is unknown how dominant frameshift (fs) mutations that encode DNase-active but mislocalized proteins cause disease. We found that the TREX1 C terminus suppressed immune activation by interacting with the ER oligosaccharyltransferase (OST) complex and stabilizing its catalytic integrity. C-terminal truncation of TREX1 by fs mutations dysregulated the OST complex, leading to free glycan release from dolichol carriers, as well as immune activation and autoantibody production. A connection between OST dysregulation and immune disorders was demonstrated in Trex1(-/-) mice, TREX1-V235fs patient lymphoblasts, and TREX1-V235fs knock-in mice. Inhibiting OST with aclacinomycin corrects the glycan and immune defects associated with Trex1 deficiency or fs mutation. This function of the TREX1 C terminus suggests a potential therapeutic option for TREX1-fs mutant-associated diseases.


Asunto(s)
Citosol/enzimología , Exodesoxirribonucleasas/metabolismo , Hexosiltransferasas/metabolismo , Proteínas de la Membrana/metabolismo , Fosfoproteínas/metabolismo , Aclarubicina/análogos & derivados , Aclarubicina/farmacología , Animales , Células Cultivadas , Embrión de Mamíferos/citología , Exodesoxirribonucleasas/antagonistas & inhibidores , Exodesoxirribonucleasas/genética , Fibroblastos/citología , Fibroblastos/efectos de los fármacos , Fibroblastos/metabolismo , Mutación del Sistema de Lectura , Células HEK293 , Células HeLa , Hexosiltransferasas/genética , Humanos , Inmunidad Innata/genética , Immunoblotting , Proteínas de la Membrana/genética , Ratones Endogámicos C57BL , Ratones Noqueados , Ratones Transgénicos , Microscopía Fluorescente , Fosfoproteínas/antagonistas & inhibidores , Fosfoproteínas/genética , Polisacáridos/metabolismo , Unión Proteica , Interferencia de ARN , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa
3.
J Virol ; 94(6)2020 02 28.
Artículo en Inglés | MEDLINE | ID: mdl-31852778

RESUMEN

Enteric viruses infect the gastrointestinal tract, and bacteria can promote replication and transmission of several enteric viruses. Viruses can be inactivated by exposure to heat or bleach, but poliovirus, coxsackievirus B3, and reovirus can be stabilized by bacteria or bacterial polysaccharides, limiting inactivation and aiding transmission. We previously demonstrated that certain N-acetylglucosamine (GlcNAc)-containing polysaccharides can stabilize poliovirus. However, the detailed virus-glycan binding specificity and glycan chain length requirements, and thus the mechanism of virion stabilization, have been unclear. A previous limitation was our lack of defined-length glycans to probe mechanisms and consequences of virus-glycan interactions. Here, we generated a panel of polysaccharides and oligosaccharides to determine the properties required for binding and stabilization of poliovirus. Poliovirus virions are nonenveloped icosahedral 30-nm particles with 60 copies of each of four capsid proteins, VP1 to VP4. VP1 surrounds the 5-fold axis, and our past work indicates that this region likely contains the glycan binding site. We found that relatively short GlcNAc oligosaccharides, such as a six-unit GlcNAc oligomer, can bind poliovirus but fail to enhance virion stability. Virion stabilization required binding of long GlcNAc polymers of greater than 20 units. Our data suggest a model where GlcNAc polymers of greater than 20 units bind and bridge adjacent 5-fold axes, thus aiding capsid rigidity and stability. This study provides a deeper understanding of enteric virus-bacterial glycan interactions, which are important for virion environmental stability and transmission.IMPORTANCE Enteric viruses are transmitted through the fecal-oral route, but how enteric viruses survive in the environment is unclear. Previously, we found that bacterial polysaccharides enhance poliovirus stability against heat or bleach inactivation, but the specific molecular requirements have been unknown. Here, we showed that certain short-chain oligosaccharides can bind to poliovirus but do not increase virion stability. Long-chain polysaccharides bind and may bridge adjacent sites on the viral surface, thus increasing capsid rigidity and stability. This work defines the unique interactions of poliovirus and glycans, which provides insight into virion environmental stability and transmission.


