Abstract
Sugar transport regulation was characterized in terms of the expression and subcellular distribution of the glucose transporter (GT) in the V79 hamster fibroblast cell line and in a respiration deficient mutant (G14) of the V79 cell line. Comparison of GT content in V79 and G14 cells and cell fractions revealed that the 3-fold elevation in basal sugar transport observed in the G14 cell line did not coincide with any significant difference in either the whole cell or plasma membrane GT content when compared to the V79 parental cell line. Determination of delta-antibody binding to intact cell monolayers supported the finding that the two cell lines demonstrate equivalent plasma membrane GT content. Further, D-glucose inhibitable cytochalasin B binding to total cell membranes indicates that additional, unrecognized GT isoforms do not occur in either cell line. A higher average molecular weight GT was detected in the G14 cell line, and treatment of GT enriched preparations with endoglycosidase F established that the G14 cell line exhibits a hyperglycosylated form of the same core GT protein expressed in V79. These results suggest that an enhancement of the intrinsic activity of the GT expressed in G14 is responsible for its increased sugar transport capabilities and this may be related to differences in GT post-translational processing.
Published Version
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