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

Cytosolic phospholipase A2-alpha (cPLA2-alpha) 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-alpha in these cells is unknown. Using high-resolution confocal microscopy of the human A549 lung epithelial cell line, we show that cPLA2-alpha 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-alpha 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-alpha, confirming that cPLA2-alpha associates with Golgi-derived membranes. Finally, a specific co-localization of cPLA2-alpha 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-alpha may be involved in membrane trafficking in epithelial cells.