Which transporter helps in glucose uptake in neurons?
Glucose entry into mammalian cells is essential for glycolysis and cannot occur through lipid phase due to hydrophilicity; therefore facilitated transporters required. GLUT family SLC2A comprises fourteen members with twelve transmembrane helices organized into two six helix bundles operating by alternating access inward outward transition mechanism. Tissue distribution optimized for function: GLUT1 widely expressed in erythrocytes and endothelial cells of blood brain barrier Km about 3 millimolar providing basal uptake, GLUT2 low affinity high Km about 17 millimolar in hepatocytes and pancreatic beta cells serving as glucose sensor, GLUT4 insulin responsive translocating from GSVs to plasma membrane in muscle adipose after Akt signaling. GLUT3 exhibits highest affinity Km approximately 1.5 millimolar and high turnover, expressed predominantly in neurons and testis where extracellular glucose lower than blood about 1 to 2 millimolar due to continuous consumption and blood brain barrier restriction. Neurons lack significant glycogen and depend exclusively on constant supply, so expression of high affinity GLUT3 ensures efficient uptake even during modest hypoglycemia sustaining synaptic activity.
Ref: Mueckler, Eur J Biochem, GLUT Family Tissue Distribution - GLUT3 High Affinity Neuronal Transporter.