GTP analogs suppress uptake but not transport of d-glucose analogs in Glut1 glucose transporter-expressing Xenopus oocytes

AbstractA Xenopus oocyte expression-co-injection system was used to study the influence of guanine nucleotides on D-glucose uptake. GTP analogs like GTPγS and GppNHp had no effect on 3-O-methylglucose transport determined by zero-trans uptake or equilibrium exchange, but suppressed 2-deoxyglucose uptake into Glutl glucose transporter-expressing oocytes by up to 86%. Both GTP analogs showed concentration dependence of their effectiveness, with GTPγS being more potent than GppNHp. No statistically significant differences were observed between groups of oocytes co-injected with water or GDPβS (250 and 500 μM intracellular concentration). Glut1 transporter expression in plasma membrane was not different between water or GTPγS-co-injected oocytes. Thus, inhibition of hexokinase catalytic activity is the most likely causative factor for down-regulation of 2-deoxyglucose uptake