Effect of brefeldin A on acetylcholine release from glioma C6BU-1 cells.

The glial C6BU-1 cell line, loaded with acetylcholine can release this neurotransmitter. This study was aimed at determining whether disruption of the Golgi-vesicular traffic by brefeldin A would change the acetylcholine release from these cells and affect proteins involved in transmitter release like the 15 kDa proteolipid, common to V-ATPase and mediatophore. Cells were treated for 24 or 36 h with brefeldin A (35.7 microM). The observed changes in cell morphology were typical for brefeldin A treated cells in which protein membrane supply has been stopped. Inhibition of membrane protein supply was confirmed in the present work. Moreover, the 15 kDa proteolipid also decayed to a very low level in the cell membrane fraction. The release of acetylcholine evoked by a calcium challenge and a calcium ionophore, or by electrical pulses decreased markedly. The life time of the release mechanism was of the order of 36 h and half decayed in 24 h. In addition, the electrically evoked release became much shorter. Considering that C6BU-1 cells are able to release large amounts of ACh and their membranes contain a sizeable amount of the 15 kDa proteolipid, these results suggest that this proteolipid may be one of the proteins forming the membrane complex responsible for transmitter release, at least in these cells.