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  • 1
    Electronic Resource
    Electronic Resource
    Expression of the brain-type glucose transporter is restricted to brain and neuronal cells in mice (1992)
    Springer
    Diabetologia 35 (1992), S. 304-309 
    Details
    ISSN: 1432-0428
    Keywords: Glucose transport ; brain-type transporter ; diabetes mellitus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Northern blot analysis of human tissues has demonstrated the expression of the brain-type glucose transporter isoform (GLUT 3) in liver, muscle and fat, raising the possibility that this transporter isoform may play a role in the regulation of glucose disposal in these tissues in response to insulin. We have raised an anti-peptide antibody against the C-terminal 13 amino acids of the murine homologue of this transporter isoform, and determined its tissue distribution in mouse tissues and murine-derived cell lines. The antibodies recognise a glycoprotein of about 50 kilodaltons, expressed at high levels in murine brain. In contrast to human tissues, the expression of GLUT 3 in mice is restricted to the brain, and no immunoreactivity was observed in either liver, fat or muscle membranes, or in murine 3T3-L1 fibroblasts or adipocytes. In contrast, high levels of expression of this isoform were observed in the NG 108 neuroblastoma x glioma cell line, a hybrid cell derived from rat glioma and mouse neuroblastoma cells. Taken together, these data suggest that the expression of GLUT 3 in rodents is restricted to non-insulin responsive neuronal cells and hence it is likely that the factors regulating the expression of this transporter in rodents differ to those in humans.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00401196
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  • 2
    Electronic Resource
    Electronic Resource
    Natural variants of human p85α phosphoinositide 3-kinase in severe insulin resistance: a novel variant with impaired insulin-stimulated lipid kinase activity (2000)
    Springer
    Diabetologia 43 (2000), S. 321-331 
    Details
    ISSN: 1432-0428
    Keywords: Keywords Keywords Genetics, insulin signalling, phosphatidylinositol 3-kinase.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Aims/hypothesis. Phosphoinositide 3-kinase (PI 3K) plays a central part in the mediation of insulin-stimulated glucose disposal. No genetic studies of this enzyme in human syndromes of severe insulin resistance have been previously reported.¶Methods. Phosphoinositide 3-kinase p85α regulatory subunit cDNA was examined in 20 subjects with syndromes of severe insulin resistance by single strand conformational polymorphism and restriction fragment length polymorphism analyses. Insulin-stimulated phosphoinositide 3-kinase activity and recruitment into phosphotyrosine complexes of variants of p85α were studied in transiently transfected HEK293 cells. Phosphopeptide binding characteristics of wild-type and mutant p85α-GST fusion proteins were examined by surface plasmon resonance.¶Results. The common p85α variant, Met326I1e, was identified in 9 of the 20 subjects. Functional studies of the Met326Ile variant showed it to have equivalent insulin-stimulated lipid kinase activity and phosphotyrosine recruitment as wild-type p85α. A novel heterozygous mutation, Arg409Gln, was detected in one subject. Within the proband's family, carriers of the mutation had a higher median fasting plasma insulin (218 pmol/l) compared with wild-type relatives (72 mol/l) (n = 8 subjects, p = 0.06). The Arg409Gln p85α subunit was associated with lower insulin-stimulated phosphoinositide 3-kinase activity compared with wild-type (mean reduction 15 %, p 〈 0.05, n = 5). The recruitment of Arg409Gln p85α into phosphotyrosine complexes was not significantly impaired. GST fusion proteins of wild-type and mutant p85α showed identical binding to phosphopeptides in surface plasmon resonance studies.¶Conclusion/interpretation. Mutations in p85α are uncommon in subjects with syndromes of severe insulin resistance. The Met326Ile p85α variant appears to have no functional effect on the insulin-stimulated phosphoinositide 3-kinase activity. The impaired phosphoinositide 3-kinase activity of the Arg409Gln mutant suggests that it could contribute to the insulin resistance seen in this family. [Diabetologia (2000) 43: 321–331]
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001250050050
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  • 3
    Electronic Resource
    Electronic Resource
    Involvement of phosphoinositide 3-kinase in insulin stimulation of MAP-kinase and phosphorylation of protein kinase-B in human skeletal muscle: implications for glucose metabolism (1997)
    Springer
    Diabetologia 40 (1997), S. 1172-1177 
    Details
    ISSN: 1432-0428
    Keywords: Keywords Muscle ; human ; insulin ; phosphoinositide 3-kinase ; Map-kinase ; protein kinase B ; glycogen synthase ; glucose transport.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Isolated skeletal muscle from healthy individuals was used to evaluate the role of phosphoinositide 3-kinase (PI 3-kinase) in insulin signalling pathways regulating mitogen activated protein kinase (MAP-kinase) and protein kinase-B and to investigate whether MAP-kinase was involved in signalling pathways regulating glucose metabolism. Insulin stimulated glycogen synthase activity ( ≈ 1.7 fold), increased 3-o-methylglucose transport into human skeletal muscle strips ( ≈ 2 fold) and stimulated phosphorylation of the p42 ERK-2 isoform of MAP-kinase. This phosphorylation of p42 ERK2 was not blocked by the PI 3-kinase inhibitors LY294002 and wortmannin although it was blocked by the MAP-kinase kinase (MEK) inhibitor PD 98059. However, PD98059 (up to 20 μmol/l) did not block insulin activation of glycogen synthase or stimulation of 3-o-methylglucose transport. Wortmannin and LY294002 did block insulin stimulation of protein kinase-B (PKB) phosphorylation and stimulation of 3-o-methylglucose transport was inhibited by wortmannin (IC50≈ 100 nmol/l). These results indicate that MAP-kinase is activated by insulin in human skeletal muscle by a PI 3-kinase independent pathway. Furthermore this activation is not necessary for insulin stimulation of glucose transport or activation of glycogen synthase in this tissue. [Diabetologia (1997) 40: 1172–1177]
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001250050803
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    Paper (German National Licenses)
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