Effect of caffeine and reduced temperature (20 degrees C) on the organization of the pre-Golgi and the Golgi stack membranes

Because of the effective inhibition of membrane traffic out of the ER at 20~ and the translocation of p58 to the periphery of the cell in the presence of caffeine, it was of great interest to study whether the morphology of the Golgi stack is affected under the conditions used. BHK-21 cells were incubated for 120 rain in the presence or absence of 10 mM caffeine at 20~ fixed, and processed for electron microscopy. In caffeine-treated cells the morphology of the Golgi stack was altered. The Golgi regions of the cells were filled with small (60-70-nm-diam) vesicles (Fig. 7 a) . In addition, some tubular membranous structures, possibly representing remnants of the Golgi stack, were also observed (Fig. 7 a, arrow) . On the contrary, control cells incubated for 120 min at 20~ possessed typical Golgi stacks (Fig. 7 b) . Taken together, caffeine at 20~ does not only inhibit the ER-exit of proteins and translocate p58 to the periphery of the cells but also induces a change in the morphology of the Golgi stack.