Compartmentation of purine and pyrimidine nucleotides in animal cells

Andersson, Marianne; Lewan, Lillemor; Stenram, Unne

doi:10.1016/0020-711x(88)90248-0

Cited by 12 publications

(12 citation statements)

References 104 publications

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“…This is in agreement with results found by others in various cell types [26,[31][32][33][34]. Compartmentation of the de novo and salvage pathways has also been described in the nucleus [16,30,35]. However, with our method of cell extraction we were unable to discriminate between different forms of RNA in the nucleus as found by the latter authors.…”

Section: Discussionsupporting

confidence: 93%

“…RNA synthesis takes place almost exclusively in the cell nucleus, whereas most activation processes that require pyrimidine ribonucleotides occur in the cytoplasm [9][10][11][12]. It is not known whether the distinct cellular locations at which these processes take place require a similar compartmentation of the nucleoside triphosphates, although many studies are in support of such a concept for pyrimidine nucleotides (for reviews, see [13][14][15][16]). …”

Section: Introductionmentioning

confidence: 99%

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Pyrimidine nucleotide metabolism in rat hepatocytes: evidence for compartmentation of nucleotide pools

Rijcken

Overdijk

Eijnden

et al. 1993

Biochemical Journal

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Pyrimidine nucleotide metabolism in rat hepatocytes was studied by measurement of the labelling kinetics of the various intermediates after double labelling with [14C]orotic acid and [3H]cytidine, the precursors for the de novo and the salvage pathways respectively. For the uridine nucleotides, differences were found for the 14C/3H ratios in the UDP-sugars, in UMP (of RNA) and in their precursor UTP, suggesting the existence of separated flows of the radioactive precursors through the de novo and the salvage pathways. Higher ratios in the UDP-sugars, which are synthesized in the cytoplasm, and a lower ratio in UMP (of RNA) relative to the 14C/3H ratio in UTP indicated that UTP derived from orotic acid is preferentially used for the cytoplasmic biosynthesis of the UDP-sugars. Uridine, derived from cytidine, is preferentially used for the nuclear-localized synthesis of RNA. In contrast to these findings, the 14C/3H ratios in the cytidine derivatives CMP-NeuAc and CMP (of RNA), and in the liponucleotides CDP-choline and CDP-ethanolamine, were

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Section: Discussionsupporting

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Pyrimidine nucleotide metabolism in rat hepatocytes: evidence for compartmentation of nucleotide pools

Rijcken

Overdijk

Eijnden

et al. 1993

Biochemical Journal

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“…The flow of the salvage pathway is relatively more directed to RNA synthesis in the nucleus, and the flow of synthesis de novo relatively more to the cytoplasmic processes. Other investigators, mostly working with cells in culture, and using different approaches and different isotopic labelling, came to the same conclusion (for reviews, see [9] and [10]). The ratio of CTP also is higher than that of 2'-+ 3'-CMP (RNA), which is a strong indication that the CTP pool is compartmentalized too.…”

Section: Discussionmentioning

confidence: 80%

“…Intracellular compartmentation of NTP pools may be the result of separate flows of nucleotide precursors through those pathways. Many studies concerning RNA synthesis have reported compartmentation of UTP pools (for reviews, see [9][10][11]). Such compartmentation might also be important for the regulation of the synthesis of the various uridine nucleotide sugars.…”

Section: Introductionmentioning

confidence: 99%

Pyrimidine metabolism and sugar nucleotide synthesis in rat liver

Rijcken

Hooghwinkel

Ferwerda

1990

Biochemical Journal

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With radioactive precursors, the labelling kinetics of the soluble pyrimidine nucleotides and of RNA were measured in rat liver to determine the contribution of the metabolic flows through synthesis de novo and the salvage pathway. To separate and quantify all pyrimidine nucleotides, an h.p.l.c. technique was developed using anion-exchange chromatography and reversed-phase chromatography. The concentrations of cytidine nucleotides were in the range of 30-45 nmol/g wet weight, and the concentrations of the uridine phosphates and of the UDP-sugars were approx. 6 and 20 times higher respectively. After a single injection of [14C]orotic acid and of [3H]cytidine, the specific radioactivities were determined as a function of time. The 1'C/3H ratio was calculated and gave a good indication of the involvement of the different flows. It could be concluded that UTP derived from synthesis de novo and from the salvage pathway is not completely mixed before being utilized. The flow of the salvage pathway is relatively more directed to RNA synthesis in the nucleus and that of synthesis de novo to cytoplasmic processes. For CTP it could also be concluded that the flow of the salvage pathway was relatively more directed to RNA synthesis in the nucleus. Because of the nuclear localization of the enzyme CMP-NeuAc (N-acetylneuraminate) synthase, special attention was paid to CMP-NeuAc. However, a conclusion about a location about the synthesis of CMP-NeuAc could not unequivocally be drawn, because of the small differences in 14C/3H ratio and the different values for the CDP-lipids.

