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)

(1) In all examined rat and human tissues and cells, PIP kinase activity was rate-limiting and PLC activity was present in great excess. (2) The steady-state activities of the signal transduction enzymes, PI kinase, PIP kinase and PLC, and the concentration of the end product, IP3, were determined in rat liver and hepatomas of different malignancies. The activities of all three enzymes were elevated in the hepatomas in a non-random fashion. A generalization emerged that the enzyme with the lowest activity in liver, PIP kinase, increased to the highest extent and the enzyme with the highest activity in liver, PLC, increased to the smallest extent in rapidly growing hepatomas. The IP3 concentration in the hepatomas was elevated in a progression-linked fashion. (3) The three signal transduction enzyme activities were elevated in human ovarian carcinoma samples and in human breast carcinoma cells. (4) When human breast carcinoma MDA-MB-435 cells were allowed to go through lag, log and plateau phases, the IP3 concentration reached a 20-fold peak at 12 hr after plating. The elevation in IP3 concentration preceded the rise in PI and PIP kinase activities which increased 11-fold in the log phase. The IP3 concentration and PI and PIP kinase activities returned to their baseline levels when the plateau phase was reached. The PLC activity did not change significantly during the whole period. (5) Administration of cycloheximide i.p. in rats revealed short half-lives in the bone marrow for the two kinases (8 min) and a long half-life for PLC (> 6 hr). In a group of 10 enzymes, the half-lives of the kinases were the shortest. In cycloheximide-injected rats, the bone marrow IP3 concentration was reduced to about 50% in 30 min. The reduction of IP3 concentration is attributed to the decline to 15 and 12%, respectively, in PI and PIP kinase activities since PLC activity did not change. (6) In 3-day starved rats, the bone marrow PI and PIP kinase were reduced to activities (13%) that were markedly lower than the decrease in the protein concentration (to 55%). By contrast, the PLC activity was preferentially maintained (to 78%) over the protein level. Under starvation, the IP3 concentration decreased (to 24%), indicating that starvation can markedly disrupt IP3 homeostasis. Refeeding returned the enzymic activities and the IP3 concentration to the normal level in bone marrow in 24 hr. (7) Comparison of the absolute activities of PI and PIP kinases and PLC showed that PLC is present in an excess; therefore, it does not appear to have a rate-limiting action in cycloheximide treated rats or in starvation. (8) Whereas PI and PIP kinases have short half-lives and apparently rapid synthetic rates, PLC has high activity, a long half-life and responds to starvation with only a small decrease. (9) The gain in function manifested in the over-expressed capacity for signal transduction confers growth advantages to cancer cells. These increased activities, particularly those of PI and PIP kinases, should be sensitive targets for chemotherapy.
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PMID:Current issues in the regulation of signal transduction. 886 39

Production of the two phospholipases C (PLCs) in Pseudomonas aeruginosa PAO1 is induced under conditions of phosphate limitation, or by the osmoprotectants choline or glycine betaine. Tn5 mutagenesis was performed on strain PAO1 to isolate mutants deficient in choline-dependent induction of PLC. Two mutants, Tn5T1 and Tn5G19, were identified which produce decreased levels of PLC in phosphate-replete media supplemented with choline. A total of 136 and 496 bp of flanking DNA from Tn5G19 and Tn5T1 was cloned by an inverse polymerase chain reaction (PCR) and sequenced. The DNA flanking the Tn5T1 insertion contains an open reading frame predicted to encode a peptide that is approx. 60% identical to the N-terminus of a previously identified protein (P35) of unknown function from Escherichia coli. The P35 gene, which is located in the nusA-infB operon in E. coll, was designated orp (osmoprotectant regulator of PLC). Haemolytic titres, total PlcH protein and beta-galactosidase activity expressed from a chromosomally inserted plcH-lacZ operon fusion were reduced in strain Tn5T1 in comparison with the parental strain (PAO1) carrying the same fusion. However, this mutant expressed several-fold higher levels of plcH message than strain PAO1 in the presence of choline, while the phosphate-starvation-dependent transcript of plcH could not be detected in this mutant. The defects in Tn5T1 are complemented by a DNA fragment, isolated from a genomic library of PAO1, that carries the orp gene. The deduced amino acid sequence of the DNA fragment cloned from Tn5G19 exhibits 84% identity with the betB gene product of E. coli that has betaine aldehyde dehydrogenase activity. This enzyme catalyses the conversion of betaine aldehyde to glycine-betaine. Unlike the parental strain, the Tn5G19 mutant could not utilize choline as a sole carbon, nitrogen and energy source, and it was deficient in betaine aldehyde dehydrogenase activity. Also, consistent with a disruption of betB in Tn5G19, choline inhibited growth of this strain in media containing 0.7 M NaCl, while glycine-betaine restores growth to wild-type levels. The defects in Tn5G19 are complemented by a DNA fragment from PAO1 that carries the betB gene. The orp gene is located between 0.6 to 6.6 min while betB is located between 10.5 to 12.5 min on the chromosome of PAO1.
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PMID:Molecular characterization of mutants affected in the osmoprotectant-dependent induction of phospholipase C in Pseudomonas aeruginosa PAO1. 900 19

