Cytosolic phospholipase A2 regulates Golgi structure and modulates intracellular trafficking of membrane proteins

Abstract

The Golgi complex and the trans-Golgi network are critical cellular organelles involved in the endocytic and biosynthetic pathways of protein trafficking. Lipids have been implicated in the regulation of membrane-protein trafficking, vesicular fusion, and targeting. We have explored the role of cytosolic group IV phospholipase A2 (cPLA2) in membrane-protein trafficking in kidney epithelial cells. Adenoviral expression of cPLA2 in LLC-PK1 kidney epithelial cells prevents constitutive trafficking to the plasma membrane of an aquaporin 2-green fluorescent protein chimera, with retention of the protein in the rough endoplasmic reticulum. Plasma membrane Na+-K+-ATPase α-subunit localization is markedly reduced in cells expressing cPLA2, whereas the trafficking of a Cl-/HCO3- anion exchanger to the plasma membrane is not altered in these cells. Expression of cPLA2 results in dispersion of giantin and β-COP from their normal, condensed Golgi localization, and in marked disruption of the Golgi cisternae. cPLA2 is present in Golgi fractions from noninfected LLC-PK1 cells and rat kidney cortex. The distribution of tubulin and actin was not altered by cPLA2, indicating that the microtubule and actin cytoskeleton remain intact. Total cellular protein synthesis is unaffected by the increase in cPLA2 activity. Thus cPLA2 plays an important role in determining Golgi architecture and selective control of constitutive membrane-protein trafficking in renal epithelial cells.