Membrane tubule-mediated reassembly and maintenance of the Golgi complex is disrupted by phospholipase A₂ antagonists

Although membrane tubules can be found extending from, and associated with, the Golgi complex of eukaryotic cells, their physiological function has remained unclear. To gain insight into the biological significance of membrane tubules, we have developed methods for selectively preventing their formation. We show here that a broad range of phospholipase A₂ (PLA₂) antagonists not only arrest membrane tubule-mediated events that occur late in the assembly of the Golgi complex but also perturb its normal steady- state tubulovesicular architecture by inducing a reversible fragmentation into separate 'mini-stacks.' In addition, we show that these same compounds prevent the formation of membrane tubules from Golgi stacks in an in vitro reconstitution system. This in vitro assay was further used to demonstrate that the relevant PLA₂ activity originates from the cytoplasm. Taken together, these results demonstrate that Golgi membrane tubules, sensitive to potent and selective PLA₂ antagonists, mediate both late events in the reassembly of the Golgi complex and the dynamic maintenance of its steady- state architecture. In addition, they implicate a role for cytoplasmic PLA₂ enzymes in mediating these membrane trafficking events.