Magnesium-dependent stimulation of protein synthesis by the insulin mimic, pervanadate.
The insulin mimic, peroxide of vanadate (pervanadate), stimulated 35S-methionine incorporation into Xenopus oocyte protein in a Mg(2+)-dependent manner. Reducing the extracellular Mg2+ concentration from 1.0 to 0.1 mM decreased the pervanadate-stimulated component of incorporation by 35%; with 0.01 mM Mg2+ or lower, the pervanadate-stimulated component was abolished. In addition, reducing extracellular Mg2+ to 0.01 mM inhibited about 50% of the insulin-stimulated component of methionine incorporation. Mg2+ depletion had no effects on incorporation in controls or when protein synthesis was stimulated by Zn2+ or bovine growth hormone. Thus, not all substances that stimulated protein synthesis showed a dependence on extracellular Mg2+. Reducing extracellular Ca2+ had no effects on methionine incorporation in control cells or in cells stimulated by pervanadate or insulin. When oocytes maintained in a paraffin oil medium were brought into contact with a 0.5 microliter droplet of buffer containing the Mg2+ indicator dye, mag-fura-2, and pervanadate, apparent droplet Mg2+ decreased rapidly, indicating net uptake by the cells. Insulin also caused a net uptake of Mg2+. In contrast, apparent extracellular Mg2+ was constant when cells were in contact with droplets containing no effectors. Together, these data indicate that extracellular Mg2+, but not Ca2+, is involved in the stimulation of protein synthesis by pervanadate, and to a lesser extent by insulin. Pervanadate appears to induce a net uptake of Mg2+, and this change in membrane transport may be an early event in signalling the increase in translation.
Barnes
D M
DM
Laboratory of Cellular and Molecular Pharmacology, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina 27709, USA.
Sykes
D B
DB
Smith
J J
JJ
Miller
D S
DS
D000818:Animals; D001692:Biological Transport; D002118:Calcium / Q000494:pharmacology; D002413:Cations, Divalent / Q000378:metabolism; D013006:Growth Hormone / Q000494:pharmacology; D006601:Hexoses / Q000493:pharmacokinetics; D007328:Insulin / Q000494:pharmacology; D007473:Ion Channels / Q000502:physiology; D008274:Magnesium / Q000502:physiology*; D008565:Membrane Proteins / Q000096:biosynthesis*; D009865:Oocytes / Q000187:drug effects / Q000378:metabolism*; D015398:Signal Transduction; D014638:Vanadates / Q000494:pharmacology*; D014982:Xenopus laevis; D015032:Zinc / Q000494:pharmacology
D002413:Cations, Divalent; D006601:Hexoses; D007328:Insulin; D007473:Ion Channels; D008565:Membrane Proteins; C076715:pervanadate; D014638:Vanadates; D013006:Growth Hormone; D008274:Magnesium; D015032:Zinc; D002118:Calcium