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)

The response of the estuarine human pathogen Vibrio vulnificus to starvation for carbon, nitrogen or phosphorus, or all three nutrients simultaneously (multiple-nutrient), was examined with respect to the maintenance of culturability during incubation at low temperature. V. vulnificus showed similar survival patterns during starvation for the individual nutrients when kept at 24 degrees C. On the other hand, cultures prestarved at 24 degrees C and then shifted to 5 degrees C maintained culturability at low temperature in a starvation-condition-dependent manner. Carbon and multiple-nutrient starvation were indistinguishable in their ability to mediate maintenance of culturability in the cold. Prolonged starvation for phosphorus had a similar effect, but nitrogen starvation did not allow for maintenance of culturability. Extracellular factors produced during starvation were not observed to have an effect on the culturability of cells incubated at low temperature. Protein synthesis during starvation for individual nutrients was analysed by two-dimensional PAGE of pulse-labelled proteins. Carbon and multiple-nutrient starvation gave nearly identical protein induction patterns involving at least 34 proteins, indicating that carbon starvation determines both responses. Nitrogen starvation for 1 h induced 24 proteins, while phosphorus starvation induced a set of 10 proteins after 1 h and about 40 proteins after 18 h. It is suggested that starvation for carbon or phosphorus induces maintenance of culturability of V. vulnificus incubated at low temperature via the synthesis of distinct sets of starvation-specific proteins.
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PMID:Analysis of starvation conditions that allow for prolonged culturability of Vibrio vulnificus at low temperature. 875 32

Sterol 12alpha-hydroxylase is an important enzyme in bile acid biosynthesis, responsible for the balance between formation of cholic acid and chenodeoxycholic acid. The enzyme has been purified to apparent homogeneity from rabbit liver (Ishida, H., Noshiro, M., Okuda, K., and Coon, M. J. (1992) J. Biol. Chem. 267, 21319-21323), and we here describe the cloning and sequencing of a cDNA coding for this enzyme. After tryptic digestion of purified protein in a polyacrylamide gel, eight different peptides were isolated and sequenced. Using oligonucleotides deduced from the amino acid sequences, clones were isolated from a rabbit liver cDNA library. In addition to several overlapping clones, one full-length clone was obtained that coded for a polypeptide of 500 amino acids, corresponding to a molecular mass of 57 kDa. All of the eight peptides and the reported NH2-terminal amino acid sequence were matched against the sequence. The peptide sequence showed a 39% similarity with human prostacyclin synthase (CYP8) and 31% similarity with the rate-limiting enzyme in over-all synthesis of bile acids, the cholesterol 7alpha-hydroxylase (CYP7) of the rabbit. The similarity with most other sterol cytochrome P-450 hydroxylases was less. Thus, this species of cytochrome P-450 should belong to a group of its own, here denoted CYP12. Transfection of COS cells with the coding part of the cDNA resulted in a significant expression of sterol 12alpha-hydroxylase activity toward 7alpha-hydroxy-4-cholesten-3-one. Northern blotting showed that the enzyme was exclusively expressed in the liver. The major mRNA fraction in rabbit liver had a size of approximately 2.9 kilobases, and those found in rat and human liver were about 2.5 and 4.5 kilobases, respectively. Fasting of rats and mice led to a severalfold increase in both enzyme activity and mRNA levels. In contrast, starvation of rabbits had little or no stimulatory effect on enzyme activity and mRNA levels.
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PMID:Molecular cloning and expression of rabbit sterol 12alpha-hydroxylase. 894 86

