Cytosolic phospholipase A(2) regulates Golgi structure and modulates intracellular trafficking of membrane proteins

The Golgi complex and the trans-Golgi network are critical cellular organel les involved in the endocytic and biosynthetic pathways of protein traffick ing. Lipids have been implicated in the regulation of membrane-protein traf ficking, vesicular fusion, and targeting. We have explored the role of cyto solic group IV phospholipase A(2) (cPLA(2)) in membrane-protein trafficking in kidney epithelial cells. Adenoviral expression of cPLA(2) in LLC-PK1 ki dney epithelial cells prevents constitutive trafficking to the plasma membr ane of an aquaporin 2-green fluorescent protein chimera, with retention of the protein in the rough endoplasmic reticulum. Plasma membrane Na+-K+-ATPa se alpha-subunit localization is markedly reduced in cells expressing cPLA( 2), whereas the trafficking of a Cl-/HCO3- anion exchanger to the plasma me mbrane is not altered in these cells. Expression of cPLA(2) results in disp ersion of giantin and beta-COP from their normal, condensed Golgi localizat ion, and in marked disruption of the Golgi cisternae. cPLA(2) is present in Golgi fractions from noninfected LLC-PK1 cells and rat kidney cortex. The distribution of tubulin and actin was not altered by cPLA(2), indicating th at the microtubule and actin cytoskeleton remain intact. Total cellular pro tein synthesis is unaffected by the increase in cPLA(2) activity. Thus cPLA (2) plays an important role in determining Golgi architecture and selective control of constitutive membrane-protein trafficking in renal epithelial c ells.