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Jörg Klepper - One of the best experts on this subject based on the ideXlab platform.
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Facilitated glucose Transporter Protein type 1 (GLUT1) deficiency syndrome: impaired glucose transport into brain – a review
European Journal of Pediatrics, 2002Co-Authors: Jörg Klepper, Thomas VoitAbstract:Facilitated glucose Transporter Protein type 1 (GLUT1) deficiency syndrome (MIM 138140) defines a prototype of a novel group of disorders resulting from impaired glucose transport across blood-tissue barriers. It is caused by a defect in glucose transport into brain, mediated by the facilitative glucose Transporter GLUT1. Since 1991, more than 70 patients have been identified. The hallmark of the disease is a low glucose concentration in the CSF (hypoglycorrhachia) in the presence of normoglycaemia (CSF/blood glucose ratio
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facilitated glucose Transporter Protein type 1 glut1 deficiency syndrome impaired glucose transport into brain a review
European Journal of Pediatrics, 2002Co-Authors: Jörg Klepper, Thomas VoitAbstract:Facilitated glucose Transporter Protein type 1 (GLUT1) deficiency syndrome (MIM 138140) defines a prototype of a novel group of disorders resulting from impaired glucose transport across blood-tissue barriers. It is caused by a defect in glucose transport into brain, mediated by the facilitative glucose Transporter GLUT1. Since 1991, more than 70 patients have been identified. The hallmark of the disease is a low glucose concentration in the CSF (hypoglycorrhachia) in the presence of normoglycaemia (CSF/blood glucose ratio <0.4). Clinical features are variable and include seizures, developmental delay, acquired microcephaly, hypotonia, and a complex motor disorder with elements of ataxia, dystonia, and spasticity. The GLUT1 defect can be confirmed in erythrocytes by glucose uptake studies and GLUT1 immunoreactivity, and by molecular analysis of the GLUT1 gene. Several heterozygous mutations resulting in GLUT1 haploinsufficiency have been identified. An effective treatment is available by means of a ketogenic diet as ketone bodies serve as an alternative fuel for the developing brain. Conclusion: this treatable condition should be suspected in children with unexplained neurological disorders associated with epilepsy and developmental delay and confirmed by a lumbar puncture.
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Erythrocyte 3-O-methyl-D-glucose uptake assay for diagnosis of glucose-Transporter-Protein syndrome.
Journal of clinical laboratory analysis, 1999Co-Authors: Jörg Klepper, Marcela Garcia-alvarez, Kevin R. O'driscoll, Michael K. Parides, Dong Wang, Darryl C. De VivoAbstract:Glucose transport into the brain is mediated by a facilitative glucose-Transporter Protein, GLUT-1. A GLUT-1 defect results in the Glucose-Transporter-Protein Syndrome (GTPS), characterized by infantile epilepsy, developmental delay, and acquired microcephaly. The diagnosis is currently based on clinical features, low to normal lactate levels and low glucose levels (hypoglycorrhachia) in the cerebrospinal fluid, and the demonstration of impaired GLUT-1 function in erythrocytes as described here. Blood samples were collected in sodium-heparin or citrate-phosphate-dextrose solution and uptake of 14C-labeled 3-O-Methyl-D-glucose (3OMG into erythrocytes (0.5 mmol/L 3OMG; 1 microCi/mL) was measured at 4C and pH 7.4. Three-OMG influx was terminated at 5-second intervals, washed cells were lysed, and uptake was quantitated by liquid scintillation counting. Patients' uptake (n = 22) was 44 +/- 8% of controls (100 +/- 22%, n = 70). Statistical analyses showed an uptake cut-off point at 60% uptake, a sensitivity of 86% (95%-confidence interval 78 to 94%), and a specificity of 97% (95%-confidence interval 93 to 100%). Gender, age, and ketosis did not influence 3OMG uptake. This assay provides a reproducible and accurate laboratory test for diagnosing the GTPS.
