Effects of 2-deoxy-d-glucose on the functional state of the rat myoblast GLUT 1 transporter.
Based on the rationale that internalized 2-deoxy-D-glucose (dGlc) is toxic to cells, glucose transport (GLUT) defective myoblast mutants have been isolated by their ability to grow in glucose-free medium containing dGlc. Recent studies revealed that the GLUT 1 transport process was activated when GLUT 3-GLUT 4-mutants were grown in glucose-free medium. It was therefore puzzling why these GLUT3-GLUT4-myoblasts could survive in the presence of dGlc during the mutant selection process. The present study revealed that GLUT 1 transport affinity in dGlc-grown cells was at least four folds lower than that in control cells. This loss of GLUT 1 transport activity was apparent only after exposure to the toxic sugar analogues for more than 10 hrs. This dGlc-mediated effect was not due to competitive inhibition by the residual dGlc carried over from growth medium, changes in glycolytic enzymes, nor accumulation of the negatively charged dGlc-6-PO4. In fact, GLUT 1 transcript level was elevated in dGlc-treated cells. Both immunoprecipitation and immunoblotting studies indicated that the size of the GLUT 1 transporter in dGlc-grown myoblasts was reduced from 52 kDa to that of the unglycosylated form (38 kDa). These findings suggest that growth in the presence of dGlc inhibits glycosylation of the GLUT 1 transporter, thus reducing its transport affinity. This inability of the GLUT 1 transporter to take up dGlc may therefore explain why GLUT 3-GLUT 4-mutants are able to grow in the presence of the toxic dGlc during the mutant selection procedure.
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Department of Biochemistry, University of Western Ontario London, Canada.
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D019325:3-O-Methylglucose / Q000378:metabolism; D000818:Animals; D001692:Biological Transport; D015152:Blotting, Northern; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D003847:Deoxyglucose / Q000378:metabolism* / Q000494:pharmacology*; D051272:Glucose Transporter Type 1; D051274:Glucose Transporter Type 3; D051275:Glucose Transporter Type 4; D007700:Kinetics; D009004:Monosaccharide Transport Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D018485:Muscle Fibers, Skeletal / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D009124:Muscle Proteins; D009154:Mutation; D009419:Nerve Tissue Proteins; D051381:Rats; D014158:Transcription, Genetic / Q000187:drug effects; D014415:Tunicamycin / Q000494:pharmacology
D051272:Glucose Transporter Type 1; D051274:Glucose Transporter Type 3; D051275:Glucose Transporter Type 4; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; D009419:Nerve Tissue Proteins; C495679:Slc2a1 protein, rat; C495690:Slc2a3 protein, rat; C495694:Slc2a4 protein, rat; D014415:Tunicamycin; D019325:3-O-Methylglucose; D003847:Deoxyglucose