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Query: UMLS:C0038187 (starvation)
 24,951 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Starvation of Saccharomyces cerevisiae cells for specific nutrients such as nitrogen, phosphate or sulphate causes arrest in the G1 phase of the cell cycle at a specific point called 'start'. Re-addition of different nitrogen sources, phosphate or sulphate to such starved cells causes activation of trehalase within a few minutes. Nitrogen-source- and sulphate-induced activation of trehalase were not associated with any change in the cAMP level, but in the case of phosphate there was a small transient increase. When nitrogen-source-activated trehalase was isolated by immuno-affinity chromatography from crude extracts, the purified enzyme showed the same activity profile as in the original crude extracts, indicating that post-translational modification is responsible for the activation. In the yeast mutants cdc25-5 and cdc35-10, which are temperature sensitive for cAMP synthesis, incubation at the restrictive temperature lowered but did not prevent nitrogen-, phosphate- or sulphate-induced activation of trehalase. Since under these conditions the cAMP level in the cells is very low, it is unlikely that cAMP acts as a second messenger in this nutrient-induced effect. Nitrogen-source-induced activation of trehalase requires the presence of glucose at a concentration similar to that able to stimulate the RAS-adenylate cyclase pathway. This indicates that the same glucose-sensing system might be involved in both phenomena. Nitrogen-starved cells fractionated according to cell size all showed nitrogen-source-induced activation of trehalase to the same extent, indicating that the nitrogen-induced signalling pathway involved is not dependent on the well-known cell size requirement for progression over the start point of the cell cycle.
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PMID:Nutrient-induced activation of trehalase in nutrient-starved cells of the yeast Saccharomyces cerevisiae: cAMP is not involved as second messenger. 133 29

A method for the detection and quantification of trehalase activity (EC 3.2.1.28) by immobilization to a membrane support has been developed. Protein samples partly enriched for porcine and Galleria mellonella wax moth larvae trehalase activities were fractionated by polyacrylamide gel electrophoresis, followed by electrophoretic transfer to PVDF membranes, and incubated in a solution containing trehalose (20 mg/ml), glucose oxidase (40 U/ml), phenazine methosulfate (0.06 mg/ml), and nitro blue tetrazolium (0.24 mg/ml) in 20 mM sodium phosphate buffer, pH 6.5. The intensity of the red-colored bands, developed directly on the membrane, was quantified using a computing, laser densitometer and shown to be linearly proportional to the original enzyme activity in extracts determined by liquid assay. The temperature inactivation profile of wax moth trehalase was measured. Alteration of the electrophoresis sample buffer composition further revealed the presence of putative trehalase isoforms in wax moth larval extracts whose relative levels of activity were altered during the course of starvation and infection with Tipula iridescent virus.
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PMID:A transfer membrane method for in situ detection and quantification of trehalase. 162 91

Exo-(1----3)-beta-glucanase, beta-glucosidase, autolysin and trehalase were assayed in situ in Candida albicans during yeast growth, starvation and germ-tube formation. Cell viability, germ-tube formation, intracellular glucose-6-phosphate dehydrogenase and beta-glucosidase were unaffected in cells incubated in 0.1 M-HC1 for 15 min at 4 degrees C. However, in situ trehalase, (1----3)-beta-glucanase and autolysin activities in acid-treated cells decreased by 95, 50 and 35% respectively, indicating that these enzymes are, in part, associated with the cell envelope. Trehalase activity increased throughout yeast growth and remained elevated during the first hour of incubation for germ-tube formation. All of the in situ trehalase activity in starved yeast cells could be measured without the permeabilizing treatment. beta-Glucosidase activity declined throughout yeast growth and did not alter during germ-tube formation. Both the (1----3)-beta-glucanase and autolysin activities were optimal at pH 5 X 6, inhibited by gluconolactone and HgCl2, and maximal at 15-16 h during yeast growth. Although autolysin activity increased by 50-100% when starved yeast cells were incubated for germ-tube formation, the in situ (1----3)-beta-glucanase remained constant. When acid-treated starved yeast cells were similarly induced, in situ (1----3)-beta-glucanase increased 100% over 3 h of germ-tube formation. Yeast cells secreted (1----3)-beta-glucanase into the growth medium. This was highest in early exponential phase cultures (34% of the maximum in situ activity) and declined throughout growth. (1----3)-beta-Glucanase was also secreted into the medium during germ-tube formation and this represented 80-100% of the in situ activity in germ-tube forming cells. Both secretion of (1----3)-beta-glucanase and germ-tube formation were inhibited by 2-deoxyglucose, ethidium bromide, trichodermin and azaserine.
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PMID:Exo-(1----3)-beta-glucanase, autolysin and trehalase activities during yeast growth and germ-tube formation in Candida albicans. 614 89