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Deficient transport of dehydroascorbic acid in the glucose Transporter Protein syndrome
Annals of neurology, 1998Co-Authors: Jörg Klepper, Juan Carlos Vera, Darryl C. De VivoAbstract:The glucose Transporter Protein syndrome (GTPS) is caused by defective transport of glucose across the blood-brain barrier via the glucose Transporter GLUT1, result-ing in hypoglycorrhachia, infantile seizures, and developmental delay. Recent reports indicated that GLUT1 is a multifunctional Transporter. We investigated the transport of vitamin C in its oxidized form (dehydroascorbic acid) via GLUT1 into erythrocytes of 2 patients with GTPS. In both patients, uptake of oxidized vitamin C was 61% of the mothers' values. Our findings are consistent with recent observations that vitamin C is transported in its oxidized form via GLUT1. We speculate that impaired transport of this substrate and perhaps other substrates in GTPS might contribute to the pathophysiology of this condition.
Thomas Voit - One of the best experts on this subject based on the ideXlab platform.
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Facilitated glucose Transporter Protein type 1 (GLUT1) deficiency syndrome: impaired glucose transport into brain – a review
European Journal of Pediatrics, 2002Co-Authors: Jörg Klepper, Thomas VoitAbstract:Facilitated glucose Transporter Protein type 1 (GLUT1) deficiency syndrome (MIM 138140) defines a prototype of a novel group of disorders resulting from impaired glucose transport across blood-tissue barriers. It is caused by a defect in glucose transport into brain, mediated by the facilitative glucose Transporter GLUT1. Since 1991, more than 70 patients have been identified. The hallmark of the disease is a low glucose concentration in the CSF (hypoglycorrhachia) in the presence of normoglycaemia (CSF/blood glucose ratio
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facilitated glucose Transporter Protein type 1 glut1 deficiency syndrome impaired glucose transport into brain a review
European Journal of Pediatrics, 2002Co-Authors: Jörg Klepper, Thomas VoitAbstract:Facilitated glucose Transporter Protein type 1 (GLUT1) deficiency syndrome (MIM 138140) defines a prototype of a novel group of disorders resulting from impaired glucose transport across blood-tissue barriers. It is caused by a defect in glucose transport into brain, mediated by the facilitative glucose Transporter GLUT1. Since 1991, more than 70 patients have been identified. The hallmark of the disease is a low glucose concentration in the CSF (hypoglycorrhachia) in the presence of normoglycaemia (CSF/blood glucose ratio <0.4). Clinical features are variable and include seizures, developmental delay, acquired microcephaly, hypotonia, and a complex motor disorder with elements of ataxia, dystonia, and spasticity. The GLUT1 defect can be confirmed in erythrocytes by glucose uptake studies and GLUT1 immunoreactivity, and by molecular analysis of the GLUT1 gene. Several heterozygous mutations resulting in GLUT1 haploinsufficiency have been identified. An effective treatment is available by means of a ketogenic diet as ketone bodies serve as an alternative fuel for the developing brain. Conclusion: this treatable condition should be suspected in children with unexplained neurological disorders associated with epilepsy and developmental delay and confirmed by a lumbar puncture.
Jeff M. Sands - One of the best experts on this subject based on the ideXlab platform.
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Urea may regulate urea Transporter Protein abundance during osmotic diuresis.
American Journal of Physiology-Renal Physiology, 2005Co-Authors: Dongun Kim, Janet D. Klein, Sandy Racine, Brian P. Murrell, Jeff M. SandsAbstract:Rats with diabetes mellitus have an increase in UT-A1 urea Transporter Protein abundance and absolute urea excretion, but the relative amount (percentage) of urea in total urinary solute is actuall...
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ut a urea Transporter Protein expressed in liver upregulation by uremia
Journal of The American Society of Nephrology, 1999Co-Authors: Janet D. Klein, Richard T. Timmer, Patricia Rouillard, James L Bailey, Jeff M. SandsAbstract:Abstract. In perfused rat liver, there is phloretin-inhibitable urea efflux, but whether it is mediated by the kidney UT-A urea Transporter family is unknown. To determine whether cultured HepG2 cells transport urea, thiourea influx was measured. HepG2 cells had a thiourea influx rate of 1739 ± 156 nmol/g Protein per min; influx was inhibited 46% by phloretin and 32% by thionicotinamide. Western analysis of HepG2 cell lysate using an antibody to UT-A1, UT-A2, and UT-A4 revealed two Protein bands: 49 and 36 kD. The same bands were detected in cultured rat hepatocytes, freshly isolated rat hepatocytes, and in liver from rat, mouse, and chimpanzee. Both bands were present when analyzed by native gel electrophoresis, and deglycosylation of rat liver lysate had no effect on either band. Differential centrifugation of rat liver lysate showed that the 49-kD Protein is in the membrane fraction and the 36-kD Protein is in the cytoplasm. To determine whether the abundance of these UT-A Proteins varies in vivo, rats were made uremic by 5/6 nephrectomy. The 49-kD Protein was significantly increased 5.5-fold in livers from uremic rats compared to pair-fed control rats. It is concluded that phloretininhibitable urea flux in liver may occur via a 49-kD Protein that is specifically detected by a UT-A antibody. Uremia increases the abundance of this 49-kD UT-A Protein in rat liver in vivo.
