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 nature and mechanism of the pancreatic exocrine dysfunction in diabetes mellitus were evaluated in vitro using isolated pancreatic acini prepared from streptozotocin-induced diabetic rats. The content of amylase and ribonuclease in diabetic acini was approximately 0.5 and 50% of the normal content, respectively. Further, reduced amounts of both enzymes were secreted by diabetic acini in response to both cholecystokinin (CCK) and carbamylcholine. However, when enzyme secretion was normalized relative to initial acinar contents, both normal and diabetic acini released enzymes at a comparable maximal rate. The time course of the release of these enzymes, and newly synthesized protein were similar in both acini. In normal acini, the effect of CCK was maximal at a concentration of 100 pM; higher concentrations led to submaximal enzyme release. The dose-response curve in diabetic acini was similarly shaped, but shifted three-fold towards higher concentration. The mobilization of cellular Ca(2+) in response to CCK was also shifted. In contrast to these results with CCK, the dose-response curve to carbamylcholine was unaltered by diabetes. The observed effects were confirmed to be due to insulin deficiency and not due to direct toxic effect of streptozotocin on acinar cells or malnutrition. Streptozotocin had no acute effect on acini when measured 24 h after administration, and alloxan, another beta cell toxin, induced similar changes in acinar enzyme content and secretory response. Moreover, the administration of exogenous insulin to diabetic rats returned the content of pancreatic amylase and the secretory response to CCK towards normal. Starvation for 48 h, although inducing a significant weight loss, did not mimic the effects of diabetes. The present studies demonstrate two major abnormalities in pancreatic exocrine secretion in the diabetic rat: (a) the content of certain digestive enzymes is markedly altered, leading to an altered amount of zymogen secretion, (b) the sensitivity to CCK is selectively reduced, most likely related to a defect in receptor activated transmembrane signaling.
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PMID:Effect of diabetes mellitus on the regulation of enzyme secretion by isolated rat pancreatic acini. 617 17

A multiple mutant strain of Escherichia coli containing mutations affecting the exoribonucleases, RNase II, RNase D, and RNase BN, and also the endonuclease, RNase I, was constructed by P1-mediated transduction. Extracts of the mutant strain were lacking the aforementioned RNase activities. The multiple mutant displayed normal growth in both rich and minimal media at a variety of temperatures, recovered from starvation essentially as the wild-type parent, and could support the growth of a variety of bacteriophages. In addition, RNA synthesis was normal and no precursor RNA accumulation was observed. The properties of the mutant strain indicate that the three exoribonucleases are not essential for the viability of E. coli. The implications of these findings to our understanding of RNA processing and degradation are discussed.
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PMID:A multiple mutant of Escherichia coli lacking the exoribonucleases RNase II, RNase D, and RNase BN. 620 70

When cells of the yeast, Saccharomyces cerevisiae, were deprived of nitrogen, a condition leading to G1 arrest, there was an immediate increase in the levels of total ribonuclease (RNase) activity within these cells. During starvation, only the cells arrested in G1 showed increased RNase activity. Although the RNase activities of extracts of starved and actively growing cells were similarly influenced by pH, the activities of starved cells were less stable on both storage and heating. Differences were also noted in substrate specificity. The results of this study suggest that arrest within G1 may increase RNase activity. However, all RNases did not appear to be influenced equally, since the total pool of RNase activity from log phase and G1 arrested cells showed differences in stability and substrate specificity.
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PMID:Ribonuclease activity during G1 arrest of the yeast Saccharomyces cerevisiae. 698 36

