Further clues concerning the vectors essential to regulation of hexose transport, as studied in fibroblast cultures from a metabolic mutant.

Kalckar, Herman Μ.; Ullrey, Donna B.

doi:10.1073/pnas.81.4.1126

Cited by 24 publications

(20 citation statements)

References 15 publications

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“…The hexose transport curb is not a passive response of cells to accumulated Glc-6-P, but rather requires initial feeding with a hexose, an intact oxidative phosphorylation pathway, and protein synthesis (13,14,27,31,34). Our data suggest that the MondoA-TXNIP negative feedback circuit is a required component of the hexose transport curb.…”

Section: Discussionmentioning

confidence: 72%

“…Collectively, these data suggest a model where MondoA senses elevations in Glc-6-P and activates TXNIP transcription, thereby initiating a negative feedback mechanism that restricts further glucose uptake (1,4,7,12). This proposed negative feedback loop is conceptually similar to the hexose transport "curb" described in the literature nearly 30 years ago (13)(14)(15)(16). The key features of this blockade of hexose uptake are that it can be triggered by a number of different sugars, e.g.…”

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confidence: 61%

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MondoA Senses Non-glucose Sugars

Stoltzman¹,

Kaadige²,

Peterson

et al. 2011

Journal of Biological Chemistry

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Background: Glucose is a fundamental metabolite that is sensed by the MondoA transcription complex. MondoA elevates transcription of thioredoxin-interacting protein to restrict glucose uptake. Results: MondoA senses the phosphorylated forms of the non-glucose hexose sugars, allose, and 3-O-methylglucose and triggers an adaptive transcriptional response. Conclusion: TXNIP is regulated by non-hexose sugars in a manner that requires their metabolism, and TXNIP is part of the hexose transport curb. Significance: Sugar is a universal metabolite, so how cells respond to changes in glucose and the transcriptional level is an important question.

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Section: Discussionmentioning

confidence: 72%

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confidence: 61%

MondoA Senses Non-glucose Sugars

Stoltzman¹,

Kaadige²,

Peterson

et al. 2011

Journal of Biological Chemistry

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“…It is concluded that the oligonucleotides are mainly oligoribonucleotides, but it is possible that oligodeoxynucleotides are also present. Falcon flasks (6). Tetrahymena cells were grown in 2% proteose peptone broth at 280C (7).…”

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confidence: 99%

Oligonucleotides with rapid turnover of the phosphate groups occur endogenously in eukaryotic cells.

Plesner¹,

Goodchild²,

Kalckar³

et al. 1987

Proc. Natl. Acad. Sci. U.S.A.

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Endogenous oligonucleotides were found in trichloroacetic acid extracts of hamster lung fibroblasts and Tetrahymena cells. Peaks of radioactivity that eluted with retention times similar to oligonucleotide markers (5-to 50-mer) were found by HPLC in cells labeled briefly with 32pl.Only minute amounts of UV-absorbing material were detected, consistent with a rapid turnover of phosphate groups. The 32P-labeled material also migrated as oligonucleotides on 20% polyacrylamide gels; it was not hydrolyzed by alkaline phosphatase but was digested by snake venom phosphodiesterase, S1 nuclease, and pancreatic RNase and was phosphorylated by T4 polynucleotide kinase. The 32P-labeled material isolated by HPLC was alkali labile and the hydrolyzate ran as nucleotides on paper chromatography. It is concluded that the oligonucleotides are mainly oligoribonucleotides, but it is possible that oligodeoxynucleotides are also present. Falcon flasks (6). Tetrahymena cells were grown in 2% proteose peptone broth at 280C (7).Preparation of the Acid-Soluble Cell Extract. To label the cell material, 0.75 mCi (1 Ci = 37 GBq) of carrier-free 32P orthophosphate (HCl-free, ICN 64014) was added to each flask. After 10 min incubation at 37°C, the medium was poured off and the cells were washed gently five times with 10 ml of medium preheated to 37°C. The cells were then extracted with 2.4 ml of ice-cold 10% trichloroacetic acid, which was removed by extraction twice with 18% (wt/vol) trioctylamine in Freon (8). Then, 1.4 ml of the final upper phase was withdrawn from each sample and lyophilized. The lyophilized extract was dissolved in 500 ,ul of water, and 125-,l aliquots were removed for digestion with alkaline phosphatase, snake venom phosphodiesterase, and S1 nuclease. The digested and control aliquots were subjected to HPLC chromatography (8, 9).Tetrahymena cells were grown to a density of 200,000 cells per ml and then diluted with 1 vol of proteose peptone broth, left for 1 hr, and then incubated with 1 mCi of carrier-free 32P, (New England Nuclear) for 90 min. The cells were pelleted by brief centrifugation and extracted with trichloroacetic acid as described above. Double-Gradient Anion Exchange HPLC. This was performed on Waters Associates Partisil (Whatman) strong anion exchange (SAX) cartridges in a Waters Z-compression module using a Waters or a Perkin-Elmer two-pump chromatograph with gradient former. The effluent was monitored for absorbance at 254 nm and for radioactivity with a Berthold (Nashua, NH) LB 505DC HPLC monitor (see Fig. 1) or with a Cerenkov-radiation monitor (a' Teflon spiral placed in front of a Geiger-Muller monitor wired to a recorder) (see Fig. 5). The strong anion exchange column was first eluted with a potassium phosphate/KCl linear gradient from 0% to 100% in 45 min as described (8). When GTP had appeared, the high-salt solvent was washed out with the low-salt solvent for at least 10 min, and then a second gradient was run from 0.0032 M to 0.64 M potassium phosphate (pH 6.8) in 20% acetonitrile ove...

