Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0038187 (starvation)
 24,951 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Although previous studies have indicated that N-linked oligosaccharides on lysosomal enzymes in Dictyostelium discoideum are extensively phosphorylated and sulfated, the role of these modifications in the sorting and function of these enzymes remains to be determined. We have used radiolabel pulse-chase, subcellular fractionation, and immunofluorescence microscopy to analyze the transport, processing, secretion, and sorting of two lysosomal enzymes in a mutant, HL244, which is almost completely defective in sulfation. [3H]Mannose-labeled N-linked oligosaccharides were released from immunoprecipitated alpha-mannosidase and beta-glucosidase of HL244 by digestion with peptide: N-glycosidase. The size, Man9-10GlcNAc2, and processing of the neutral species were similar to that found in the wild type, but the anionic oligosaccharides were less charged than those from the wild-type enzymes. All of the negative charges on the oligosaccharides for HL244 were due to the presence of 1, 2, or 3 phosphodiesters and not to sulfate esters. The rate of proteolytic processing of precursor forms of alpha-mannosidase and beta-glucosidase to mature forms in HL244 was identical to wild type. The precursor polypeptides in the mutant and the wild type were membrane associated until being processed to mature forms; therefore, sulfated sugars are not essential for this association. Furthermore, the rate of transport of alpha-mannosidase and beta-glucosidase from the endoplasmic reticulum to the Golgi complex was normal in the mutant as determined by the rate at which the newly synthesized proteins became resistant to the enzyme, endo-beta-N-acetylglucosaminidase H. There was no increase in the percentage of newly synthesized mutant precursors which escaped sorting and were secreted, and the intracellularly retained lysosomal enzymes were properly localized to lysosomes as determined by fractionation of cell organelles on Percoll gradients and immunofluorescence microscopy. However, the mutant secreted lysosomally localized mature forms of the enzymes at 2-fold lower rates than wild-type cells during both growth and during starvation conditions that stimulate secretion. Furthermore, the mutant was more resistant to the effects of chloroquine treatment which results in the missorting and oversecretion of lysosomal enzymes. Together, these results suggest that sulfation of N-linked oligosaccharides is not essential for the transport, processing, or sorting of lysosomal enzymes in D. discoideum, but these modified oligosaccharides may function in the secretion of mature forms of the enzymes from lysosomes.
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PMID:Sulfated N-linked oligosaccharides affect secretion but are not essential for the transport, proteolytic processing, and sorting of lysosomal enzymes in Dictyostelium discoideum. 211 25

Thyroid-stimulating hormone (TSH) alpha- and beta-subunit glycosylation was investigated in mouse thyrotropic tumor and in normal and hypothyroid pituitary cells for various periods of time in the presence of [3H]mannose or [3H]galactose. After sequential precipitation with anti-alpha and anti-beta sera, subunits were treated with Pronase followed by endo-beta-N-acetylglucosaminidase H (Endo H) and analyzed by paper chromatography. In primary cultures of thyrotropic tumor cells incubated for 60 min with [3H]mannose, primarily Man9GlcNAc and Man8GlcNAc were found on TSH + alpha subunits, whereas Glc1Man9GlcNAc and Man9GlcNAc were prominent on free beta subunits. After preincubation of cells for 16 h in the presence or absence of glucose followed by a 60-min pulse of [3H]mannose, there was an 8-fold increase in labeled TSH + alpha but only a minimal change in free beta or total proteins. In the absence of glucose, there was a selective accumulation of Man8GlcNAc on TSH + alpha but not on free beta or total proteins; however, there was no detectable accumulation of Endo H resistant forms during glucose starvation on TSH subunits or total proteins. Normal mouse and rat pituitary minces incubated for 60 min with either [3H]mannose or [3H]galactose showed no glucose-containing species on TSH subunits, but equal amounts of Man9GlcNAc and Man8GlcNAc on TSH + alpha, and mostly Man9GlcNAc on free beta subunits. In contrast, hypothyroid mouse and rat pituitaries exhibited an increase in Glc1Man9NAc and Glc1Man8GlcNAc on free beta but not on TSH + alpha or total proteins.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Differential processing and regulation of thyroid-stimulating hormone subunit carbohydrate chains in thyrotropic tumors and in normal and hypothyroid pituitaries. 407 17

