Ontogeny of the catalytic subunit and putative glucose-6-phosphate transporter proteins of the rat microsomal liver glucose-6-phosphatase system

Méchin, Marie-Claire; Annabi, Borhane; Pégorier, Jean‐Paul; Werve, Gérald van de

doi:10.1053/meta.2000.7714

Cited by 8 publications

(6 citation statements)

References 21 publications

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“…Its concentration increases, reaching a maximum during the 3 days before birth, and decreases slightly after birth [86]. Western blots using an anti-peptide antibody indicate that the Glc-6-P translocase, also called p46 by some authors, is present at day 20 of intrauterine life, and that its concentration does not vary to a significant extent afterwards [175]. Light-scattering measurements indicate that Glc-6-P transport is active before birth [87].…”

Section: Tissue Distribution and Regulation Of Expressionmentioning

confidence: 91%

“…Light-scattering measurements indicate that Glc-6-P transport is active before birth [87]. However, filtration assays measuring the uptake of ["%C]Glc-6-P indicate that Glc-6-P transport appears only after birth [175] and reaches the adult level after 4 weeks. The disagreement between these results is probably due to the fact that the second type of assay, but not the first, depends on the presence of an active G6Pase (see above), which appears in the liver around birth.…”

Section: Tissue Distribution and Regulation Of Expressionmentioning

confidence: 99%

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The glucose-6-phosphatase system

Schaftingen¹,

Gerin²

2002

Biochemical Journal

322

205

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Glucose-6-phosphatase (G6Pase), an enzyme found mainly in the liver and the kidneys, plays the important role of providing glucose during starvation. Unlike most phosphatases acting on water-soluble compounds, it is a membrane-bound enzyme, being associated with the endoplasmic reticulum. In 1975, W. Arion and co-workers proposed a model according to which G6Pase was thought to be a rather unspecific phosphatase, with its catalytic site oriented towards the lumen of the endoplasmic reticulum [Arion, Wallin, Lange and Ballas (1975) Mol. Cell. Biochem. 6, 75–83]. Substrate would be provided to this enzyme by a translocase that is specific for glucose 6-phosphate, thereby accounting for the specificity of the phosphatase for glucose 6-phosphate in intact microsomes. Distinct transporters would allow inorganic phosphate and glucose to leave the vesicles. At variance with this substrate-transport model, other models propose that conformational changes play an important role in the properties of G6Pase. The last 10 years have witnessed important progress in our knowledge of the glucose 6-phosphate hydrolysis system. The genes encoding G6Pase and the glucose 6-phosphate translocase have been cloned and shown to be mutated in glycogen storage disease type Ia and type Ib respectively. The gene encoding a G6Pase-related protein, expressed specifically in pancreatic islets, has also been cloned. Specific potent inhibitors of G6Pase and of the glucose 6-phosphate translocase have been synthesized or isolated from micro-organisms. These as well as other findings support the model initially proposed by Arion. Much progress has also been made with regard to the regulation of the expression of G6Pase by insulin, glucocorticoids, cAMP and glucose.

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Section: Tissue Distribution and Regulation Of Expressionmentioning

confidence: 91%

Section: Tissue Distribution and Regulation Of Expressionmentioning

confidence: 99%

The glucose-6-phosphatase system

Schaftingen¹,

Gerin²

2002

Biochemical Journal

322

205

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“…The rabbit polyclonal antiserum against the recombinant G6Pase catalytic subunit (p36) was a kind gift from Dr. Howard Haspel (Denver, CO). The rabbit antiserum against a peptide from the N-terminus of the p46 protein was produced in our laboratory as described before [17]. The BCIP/NBT stock solutions and the anti-rabbit IgG-AP conjugate were from Promega Co (Madison, WI).…”

Section: Methodsmentioning

confidence: 99%

“…Western blots were performed with 50 g of microsomal protein as described before [15,17]. The quantification of each specific band was analyzed by using a Dual Light Transilluminator.…”