Rho-like GTPases, including Cdc42, Rac, and Rho, regulate signaling pathways that control actin cytoskeletal structures and transcriptional activation. The Tiam1 gene encodes an activator of Rac1, and similarly to constitutively activated (V12)Rac1, overexpression of Tiam1 in fibroblasts induces the formation of membrane ruffles. Tiam1 contains a Dbl homology (DH) domain and adjacent pleckstrin homology (PH) domain, hallmarks for activators of Rho-like GTPases. Unique for Tiam1 are an additional PH domain and a Discs-large homology region in the NH2-terminal part of the protein. Here we show that both in fibroblasts and COS cells, membrane localization of Tiam1 is required for the induction of membrane ruffling. A detailed mutational analysis, in combination with confocal laser scanning microscopy and immunoelectron microscopy, demonstrates that the NH2-terminal PH domain of Tiam1, but not the DH-adjacent PH domain, is essential for membrane association. This NH2-terminal PH domain of Tiam1 can be functionally replaced by the myristoylated membrane localization domain of c-Src, indicating that the primary function of this PH domain is to localize the protein at the membrane. After serum starvation, both membrane association of Tiam1 and ruffling can be induced by serum, suggesting that receptor stimulation induces membrane translocation of Tiam1. Similar to V12Rac1, Tiam1 stimulates the activity of the c-Jun NH2-terminal kinase (JNK). This Rac-dependent stimulation of JNK also requires membrane association of Tiam1. We conclude that the regulated membrane localization of Tiam1 through its NH2-terminal PH domain determines the activation of distinct Rac-mediated signaling pathways.
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PMID:Regulated membrane localization of Tiam1, mediated by the NH2-terminal pleckstrin homology domain, is required for Rac-dependent membrane ruffling and C-Jun NH2-terminal kinase activation. 912 50

During their autumn migratory phase, thrush nightingales (Luscinia luscinia) previously starved for 2 d were allowed to refuel under three different ambient temperature conditions (-7 degrees, 7 degrees, and 22 degrees C). During the refueling period, as well as during the preceding control and starvation periods, food intake, body mass, and feces production were monitored. In addition, daily energy expenditure was measured during the refueling period. The compilation of the energy balance during the refueling period revealed an energy density of the deposited tissue of 33.6 kJ g-1. Assuming that the deposited tissue consists of fat and protein exclusively, with energy densities of 39.6 and 5.5 kJ g-1 wet mass, respectively, we estimated the deposited tissue to consist of 82% fat and 18% wet protein (6% dry protein and 12% water). Nitrogen balances during control, starvation, and refueling phases and during a period of prolonged and complete starvation indicated that 5% of the nutrient stores consisted of dry protein. Our results support recent findings that nutrient stores for migration often contain protein in addition to fat and consequently are 15%-25% less energy rich than pure fat stores. These proteins might be stored as muscle or other functional tissue and may be required to support the extra mass of the stores and/or reflect an incapacity of the metabolic machinery to catabolize far exclusively. Fuel deposition rate was positively related with ambient temperature, whereas food intake rate was unaffected by temperature. These results indicate that the rate of fuel deposition is limited by a ceiling in food intake rate; when this ceiling is reached, fuel deposition rate is negatively affected by daily energy expenditure rate. To a certain extent, the ceiling in food intake rate varies depending on feeding conditions over the previous days. These variations in food intake capacity probably reflect the building and breakdown of gut tissues and/or gut enzyme systems and might be insensible and not evolutionary adaptive. Significant energetic costs, however, are probably associated with the maintenance of gut tissues. It is therefore feasible that changes in digestive capacity are regulated and are directed at energy economization.
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PMID:Composition of fuel stores and digestive limitations to fuel deposition rate in the long-distance migratory thrush nightingale, Luscinia luscinia. 923 84

The purpose of this work was to clarify the essentiality of glucose production from amino acids in obese subjects undergoing prolonged starvation and to provide an explanation for death after the depletion of lean body mass when some body fat is still available to meet body energy requirements. Five obese subjects fasted for 21 d. Nitrogen balance studies were combined with measurements of blood metabolite and hormone concentrations, indirect calorimetry, determination of body-composition changes, and catheterization techniques. Phenylacetate was administered from day 19 to day 21 to remove glutamine from the body and to assess this perturbation on energy requirements, ammoniagenesis, ureagenesis, gluconeogenesis, and ketogenesis. The obese subjects lost body fat and fat-free mass in parallel and resting metabolic energy requirements per mass remained constant during starvation. Urinary nitrogen excretion reflected continuous demands for amino acid oxidation. Phenylacetate administration decreased blood glutamine concentrations, increased plasma epinephrine concentrations, and increased urinary nitrogen loss through phenylacetylglutamine excretion; urinary excretion rates of urea, ammonium, urate, creatinine, and ketone bodies remained unchanged. The essentiality of amino acid oxidation was therefore shown. Late in prolonged starvation, aminogenic oxidation amounted to 7% and fat provided the remaining energy requirements. Hepatic and renal gluconeogenesis were not curtailed. Blood glutamate served as a vehicle for carbon and nitrogen transport; the contribution of glycerol to gluconeogenesis equaled that of all amino acids combined. The minimal quantities of amino acid (0.27 +/- 0.08 and 0.52 +/- 0.10 g) and fat (1.53 +/- 0.21 and 2.98 +/- 0.15 g) oxidized per kg body wt or fat-free mass/d, respectively, were determined. Included within amino acid and fat oxidation were the minimal amounts of precursors needed for synthesizing the essential quantity of glucose (0.34 +/- 0.14 and 0.66 +/- 0.20 g) oxidized per kg body wt or fat-free mass, respectively.
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PMID:Protein, fat, and carbohydrate requirements during starvation: anaplerosis and cataplerosis. 966 88

