Fig. 6.

Effects of brefeldin A and temperature on the localization of newly synthesized glycoproteins in hippocampal neurons. Fifteen-day-old neurons were pulse-labeled for 1 hr with [³H]mannose at 37°C with or without (control) brefeldin A (5 μg/ml) to block the exit of newly synthesized glycoproteins from the ER. Another group of cells was pulse-labeled with [³H]galactose at 37°C (control) or 20°C to block the exit of proteins from the trans-Golgi compartment. The distribution of newly synthesized glycoproteins was evaluated by autoradiography. A, Control cells pulse-labeled with [³H]mannose. B, Cells labeled with [³H]mannose in the presence of brefeldin A. C, Control cells pulse-labeled with [³H]galactose at 37°C. D,E, Cells labeled with [³H]galactose at 20°C. In control cells, newly synthesized glycoproteins were localized in the cell body, dendrites (large arrows), and axons (small arrows). In cells treated with brefeldin A or at 20° C, silver grains concentrate in the cell body and proximal or medial dendrites that were identified by their morphology (B, D) or MAP2 staining (E′). The label was significantly reduced in axons. Scale bar, 50 μm.