Section: Western-blot Analysismentioning

confidence: 99%

Up-Regulation of Liver Glucose-6-Phosphatase in X-Linked Hypophosphatemic Mice

et al. 2002

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We previously showed that a phosphate-deficient diet resulting in hypophosphatemia upregulated the catalytic subunit p36 of rat liver glucose-6-phosphatase, which is responsible for hepatic glucose production. A possible association between phosphate and glucose homeostasis was now further evaluated in the Hyp mouse, a murine homologue of human X-linked hypophosphatemia. We found that in the Hyp mouse as in the dietary Pi deficiency model, serum insulin was reduced while glycemia was increased, and that liver glucose-6-phosphatase activity was enhanced as a consequence of increased mRNA and protein levels of p36. In contrast, the Hyp model had decreased mRNA and protein levels of the putative glucose-6-phosphate translocase p46 and liver cyclic AMP was not increased as in the phosphate-deficient diet rats. It is concluded that in genetic as in dietary hypophosphatemia, elevated glucose-6-phosphatase activity could be partially responsible for the impaired glucose metabolism albeit through distinct mechanisms.

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“…In the fetal‐to‐neonatal transition, however, there seems to be a dissociation between the regulation of the expression of P36 and P46 [35,40,42,173a]. These studies show that Glc6 P ase hydrolytic activity before birth can occur without detectable any Glc6 P uptake function, that the presence of the putative Glc6 P transporter protein is not sufficient to elicit Glc6 P uptake and that full Glc6 P ase activity requires the presence of both P36 and P46 proteins.…”

Section: Gene Regulation Of the Expression Of Glc6pasementioning

confidence: 99%

New lessons in the regulation of glucose metabolism taught by the glucose 6‐phosphatase system

Werve¹,

Lange

Newgard³

et al. 2000

European Journal of Biochemistry

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130

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The operation of glucose 6-phosphatase (EC 3.1.3.9) (Glc6Pase) stems from the interaction of at least two highly hydrophobic proteins embedded in the ER membrane, a heavily glycosylated catalytic subunit of m 36 kDa (P36) and a 46-kDa putative glucose 6-phosphate (Glc6P) translocase (P46). Topology studies of P36 and P46 predict, respectively, nine and ten transmembrane domains with the N-terminal end of P36 oriented towards the lumen of the ER and both termini of P46 oriented towards the cytoplasm. P36 gene expression is increased by glucose, fructose 2,6-bisphosphate (Fru-2,6-P2) and free fatty acids, as well as by glucocorticoids and cyclic AMP; the latter are counteracted by insulin. P46 gene expression is affected by glucose, insulin and cyclic AMP in a manner similar to P36. Accordingly, several response elements for glucocorticoids, cyclic AMP and insulin regulated by hepatocyte nuclear factors were found in the Glc6Pase promoter. Mutations in P36 and P46 lead to glycogen storage disease (GSD) type-1a and type-1 non a (formerly 1b and 1c), respectively. Adenovirus-mediated overexpression of P36 in hepatocytes and in vivo impairs glycogen metabolism and glycolysis and increases glucose production; P36 overexpression in INS-1 cells results in decreased glycolysis and glucose-induced insulin secretion. The nature of the interaction between P36 and P46 in controling Glc6Pase activity remains to be defined. The latter might also have functions other than Glc6P transport that are related to Glc6P metabolism.

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Ontogeny of the catalytic subunit and putative glucose-6-phosphate transporter proteins of the rat microsomal liver glucose-6-phosphatase system

Cited by 8 publications

References 21 publications

The glucose-6-phosphatase system

The glucose-6-phosphatase system

Up-Regulation of Liver Glucose-6-Phosphatase in X-Linked Hypophosphatemic Mice

New lessons in the regulation of glucose metabolism taught by the glucose 6‐phosphatase system

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