The glucose sensor in HIT cells is the glucose transporter

Abstract

The nature of the rate-limiting step for glucose utilization by the clonal insulin-producing cell line HIT-T 15 has been investigated. In contrast to the situation in islets of Langerhans, we find that the HIT cell glucose metabolism is limited by the rate of entry of glucose into the cell. This is evidenced by the low rate of sugar transport and by the marked reduction in the rate of glucose utilization elicited by inhibitors of the glucose transporter. As judged by competition with glucose, the HIT cell glucose transporter also transports mannose, 2-deoxyglucose and 3-0-methylglucose but not L-glucose or N-acetylglucosamine. The K,,, for glucose of the glucose transporter, measured as the concentration of glucose required for a half-maximal rate of glucose utilization, is 4.3 mM, similar to the concentration reported to give half-maximal insulin release. Glucose-stimulated insulin release from HIT cells is inhibited by phloretin or cytochalasin B but not by mannoheptulose. We conclude that the secretory responses of HIT cells are consistent with the substrate-site hypothesis, but that, in contrast to normal B-cells, the glucose sensor which confers concentration-dependence and specificity to sugar-stimulated insulin release, is the glucose transporter.

Effect of disruption of actin filaments by Clostridium botulinum C2 toxin on insulin secretion in HIT-T15 cells and pancreatic islets.

“…In our study both CE and CB, like C2 toxin, inhibited the stimulated insulin secretion in HIT cells. Although CB reduced the MTT reduction, an effect probably because of blockade of glucose transport in these cells (Ashcroft and Stubbs, 1987), there are two reasons to believe that this effect is not the main cause for the inhibition of insulin secretion. First, CE does not affect glucose transport (Cooper, 1987), whereas inhibiting insulin secretion to the same extent.…”

“…Many actin-binding proteins are associated with the barbed end of F-actin and therefore regulate actin polymerization (Korn, 1982;Pollard and Cooper, 1986;Weeds and Maciver, 1993). There is evidence for a role of AFs in insulin secretion (Orci et al, 1972;Howell and Tyhurst, 1980, 1986;Swanston-Flatt et al, 1980;Stutchfield and Howell, 1984;Ashcroft and Stubbs, 1987), but the underlying mechanism is poorly understood. Agents such as cytochalasins, which affect AF assembly (Flanagan and Lin, 1980;Goddette and Frieden, 1986;Cooper, 1987), enhance insulin secretion from pancreatic islets (Orci et al, 1972;Lacy et al, 1973;Wang et al, 1990).…”

“…In particular, we tested the hypothesis that AFs participate in the recruitment of secretory granules for the sustained phase of secretion. For most studies HIT-T15 cells were employed; these cells are a widely used cell line with retained sensitivity to both nutrient secretagogues and receptor agonists (Nelson and Boyd, 1985;Ashcroft and Stubbs, 1987;Wollheim et al, 1990;Li et al, 1992Li et al, , 1993. For control purposes, the less selective cytochalasins were also used; some experiments were performed in isolated rat islets.…”

Cloning and functional expression of a human pancreatic islet glucose-transporter cDNA.

“…These studies suggested that islet glucose transport is mediated by a high-Km, low-affinity transporter as in liver (6) and that transport is not rate limiting for glucose metabolism. In three different transformed islet cell lines, however, in which glucose-stimulated insulin secretion was impaired, the uptake of 3-0-methylglucose was slow (6,7). Thus, while glucose transport in normal islets is rapid, impaired glucose transport may, in certain circumstances, be the rate-limiting step for glucose control of insulin secretion.…”

Interleukin‐1β inhibits glucokinase activity in clonal HIT‐T15 β‐cells

“…Retention times for ATP and ADP were 7.87 kO.21 (16) and 18.27 +0.22 (16) min respectively. Intracellular concentrations of ATP and ADP in controls were 3.18kO.70 (4) and 0.26&0.04 (4) mM respectively (calculated assuming a HIT-T 15 intracellular water space of 0.81 pl/ceII [31]). Results are means *SE, for 3 experiments.…”