Glucose regulates its transport in L8 myocytes by modulating cellular trafficking of the transporter GLUT-1

R. Greco-Perotto, E. Wertheimer, B. Jeanrenaud, E. Cerasi, S. Sasson*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

The effect of cu]ture conditions simulating hypo- and hyper-glycaemia on glucose transport and on the subcellular localization of the glucose transporter GLUT-1 was studied in L8 myocytes. Incubation of the cells with 20 mM-glucose for 25 h decreased the rate of 2-deoxy-D-[3H]glucose (dGlc) uptake to 0.106 ± 0.016 nmol/min per 106 cells compared with 0.212 ± 0.025 in cells maintained at 2 mM-glucose (final glucose concentrations at the end of the incubation period were 16-17 mM and 0.7-1.0 mM respectively). An additional 5 h incubation of these cells with medium containing the opposite glucose concentration (i.e. change from 17mM to 1 mM and from 1 mM to 17mM) increased the transport rate to 0.172 ± 0.033 nmol/min per 106 cells in cultures initially conditioned at high glucose, and decreased the transport to 0.125 ± 0.029 in those conditioned at low glucose. Plasma-membrane- and microsomal-membrane-enriched fractions were prepared from these cells for [3H]cytochalasin B (CB) binding and Western-blot analysis with antibodies against GLUT-1 and GLUT-4. A decrease in glucose concentration increased the number of D-glucose-displaceable CB-binding sites and GLUT-1 protein in the plasma-membrane fraction to the same extent as the increase in dGlc transport. Under downregulatory conditions, the lower dGlc-transport capacity could be accounted for by a decreased number of transporters in the plasma membrane of the cells. No apparent modification of the intrinsic activity of the glucose transporters was observed in up- or down-regulated cells. Under downregulatory conditions, the CB-binding data indicated a large increase in the number of transporters in the intracellular membranes of the myocytes. Western blots of the same membranes also indicated an increase in GLUT-1 content. However, the interaction of the intracellular GLUT-1 protein with the polyclonal antibodies was much weaker than that of the plasma-membrane-associated GLUT-1. The GLUT-4 concentration was too low to permit quantification in membrane fractions. Our findings suggest that autoregulation of glucose transport in L8 myocytes is accompanied by parallel changes in the number of GLUT-1 transporters in the plasma membrane, and that the rate of transporter degradation may be augmented in the upregulated myocytes. These glucose-induced changes are fully reversible.

Original languageEnglish
Pages (from-to)157-163
Number of pages7
JournalBiochemical Journal
Volume286
Issue number1
DOIs
StatePublished - 1992
Externally publishedYes

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