Dithiothreitol (DTT) extraction of N-acetylglucosaminidase and trehalase from intact Candida albicans ATCC 10261 cells was monitored as an index of cell envelope porosity during N-acetylglucosamine-induced morphogenesis. Trehalase, which is secreted into the cell envelope during starvation and bud-formation, displayed similar extraction kinetics in starved, germ tube-forming, and bud-forming cells, indicating that the mother cell wall remains largely unchanged during morphogenic outgrowth and that the porosity of bud and mother cell walls is similar. N-acetylglucosaminidase, which is secreted specifically during morphogenesis, was released eightfold more rapidly from germ tube-forming than bud-forming cells, reflecting major differences in porosity between bud and germ tube. In addition, by assaying DTT extracts and extracted cell residues, it was found that the total extracellular N-acetylglucosaminidase activity increased 2- to 2.5-fold during DTT treatment. Thus, DTT unmasks a cryptic form of N-acetylglucosaminidase. The cryptic activity was associated with the cell wall fraction.
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PMID:Differential extraction of N-acetylglucosaminidase and trehalase from the cell envelope of Candida albicans. 755 68

The dynamic responses of reserve carbohydrates with respect to shortage of either carbon or nitrogen source was studied to obtain a sound basis for further investigations devoted to the characterization of mechanisms by which the yeast Saccharomyces cerevisiae can cope with nutrient limitation during growth. This study was carried out in well-controlled bioreactors which allow accurate monitoring of growth and frequent sampling without disturbing the culture. Under glucose limitation, genes involved in glycogen and trehalose biosynthesis (GLG1, GSY1, GSY2, GAC1, GLC3, TPS1), in their degradation (GPH1, NTHI), and the typical stress-responsive CTT1 gene were coordinately induced in parallel with glycogen, when the growth has left the pure exponential phase and while glucose was still plentiful in the medium. Trehalose accumulation was delayed until the diauxic shift, although TPS1 was induced much earlier, due to hydrolysis of trehalose by high trehalase activity. In contrast, under nitrogen limitation, both glycogen and trehalose began to accumulate at the precise time when the nitrogen source was exhausted from the medium, coincidentally with the transcriptional activation of genes involved in their metabolism. While this response to nitrogen starvation was likely mediated by the stress-responsive elements (STREs) in the promoter of these genes, we found that these elements were not responsible for the co-induction of genes involved in reserve carbohydrate metabolism during glucose limitation, since GLG1, which does not contain any STRE, was coordinately induced with GSY2 and TPS1.
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PMID:Dynamic responses of reserve carbohydrate metabolism under carbon and nitrogen limitations in Saccharomyces cerevisiae. 1007 86

The influence of the cAMP-signalling pathway on the metabolism of trehalose in Neurospora crassa was investigated. The changes in intracellular trehalose concentration were measured in two mutants affected in components of the cAMP-signalling pathway: cr-1 (crisp-1), deficient in adenylyl cyclase activity, and mcb (microcyclic conidiation), deficient in the regulatory subunit of PKA. Rapid mobilisation of intracellular trehalose in the wild-type occurred, either at the onset of germination, or after a heat shock, and by carbon starvation. Mutant cr-1 failed to mobilise trehalose at germination, but behaved almost normally after a heat shock, or during carbon starvation. On the other hand, the levels of trehalose in mcb fell to values much lower than in the wild-type at germination, but accumulated trehalose normally during a heat shock. These results are consistent with the involvement of cAMP in the activation of the neutral trehalase at the onset of germination. However, the control of the enzyme under the other physiological conditions which also promote mobilisation of intracellular trehalose was apparently independent of cAMP-signalling.
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PMID:Mobilisation of trehalose in mutants of the cyclic AMP signalling pathway, cr-1 (CRISP-1) and mcb (microcycle conidiation), of Neurospora crassa. 1135 72

The physiological hallmark of heat-shock response in yeast is a rapid, enormous increase in the concentration of trehalose. Normally found in growing yeast cells and other organisms only as traces, trehalose becomes a crucial protector of proteins and membranes against a variety of stresses, including heat, cold, starvation, desiccation, osmotic or oxidative stress, and exposure to toxicants. Trehalose is produced from glucose 6-phosphate and uridine diphosphate glucose in a two-step process, and recycled to glucose by trehalases. Even though the trehalose cycle consists of only a few metabolites and enzymatic steps, its regulatory structure and operation are surprisingly complex. The article begins with a review of experimental observations on the regulation of the trehalose cycle in yeast and proposes a canonical model for its analysis. The first part of this analysis demonstrates the benefits of the various regulatory features by means of controlled comparisons with models of otherwise equivalent pathways lacking these features. The second part elucidates the significance of the expression pattern of the trehalose cycle genes in response to heat shock. Interestingly, the genes contributing to trehalose formation are up-regulated to very different degrees, and even the trehalose degrading trehalases show drastically increased activity during heat-shock response. Again using the method of controlled comparisons, the model provides rationale for the observed pattern of gene expression and reveals benefits of the counterintuitive trehalase up-regulation.
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PMID:Biochemical and genomic regulation of the trehalose cycle in yeast: review of observations and canonical model analysis. 1278 17