Asunto(s)
Enterovirus/metabolismo , Oligosacáridos/metabolismo , Poliovirus/fisiología , Polisacáridos , Virión/fisiología , Animales , Bacterias/metabolismo , Proteínas de la Cápside/metabolismo , Chlorocebus aethiops , Infecciones por Enterovirus/virología , Células HeLa , Humanos , Lipopolisacáridos/metabolismo , Células Vero
4.
Proc Natl Acad Sci U S A ; 115(38): 9557-9562, 2018 09 18.
Artículo en Inglés | MEDLINE | ID: mdl-30181269

RESUMEN

Oligosaccharyltransferases (OSTs) N-glycosylate proteins by transferring oligosaccharides from lipid-linked oligosaccharides (LLOs) to asparaginyl residues of Asn-Xaa-Ser/Thr acceptor sequons. Mammals have OST isoforms with STT3A or STT3B catalytic subunits for cotranslational or posttranslational N-glycosylation, respectively. OSTs also hydrolyze LLOs, forming free oligosaccharides (fOSs). It has been unclear whether hydrolysis is due to one or both OSTs, segregated from N-glycosylation, and/or regulated. Transfer and hydrolysis were assayed in permeabilized HEK293 kidney and Huh7.5.1 liver cells lacking STT3A or STT3B. Transfer by both STT3A-OST and STT3B-OST with synthetic acceptors was robust. LLO hydrolysis by STT3B-OST was readily detected and surprisingly modulated: Without acceptors, STT3B-OST hydrolyzed Glc3Man9GlcNAc2-LLO but not Man9GlcNAc2-LLO, yet it hydrolyzed both LLOs with acceptors present. In contrast, LLO hydrolysis by STT3A-OST was negligible. STT3A-OST however may be regulatory, because it suppressed STT3B-OST-dependent fOSs. TREX1, a negative innate immunity factor that diminishes immunogenic fOSs derived from LLOs, acted through STT3B-OST as well. In summary, only STT3B-OST hydrolyzes LLOs, depending upon LLO quality and acceptor site occupancy. TREX1 and STT3A suppress STT3B-OST-dependent fOSs. Without strict kinetic limitations during posttranslational N-glycosylation, STT3B-OST can thus moonlight for LLO hydrolysis. In contrast, the STT3A-OST/translocon complex preserves LLOs for temporally fastidious cotranslational N-glycosylation.


Asunto(s)
Hexosiltransferasas/metabolismo , Lipopolisacáridos/metabolismo , Proteínas de la Membrana/metabolismo , Oligosacáridos/metabolismo , Procesamiento Proteico-Postraduccional/fisiología , Animales , Línea Celular , Retículo Endoplásmico/metabolismo , Exodesoxirribonucleasas/genética , Exodesoxirribonucleasas/metabolismo , Técnicas de Inactivación de Genes , Glicosilación , Hexosiltransferasas/genética , Humanos , Hidrólisis , Isoenzimas , Proteínas de la Membrana/genética , Ratones , Fosfoproteínas/genética , Fosfoproteínas/metabolismo , Transporte de Proteínas/fisiología
5.
FASEB J ; 33(6): 6801-6812, 2019 06.
Artículo en Inglés | MEDLINE | ID: mdl-30811219

RESUMEN

Herpes simplex virus 1 (HSV-1) is a contagious neurotropic herpesvirus responsible for oral lesions and herpesviral encephalitis. The HSV-1 envelope contains N-glycosylated proteins involved in infection and that are candidate drug targets. NGI-1 is a small-molecule inhibitor of oligosaccharyltransferase (OST) complexes STT3A-OST and STT3B-OST, which catalyze cotranslational and post-translational N-glycosylation, respectively. Because host OSTs attach HSV-1 glycans, NGI-1 might have anti-HSV-1 activity. We evaluated HSV-1 function using NGI-1 and human embryonic kidney 293 knockout lines for OST isoform-specific catalytic and accessory subunits. N-glycosylation of 2 representative envelope proteins (gC and gD) was primarily dependent upon STT3A-OST, but to a large extent replaceable by STT3B-OST. Knockouts impairing STT3A- or STT3B-OST activity, by themselves, did not appreciably affect HSV-1 function (plaque-forming units, normalized to viral particles measured by unglycosylated capsid protein VP5 content). However, with cells lacking STT3B-OST activity (missing the catalytic subunit STT3B or the oxidoreductase subunits magnesium transporter 1/tumor suppressor candidate 3) and thus solely dependent upon STT3A-OST for N-glycosylation, NGI-1 treatment resulted in HSV-1 having cell type-dependent dysfunction (affecting infectivity with Vero cells much more than with the 293 lines). Ablation of post-translational N-glycosylation can therefore make HSV-1 infectivity, and possibly masking of immunogenic peptide epitopes by glycans, highly sensitive to pharmacological inhibition of cotranslational N-glycosylation.-Lu, H., Cherepanova, N. A., Gilmore, R., Contessa, J. N., Lehrman, M. A. Targeting STT3A-oligosaccharyltransferase with NGI-1 causes herpes simplex virus 1 dysfunction.


