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)

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

Higher eukaryotes contain tRNA transglycosylases that incorporate the guanine derivative queuine from the nutritional environment into specific tRNAs by exchange with guanine at position 34. Alterations in the queuosine content of specific tRNAs are suggested to be involved in regulatory mechanisms of major routes of metabolism during differentiation. Dictyostelium discoideum has been applied as a model to investigate the function of queuine or queuine-containing tRNAs. Axenic strains are supplied with queuine by peptone, but they grow equally well in a defined queuine-free medium. Queuine-lacking amoebae, starved in suspension culture for 24 h, lose their ability to differentiate into stalk cells and spores, whereas amoebae sufficiently supplied with queuine will overcome this metabolic stress and undergo further development when plated on agar. The results presented here show that D(-)-lactate occurs in the slime mould in millimolar amounts and that its level is remarkably decreased in queuine-lacking cells after 24 h of starvation in suspension culture. On isoelectric-focusing polyacrylamide gels, nine different forms of NAD-dependent D(-)-lactate dehydrogenase can be separated from extracts of vegetative cells, and six forms from extracts of the starved cells. Under queuine limitation, one form is missing in the starved cells. Low amounts of L(+)-lactate are usually found in vegetative amoebae but significantly less in queuine-lacking cells. Five forms of NAD-dependent L(+)-lactate dehydrogenase are detectable in extracts from vegetative, queuine-treated cells, and slight alterations occur in queuine-deficient amoebae. In the starved cells only one form of L(+)-lactate dehydrogenase is found, irrespective of the supply of queuine to the cells. A cytochrome of type b with an absorption maximum at 559 nm accumulates during starvation only in queuine-lacking cells; it might be a component of an NAD-independent lactic acid oxidoreductase as is cytochrome b 557 in yeast and be responsible for the reduced level of lactate in cells lacking queuine in tRNA.
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PMID:Specific changes in lactate levels, lactate dehydrogenase patterns and cytochrome b559 in Dictyostelium discoideum caused by queuine. 669 26

Dictyostelium discoideum MC2 is a temperature-sensitive motility mutant of AX3. Mutant cells are incapable of growth, phagocytosis, and migration under restrictive conditions (Kayman et al., J. Cell Biol. 92:705-711, 1982). We show here that at the restrictive temperature MC2 cells grown axenically or on bacteria synthesized excessive quantities of the lectin discoidin I. By two-dimensional gel electrophoresis and peptide mapping, the proteins overproduced by MC2 cells were indistinguishable from discoidin I synthesized at lower levels in AX3 cells. At least two of the three species of discoidin I were overproduced. This protein family constituted 9% of the total protein in cells that were incubated overnight at 27 degrees C in axenic medium. Although MC2 cells are defective in nutrient uptake under restrictive conditions, the overproduction of discoidin I did not appear to be part of a pleiotropic response to starvation. We propose that transcription of the coordinately regulated discoidin I genes is altered in mutant cells. This alteration may be related to the motility defects manifested by MC2.
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PMID:Overproduction of discoidin I by a temperature-sensitive motility mutant of Dictyostelium discoideum. 673 29

Folic acid is a chemoattractant for the slime mold Dictyostelium minutum V3. The activity of extracellular folic acid is regulated by a folic acid C9-N10 splitting enzyme (FAS). The products were identified as pterin-6-aldehyde and p-amino-benzoylglutamic acid. The enzyme was stabilized by EDTA. For the extracellular enzyme, the Km was 10(-7) M, and the optimal pH was 4.0. During starvation, FAS activity was mainly secreted into the medium; after 3 h, a plateau was reached. The membrane-bound activity was constant, but only 12% of the extracellular activity at 3 h. Intracellular activity also increased up to 3 h to a level of 23% of the extracellular FAS. The substrate recognition of FAS was found to be based on 4-O or N3 or both, N5 or N8 or both, N10, and the p-aminobenzoic acid moiety, whereas 2-NH2, N1, and the glutamic acid moiety were not recognized. Other slime mold species were found to secrete FAS with 20-fold or more reduced activity than D. minutum V3.
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PMID:Characterization of the folic acid C9-N10-cleaving enzyme of Dictyostelium minutum V3. 684 18