Expression of the hemolytic phospholipase C (PlcH) of Pseudomonas aeruginosa is induced under phosphate starvation conditions or in the presence of the osmoprotectants choline and glycine betaine. Because choline and glycine betaine may serve as carbon and energy sources in addition to conferring osmoprotection to P. aeruginosa, it seemed possible that induction of plcH is subject to catabolite repression control (CRC) by tricarboxylic cycle intermediates such as succinate. Total phospholipase (PLC) activity in osmoprotectant-induced cultures of P. aeruginosa PAO1 supplemented with 20 mM succinate was three- to fourfold lower than the levels in cultures supplemented with the non-catabolite-repressive substrate lactate. Analyses of osmoprotectant-dependent plcH expression in a derivative of strain PAO1 containing a plcH::lacZ operon fusion showed that (i) succinate prevented induction of plcH expression by osmoprotectants; and (ii) addition of succinate reduced or shut down further expression of plcH in osmoprotectant-induced bacteria, while cultures supplemented with lactate had little or no change in plcH expression. RNase protection analysis confirmed that repression of plcH occurs at the transcriptional level. However, a P. aeruginosa mutant decoupled in CRC exhibited a phenotype similar to that of the wild-type strain (PAO1) with respect to succinate-dependent repression of plcH expression. Osmoprotectant-induced total PLC activities, levels of expression of plcH measured with the same plcH::lacZ fusion, and levels of plcH transcription in a CRC-deficient strain reflected those seen in strain PAO1. This indicates that CRC of plcH functions by a distinct mechanism which differs from that regulating the glucose or mannitol catabolic pathway. A strain carrying a mutation in vfr, which encodes the Escherichia coli Crp homolog in P. aeruginosa, still exhibited a wild-type phenotype with respect to osmoprotectant-dependent expression and CRC of plcH. These data indicate that there is a novel CRC system that regulates the expression of plcH in P. aeruginosa.
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PMID:Osmoprotectant-dependent expression of plcH, encoding the hemolytic phospholipase C, is subject to novel catabolite repression control in Pseudomonas aeruginosa PAO1. 924 77

The purpose of this paper was to clarify critical aspects of the behavior of signal transduction activity in normal and cancer cells. 1. Signal transduction activity in the conversion of phosphatidylinositol through PI and PIP kinases and PLC to IP3 is regulated at multiple sites. In liver, hepatomas and human carcinomas PIP kinase is the rate limiting enzyme and PLC activity is present in great excess. 2. The steady-state signal transduction activity as measured by the three enzyme activities and IP3 concentration was markedly up-regulated in rat hepatomas of different growth rates. The steady-state specific activities of the three signal transduction enzymes were elevated in ovarian carcinomas as compared to normal ovary. Increased enzyme activities were also observed in human breast carcinoma cells as compared to normal human breast parenchymal cells. In breast, ovarian and rat hepatoma cells as they go through lag, log and plateau phases, IP3 concentration in the early lag phase increased 4.5- to 20-fold and PI and PIP kinase activities peaked in mid-log phase. These events returned to baseline levels in the plateau phase. PLC activity did not change. 3. The bone marrow PI and PIP kinase activities in 3-day starvation were decreased to 13% and IP3 concentration was reduced to 24%; at 1-day refeeding they returned to normal. PLC activity changed little. These alterations are in line with the rapid t1/2 degradation rates (12 min) of PI and PIP kinases observed in studies with cycloheximide. By contrast, PLC has a long half-life. 4. The molecular action of tiazofurin entails inhibition of IMP DH activity, decrease in GTP and IP3 concentrations, reduction of ras and myc oncogene expression, and signal transduction enzyme activities. These events are followed by induced differentiation and apoptosis. There are also decreases in enzyme activities which have rapid turnover, including TdR kinase, dTMP synthase, and GPRT. In vitro studies indicated that these events are abrogated by addition of guanine which restores GTP concentrations. Therefore, most or all these events were brought about by the reduced GTP concentration in the tiazofurin target cells. 5. Quercetin and genistein are able to inhibit PI and PIP kinase activities and reduce IP3 concentration in vivo and in tissue culture systems. These flavonoids are also inhibitors of cell proliferation and clonogenic ability in rat hepatoma 3924A and in human OVCAR-5 and MDA-MB-435 cells. Quercetin down-regulated the expression of c-myc and Ki-ras oncogenes and led to induced differentiation and apoptosis in K562 cells. Genistein reduced IP3 concentration in vivo and in the tissue culture system. Genistein is antiproliferative and has cytototoxicity in human carcinoma cells. All three drugs, tiazofurin, quercetin and genistein, act, in part at least, through depression of cellular IP3 concentration although the mechanisms may not be identical. 6. Quercetin and genistein, which attack different targets and different phases of the cell cycle, proved to be synergistic in OVCAR-5 cells. The impact of tiazofurin, genistein and quercetin is of interest because the drugs crucially inhibit the display of the neoplastic program of cells and lead to induced differentiation and apoptosis.
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PMID:Regulation of the signal transduction program by drugs. 938 80

