EVIDENCE THAT PHOSPHOLIPASE A(2) ACTIVITY IS REQUIRED FOR GOLGI-COMPLEX AND TRANS-GOLGI NETWORK MEMBRANE TUBULATION

Membrane tubules of uniform diameter (60-80 nm) and various lengths (u p to several micrometers) emanate from elements of the Golgi stack and trans Golgi network (TGN). These organelle membrane tubules are thoug ht to be involved in membrane trafficking and maintenance of Golgi/TGN architecture. The number of these tubules, and their frequency of for mation, can be greatly enhanced by the fungal metabolite brefeldin A ( BFA), an inhibitor of Golgi/TGN-associated coated vesicle formation. W e show here that BFA stimulation of Golgi and TGN membrane tubulation, and the resultant retrograde transport of resident Golgi enzymes to t he endoplasmic reticulum, was potently inhibited by a number of membra ne-permeant antagonists of phospholipase A(2) (PLA(2); EC 3.1.1.4) act ivity. In addition, PLA(2) inhibitors on their own caused a reversible fragmentation of the Golgi complex into juxtanuclear, stacked cistern al elements. We conclude from these observations that tubulation of Go lgi complex and TGN membranes requires a PLA(2) activity, and that thi s activity may participate not only in Golgi tubule-mediated retrograd e trafficking to the endoplasmic reticulum, but also in the maintenanc e of Golgi complex architecture.