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

The glial C6BU-1 cell line, loaded with acetylcholine can release this neur otransmitter. This study was aimed at determining whether disruption of the Golgi-vesicular traffic by brefeldin A would change the acetylcholine rele ase from these cells and affect proteins involved in transmitter release li ke the 15 kDa proteolipid, common to V-ATPase and mediatophore. Cells were treated for 24 or 36 h with brefeldin A (35.7 mu M). The observed changes i n cell morphology were typical for brefeldin A treated cells in which prote in membrane supply has been stopped. Inhibition of membrane protein supply was confirmed in the present work. Moreover, the 15 kDa proteolipid also de cayed to a very low level in the cell membrane fraction. The release of ace tylcholine evoked by a calcium challenge and a calcium ionophore, or by ele ctrical pulses decreased markedly. The life time of the release mechanism w as of the order of 36 h and half decayed in 24 h. In addition, the electric ally 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 proteoli pid may be one of the proteins forming the membrane complex responsible for transmitter release, at least in these cells. (C) 2000 Elsevier Science Lt d. All rights reserved.