Asunto(s)
Benzamidas/farmacología , Herpes Simple/tratamiento farmacológico , Herpesvirus Humano 1/efectos de los fármacos , Hexosiltransferasas/antagonistas & inhibidores , Proteínas de la Membrana/antagonistas & inhibidores , Procesamiento Proteico-Postraduccional/efectos de los fármacos , Sulfonamidas/farmacología , Animales , Chlorocebus aethiops , Retículo Endoplásmico/efectos de los fármacos , Retículo Endoplásmico/metabolismo , Retículo Endoplásmico/virología , Glicosilación , Células HEK293 , Herpes Simple/metabolismo , Herpes Simple/virología , Humanos , Células Vero
6.
Trends Biochem Sci ; 40(12): 715-717, 2015 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-26476576

RESUMEN

The mechanism for flipping large lipid-linked oligosaccharides across membranes has remained a paradox. Perez et al. now report the structure of the PglK protein of C. jejuni, a flippase for a bacterial lipid-linked oligosaccharide, and reveal an unexpected whip-like mechanism.


Asunto(s)
Transportadoras de Casetes de Unión a ATP/química , Transportadoras de Casetes de Unión a ATP/metabolismo , Biocatálisis , Campylobacter jejuni/enzimología , Lipopolisacáridos/metabolismo
7.
Glycobiology ; 29(2): 106-109, 2019 02 01.
Artículo en Inglés | MEDLINE | ID: mdl-30388226

RESUMEN

Discovered 40 years ago, the Lec5 glycosylation mutant cell line has a complex recessive genotype and is characterized by accumulation of lipid-linked oligosaccharide assembly intermediates, reduced conversion of polyprenols to dolichols, and an unusual phenotypic dependence upon cell culture conditions such as temperature, plating density and medium quality. The heritable defect in Lec5 is unknown. Here we demonstrate an unexpected epigenetic basis for Lec5, with a surprising linkage to increased expression of homeobox genes, which in turn is associated with increased transcription of cholesterol biosynthesis genes. These results suggest testable hypotheses for the biochemical abnormalities of the Lec5 mutant.


Asunto(s)
Colesterol/genética , Genes Homeobox/genética , Lectinas/genética , Lipopolisacáridos/genética , Colesterol/metabolismo , Glicosilación , Humanos , Lectinas/metabolismo , Lipopolisacáridos/metabolismo , Mutación
8.
Nat Chem Biol ; 12(12): 1023-1030, 2016 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-27694802

RESUMEN

Asparagine (N)-linked glycosylation is a protein modification critical for glycoprotein folding, stability, and cellular localization. To identify small molecules that inhibit new targets in this biosynthetic pathway, we initiated a cell-based high-throughput screen and lead-compound-optimization campaign that delivered a cell-permeable inhibitor, NGI-1. NGI-1 targets oligosaccharyltransferase (OST), a hetero-oligomeric enzyme that exists in multiple isoforms and transfers oligosaccharides to recipient proteins. In non-small-cell lung cancer cells, NGI-1 blocks cell-surface localization and signaling of the epidermal growth factor receptor (EGFR) glycoprotein, but selectively arrests proliferation in only those cell lines that are dependent on EGFR (or fibroblast growth factor, FGFR) for survival. In these cell lines, OST inhibition causes cell-cycle arrest accompanied by induction of p21, autofluorescence, and cell morphology changes, all hallmarks of senescence. These results identify OST inhibition as a potential therapeutic approach for treating receptor-tyrosine-kinase-dependent tumors and provides a chemical probe for reversibly regulating N-linked glycosylation in mammalian cells.


Asunto(s)
Benzamidas/farmacología , Senescencia Celular/efectos de los fármacos , Inhibidores Enzimáticos/farmacología , Hexosiltransferasas/antagonistas & inhibidores , Proteínas de la Membrana/antagonistas & inhibidores , Proteínas Tirosina Quinasas Receptoras/antagonistas & inhibidores , Sulfonamidas/farmacología , Benzamidas/química , Puntos de Control del Ciclo Celular/efectos de los fármacos , Línea Celular Tumoral , Proliferación Celular/efectos de los fármacos , Relación Dosis-Respuesta a Droga , Inhibidores Enzimáticos/química , Hexosiltransferasas/metabolismo , Ensayos Analíticos de Alto Rendimiento , Humanos , Proteínas de la Membrana/metabolismo , Estructura Molecular , Proteínas Tirosina Quinasas Receptoras/metabolismo , Relación Estructura-Actividad , Sulfonamidas/química
9.
EMBO J ; 30(12): 2490-500, 2011 May 13.
Artículo en Inglés | MEDLINE | ID: mdl-21572394