The cyclin-dependent kinase (cdk) inhibitor p27Kip1 is known to play a role in cell-cycle regulation at G1 and G1/S phase. We investigated the effect of the putative growth-inhibiting agent dibutyryl cyclic AMP (DBcAMP) on the serial changes of p27Kip1 expression in the human hepatoma cells PLC/PRF/5 in culture. The p27Kip1 protein level increased at an early stage of G1 phase (2 hours) after a release from serum-starvation and subsequently maintained the level until the entry to S phase, whereas an addition of DBcAMP at 1mM increased the p27Kip1 protein level during G1 phase. In contrast, the relative expression levels of p27Kip1 mRNA at 2 hours, 4 hours and 6 hours were lower in DBcAMP-added cells. The effects of DBcAMP on cell growth were, reduction of S-phase cells, inhibition of DNA synthesis, and accumulation of G2-phase cells. In the presence of the antisense oligodeoxynucleotides against p27Kip1 mRNA, DBcAMP-induced growth inhibition was partially abolished. These findings suggest that DBcAMP elevates p27Kip1 protein expression during G1 phase, which could be associated with growth inhibition. DBcAMP may inhibit the degradation of p27Kip1 protein.
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PMID:Effect of dibutyryl cyclic AMP on the cyclin-dependent kinase inhibitor p27Kip1 in the human hepatoma cells PLC/PRF/5. 941 61

Dibutyryl cyclic AMP (DBcAMP) was previously reported to enhance the down-regulation of the retinoblastoma (RB) protein during G1 phase in proliferating primary rat hepatocytes, but to inhibit their entry into S phase and RB phosphorylation. In the present study, DBcAMP was also found to enhance the down-regulation of RB protein in the human hepatoma cells PLC/PRF/5 after hydroxyurea-induced synchronization at G1/S phase. One hour after synchronization, CPP32 activity was detected in the cells and was further enhanced in the presence of DBcAMP. CPP32-specific cleavage of the RB protein was also detected and enhanced by the addition of DBcAMP in a dose-dependent manner. DNA analysis by flow cytometry after serum starvation-induced synchronization at G0/G1 phase revealed that DBcAMP elicited an apoptotic peak after the S phase. Based on these findings, DBcAMP was suspected of inducing apoptosis by RB protein degradation during G1/S transition and thereby inhibit the growth of PLC/PRF/5 cells. Under serum-deficient culture conditions, addition of the CPP32 inhibitor DEVD or the ICE inhibitor YVAD enhanced cell growth but did not abolish the DBcAMP-induced growth inhibition. On the other hand, antisense oligodeoxynucleotides against Bcl-2 mRNA showed a growth inhibitory effect on PLC/PRF/5 cells, but did not show an additive effect on the DBcAMP-induced growth inhibition. DBcAMP itself inhibited bcl-2 protein expression. DBcAMP-induced growth inhibition may be mediated by different mechanisms, including apoptosis.
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PMID:Dibutyryl cyclic AMP-induced enhancement of RB protein degradation in human hepatoma cells. 1069 31

