INTERLEUKIN-3 FACILITATES GLUCOSE-TRANSPORT IN A MYELOID CELL-LINE BYREGULATING THE AFFINITY OF THE GLUCOSE-TRANSPORTER FOR GLUCOSE - INVOLVEMENT OF PROTEIN-PHOSPHORYLATION IN TRANSPORTER ACTIVATION

Growth factors promote cell survival and proliferation by activating s ignal transduction pathways that result in progression through the cel l cycle and differential gene expression. Uptake of simple sugars need ed for basal cell metabolism, and for macromolecular synthesis necessa ry for cell growth and proliferation, is thought to follow as a conseq uence of signal transduction to the nucleus. However, in the presence of inhibitors of DNA synthesis and respiration, growth factors can sti ll promote cell survival responses in the short term, raising the poss ibility that they may also regulate critical membrane and cytosolic pr ocesses necessary for cell survival. We have tested this hypothesis di rectly by investigating the role of the haemopoietic growth factor, in terIeukin-3 (IL-3), in the regulation of glucose transport in the bone marrow-derived cell line, 32D. We show that IL-3 promotes glucose tra nsport by actively maintaining the affinity of the plasma membrane glu cose transporter for glucose (K-m 1.35+/-0.15 mM, n = 4). Withdrawal o f IL-3 for 1 h resulted in reduced affinity for glucose (K-m 2.96+/-0. 28 mM, n = 4) without an associated change in V-max. Furthermore, gluc ose transporter molecules at the cell surface, as determined by cytoch alasin B binding to isolated plasma membranes, did not differ signific antly between control and IL-3-treated cells. Inhibition of DNA synthe sis with mitomycin C or with the respiratory poison, sodium azide, did not affect the ability of IL-3 to promote glucose transport. In contr ast, the tyrosine kinase inhibitors genistein and erbstatin extensivel y inhibited control and IL-3-stimulated glucose transport, some prefer ence for IL-3-stimulated responses being observed at low inhibitor con centrations. The light-activated protein kinase C inhibitor, calphosti n C, also inhibited control and IL-3-stimulated glucose transport but without preference for IL-3 responses. Additionally, the tyrosine phos phatase inhibitor, orthovanadate, stimulated control and IL-3-dependen t glucose transport by 50-80% while the protein kinase A inhibitor, KT 5720, inhibited glucose transport by about 20% at plateau values. Thes e results indicate that IL-3 is involved in continuous maintenance of glucose transporter activity by a mechanism that involves tyrosine kin ases and protein kinase C, and demonstrate that this activation is not dependent on respiration or signal transduction to the nucleus.