RESUMEN

Dolichol monophosphate (Dol-P) functions as an obligate glycosyl carrier lipid in protein glycosylation reactions. Dol-P is synthesized by the successive condensation of isopentenyl diphosphate (IPP), with farnesyl diphosphate catalysed by a cis-isoprenyltransferase (cis-IPTase) activity. Despite the recognition of cis-IPTase activity 40 years ago and the molecular cloning of the human cDNA encoding the mammalian enzyme, the molecular machinery responsible for regulating this activity remains incompletely understood. Here, we identify Nogo-B receptor (NgBR) as an essential component of the Dol-P biosynthetic machinery. Loss of NgBR results in a robust deficit in cis-IPTase activity and Dol-P production, leading to diminished levels of dolichol-linked oligosaccharides and a broad reduction in protein N-glycosylation. NgBR interacts with the previously identified cis-IPTase hCIT, enhances hCIT protein stability, and promotes Dol-P production. Identification of NgBR as a component of the cis-IPTase machinery yields insights into the regulation of dolichol biosynthesis.


Asunto(s)
Dolicoles/biosíntesis , Receptores de Superficie Celular/fisiología , Transferasas Alquil y Aril/antagonistas & inhibidores , Transferasas Alquil y Aril/deficiencia , Transferasas Alquil y Aril/metabolismo , Animales , Células COS , Proteínas Portadoras/metabolismo , Chlorocebus aethiops , Fosfatos de Dolicol/biosíntesis , Fosfatos de Dolicol/deficiencia , Dolicoles/deficiencia , Activación Enzimática/genética , Glicoproteínas/metabolismo , Humanos , Conformación Proteica , Receptores de Superficie Celular/química , Receptores de Superficie Celular/deficiencia , Proteínas de Transporte Vesicular
10.
J Biol Chem ; 288(28): 20616-23, 2013 Jul 12.
Artículo en Inglés | MEDLINE | ID: mdl-23720757

RESUMEN

Mature dolichol-linked oligosaccharides (mDLOs) needed for eukaryotic protein N-glycosylation are synthesized by a multistep pathway in which the biosynthetic lipid intermediate Man5GlcNAc2-PP-dolichol (M5-DLO) flips from the cytoplasmic to the luminal face of the endoplasmic reticulum. The endoplasmic reticulum membrane protein Rft1 is intimately involved in mDLO biosynthesis. Yeast genetic analyses implicated Rft1 as the M5-DLO flippase, but because biochemical tests challenged this assignment, the function of Rft1 remains obscure. To understand the role of Rft1, we sought to analyze mDLO biosynthesis in vivo in the complete absence of the protein. Rft1 is essential for yeast viability, and no Rft1-null organisms are currently available. Here, we exploited Trypanosoma brucei (Tb), an early diverging eukaryote whose Rft1 homologue functions in yeast. We report that TbRft1-null procyclic trypanosomes grow nearly normally. They have normal steady-state levels of mDLO and significant N-glycosylation, indicating robust M5-DLO flippase activity. Remarkably, the mutant cells have 30-100-fold greater steady-state levels of M5-DLO than wild-type cells. All N-glycans in the TbRft1-null cells originate from mDLO indicating that the M5-DLO excess is not available for glycosylation. These results suggest that rather than facilitating M5-DLO flipping, Rft1 facilitates conversion of M5-DLO to mDLO by another mechanism, possibly by acting as an M5-DLO chaperone.


Asunto(s)
Células Eucariotas/metabolismo , Glicoproteínas/metabolismo , Proteínas de la Membrana/metabolismo , Proteínas Protozoarias/metabolismo , Trypanosoma brucei brucei/metabolismo , Electroforesis en Gel de Poliacrilamida , Retículo Endoplásmico/metabolismo , Citometría de Flujo , Glucosa/farmacología , Glicoproteínas/genética , Glicosilación , Proteínas de Membrana de los Lisosomas/metabolismo , Glicoproteínas de Membrana/genética , Glicoproteínas de Membrana/metabolismo , Proteínas de la Membrana/genética , Proteínas de Transporte de Membrana/genética , Proteínas de Transporte de Membrana/metabolismo , Microscopía Fluorescente , Modelos Biológicos , Mutación , Oligosacáridos de Poliisoprenil Fosfato/metabolismo , Polisacáridos/metabolismo , Biosíntesis de Proteínas , Proteínas Protozoarias/genética , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/crecimiento & desarrollo , Saccharomyces cerevisiae/metabolismo , Proteínas de Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/metabolismo , Transformación Genética , Trypanosoma brucei brucei/genética , Trypanosoma brucei brucei/crecimiento & desarrollo
11.
Chembiochem ; 13(3): 392-401, 2012 Feb 13.
Artículo en Inglés | MEDLINE | ID: mdl-22262650