Dictyostelium mutants expressing aequorin were used to study and compare the roles of heterotrimeric G-proteins and the second messengers IP3 and cGMP in regulating folate- and cAMP receptor-activated [Ca2+]i signals. The calcium responses of vegetative cells to folate were dramatically impaired in Gbeta and Galpha4 null mutants but were restored with altered kinetics and temperature-sensitivity in Gbeta null mutants overexpressing wild type and temperature-sensitive Gbeta isoforms. Folic acid receptors thus mediate changes in [Ca2+]i via a Galpha4betagamma-dependent pathway. Neither folate nor cAMP-induced [Ca2+]i signals were significantly altered in PLC null transformants, but [Ca2+]i changes elicited by both attractants were significantly prolonged in two stmF mutants lacking cGMP-specific phosphodiesterase activity. This confirms an important role of cGMP in regulating receptor-activated Ca2+ uptake and/or extrusion systems. This cGMP-dependent part of the Ca2+ response to cAMP stimuli was developmentally down-regulated and all but disappeared by the time the cells reached full aggregation competence after 8 h of starvation. The results suggest that folate and cAMP receptor-activated [Ca2+]i signals are regulated in a complex manner via multiple signalling pathways, one that is G-protein- and cGMP-dependent (present at the vegetative and early poststarvation stage) and another that is G-protein-independent (dominant in fully aggregation-competent cells at approximately 8 h poststarvation).
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PMID:Multiple signalling pathways connect chemoattractant receptors and calcium channels in Dictyostelium. 1295 83

HLA class I polymorphism creates diversity in epitope specificity and T cell repertoire. We show that HLA polymorphism also controls the choice of Ag presentation pathway. A single amino acid polymorphism that distinguishes HLA-B*4402 (Asp116) from B*4405 (Tyr116) permits B*4405 to constitutively acquire peptides without any detectable incorporation into the transporter associated with Ag presentation (TAP)-associated peptide loading complex even under conditions of extreme peptide starvation. This mode of peptide capture is less susceptible to viral interference than the conventional loading pathway used by HLA-B*4402 that involves assembly of class I molecules within the peptide loading complex. Thus, B*4402 and B*4405 are at opposite extremes of a natural spectrum in HLA class I dependence on the PLC for Ag presentation. These findings unveil a new layer of MHC polymorphism that affects the generic pathway of Ag loading, revealing an unsuspected evolutionary trade-off in selection for optimal HLA class I loading versus effective pathogen evasion.
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PMID:Natural HLA class I polymorphism controls the pathway of antigen presentation and susceptibility to viral evasion. 1522 59

The c-ret protooncogene, RET, encodes a receptor tyrosine kinase. RET is activated by members of the glial cell line-derived neurotrophic factor (GDNF) family of ligands, which include GDNF, neurturin, artemin, and persephin. The ligands bind RET through GDNF family receptor alpha, termed GFRalpha1-4. Despite the importance of RET signaling in the development of the enteric nervous system and the kidney, the differential signaling mechanisms between RET ligands are poorly established. It has been suggested that signal specificity is achieved through binding of the ligand to its preferred GFRalpha. To compare the signaling profiles of GDNF and neurturin, we have identified a cell line, NG108-15, which endogenously expresses RET and GFRalpha1 but not GFRalpha2-4. Immunoblot data showed that GDNF caused a transient activation, whereas neurturin caused a sustained activation, of both p44/p42 MAP kinases and PLCgamma. Under serum starvation, NG108-15 cells differentiate and form neurites. Neurturin but not GDNF stimulated neurite outgrowth, which could be blocked by the selective PLC inhibitor U73122. On the other hand, GDNF but not neurturin promoted cell survival, and this could be blocked by the p44/p42 MAP kinase inhibitor PD98059. Our findings not only show the differential signaling of GDNF and neurturin but also suggest that this can be achieved through binding to the same GFRalpha subtype, leading to distinct biological responses.
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PMID:Differential effects of glial cell line-derived neurotrophic factor and neurturin in RET/GFRalpha1-expressing cells. 1629 36

In this study, the effects of phosphate concentration and carbon source on the patterns of alkaline phosphatase (APase) and phospholipase (PLase) expression in Vibrio vulnificus ATCC 29307 were assessed under various conditions. The activities of these enzymes were repressed by excess phosphate (4 mM) in the culture medium, but this repression was reversed upon the onset of phosphate starvation in low phosphate defined medium (LPDM) containing 0.2 mM of phosphate at approximately the end of the exponential growth phase. The expressions of the two enzymes were also influenced by different carbon sources, including glucose, fructose, maltose, glycerol, and sodium acetate at different levels. The APase activity was derepressed most profoundly in LPDM containing fructose as a sole carbon source. However, the repression/derepression of the enzyme by phosphate was not observed in media containing glycerol or sodium acetate. In LPDM-glycerol or sodium acetate, the growth rate was quite low. The highest levels of PLase activity were detected in LPDMsodium acetate, followed by LPDM-fructose. PLase was not fully repressed by high phosphate concentrations when sodium acetate was utilized as the sole carbon source. These results showed that multiple regulatory systems, including the phosphate regulon, may perform a function in the expression of both or either APase and PLC, in the broader context of the survival of V. vulnificus.
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PMID:Phosphate and carbon source regulation of alkaline phosphatase and phospholipase in Vibrio vulnificus. 1784 84


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