Abstract

In this thesis, 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. In V79, increases in the plasma membrane GT content correlated with the stimulatory effects of insulin and glucose deprivation. In contrast, 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 V79--suggesting an enhancement of the intrinsic activity of the GT expressed in G14. A difference in the average molecular weights of the transporters was observable between the two cell lines, however. Treatment with endoglycosidase F or tunicamycin established that the G14 cell line exhibited a hyperglycosylated form of the same core GT protein expressed in V79. In a second study, the dramatic down-regulatory effects of D-allose were examined in both the G14 and V79 cell lines. In both cell lines, however, D-allose treatment did not alter GT content in either the whole cell or plasma membrane fractions. In this case, a negative regulatory effect on the intrinsic activity of the GT is implicated. The regulation of sugar transport through modulation of the intrinsic activity of the GT is a rapidly evolving theory. The continued study of novel instances of sugar uptake regulation such as these could provide clues as to the factors involved in such a mechanism.