RESUMEN

In a cell-based assay for novel inhibitors, we have discovered that two glycosides of 5-thiomannose, each containing an interglycosidic nitrogen atom, prevented the correct zymogen processing of the prohormone proopiomelanocortinin (POMC) and the transcription factor sterol-regulatory element-binding protein-2 (SREBP-2) in mouse pituitary cells and Chinese hamster ovary (CHO) cells, respectively. In the case of SREBP-2, these effects were correlated with the altered N-linked glycosylation of subtilisin/kexin-like isozyme-1 (SKI-1), the protease responsible for SREBP-2 processing under sterol-limiting conditions. Further examination of the effects of these compounds in CHO cells showed that they cause extensive protein hypoglycosylation in a manner similar to type I congenital disorders of glycosylation (CDGs) since the remaining N-glycans in treated cells were complete (normal) structures. The under-glycosylation of glycoproteins in 5-thiomannoside-treated cells is now shown to be caused by the compromised biosynthesis of the dolichol-linked oligosaccharide (DLO) N-glycosylation donor, although the nucleotide sugars required for the synthesis of DLOs were neither reduced under these conditions, nor were their effects reversed upon the addition of exogenous mannose. Analysis of DLO intermediates by fluorophore-assisted carbohydrate electrophoresis demonstrated that 5-thiomannose-containing glycosides block DLO biosynthesis most likely at a stage prior to the GlcNAc(2) Man(3) intermediate, on the cytosolic face of the endoplasmic reticulum.


Asunto(s)
Trastornos Congénitos de Glicosilación/metabolismo , Dolicoles/antagonistas & inhibidores , Manosa/farmacología , Oligosacáridos/antagonistas & inhibidores , Animales , Células CHO , Células Cultivadas , Trastornos Congénitos de Glicosilación/prevención & control , Cricetinae , Modelos Animales de Enfermedad , Dolicoles/biosíntesis , Dolicoles/química , Manosa/análogos & derivados , Manosa/química , Ratones , Oligosacáridos/biosíntesis , Oligosacáridos/química
12.
J Cell Biol ; 176(5): 605-16, 2007 Feb 26.
Artículo en Inglés | MEDLINE | ID: mdl-17325203

RESUMEN

Endoplasmic reticulum (ER) homeostasis requires transfer and subsequent processing of the glycan Glc(3)Man(9)GlcNAc(2) (G(3)M(9)Gn(2)) from the lipid-linked oligosaccharide (LLO) glucose(3)mannose(9)N-acetylglucosamine(2)-P-P-dolichol (G(3)M(9)Gn(2)-P-P-Dol) to asparaginyl residues of nascent glycoprotein precursor polypeptides. However, it is unclear how the ER is protected against dysfunction from abnormal accumulation of LLO intermediates and aberrant N-glycosylation, as occurs in certain metabolic diseases. In metazoans phosphorylation of eukaryotic initiation factor 2alpha (eIF2alpha) on Ser(51) by PERK (PKR-like ER kinase), which is activated by ER stress, attenuates translation initiation. We use brief glucose deprivation to simulate LLO biosynthesis disorders, and show that attenuation of polypeptide synthesis by PERK promotes extension of LLO intermediates to G(3)M(9)Gn(2)-P-P-Dol under these substrate-limiting conditions, as well as counteract abnormal N-glycosylation. This simple mechanism requires eIF2alpha Ser(51) phosphorylation by PERK, and is mimicked by agents that stimulate cytoplasmic stress-responsive Ser(51) kinase activity. Thus, by sensing ER stress from defective glycosylation, PERK can restore ER homeostasis by balancing polypeptide synthesis with flux through the LLO pathway.


