Association of cPLA2-α and COX-1 with the Golgi apparatus of A549 human lung epithelial cells

Abstract

Cytosolic phospholipase A₂-α (cPLA₂-α) is an 85 kDa, Ca²⁺-sensitive enzyme involved in receptor-mediated prostaglandin synthesis. In airway epithelial cells, the release of prostaglandins is crucial in regulating the inflammatory response. Although prostaglandin release has been studied in various epithelial cell models, the subcellular location of cPLA₂-α in these cells is unknown. Using high-resolution confocal microscopy of the human A549 lung epithelial cell line, we show that cPLA₂-α relocates from the cytosol and nuclei to a juxtanuclear region following stimulation with the Ca²⁺ ionophore A23187. Double staining with rhodamine-conjugated wheat germ agglutinin confirmed this region to be the Golgi apparatus. Markers specific for Golgi subcompartments revealed that cPLA₂-α is predominantly located at the trans-Golgi stack and the trans-Golgi network following elevation of cytosolic Ca²⁺. Furthermore, treatment of cells with the Golgi-disrupting agent brefeldin A caused a redistribution of cPLA₂-α, confirming that cPLA₂-α associates with Golgi-derived membranes. Finally, a specific co-localization of cPLA₂-α with cyclooxygenase-1 but not cyclooxygenase-2 was evident at the Golgi apparatus. These results, combined with recent data on the role of PLA₂ activity in maintaining Golgi structure and function, suggest that Golgi localization of cPLA₂-α may be involved in membrane trafficking in epithelial cells.