Nitrogen-starved diploid cells of the yeast Saccharomyces cerevisiae differentiate into a filamentous, pseudohyphal growth form. Recognition of nitrogen starvation is mediated, at least in part, by the ammonium permease Mep2p and the Galpha subunit Gpa2p. Genetic activation of the pheromone-responsive MAP kinase cascade, which is also required for filamentous growth, only weakly suppresses the filamentation defect of Deltamep2/Deltamep2 and Deltagpa2/Deltagpa2 strain. Surprisingly, deletion of Mep1p, an ammonium permease not previously thought to regulate differentiation, significantly enhances the potency of MAP kinase activation, such that the STE11-4 allele induces filamentation to near wild-type levels in Deltamep1/Deltamep1 Deltamep2/Deltamep2 and Deltamep1/Deltamep1 Deltagpa2/Deltagpa2 strains. To identify additional regulatory components, we isolated high-copy suppressors of the filamentation defect of the Deltamep1/Deltamep1 Deltamep2/Deltamep2 mutant. Multicopy expression of TEC1, PHD1, PHD2 (MSS10/MSN1/FUP4), MSN5, CDC6, MSS11, MGA1, SKN7, DOT6, HMS1, HMS2, or MEP2 each restored filamentation in a Deltamep1/Deltamep1 Deltamep2/Deltamep2 strain. Overexpression of SRK1 (SSD1), URE2, DAL80, MEP1, or MEP3 suppressed only the growth defect of the Deltamep1/Deltamep1 Deltamep2/Deltamep2 mutant strain. Characterization of these genes through deletion analysis and epistasis underscores the complexity of this developmental pathway and suggests that stress conditions other than nitrogen deprivation may also promote filamentous growth.
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PMID:Regulators of pseudohyphal differentiation in Saccharomyces cerevisiae identified through multicopy suppressor analysis in ammonium permease mutant strains. 983 22

Vascular endothelial growth factor (VEGF), an endothelial cell-specific mitogen, promotes endothelial cell survival and angiogenesis. We recently showed that VEGF can support the growth of human dermal microvascular endothelial cells (HDMEC) and human umbilical vein endothelial cells in serum-free medium. Reasoning that VEGF might be modulating apoptotic signal transduction pathways, we examined mechanisms involved in the anti-apoptotic effect of VEGF on starvation- and ceramide-induced apoptosis in HDMEC. We observed that VEGF ameliorated the time-dependent increase in apoptosis, as demonstrated by morphologic observations, TUNEL assay, and DNA fragmentation. On the other hand, basic fibroblast growth factor only partially prevented apoptosis in serum-starved HDMEC; platelet-derived growth factor-BB was completely ineffective. VEGF activated the phosphorylation of extracellular signal regulated kinase (ERK)1 (p44 mitogen-activated protein kinase; MAPK) and ERK2 (p42 MAPK) in a time- and concentration-dependent manner. Both the VEGF-induced activation and its anti-apoptotic effect were prevented by the specific MAPK/ERK inhibitor PD98059. The presence of VEGF also inhibited the sustained activation of stress-activated protein kinase/c-jun-NH2-kinase (SAPK/JNK) caused by serum starvation and ceramide treatment. Activation of the MAPK pathway together with inhibition of SAPK/JNK activity by VEGF appears to be a key event in determining whether an endothelial cell survives or undergoes programmed cell death.
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PMID:VEGF prevents apoptosis of human microvascular endothelial cells via opposing effects on MAPK/ERK and SAPK/JNK signaling. 1006 77