The distribution of lipid-linked oligosaccharide intermediates in cultured mammalian cells has been studied under conditions of glucose deprivation. It was found that at low to moderate cell densities within 20 min of glucose starvation, the major species of lipid-linked oligosaccharide shifted from mainly a single species containing three glucose, nine mannose, and two N-acetylglucosamine residues to a pattern dominated by two species containing either five mannose and two N-acetylglucosamine residues or two mannose and two N-acetylglucosamine residues. At high cell densities, this effect was not evident. Continued glucose starvation at low density resulted in a second shift in distribution in which the proportions of these two species decreased and that of the original major species (Glc3Man9GlcNAc2) increased. Addition of glucose or mannose, but not pyruvate, glutamine, galactose, inositol, or glycine, prevented the shift to the Man5GlcNAc2 and Man2GlcNAc2 species. The intermediates that accumulate during glucose starvation were identified by their elution position on gel filtration columns, sensitivity to digestion with alpha-mannosidase, resistance to digestion with endo-beta-N-acetylglucosaminidase H, and by the products of Smith degradation. These data suggest that a regulatory point in the lipid-linked oligosaccharide synthetic pathway exists at the reaction in which Man5GlcNAc2-P-P-dolichol is converted to Man6GlcNAc2-P-P-dolichol.
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PMID:Transitory effects of glucose starvation on the synthesis of dolichol-linked oligosaccharides in mammalian cells. 626 25

Within minutes of glucose starvation confluent monolayers of rat hepatoma cells synthesize glycoproteins, including alpha 1-acid glycoprotein, which appear on two-dimensional gels as size heterogeneous spot series. The longer the period of glucose starvation the more the production of the glycoproteins is shifted toward smaller molecular weight forms. To compare these forms with the corresponding glycoproteins synthesized either in a cell-free system or by nonstarved cells, a mapping of the N-glycan was done by endo-beta-N-acetylglucosaminidase digestion within a polyacrylamide gel. Glycoproteins from glucose-starved cells contain a reduced number of N-glycans which belong to both the endo H-sensitive and resistant type. The decrease of N-glycosylation may be correlated with the accumulation of truncated lipid-bound oligosaccharides, for the gel chromatography of the oligosaccharides released from the lipid and protein fractions of glucose-starved cells revealed a drastic reduction in their size. Most of the lipid-linked oligosaccharides synthesized during glucose starvation are resistant to endo H digestion. Under conditions of limiting glycosylation we were able to show by glycopeptide analysis, that in the case of alpha 1-acid glycoprotein, N-glycans are added randomly to the 6 possible N-glycosylation sites. Furthermore, non- or partially N-glycosylated proteins do not acquire additional oligosaccharide units after restoration of glucose although the proteins can undergo secondary modification and, in the case of the secretory proteins, can be exported.
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PMID:Glucose starvation leads in rat hepatoma cells to partially N-glycosylated glycoproteins including alpha 1-acid glycoproteins. Identification by endoglycolytic digestions in polyacrylamide gels. 640 21

alpha-Mannosidase from Dictyostelium discoideum is a heterogenous glycoprotein which is derived from a precursor as a result of proteolytic processing. Its oligosaccharides are phosphorylated and sulfated. We investigated the sulfation of the enzyme by means of pulse-chase labeling and specific immunoprecipitation followed by endoglycosidase H treatment and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The earliest detectable form of the precursor was shown to be glycosylated and sensitive to endoglycosidase H. With time some of its oligosaccharides were sulfated and became partially resistant to endoglycosidase H. In the same time period, the precursor was proteolytically cleaved, yielding four species with different molecular masses (46-58 X 10(3) daltons). When first generated each of these was sensitive to endoglycosidase H but with time the 54,000- and 58,000-dalton forms developed degrees of endoglycosidase H resistance. The fully mature cleaved forms all contained sulfate. Sulfate from pulse-labeled precursor could only be detected in two of the forms implying that sulfation of the others occurs either after precursor cleavage or before cleavage but subsequent to the pulse period. When secretion of precursor was triggered by starvation only the endoglycosidase H-resistant forms were secreted.
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PMID:Maturation of alpha-mannosidase in Dictyostelium discoideum. Acquisition of endoglycosidase H resistance and sulfate. 643 94

After the demonstration that Stigmatella aurantiaca DW4 secretes an endo-N-acetyl-beta-D-glucosaminidase (ENGase), acting on the di-N-acetylchitobiosyl part of N-linked glycans (S. Bourgerie, Y. Karamanos, T. Grard, and R. Julien, J. Bacteriol. 176:6170-6174, 1994), an ENGase activity having the same substrate specificity was also found to be secreted during vegetative growth of Myxococcus xanthus DK1622. The activity decreased in mutants known to secrete less protein than the wild type (Exc +/-). During submerged development, the activity was produced in two steps: the first increase occurred during the aggregation phase, and the second one occurred much later, during spore formation. This production was lower in developmental mutants impairing cell-cell signaling, the late mutants (csg and dsg) being the most deficient. Finally, when sporulation was obtained either by starvation in liquid shake flask culture or by glycerol induction, the activity was produced exclusively by the wild-type cells during the maturation of the coat.
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PMID:An endo-N-acetyl-beta-D-glucosaminidase, acting on the di-N-acetylchitobiosyl part of N-linked glycans, is secreted during sporulation of Myxococcus xanthus. 786 Jun

