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XB-ART-24929
Cell Regul 1991 Apr 01;24:317-27. doi: 10.1091/mbc.2.4.317.
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Insulin-like effects of vanadate on glucose uptake and on maturation in Xenopus laevis oocytes.

Hainaut P, Giorgetti S, Kowalski A, Van Obberghen E.


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Vanadate, an inhibitor of phosphotyrosyl phosphatases that exerts insulin-like effects in intact cells, stimulated both maturation and glucose uptake in isolated Xenopus laevis oocytes. Vanadate enhanced the effects of insulin/IGF-I and progesterone on maturation in a dose-dependent manner, with an effective concentration of 750 microM and a maximum at 2 mM, whereas, in the absence of hormone, activation of maturation was seen at 10 mM vanadate. Further, vanadate at 2 mM increased glucose uptake, but this effect was not additive to that of the hormone. In cell-free systems, vanadate caused a 12-fold stimulation of autophosphorylation of the oocyte IGF-I receptor in the absence, but not in the presence, of IGF-I and inhibited largely, but not totally, receptor dephosphorylation induced by an extract of oocytes rich in phosphotyrosyl phosphatase activities. These effects were dose dependent, with effective concentrations of 50-100 microM and maxima at 2 mM. Moreover, using an acellular assay to study the effect of vanadate on the activation of maturation promoting factor (MPF), we found that vanadate at 2 mM stimulated the activation of the MPF H1 kinase. This suggests that vanadate did not prevent dephosphorylation of p34cdc2 on tyrosine residues. Vanadate thus exerted insulin-like effects in oocytes, including stimulation of maturation. These effects might result from a direct or indirect action of vanadate on the IGF-I receptor kinase and on MPF activity.

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Species referenced: Xenopus laevis
Genes referenced: cdk1 ins

References [+] :
Boivin, The human red cell acid phosphatase is a phosphotyrosine protein phosphatase which dephosphorylates the membrane protein band 3. 1986, Pubmed