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“…UTP potentially can be detected in biological samples by utilizing radioactive precursors to radiolabel the intracellular uridine nucleotide pool (25). The disadvantage of such an approach is that the specific radioactivity of UTP cannot be determined and, therefore, no quantitation of mass can be made.…”

Section: Discussionmentioning

confidence: 99%

Direct Demonstration of Mechanically Induced Release of Cellular UTP and Its Implication for Uridine Nucleotide Receptor Activation

Lazarowski¹,

Homolya

Boucher³

et al. 1997

Journal of Biological Chemistry

271

227

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ATP is released from most cell types and functions as an extracellular signaling molecule through activation of members of the two large families of P2X and P2Y receptors. Although three mammalian P2Y receptors have been cloned that are selectively activated by uridine nucleotides, direct demonstration of the release of cellular UTP has not been reported. Pharmacological studies of the P2Y 4 receptor expressed in 1321N1 human astrocytoma cells indicated that this receptor is activated by UTP but not by ATP. Mechanical stimulation of 1321N1 cells also resulted in release of a molecule that markedly activated the expressed P2Y 4 receptor. This nucleotide was shown to be UTP by two means. First, high performance liquid chromatography analysis of the medium from [ 33 P]H 3 PO 4 -loaded 1321N1 cells illustrated that mechanical stimulation resulted in a large increase in a radioactive species that co-eluted with authentic UTP. This species was degraded by incubation with the nonspecific pyrophosphohydrolase apyrase or with hexokinase and was specifically lost by incubation with the UTP-specific enzyme UDP-glucose pyrophosphorylase. Second, a sensitive assay that quantitates UTP mass at low nanomolar concentrations was devised based on the nucleotide specificity of UDP-glucose pyrophosphorylase. Using this assay, mechanical stimulation of 1321N1 cells was shown to result in an increase of medium UTP levels from 2.6 to 36.4 pmol/10 6 cells within 2 min. This increase was paralleled by a similar augmentation of extracellular ATP levels. A calcein-based fluorescence quenching method was utilized to confirm that none of the increases in medium nucleotide levels could be accounted for by cell lysis. Taken together, these results directly demonstrate the mechanically induced release of UTP and illustrate the efficient coupling of this release to activation of P2Y 4 receptors.Extracellular nucleotides regulate a myriad of physiological responses by interacting with two types of cell surface P2 receptors (1). The P2X receptors are ATP-activated cation channels, and seven members of this class of signaling proteins have been identified. In addition, four members of a G proteincoupled P2Y receptor family have been unambiguously identified. These include the P2Y 1 receptor, which is activated by adenine nucleotides (2, 3); the P2Y 2 receptor, which is activated equipotently by ATP and UTP (4); the P2Y 4 receptor, which is potently activated by UTP (5, 6); and the P2Y 6 receptor, which is selectively activated by UDP (7, 8).The broad tissue distribution of these adenine and uridine nucleotide-activated P2 receptors supports the idea that endogenously released nucleotides act as important extracellular signaling molecules. Indeed, a large body of evidence exists demonstrating that ATP is released in a regulated fashion from most cell types and that its availability for target receptor activation is tightly controlled by cell surface nucleotidases (9, 10). In contrast, little is known about the regulated release of UTP from cells or...

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Compartmentation of purine and pyrimidine nucleotides in animal cells

Cited by 12 publications

References 104 publications

Pyrimidine nucleotide metabolism in rat hepatocytes: evidence for compartmentation of nucleotide pools

Pyrimidine nucleotide metabolism in rat hepatocytes: evidence for compartmentation of nucleotide pools

Pyrimidine metabolism and sugar nucleotide synthesis in rat liver

Direct Demonstration of Mechanically Induced Release of Cellular UTP and Its Implication for Uridine Nucleotide Receptor Activation

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