We previously reported the occurrence of oligomannosides and xylomannosides corresponding to unconjugated N-glycans (UNGs) in the medium of a white campion (Silene alba) cell suspension. Attention has been focused on these oligosaccharides since it was shown that they confer biological activities in plants. In an attempt to elucidate the origin of these oligosaccharides, we studied two endoglycosidase activities, putative enzymes involved in their formation. The previously described peptide-N4-(N-acetyl-glucosaminyl) asparagine amidase activity and the endo-N-acetyl-beta-D-glucosaminidase activity described in this paper were both quantified in white campion cells during the culture cycle with variable initial concentrations of sucrose. The lower the sucrose supply, the higher the two activities. Furthermore, endoglycosidase activities were greatly enhanced after the disappearance of sugar from the medium. The production of UNGs in the culture medium rose correlatively. These data strongly suggest that the production of UNGs in our white campion cell-suspension system is due to the increase of these endoglycosidase activities, which reach their highest levels of activity during conditions of carbon starvation.
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PMID:Carbon starvation increases endoglycosidase activities and production of "unconjugated N-glycans" in Silene alba cell-suspension cultures. 799 89

Two forms of N-acetylglucosaminidase were purified to homogeneity by ion exchange (TSK DEAE-3SW, Aquapore CX-300) and gel filtration (TSK G4000 SW) HPLC of Candida albicans ATCC 10261 culture filtrates. Synthesis and secretion of N-acetylglucosaminidase were induced by incubating starved yeast cells at 37 degrees C in medium containing N-acetylglucosamine (GlcNAc). The form of the enzyme depended on the cell growth and starvation conditions before GlcNAc induction. N-Acetylglucosaminidase A (32% total carbohydrate, M(r) 85,000 subunit) was isolated from cells grown in glucose/salts/biotin medium, and N-acetylglucosaminidase B (56% carbohydrate, M(r) 132,000 subunit) was isolated from cells grown in yeast extract/peptone/dextrose. The estimated relative molecular masses of the native enzymes, based on Sephacryl S-300 gel filtration were: A form, 350,000; B form, 600,000; A and B forms after endoglycosidase H (endo H) treatment, 180,000. The purified enzymes migrated on SDS polyacrylamide gels as heterogeneous glycoproteins of M(r) centred at approximately 100,000 (A) and approximately 150,000 (B) but were reduced to a single 58,000 band after denaturation with SDS and cleavage of asparagine-linked sidechains by endo H. When the native glycoproteins were treated with endo H, both enzyme forms had three oligosaccharide sidechains of M(r) approximately 3000 that were endo H resistant. Therefore the difference in the size of N-acetylglucosaminidase A and B was due to variations in outer chain glycosylation of endo H-sensitive inner core structures. N-Acetylglucosaminidase was active and stable over a broad pH range with maximum activity against both p-nitrophenylGlcNAc (pNPGlcNAc) and pNPGalNAc at pH 4.0. The kinetic parameters kcat (s-1) and Km (mM) of N-acetylglucosaminidase A using the following substrates were, respectively: pNPGlcNAc, 740, 0.77; pNPGalNAc, 910, 1.26; N,N'-diacetylchitobiose 620, 0.20; and N,N',N"-triacetylchitotriose, 170, 0.044. The enzyme showed substrate inhibition with all substrates above 0.5 mM except for pNPGalNAc.
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PMID:Purification and characterization of two forms of N-acetylglucosaminidase from Candida albicans showing widely different outer chain glycosylation. 807 97

A secreted phosphate-repressible acid phosphatase from Kluyveromyces lactis has been purified and the N-terminal region and an internal peptide have been sequenced. Using synthetic oligodeoxyribonucleotides based on the sequenced regions, the genomic sequence, KIPHO5, encoding the protein has been isolated. The deduced protein, named KIPho5p, consists of 469 amino acids and has a molecular mass of 52520 Da (in agreement with the data obtained after treatment of the protein with endoglycosidase H). The purified enzyme shows size heterogeneity, with an apparent molecular mass in the range 90-200 kDa due to the carbohydrate content (10 putative glycosylation sites were identified in the sequence). A 16 amino acid sequence at the N-terminus is similar to previously identified signal peptides in other fungal secretory proteins. The putative signal peptide is removed during secretion since it is absent in the mature secreted acid phosphatase. The gene can be induced 400-600-fold by phosphate starvation. Consensus signals corresponding to those described for Saccharomyces cerevisiae PHO4- and PHO2-binding sites are found in the 5' region. Northern blot analysis of total cellular RNA indicates that the KIPHO5 gene codes for a 1.8 kb transcript and that its expression is regulated at the transcriptional level. Chromosomal hybridization indicated that the gene is located on chromosome II. The KIPHO5 gene of K. lactis is able to functionally complement a pho5 mutation of Sacch. cerevisiae. Southern blot experiments, using the KIPHO5 gene as probe, show that some K. lactis reference strains lack repressible acid phosphatase, revealing a different gene organization for this kind of multigene family of proteins as compared to Sacch. cerevisiae.
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PMID:The KIPHO5 gene encoding a repressible acid phosphatase in the yeast Kluyveromyces lactis: cloning, sequencing and transcriptional analysis of the gene, and purification and properties of the enzyme. 927 15