Asunto(s)
Retículo Endoplásmico/metabolismo , Glicoproteínas/biosíntesis , Lipopolisacáridos/metabolismo , Biosíntesis de Proteínas/fisiología , eIF-2 Quinasa/fisiología , Animales , Células CHO , Cricetinae , Cricetulus , Cicloheximida/farmacología , Activación Enzimática , Factor 2 Eucariótico de Iniciación/metabolismo , Glicosilación , Homeostasis , Fosforilación
13.
Cancer Cell ; 40(9): 939-956.e16, 2022 09 12.
Artículo en Inglés | MEDLINE | ID: mdl-35985343

RESUMEN

Mutations affecting isocitrate dehydrogenase (IDH) enzymes are prevalent in glioma, leukemia, and other cancers. Although mutant IDH inhibitors are effective against leukemia, they seem to be less active in aggressive glioma, underscoring the need for alternative treatment strategies. Through a chemical synthetic lethality screen, we discovered that IDH1-mutant glioma cells are hypersensitive to drugs targeting enzymes in the de novo pyrimidine nucleotide synthesis pathway, including dihydroorotate dehydrogenase (DHODH). We developed a genetically engineered mouse model of mutant IDH1-driven astrocytoma and used it and multiple patient-derived models to show that the brain-penetrant DHODH inhibitor BAY 2402234 displays monotherapy efficacy against IDH-mutant gliomas. Mechanistically, this reflects an obligate dependence of glioma cells on the de novo pyrimidine synthesis pathway and mutant IDH's ability to sensitize to DNA damage upon nucleotide pool imbalance. Our work outlines a tumor-selective, biomarker-guided therapeutic strategy that is poised for clinical translation.


Asunto(s)
Neoplasias Encefálicas , Glioma , Leucemia , Animales , Neoplasias Encefálicas/tratamiento farmacológico , Neoplasias Encefálicas/genética , Inhibidores Enzimáticos/uso terapéutico , Glioma/tratamiento farmacológico , Glioma/genética , Isocitrato Deshidrogenasa/genética , Isocitrato Deshidrogenasa/metabolismo , Ratones , Mutación , Pirimidinas/farmacología , Pirimidinas/uso terapéutico , Salicilanilidas , Triazoles
14.
JCI Insight ; 6(24)2021 12 22.
Artículo en Inglés | MEDLINE | ID: mdl-34784297

RESUMEN

The genetic bases for the congenital disorders of glycosylation (CDG) continue to expand, but how glycosylation defects cause patient phenotypes remains largely unknown. Here, we combined developmental phenotyping and biochemical studies in a potentially new zebrafish model (pmm2sa10150) of PMM2-CDG to uncover a protease-mediated pathogenic mechanism relevant to craniofacial and motility phenotypes in mutant embryos. Mutant embryos had reduced phosphomannomutase activity and modest decreases in N-glycan occupancy as detected by matrix-assisted laser desorption ionization mass spectrometry imaging. Cellular analyses of cartilage defects in pmm2sa10150 embryos revealed a block in chondrogenesis that was associated with defective proteolytic processing, but seemingly normal N-glycosylation, of the cell adhesion molecule N-cadherin. The activities of the proconvertases and matrix metalloproteinases responsible for N-cadherin maturation were significantly altered in pmm2sa10150 mutant embryos. Importantly, pharmacologic and genetic manipulation of proconvertase activity restored matrix metalloproteinase activity, N-cadherin processing, and cartilage pathology in pmm2sa10150 embryos. Collectively, these studies demonstrate in CDG that targeted alterations in protease activity create a pathogenic cascade that affects the maturation of cell adhesion proteins critical for tissue development.


Asunto(s)
Cadherinas/metabolismo , Péptido Hidrolasas/metabolismo , Fosfotransferasas (Fosfomutasas)/metabolismo , Animales , Modelos Animales de Enfermedad , Humanos , Ratones
15.
Nat Commun ; 10(1): 2377, 2019 05 30.
Artículo en Inglés | MEDLINE | ID: mdl-31147550

RESUMEN

Glycans from microbial pathogens are well known pathogen-associated molecular patterns that are recognized by the host immunity; however, little is known about whether and how mammalian self-glycans activate the host immune response, especially in the context of autoimmune disease. Using biochemical fractionation and two-dimensional HPLC, we identify an abundant and bioactive free glycan, the Manß1-4GlcNAc disaccharide in TREX1-associated autoimmune diseases. We report that both monosaccharide residues and the ß1-4 linkage are critical for bioactivity of this disaccharide. We also show that Manß1-4GlcNAc is produced by oligosaccharyltransferase hydrolysis of lipid-linked oligosaccharides in the ER lumen, followed by ENGase and mannosidase processing in the cytosol and lysosomes. Furthermore, synthetic Manß1-4GlcNAc disaccharide stimulates a broad immune response in vitro, which is in part dependent on the STING-TBK1 pathway, and enhances antibody response in vivo. Together, our data identify Manß1-4GlcNAc as a novel innate immune modulator associated with chronic autoimmune diseases.


