GUANINE-NUCLEOTIDES MODULATE THE EFFECTS OF BREFELDIN-A IN SEMIPERMEABLE CELLS - REGULATION OF THE ASSOCIATION OF A 110-KD PERIPHERAL MEMBRANE-PROTEIN WITH THE GOLGI-APPARATUS

The release of a 110-kD peripheral membrane protein from the Golgi apparatus is an early event in brefeldin A (BFA) action, preceding the movement of Golgi membrane into the ER. ATP depletion also causes the reversible redistribution of the 110-kD protein from Golgi membrane into the cytosol, although no Golgi disassembly occurs. To further define the effects of BFA on the association of the 110-kD protein with the Golgi apparatus we have used filter perforation techniques to produce semipermeable cells. All previously observed effects of BFA, including the rapid redistribution of the 110-kD protein and the movement of Golgi membrane into the ER, could be reproduced in the semipermeable cells. The role of guanine nucleotides in this process was investigated using the nonhydrolyzable analogue of GTP, GTP-gamma-S. Pretreatment of semipermeable cells with GTP-gamma-S prevented the BFA-induced redistribution of the 110-kD protein from the Golgi apparatus and movement of Golgi membrane into the ER. GTP-gamma-S could also abrogate the observed release of the 110-kD protein from Golgi membranes which occurred in response to ATP depletion. Additionally, when the 110-kD protein had first been dissociated from Golgi membranes by ATP depletion, GTP-gamma-S could restore Golgi membrane association of the 110-kD protein, but not if BFA was present. All of these effects observed with GTP-gamma-S in semipermeable cells could be reproduced in intact cells treated with AlF4-. These results suggest that guanine nucleotides regulate the dynamic association/dissociation of the 110-kD protein with the Golgi apparatus and that BFA perturbs this process by interfering with the association of the 110-kD protein with the Golgi apparatus.