Saccharomyces cerevisiae responds to nitrogen availability in several ways. (i) The cell is able to distinguish good nitrogen sources from poor ones through a process designated nitrogen catabolite repression (NCR). Good and poor nitrogen sources do not demonstrably affect the cell cycle other than to influence the cell's doubling time. (ii) Nitrogen starvation promotes the initiation of sporulation and pseudohyphal growth. (iii) Nitrogen starvation strongly affects the cell cycle; nitrogen-starved cells arrest in G1. A specific allele of the SUP70/CDC65 tRNAGln gene (sup70-65) has been reported to be defective in nitrogen signaling associated with pseudohyphal formation, sporulation, and NCR. Our data confirm that pseudohyphal growth occurs gratuitously in sup70-65 mutants cultured in nitrogen-rich medium at 30 degrees C. However, we find neither any defect in NCR in the sup70-65 mutant nor any alteration in the control of YVH1 expression, which has been previously shown to be specifically induced by nitrogen starvation.
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PMID:Control of nitrogen catabolite repression is not affected by the tRNAGln-CUU mutation, which results in constitutive pseudohyphal growth of Saccharomyces cerevisiae. 1019 11

Nitrogen starvation enhances up to 8-fold the cellular level of the NADP+-dependent isocitrate dehydrogenase activity (isocitrate:NADP+ oxidoreductase (decarboxylating), IDH, EC 1.1.1.42) in the thermophilic filamentous non-N2-fixing cyanobacterium Phormidium laminosum. The enzyme was purified 650-fold to electrophoretic homogeneity from nitrogen-starved cells with an activity yield of 25% and a specific activity of 500 U (mg protein)-1. The native enzyme showed a pI of 5.9 and it was a dimer of 107 kDa consisting of two identical subunits of 53 kDa. The activity required the presence of a divalent metal cation as an essential activator, Mn2+ or Mg2+ being the most effective. The optimum temperature for activity was 55 degrees C and the Ea for catalysis was 39.7 kJ mol-1. An optimum pH for activity of 8.5 was found and the calculated pKE1, pKE2 and pKES1 of enzyme ionisation groups were 6.0, 8.9 and 6.3, respectively. Km values of 22, 50 and 24 microM were calculated for d,l-isocitrate, NADP and Mn2+, respectively, in the Mn2+-dependent reaction and 70, 32 and 159 microM for d,l-isocitrate, NADP and Mg2+, respectively, in the Mg2+-dependent reaction. The decarboxylating activity was inhibited by ATP, ADP and by its reaction products 2-oxoglutarate and NADPH2. Polyclonal antibodies raised against the pure IDH were used to assess the presence of the enzyme in cells subjected to nitrogen starvation.
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PMID:Purification, properties and enhanced expression under nitrogen starvation of the NADP+-isocitrate dehydrogenase from the cyanobacterium Phormidium laminosum. 1020 82

To analyze the role of phosphoenolpyruvate carboxylase (PEPCase, EC 4.1.1.31) during seed development, two cDNA clones encoding two isoforms of PEPCase were isolated from a seed-specific library of Vicia faba. The two sequences (VfPEPCase1 and VfPEPCase2) have a sequence identity of 82 and 89% on the nucleotide and amino acid levels. The VfPEPCase1 mRNA was found to be predominantly expressed in roots and developing cotyledons whereas the VfPEPCase2 mRNA was more abundant in green and maternal tissues. In the cotyledons, PEPCase mRNAs accumulated from early to mid cotyledon stage and decreased thereafter. The PEPCase activity increased continuously during cotyledon development. The enzyme was strongly activated by glucose-6-phosphate, but not by glucose, fructose or sucrose. Asparagine was weakly activating whereas malate, aspartate and glutamate were inhibitory. The inhibitors became less effective with increasing pH. Aspartate was a much stronger inhibitor of cotyledonary PEPCase than glutamate at both pH 7.0 and 7.5. The sensitivity of PEPCase to malate inhibition decreased from early to mid cotyledon stage at a time when storage proteins are synthesized. This indicates activation on the protein level, possibly by protein phosphorylation. Nitrogen starvation in the presence of hexoses but not sucrose decreased mRNA levels of VfPEPCase1 and enzyme activity, indicating control on the mRNA level by both carbon and nitrogen. It is concluded that in developing cotyledons PEPCase is probably important for the synthesis of organic acids to provide carbon skeletons for amino acid synthesis.
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PMID:Phosphoenolpyruvate carboxylase in developing seeds of Vicia faba L.: gene expression and metabolic regulation. 1021 2


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