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Long-term regulation of renal urea Transporter Protein expression in rat.
Journal of the American Society of Nephrology : JASN, 1998Co-Authors: James Terris, Jeff M. Sands, Carolyn A. Ecelbarger, M. A. KnepperAbstract:To test the hypothesis that the abundance of the apical urea Transporter of the inner medullary collecting duct (IMCD) is regulated in vivo by factors associated with altered water balance, immunoblots of rat inner medullary membrane fractions were probed with rabbit polyclonal antibodies against the renal urea Transporter (RUT) gene product. In inner medullas of Brattleboro rats, which manifest severe chronic water diuresis, a 117-kD band was seen, in addition to the previously described 97-kD band. These two bands were detectable by antibodies directed against two different regions of the RUT sequence. When Brattleboro rats were treated with a 5-d infusion of arginine vasopressin (AVP) by osmotic minipump, the 117-kD band was markedly diminished, whereas the 97-kD band was unchanged. Simultaneous infusion of the diuretic agent furosemide prevented the AVP-induced decrease in the 117-kD band. In AVP-infused Sprague Dawley rats, the 117-kD band was barely perceptible. However, when AVP-treated rats were infused with furosemide for 5 d, the 117-kD band was markedly accentuated, whereas the 97-kD band was unchanged. The abundance of the 117-kD RUT Protein in the renal papilla was inversely correlated with dietary Protein intake. Further immunoblotting studies revealed that the 117-kD Protein is heavily expressed in IMCD cells and not in non-collecting duct components of the inner medulla, and is present in low-density microsome fractions from inner medulla. From this study, the following conclusions can be made: (1) The collecting duct urea Transporter is present in at least two forms (97 and 117 kD) in the IMCD. (2) The expression level of the 117-kD urea Transporter Protein is regulated and is inversely correlated with medullary osmolality and urea concentration, but does not correlate with circulating AVP level. (3) Although AVP regulates RUT function on a short-term basis, long-term changes in AVP levels do not increase RUT abundance.
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Glucocorticoids downregulate the vasopressin-regulated urea Transporter in rat terminal inner medullary collecting ducts.
Journal of the American Society of Nephrology : JASN, 1997Co-Authors: M Naruse, Janet D. Klein, Z M Ashkar, J D Jacobs, Jeff M. SandsAbstract:This study tested whether glucocorticoids regulate tubular urea transport. Urea permeability was measured in perfused inner medullary collecting duct (IMCD) subsegments from rats that underwent adrenalectomy, adrenalectomy plus replacement with a physiologic dose of glucocorticoid (dexamethasone), or sham operation. Compared with sham rats, basal urea permeability in terminal IMCD was significantly increased in adrenalectomized rats and reduced in dexamethasone-treated rats. Vasopressin significantly increased urea permeability in all three groups. In contrast, there was no difference in basal or vasopressin-stimulated urea permeability in initial IMCD between the three groups. Next, membrane and vesicle fraction Proteins were isolated from inner medullary tip or base and Western analysis was performed by use of an antibody to the rat vasopressin-regulated urea Transporter. Vasopressin-regulated urea Transporter Protein was significantly increased in both membrane and vesicle fractions from the inner medullary tip of adrenalectomized rats. There was no change in vasopressin-regulated urea Transporter Protein in the inner medullary base, and Northern analysis showed no change in urea Transporter mRNA abundance in either inner medullary region. It was concluded that glucocorticoids can downregulate function and expression of the vasopressin-regulated urea Transporter in rat terminal IMCD.