In the yeast Saccharomyces cerevisiae starvation for nitrogen on a glucose-containing medium causes entrance into G0 and downregulation of all targets of the PKA pathway. Re-addition of a nitrogen source in the presence of glucose causes rapid activation of trehalase and other PKA targets. Trehalase activation upon ammonium re-supplementation is dependent on PKA activity, but not on its regulatory subunit nor is it associated with an increase in cAMP. In nitrogen-starved cells, ammonium transport and activation of trehalase are most active in strains expressing either the Mep2 or Mep1 ammonium permease, as opposed to Mep3. The non-metabolizable ammonium analogue, methylamine, also triggers activation of trehalase when transported by Mep2 but not when taken up by diffusion. Inhibition of ammonium incorporation into metabolism did not prevent signalling. Extensive site-directed mutagenesis of Mep2 showed that transport and signalling were generally affected in a similar way, although they could be separated partially by specific mutations. Our results suggest an ammonium permease-based sensing mechanism for rapid activation of the PKA pathway. Mutagenesis of Asn246 to Ala in Mep2 abolished transport and signalling with methylamine but had no effect with ammonium. The plant AtAmt1;1, AtAmt1;2, AtAmt1;3 and AtAmt2 ammonium transporters sustained transport and trehalase activation to different extents. Specific mutations in Mep2 affected the activation of trehalase differently from induction of pseudohyphal differentiation. We also show that Mep permease involvement in PKA control is different from their role in haploid invasive growth, in which Mep1 sustains and Mep2 inhibits, in a way independent of the ammonium level in the medium.
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PMID:Ammonium permease-based sensing mechanism for rapid ammonium activation of the protein kinase A pathway in yeast. 1646 90

The strong regulation of plant carbon allocation and growth by trehalose metabolism is important for our understanding of the mechanisms that determine growth and yield, with obvious applications in crop improvement. To gain further insight on the growth arrest by trehalose feeding, we first established that starch-deficient seedlings of the plastidic phosphoglucomutase1 mutant were similarly affected as the wild type on trehalose. Starch accumulation in the source cotyledons, therefore, did not cause starvation and consequent growth arrest in the growing zones. We then screened the FOX collection of Arabidopsis (Arabidopsis thaliana) expressing full-length cDNAs for seedling resistance to 100 mm trehalose. Three independent transgenic lines were identified with dominant segregation of the trehalose resistance trait that overexpress the bZIP11 (for basic region/leucine zipper motif) transcription factor. The resistance of these lines to trehalose could not be explained simply through enhanced trehalase activity or through inhibition of bZIP11 translation. Instead, trehalose-6-phosphate (T6P) accumulation was much increased in bZIP11-overexpressing lines, suggesting that these lines may be insensitive to the effects of T6P. T6P is known to inhibit the central stress-integrating kinase SnRK1 (KIN10) activity. We confirmed that this holds true in extracts from seedlings grown on trehalose, then showed that two independent transgenic lines overexpressing KIN10 were insensitive to trehalose. Moreover, the expression of marker genes known to be jointly controlled by SnRK1 activity and bZIP11 was consistent with low SnRK1 or bZIP11 activity in seedlings on trehalose. These results reveal an astonishing case of primary metabolite control over growth by way of the SnRK1 signaling pathway involving T6P, SnRK1, and bZIP11.
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PMID:Growth arrest by trehalose-6-phosphate: an astonishing case of primary metabolite control over growth by way of the SnRK1 signaling pathway. 2175 16

During yeast biomass production, cells are grown through several batch and fed-batch cultures on molasses. This industrial process produces several types of stresses along the process, including thermic, osmotic, starvation, and oxidative stress. It has been shown that Saccharomyces cerevisiae strains with enhanced stress resistance present enhanced fermentative capacity of yeast biomass produced. On the other hand, storage carbohydrates have been related to several types of stress resistance in S. cerevisiae. Here we have engineered industrial strains in storage carbohydrate metabolism by overexpressing the GSY2 gene, that encodes the glycogen synthase enzyme, and deleting NTH1 gene, that encodes the neutral trehalase enzyme. Industrial biomass production process simulations were performed with control and modified strains to measure cellular carbohydrates and fermentation capacity of the produced biomass. These modifications increased glycogen and trehalose levels respectively during bench-top trials of industrial biomass propagation. We finally show that these strains display an improved fermentative capacity than its parental strain after biomass production. Modification of storage carbohydrate content increases fermentation or metabolic capacity of yeast which can be an interesting application for the food industry.
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PMID:Enhanced fermentative capacity of yeasts engineered in storage carbohydrate metabolism. 2521 77


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