Although GLUT3 was found to be expressed in various tissues, it is most specifically expressed in neurons, found predominantly in axons and dendrites and also, but less prominently, in the cell body. GLUT3 has at least a fivefold greater transport capacity than GLUT1 or GLUT4, as well as a higher glucose affinity than GLUT1, GLUT2 or GLUT4. This is significant as glucose levels surrounding the neurons are only 1–2 mM, compared to 5–6 mM in the serum. and a positive correlation between protein levels of GLUT1, GLUT3 and regional cerebral glucose use was observed in mouse. The central role of GLUT3 in cerebral metabolism has been challenged by the astrocyte-neuron lactate shuttle (ANLS) hypothesis, which proposes that
astrocytes play the key role in the coupling of neuronal activity and cerebral glucose use. In this hypothesis, the astrocyte, which relies on GLUT1 for glucose transport, is the primary consumer of glucose in the brain, providing lactate as the primary energetic fuel for neurons. However, by modeling the kinetic characteristics and glucose concentrations in neurons and glia, it was concluded that the glucose capacity of neurons via GLUT3 far exceeds that of astrocytes via GLUT1. Additionally, demonstrations of increase in GLUT3 expression associated with increased cerebral glucose use provides further confirmation of the central role of GLUT3.
Other tissues Expression of GLUT3 is also found in sperm, embryos, white blood cells and carcinoma cell lines. ==Interactive pathway map==