Pascal Bailly - One of the best experts on this subject based on the ideXlab platform.
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At physiological expression levels the Kidd blood group/urea Transporter Protein is not a water channel.
Journal of Biological Chemistry, 1999Co-Authors: Frédéric Sidoux-walter, Bernadette Olives, Jean-pierre Cartron, Pierre Ripoche, Germain Rousselet, Nicole Lucien, Renée Gobin, Erik-jan Kamsteeg, Peter M. T. Deen, Pascal BaillyAbstract:The Kidd (JK) blood group locus encodes a urea Transporter that is expressed on human red cells and on endothelial cells of the vasa recta in the kidney. Here, we report the identification in human erythroblasts of a novel cDNA, designated HUT11A, which encodes a Protein identical to the previously reported erythroid HUT11 urea Transporter, except for a Lys(44) --> Glu substitution and a Val-Gly dipeptide deletion after proline 227, which leads to a polypeptide of 389 residues versus 391 in HUT11. Genomic typing by polymerase chain reaction and transcript analysis by ribonuclease protection assay demonstrated that HUT11A encodes the true Kidd blood group/urea Transporter Protein, which carries only 2 Val-Gly motifs. Upon expression at high levels in Xenopus oocytes, the physiological Kidd/urea Transporter HUT11A conferred a rapid transfer of urea (which was insensitive to p-chloromercuribenzene sulfonate or phloretin), a high water permeability, and a selective uptake of small solutes including amides and diols, but not glycerol and meso-erythritol. However, at plasma membrane expression levels close to the level observed in the red cell membrane, HUT11A-mediated water transport and small solutes uptake were absent and the urea transport was poorly inhibited by p-chloromercuribenzene sulfonate, but strongly inhibited by phloretin. These findings show that, at physiological expression levels, the HUT11A Transporter confers urea permeability but not water permeability, and that the observed water permeability is a feature of the red cell urea Transporter when expressed at unphysiological high levels.
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at physiological expression levels the kidd blood group urea Transporter Protein is not a water channel
Journal of Biological Chemistry, 1999Co-Authors: Frederic Sidouxwalter, Bernadette Olives, Jean-pierre Cartron, Pierre Ripoche, Germain Rousselet, Nicole Lucien, Renée Gobin, Erik-jan Kamsteeg, Peter M. T. Deen, Pascal BaillyAbstract:The Kidd (JK) blood group locus encodes a urea Transporter that is expressed on human red cells and on endothelial cells of the vasa recta in the kidney. Here, we report the identification in human erythroblasts of a novel cDNA, designated HUT11A, which encodes a Protein identical to the previously reported erythroid HUT11 urea Transporter, except for a Lys(44) --> Glu substitution and a Val-Gly dipeptide deletion after proline 227, which leads to a polypeptide of 389 residues versus 391 in HUT11. Genomic typing by polymerase chain reaction and transcript analysis by ribonuclease protection assay demonstrated that HUT11A encodes the true Kidd blood group/urea Transporter Protein, which carries only 2 Val-Gly motifs. Upon expression at high levels in Xenopus oocytes, the physiological Kidd/urea Transporter HUT11A conferred a rapid transfer of urea (which was insensitive to p-chloromercuribenzene sulfonate or phloretin), a high water permeability, and a selective uptake of small solutes including amides and diols, but not glycerol and meso-erythritol. However, at plasma membrane expression levels close to the level observed in the red cell membrane, HUT11A-mediated water transport and small solutes uptake were absent and the urea transport was poorly inhibited by p-chloromercuribenzene sulfonate, but strongly inhibited by phloretin. These findings show that, at physiological expression levels, the HUT11A Transporter confers urea permeability but not water permeability, and that the observed water permeability is a feature of the red cell urea Transporter when expressed at unphysiological high levels.