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“…The two cell lines used were hamster fibroblast lines 023 and DS7, the latter being a PGI mutant of 023 (8). The two lines were grown as described (3,4) in Dulbecco's modified Eagle's medium (DMEM) with 10% fetal bovine serum. Near-confluent cultures were then transferred to sugar-free medium with 10% dialyzed fetal bovine serum for 20 hr.…”

Section: Methodsmentioning

confidence: 99%

“…The hamster fibroblast mutant that is highly defective in the enzyme phosphoglucose isomerase (D-glucose-6-phosphate ketolisomerase, EC 5.3.1.9) (the PGI mutant) has been used for studies on metabolic regulation of the hexose transport or uptake system, the so-called mediated transport "curb" (1)(2)(3). Recently it became clear to us that the PGI mutant showed a highly specific pattern of its regulatory transport curb-i.e., only two D-aldohexoses were able to promote a curb, glucose and the all-cis D-aldohexose, allose.…”

mentioning

confidence: 99%

Tunicamycin tightens the glucose- and D-allose-mediated control of hexose transport in a metabolic fibroblast mutant.

Ullrey¹,

Kalckar²

1987

Proc. Natl. Acad. Sci. U.S.A.

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The hexose transport system of a fibroblast mutant, DS7, unable to convert glucose 6-phosphate to fructose 6-phosphate ("the phosphoglucose isomerase mutant"), is subject to a specific down-regulation ("curb") evoked by only glucose or D-allose. Neither fructose nor mannose has a curbing effect on this mutant. Further addition of tunicamycin intensified the transport curb on the mutant mediated by glucose or allose. Mannose added to the parental cell line 023 seems able to mimic a glucose-mediated transport curb. In this line, but not the mutant, tunicamycin also intensifies a mannosemediated curb. It seems that the tightening of the allosemediated curb is a function of a specific type of transport regulation and perhaps too of interference with glycosylation of the hexose transporter. Furthermore, this type of curb can be strikingly reversed by shifting the cultures to medium containing fructose.The hamster fibroblast mutant that is highly defective in the enzyme phosphoglucose isomerase (D-glucose-6-phosphate ketolisomerase, EC 5.3.1.9) (the PGI mutant) has been used for studies on metabolic regulation of the hexose transport or uptake system, the so-called mediated transport "curb" (1-3). Recently it became clear to us that the PGI mutant showed a highly specific pattern of its regulatory transport curb-i.e., only two D-aldohexoses were able to promote a curb, glucose and the all-cis D-aldohexose, allose. The latter sugar actually provoked an intense curb at concentrations as low as 1 mM (4). The curbing effect could be arrested by cycloheximide as well as by a respiratory inhibitor such as malonate (4).The transport curb in the parental cell line 023 (which is PGI+) was not confined to allose and glucose; D-glucosamine as well as mannose were also able to promote the development of this curb (1, 2, 4). This is presumably due to the fact that the 6-phosphoric esters of the two latter sugars can be freely converted to glucose 6-phosphate (by way of fructose 6-phosphate) in the parental line. The effects of glucosamine and mannose on the curb ofhexose transport into the parental line seem therefore merely to mimic the glucose effect.All of these features became evident in the parental and in the PGI mutant by using either the usual transport test (after preloading) or by using a simple uptake test (see below). Tunicamycin (TN), a specific inhibitor of glycosylation of asparaginyl glycoproteins (5, 6), has also been found to inhibit glucose transport in chicken embryo fibroblasts in terms of a decrease of Vma, (7). As will appear from the present work, in the PGI mutant, the hexose transport or uptake system does not seem to undergo any discernable inhibition by exposure to TN unless one of the two specific aldohexoses, D-allose or glucose, is also present. If fructose replaces the aldohexoses, TN does not show any inhibition of the uptake system whatsoever. MATERIALS AND METHODSCells and Culture Conditions. The two cell lines used were hamster fibroblast lines 023 and DS7, the latter being a PGI mutant ...

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Further clues concerning the vectors essential to regulation of hexose transport, as studied in fibroblast cultures from a metabolic mutant.

Cited by 24 publications

References 15 publications

MondoA Senses Non-glucose Sugars

MondoA Senses Non-glucose Sugars

Oligonucleotides with rapid turnover of the phosphate groups occur endogenously in eukaryotic cells.

Tunicamycin tightens the glucose- and D-allose-mediated control of hexose transport in a metabolic fibroblast mutant.

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