Glucose transporter Glut3 is targeted to secretory vesicles in neurons andPC12 cells

In rat brain and cultured neuroendocrine PC12 cells, Glut3 is localized at the cell surface and, also, in a distinct population of homogenous synaptic -like vesicles. Glut3-containing vesicles co-purify with "classical" synapt ic vesicles, but can be separated from the latter by sucrose gradient centr ifugation. Unlike classical synaptic vesicles, Glut3-containing vesicles po ssess a high level of aminopeptidase activity, which has been identified as aminopeptidase B. This enzyme has recently been shown to be a marker of th e secretory pathway in PC12 cells (Balogh, A., Cadel, S., Foulon, T., Picar t, R., Der Garabedian, A., Rousselet, A., Tougard, C., and Cohen, P. (1998) J. Cell Sci. 111, 161-169). We, therefore, conclude that Glut3 is targeted to secretory vesicles in both neurons and PC12 cells.