We are studying the fate of alpha-mannosidase, a lysosomal enzyme, in Dictyostelium discoideum. alpha-Mannosidase is synthesized as a 150,000-dalton precursor which becomes proteolytically cleaved to mature (56,000-62,000 dalton) forms. When cells are shifted into starvation buffer (5 mM phosphate, pH 6.5), the enzyme is secreted. We compared the kinetics of secretion of newly processed alpha-mannosidase with that of bulk forms. After 2 h in phosphate buffer less than 20% of the newly processed forms but as much as 50% of the bulk enzyme activity was secreted. During the course of the experiments, the total alpha-mannosidase activity remains constant, cells remain viable, and there is no evidence of degradation of enzyme. Furthermore, a 4-h chase period prior to starvation is required before the newly processed forms are secreted to the same extent as the bulk forms. On the basis of these results we propose that the enzyme is present in at least two pools and that it is transferred from a newly processed to an efficiently secreted pool.
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PMID:Linked pools of processed alpha-mannosidase in Dictyostelium discoideum. 687 94

Changes in the patterns of isoacceptors of tRNAAsn and alterations in modification of the guanine residue 34, the first position of the anticodon of tRNAAsn, have been observed in eukaryotes during differentiation. We use Dictyostelium discoideum as a model system to elucidate the possible involvement of tRNAAsn in developmental processes. Vegetative amoebae were induced to undergo developmental transition by nutrient starvation. Since amino acid starvation alone is a specific stimulus initiating development and unacylated tRNAs might be involved in control mechanisms of protein synthesis, the level of aminoacylation of tRNAAsn isoacceptors has been investigated. As early as two minutes after the onset of development, the aminoacylation of tRNAAsn specifically was reduced to about 30%, whereas at the same time 10 other tRNA species were found to be charged normally, i.e. to 70-100%. One of the two major isoacceptors, tRNAAsn3, was completely deacylated, whereas the other one, tRNAAsn2, accounted for the residual aminoacylation. Analyses of the modified nucleosides of highly purified tRNAAsn2 and tRNAAsn3 are respectively, show that both isoacceptors are identical in their modification patterns except for the modification at the first position of the anticodon; tRNAAsn2 comprises queuine (Q), 7-[(4,5-cis-dihydroxy-2-cyclopenten-1-ylamino)methyl]-7-deazaguanine, whereas tRNAAsn3 contains guanine.
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PMID:Reduced aminoacylation of asparagine-transfer RNA early in the developmental cycle of Dictyostelium discoideum: modification pattern and possible significance of the uncharged isoacceptor tRNAAsn3. 691 78

We are studying the biosynthesis and processing of acid hydrolases from Dictyostelium discoideum. We prepared antibody to highly purified alpha-mannosidase from the spent medium of stationary phase cultures. It precipitated alpha-mannosidase but not beta-hexosaminidase, alpha-glucosidase, beta-glucosidase, or any of the major proteins in cell lysates or secretions. The antibody precipitated a 150,000- and an 80,000-dalton protein in addition to mature forms (56,000-62,000 daltons) of alpha-mannosidase subunits. The possibility that the 150,000 and 80,000 dalton bands were precursors of mature forms was evaluated by pulse-chase experiments. Following a 20-min pulse labeling period, only the 150,000-dalton protein was detected in the immunoprecipitate. Apparent conversion of this form into 80,000- and 60,000-dalton forms was observed following a 30-min chase. During the next 90 min continued accumulation of 60,000-dalton and appearance of 62,000-dalton forms was observed while the 80,000-dalton form disappeared. The fate of the 150,000-dalton precursor depended on nutritional conditions. In cells conditioned with fresh growth medium intracellular processing predominated. Less than 10% of either the precursor or mature forms was secreted in 8 hr. However, when cells were shifted from growth medium to starvation buffer, secretion of precursor soon predominated. After a 1-hr lag period, cells began secreting 150,000-dalton precursor into the medium. After 4 hr in starvation buffer, the rate of secretion of 150,000-dalton form increased by at least an order of magnitude while processing was markedly diminished. This may be a case where nutritional conditions control the sorting of an acid hydrolase precursor.
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PMID:Processing and secretion of alpha-mannosidase forms by Dictyostelium discoideum. 705 Jan 3