1. The loss of liver protein occurring in rats starved for 24 h was largely prevented by the administration of repeated doses of cycloheximide, an inhibitor of protein synthesis. Similar effects were produced on tubulin, a 'fixed' liver protein. 2. Starvation accelerated, whereas cycloheximide markedly lowered, the rate of protein radioactivity decay after labelling with [3H]valine or [14C]bicarbonate, indicating that changes in catabolic rates played an important role in the above regulations of liver protein mass. 3. The total activity of several lysosomal hydrolases showed little change in livers of starved rats, but a marked progressive decline developed after the administration of cycloheximide, particularly in the activities of cathepsins B, D and L as well as acid ribonuclease. There was no evidence that these changes might be due to endogenous inhibitors (at least for cathepsin B activity, which fell to less than 30% of the control values) or enzyme leakage into the bloodstream; rather, plasma beta-galactosidase and beta-N-acetylglucosaminidase activities fell progressively during the cycloheximide treatment. 4. Endogenous proteolytic rates, measured in vitro by incubating subcellular preparations from livers prelabelled in vivo with [3H]valine, were markedly decreased in cycloheximide-treated animals. 5. The osmotic fragility of hepatic lysosomes, appreciably enhanced in starved animals, after cycloheximide treatment was found to be even lower than in fed controls. 6. The present data are consistent with the view that in starved animals the loss of liver protein is mostly accounted for by increased breakdown, due, in part at least, to enhanced autophagocytosis. 7. Cycloheximide largely counteracted these effects of starvation, altering the liver from being 'poised' in a proteolytic direction to a protein-sparing condition. The present data suggest that, besides suppression of the autophagic processes, a decrease in the lysosomal proteolytic enzyme system may also play a role in this regulation, and they seem to provide further circumstantial evidence for the existence of co-ordinating mechanisms between protein synthesis and degradation.
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PMID:Control of cell protein catabolism in rat liver. Effects of starvation and administration of cycloheximide. 715 Feb 50

Ribonuclease A was introduced into the cytoplasm of IMR-90 human diploid fibroblasts by red cell-mediated microinjection. Early passage fibroblasts degraded ribonuclease A with a half-life of approximately 90 h in the presence of 10% fetal calf serum and enhanced the degradative rate 1.6-fold upon serum withdrawal. Senescent cells degraded ribonuclease A more slowly with half-lives ranging between 125 and 250 h and had diminished capacities to enhance the catabolism of this protein during serum starvation. Decreased protein degradation in senescent cells was also evident for microinjected RNase S-protein, RNase B, aldolase, lysozyme, and the synthetic copolymer polyglutamate: tyrosine:alanine (1:1:1). These alterations in the mechanisms and regulation of intracellular protein degradation may contribute to several biochemical abnormalities characteristic of aging cells and organisms.
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PMID:Altered degradation of proteins microinjected into senescent human fibroblasts. 717 58

Lysosomal uptake and degradation of polypeptides such as glyceraldehyde-3-phosphate dehydrogenase (GAPDH), ribonuclease A (RNase A), and RNase S-peptide (residues 1-20 of RNase A) are progressively activated in rat liver by starvation before isolation of lysosomes. This pathway of proteolysis is selective, since it is stimulated by the heat shock cognate protein of 73 kDa (HSC73) and ATP-MgCl2, and lysosomal uptake of RNase A could be competed by GAPDH but not by ovalbumin. A portion of intracellular HSC73 is associated with certain lysosomes, and the amount of lysosomal HSC73 increases by 5- to 10-fold during prolonged starvation. The lysosome-associated HSC73 is primarily within the lysosomal lumen. Double immunogold labeling of lysosomes incubated in vitro with RNase A detects this protein substrate as well as HSC73 within lysosomes. More than two-thirds of the labeled lysosomes contain both RNase A and HSC73. The possible physiological significance of the activation of this selective pathway of lysosomal proteolysis in long-term starvation is discussed.
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PMID:Activation of a selective pathway of lysosomal proteolysis in rat liver by prolonged starvation. 749 10

Under certain conditions, Escherichia coli cells exhibit either of two altered modes of chromosomal DNA replication. These are inducible stable DNA replication (iSDR), seen in SOS-induced cells, and constitutive stable DNA replication (cSDR), seen in rnhA mutants. Both iSDR and cSDR can continue to occur in the absence of protein synthesis. They are dependent on RecA protein, but do not require DnaA protein or the oriC site. Here we report the requirement for PriA, a protein essential for assembly of the phi X174-type primosome, for both iSDR and cSDR. In priA1(Null)::kan mutant cells, iSDR is not observed after induction by thymine starvation. Replication from one of the origins (oriM1) specific to iSDR is greatly reduced by the priA1::kan mutation. cSDR in rnhA224 mutant cells deficient in RNase HI is also completely abolished by the same priA mutation. In both cases, SDR is restored by introduction of a plasmid carrying a wild-type priA gene. Furthermore, the viability of an rnhA::cat dnaA46 strain is lost at 42 degrees C upon inactivation of the priA gene, indicating the lethal effect of priA inactivation on those cells whose viability depends on cSDR. These results demonstrate that a function of PriA protein is essential for iSDR and cSDR and suggest the involvement of the PriA-dependent phi X174-type primosome in these DnaA/oriC-independent pathways of chromosome replication. Whereas ColE1-type plasmids, known to be independent of DnaA, absolutely require PriA function for replication, DnaA-dependent plasmid replicons such as pSC101, F, R6K, Rts1 and RK2 are able to transform and to be maintained in the priA1::kan strain.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Escherichia coli PriA protein is essential for inducible and constitutive stable DNA replication. 752 76

