The hemopoietic growth factor, interleukin-3, promotes glucose transport by increasing the specific activity and maintaining the affinity for glucose of plasma membrane glucose transporters

Most mammalian cells rely on an external supply of glucose for survival, proliferation, and function, Glucose enters cells through specific transporter molecules at the plasma membrane by a facilitative process that does not expend energy, Regulation of glucose transport into cells is thought to occur largely through transporter expression at the cell surface, but the extent to which the intrinsic properties of glucose transporters are regulated is at present controversial, Using a bone marrow-derived cell line that responds to the hemopoietic growth factor, interleukin-3 (IL-3), we investigated IL-3 regulation of glucose transport, IL-3 significantly increased 2-deoxyglucose (2-DOG) uptake within 1 h (26 +/- 8.0%, n = 11) with a maximum 73% increase after 6 h, Withdrawal of IL-3 resulted in decreased uptake within 1 h rand this continued to decline to 43% of initial uptake by 16 h, To determine whether these changes in 2-DOG uptake were associated with corresponding changes in glucose transporter expression, subtype-specific antisera against. Glut-1 and Glut-3 were used, Little change in membrane expression of these transporters was observed prior to 16 h, Fractionation of cell membranes on Nycodenz gradients showed that the majority of each transporter subtype was associated with the plasma membrane (63-93%) and that transporter distribution did not change markedly in response to addition or withdrawal of IL-3, These results demonstrate that IL-3 regulates glucose uptake by modulating the: intrinsic transporting ability of glucose transporters, Decreased transporter affinity for 2-DOG and 3-8-methylglucose was observed following IL-3 withdrawal, Similar affinity changes were observed with 2-DOG following exposure of IL-3-stimulated cells to the protein kinase inhibitors, genistein and staurosporine, In contrast, the tyrosine phosphatase inhibitor, vanadate, acted hire IL-3 to increase transporter affinity for glucose, Together these results demonstrate that IL-3 acts to maintain the intrinsic transport properties of glucose transporters without markedly affecting their expression or translocation.