The uptake of fucose and uracil by Dictyostelium discoideum in either a starvation or drug-induced growth-arrest state was studied. For both nutrients, the uptake was an energy-dependent process. The rate of fucose uptake remained constant for over four hours, while the uracil rate declined after about one hour, in starvation-induced growth-arrest. Under these conditions, fucose was found to be incorporated into membrane-associated glycoproteins and glycolipids, while uracil was incorporated into RNA. The rate of fucose uptake was the same for starvation or hadacidin-induced growth-arrest, but significantly lower for cerulenin-treated cells. In contrast, uracil uptake was slower in hadacidin-treated cells as opposed to starvation or cerulenin-induced growth-arrest cells. Further experiments showed that the incorporation rate of uracil into RNA was faster in hadacidin-treated cells than controls, and the cerulenin-treated cells were slower. The data suggest that the cells arrested in growth by nutrient deprivation retain the capacity to take-up and incorporate nutrients such as fucose and uracil and that pinocytosis is probably the process responsible for uptake.
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PMID:Permeability of Dictyostelium discoideum to fucose and uracil following growth-arrest induced by starvation, hadacidin, and cerulenin. 715 66

The binding of the chemoattractant folic acid to intact Dictyostelium discoideum cells has been studied. A few hundred thousand ligand molecules can be bound per cell with a dissociation constant in the order of 3 X 10(-7) M. Intact cells equilibrate rapidly with extracellular folic acid, suggesting that the binding sites are located on the outer cell surface. The folic-acid-binding properties do not change during early cell development induced by starvation for nutrients. A number of putative folate-binding proteins have been identified in a detergent-solubilized plasma membrane fraction by affinity chromatography on folate-Sepharose and specific elution with free folate. One of these proteins appeared to be an integral membrane protein as was deduced from its amphiphilic behaviour. It may be that among these proteins is the chemotactic receptor for folate.
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PMID:Binding of the chemoattractant folic acid by Dictyostelium discoideum cells. 723 11

When Dictyostelium discoideum amoebae were harvested from nutrient medium and suspended in a starvation buffer to initiate development, approximately 30% of the total cellular beta-N-acetylglucosaminidase activity was secreted into the extracellular fluid within 4 h. During this same period, only 10% of the total cellular acid phosphatase and acid protease activities were secreted. When the cells were pretreated overnight with 5 mg sodium hadacidin ml-1 and then suspended in starvation buffer, 60% of the glucosaminidase and 30% of the acid phosphatase activities were secreted, while the level of acid protease secretin remained at 10%. The secretory behaviour of hadacidin-treated cells was, however, identical to that of untreated cells when 0.1 M-sucrose was added to the starvation buffer to enhance lysosomal enzyme secretion. Treatment with hadacidin also affected the intracellular content of these enzyme activities. After 16 h exposure to 5 mg hadacidin ml-1, the cellular levels of glucosaminidase and acid protease activity were decreased by 50% and 30% respectively, while acid phosphatase activity remained unchanged. All of the changes observed upon hadacidin treatment were time dependent and were not evident if the cells were exposed to the drug for only 4 h. These results suggest that hadacidin treatment affects the lysosomal system of D. discoideum.
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PMID:Lysosomal abnormalities in hadacidin-treated Dictyostelium discoideum amoebae. 732 Jun 97


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