Asunto(s)
Enfermedades Autoinmunes/inmunología , Autoinmunidad/inmunología , Disacáridos/inmunología , Inmunidad Innata/inmunología , Proteínas de la Membrana/inmunología , Proteínas Serina-Treonina Quinasas/inmunología , Animales , Enfermedades Autoinmunes/genética , Modelos Animales de Enfermedad , Retículo Endoplásmico , Exodesoxirribonucleasas/genética , Fibroblastos , Ratones , Fosfoproteínas/genética , Células RAW 264.7
17.
Glycobiology ; 18(1): 125-34, 2008 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-17913728

RESUMEN

GlcNAc-1-P transferase (GPT) transfers GlcNAc-1-P from UDP-GlcNAc to dolichol-P (Dol-P), forming GlcNAc-P-PDol to initiate synthesis of the lipid-linked oligosaccharide Glc3Man9GlcNAc2-P-P-dolichol (G3M9Gn2-P-P-Dol). Elevated expression of GPT in CHO-K1 cells is known to cause accumulation of the intermediate M5Gn2-P-P-Dol, presumably by excessively consuming Dol-P and thereby hindering Dol-P-dependent synthesis of Man-P-Dol (MPD) and Glc-P-Dol (GPD), which provide the residues for extending M5Gn2-P-P-Dol to G3M9Gn2-P-P-Dol. If so, elevated GPT expression should increase oligosaccharide-P-P-Dol quantities and reduce monosaccharide-P-Dol quantities, while requiring GPT enzymatic activity. Here we report that elevated GPT expression failed to appreciably alter the quantities of the two classes of dolichol-linked saccharide, and that neither a GPT inhibitor nor introduction of an inactivating mutation into GPT prevented M5Gn2-P-P-Dol accumulation,arguing against excessive Dol-P consumption. Unexpectedly,we noticed similarities between the phenotypes of GPT overexpressers and of CHO-K1 cells lacking Lec35p (encoded by MPDU1, the congenital disorder of glycosylation(CDG)-If locus), which is required for utilization of MPD and GPD. By compensatory overexpression of Lec35p, G3M9Gn2-P-P-Dol synthesis in GPT overexpressers could be restored. However, GPT overexpression did not affect the levels of Lec35 mRNA or protein. These results suggest that GPT may impair Lec35p function, and imply that upper as well as lower limits on GPT expression exist in normal cells. Since the mammalian GPT gene can undergo spontaneous amplification, the data also indicate a potential basis for forms of pseudo-CDG-If.


Asunto(s)
Azúcares de Poliisoprenil Fosfato/biosíntesis , Transferasas (Grupos de Otros Fosfatos Sustitutos)/genética , Animales , Células CHO , Cricetinae , Cricetulus , Expresión Génica , Glicosilación , Proteínas de la Membrana/genética , Proteínas de la Membrana/metabolismo , Proteínas Represoras/genética , Proteínas Represoras/metabolismo , Transferasas (Grupos de Otros Fosfatos Sustitutos)/metabolismo
18.
Mol Cancer Ther ; 6(11): 3049-58, 2007 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-18025288

RESUMEN

In tumor cells growing under hypoxia, inhibiting glycolysis with 2-deoxy-d-glucose (2-DG) leads to cell death, whereas under normoxic conditions cells similarly treated survive. Surprisingly, here we find that 2-DG is toxic in select tumor cell lines growing under normal oxygen tension. In contrast, a more potent glycolytic inhibitor, 2-fluorodeoxy-d-glucose, shows little or no toxicity in these cell types, indicating that a mechanism other than inhibition of glycolysis is responsible for their sensitivity to 2-DG under normoxia. A clue to this other mechanism comes from previous studies in which it was shown that 2-DG interferes with viral N-linked glycosylation and is reversible by exogenous addition of mannose. Similarly, we find that 2-DG interferes with N-linked glycosylation more potently in the tumor cell types that are sensitive to 2-DG under normoxia, which can be reversed by exogenous mannose. Additionally, 2-DG induces an unfolded protein response, including up-regulation of GADD153 (C/EBP-homologous protein), an unfolded protein response-specific mediator of apoptosis, more effectively in 2-DG-sensitive cells. We conclude that 2-DG seems to be toxic in select tumor cell types growing under normoxia by inhibition of N-linked glycosylation and not by glycolysis. Because in a phase I study 2-DG is used in combination with an anticancer agent to target hypoxic cells, our results raise the possibility that in certain cases, 2-DG could be used as a single agent to selectively kill both the aerobic (via interference with glycosylation) and hypoxic (via inhibition of glycolysis) cells of a solid tumor.