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characterization of the gene encoding the human kidd blood group urea Transporter Protein evidence for splice site mutations in jknullindividuals
Journal of Biological Chemistry, 1998Co-Authors: Nicole Lucien, Bernadette Olives, Jean-pierre Cartron, Frederic Sidouxwalter, Joann M Moulds, Pierreyves Le Pennec, Pascal BaillyAbstract:Abstract The Kidd (JK) blood group is carried by an integral membrane glycoProtein which transports urea through the red cell membrane and is also present on endothelial cells of the vasa recta in the kidney. The exon-intron structure of the human blood group Kidd/urea Transporter gene has been determined. It is organized into 11 exons distributed over 30 kilobase pairs. The mature Protein is encoded by exons 4–11. The transcription initiation site was identified by 5′-rapid amplification of cDNA ends-polymerase chain reaction at 335 base pairs upstream of the translation start point located in exon 4. The 5′-flanking region, from nucleotide −837 to −336, contains TATA and inverted CAAT boxes as well as GATA-1/SP1 erythroid-specificcis-acting regulatory elements. Analysis of the 3′-untranslated region reveals that the two equally abundant erythroid transcripts of 4.4 and 2.0 kilobase pairs arise from usage of different alternative polyadenylation signals. No obvious abnormality of the Kidd/urea Transporter gene, including the 5′- and 3′-untranslated regions, has been detected by Southern blot analysis of the blood of two unrelated Jknull individuals (B.S. and L.P.), which lacks all Jk antigens and Jk Proteins on red cells, but was genotyped as homozygous for a “silent”Jk b allele. Further analysis indicated that different splice site mutations occurred in each variant. The first mutation affected the invariant G residue of the 3′-acceptor splice site of intron 5 (variant B.S.), while the second mutation affected the invariant G residue of the 5′-donor splice site of intron 7 (variant L.P.). These mutations caused the skipping of exon 6 and 7, respectively, as seen by sequence analysis of the Jk transcripts present in reticulocytes. Expression studies in Xenopusoocytes demonstrated that the truncated Proteins encoded by the spliced transcripts did not mediate a facilitated urea transport compared with the wild type Kidd/urea Transporter Protein and were not expressed on the oocyte’s plasma membrane. These findings provide a rational explanation for the lack of Kidd/urea Transporter Protein and defect in urea transport of Jknull cells.
Noriyuki Ishii - One of the best experts on this subject based on the ideXlab platform.
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Investigation on Stability of Transporter Protein, Glucuronide Transporter from Escherichia coli
Journal of Membrane Biology, 2010Co-Authors: Noriyuki IshiiAbstract:The glucuronide Transporter GusB, the product of the gusB gene from Escherichia coli , is responsible for detoxification of metabolites. In this study, we successfully expressed GusB homologously in E. coli and investigated its oligomeric state in n -dodecyl-β- d -maltoside (DDM) detergent solution. Evidence for a pentameric state with a Stokes radius of 57 ± 2 Å for the purified GusB Protein in DDM solution was obtained by analytical size-exclusion HPLC. The elution peak corresponding to pentameric GusB is commonly seen in elution profiles in the different buffer systems examined over a wide pH range. Hence, it is likely that GusB resides in the membrane as a pentamer. Stability studies with different incubation periods with the typical lipids, such as dimyristoylphosphatidylcholine, and total E. coli phospholipids, as the representatives of both phosphatidylcholine and phosphatidylethanolamine, show some clues to two-dimensional crystallization of GusB with lipids.
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Investigation on Stability of Transporter Protein, Glucuronide Transporter from Escherichia coli
Journal of Membrane Biology, 2010Co-Authors: Noriyuki IshiiAbstract:The glucuronide Transporter GusB, the product of the gusB gene from Escherichia coli , is responsible for detoxification of metabolites. In this study, we successfully expressed GusB homologously in E. coli and investigated its oligomeric state in n -dodecyl-β- d -maltoside (DDM) detergent solution. Evidence for a pentameric state with a Stokes radius of 57 ± 2 Å for the purified GusB Protein in DDM solution was obtained by analytical size-exclusion HPLC. The elution peak corresponding to pentameric GusB is commonly seen in elution profiles in the different buffer systems examined over a wide pH range. Hence, it is likely that GusB resides in the membrane as a pentamer. Stability studies with different incubation periods with the typical lipids, such as dimyristoylphosphatidylcholine, and total E. coli phospholipids, as the representatives of both phosphatidylcholine and phosphatidylethanolamine, show some clues to two-dimensional crystallization of GusB with lipids.