The Escherichia coli rnt gene, which encodes the RNA-processing enzyme RNase T, is cotranscribed with a downstream gene. Complete sequencing of this gene indicates that its coding region encompasses 1,538 amino acids, making it the longest known protein in E. coli. The gene (tentatively termed lhr for long helicase related) contains the seven conserved motifs of the DNA and RNA helicase superfamily II. An approximately 170-kDa protein is observed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of 35S-labeled extracts prepared from cells in which lhr is under the control of an induced T7 promoter. This protein is absent when lhr is interrupted or when no plasmid is present. Downstream of lhr is the C-terminal region of a convergent gene with homology to glutaredoxin. Interruptions of chromosomal lhr at two different positions within the gene do not affect the growth of E. coli at various temperatures in rich or minimal medium, indicating that lhr is not essential for usual laboratory growth. lhr interruption also has no effect on anaerobic growth. In addition, cells lacking Lhr recover normally from starvation, plate phage normally, and display normal sensitivities to UV irradiation and H2O2. Southern analysis showed that no other gene closely related to lhr is present on the E. coli chromosome. These data expand the known size range of E. coli proteins and suggest that very large helicases are present in this organism.
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PMID:The gene for the longest known Escherichia coli protein is a member of helicase superfamily II. 755 21

Members of the Rh/T2/S-glycoprotein family of ribonuclease(RNase)-encoding genes have been found predominantly in fungi, plants and bacteria, where they have been implicated in functions as diverse as the phosphate-starvation response and self-incompatibility. We report the isolation and sequence of DmRNase-66B, the first member of this family to be found in an insect genome. This gene was identified by the analysis of a cDNA clone derived from cytological region 66B1-2 of the genome of Drosophila melanogaster. In a search of sequence databases for homologs of this gene, two animal viral proteins, gp53 of the bovine viral diarrhea virus (BVDV) and gp44/48 of the hog cholera virus (HCV), were also found to exhibit the characteristic features of this class of RNases. In all cases, the proteins contain two conserved pentameric amino-acid regions that have been shown to lie in the active site of these RNases. A series of Cys residues are also conserved in all members of this gene family. The discovery of members of this family of genes in an insect genome indicates that these RNases are widely conserved and play important roles in the animal, as well as the plant and prokaryotic kingdoms.
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PMID:The Drosophila melanogaster genome contains a member of the Rh/T2/S-glycoprotein family of ribonuclease-encoding genes. 760 42

In previous work we have determined the primary structure of two of the five ribonucleases which are induced by phosphate starvation in cultured tomato cells. Here, we present the isolation and characterization of the cDNAs for the extracellular ribonuclease LE and the intracellular, but extravacuolar ribonuclease LX. Structural analysis of these cDNAs together with partial protein-sequencing of vacuolar ribonucleases LV1, LV2 and LV3 revealed a family of very similar ribonucleases. From these data we assume identify between ribonucleases LE and LV3 for which the targeting mechanism has to be shown. Furthermore, RNase LV1 and RNase LV2 might be posttranslational processing products of RNase LX which travel to the vacuoles after splitting off the putative ER retention signal present at RNase LX. Additionally, we show by northern blot analysis that phosphate starvation in plant cells leads to an increase in the steady-state level of this type of enzymes revealing close similarities of the plant response to a limited supply of inorganic phosphate with the PHO regulation in bacteria and fungi.
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PMID:cDNA structure and regulatory properties of a family of starvation-induced ribonucleases from tomato. 789 13


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