Asunto(s)
Desoxiglucosa/farmacología , Glucólisis/efectos de los fármacos , Neoplasias/patología , Oxígeno/metabolismo , Adenosina Trifosfato/metabolismo , Aerobiosis/efectos de los fármacos , Anaerobiosis/efectos de los fármacos , Muerte Celular/efectos de los fármacos , Línea Celular Tumoral , Supervivencia Celular/efectos de los fármacos , Fluorodesoxiglucosa F18/farmacología , Glicosilación/efectos de los fármacos , Humanos , Manosa/farmacología , Modelos Biológicos , Oligosacáridos/metabolismo , Consumo de Oxígeno/efectos de los fármacos , Pliegue de Proteína , Factor de Transcripción CHOP/genética , Regulación hacia Arriba/efectos de los fármacos
19.
Methods Enzymol ; 415: 3-20, 2006.
Artículo en Inglés | MEDLINE | ID: mdl-17116464

RESUMEN

Lipid-linked oligosaccharides (LLOs) are the donors of glycans that modify newly synthesized proteins in the endoplasmic reticulum (ER) of eukaryotes, resulting in formation of N-linked glycoproteins. The vast majority of LLO analyses have relied on metabolic labeling with radioactive sugar precursors, but these approaches have technical limitations resulting in many important questions about LLO synthesis being left unanswered. Here we describe the application of a facile non-radioactive technique, fluorophore-assisted carbohydrate electrophoresis (FACE), which circumvents these limitations. With FACE, steady-state LLO compositions can be determined quantitatively from cell cultures and animal tissues. We also present FACE methods for analysis of phosphosugars and nucleotide sugars, which are metabolic precursors of LLOs.


Asunto(s)
Electroforesis/métodos , Colorantes Fluorescentes/química , Lipopolisacáridos/química , Animales , Electroforesis/instrumentación , Lipopolisacáridos/metabolismo , Ratones , Naftalenosulfonatos/química , Fosfatos/química , Radioisótopos/química , Distribución Tisular
20.
Mol Biol Cell ; 27(8): 1220-34, 2016 Apr 15.
Artículo en Inglés | MEDLINE | ID: mdl-26912795

RESUMEN

Activation of the unfolded protein response (UPR) can be either adaptive or pathological. We term the pathological UPR that causes fatty liver disease a "stressed UPR." Here we investigate the mechanism of stressed UPR activation in zebrafish bearing a mutation in thetrappc11gene, which encodes a component of the transport protein particle (TRAPP) complex.trappc11mutants are characterized by secretory pathway defects, reflecting disruption of the TRAPP complex. In addition, we uncover a defect in protein glycosylation intrappc11mutants that is associated with reduced levels of lipid-linked oligosaccharides (LLOs) and compensatory up-regulation of genes in the terpenoid biosynthetic pathway that produces the LLO anchor dolichol. Treating wild-type larvae with terpenoid or LLO synthesis inhibitors phenocopies the stressed UPR seen intrappc11mutants and is synthetically lethal withtrappc11mutation. We propose that reduced LLO level causing hypoglycosylation is a mechanism of stressed UPR induction intrappc11mutants. Of importance, in human cells, depletion of TRAPPC11, but not other TRAPP components, causes protein hypoglycosylation, and lipid droplets accumulate in fibroblasts from patients with theTRAPPC11mutation. These data point to a previously unanticipated and conserved role for TRAPPC11 in LLO biosynthesis and protein glycosylation in addition to its established function in vesicle trafficking.


Asunto(s)
Oligosacáridos/metabolismo , Respuesta de Proteína Desplegada , Proteínas de Transporte Vesicular/metabolismo , Proteínas de Pez Cebra/metabolismo , Animales , Animales Modificados Genéticamente , Atorvastatina/farmacología , Dolicoles/biosíntesis , Dolicoles/genética , Glicosilación , Aparato de Golgi/genética , Aparato de Golgi/metabolismo , Humanos , Larva/efectos de los fármacos , Larva/metabolismo , Lípidos/química , Hígado/metabolismo , Hígado/patología , Mutación , Oligosacáridos/química , Terpenos/metabolismo , Terpenos/farmacología , Respuesta de Proteína Desplegada/efectos de los fármacos , Respuesta de Proteína Desplegada/genética , Proteínas de Transporte Vesicular/genética , Pez Cebra/genética , Proteínas de Pez Cebra/genética
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