Effect of retinoic acid on the Ca2+-Independent phospholipase A(2) in nuclei of LA-N-1 neuroblastoma cells

LA-N-1 neuroblastoma cell cultures contain Ca2+-independent phospholipases Az hydrolyzing phosphatidylethanolamine and ethanolamine plasmalogens. Thes e enzymes differ from each other in their molecular mass, substrate specifi city, and kinetic properties. Subcellular distribution studies have indicat ed that the activity of these phospholipases is not only localized in the c ytosol but also in non-nuclear membranes and in nuclei. The treatment of LA -N-1 neuroblastoma cell cultures with retinoic acid results in a marked sti mulation of Ca2+-independent phospholipases A(2) hydrolyzing phosphatidylet hanolamine and plasmenylethanolamine. The increase of the activities of bot h enzymes was first observed in nuclei followed by those present in the cyt osol. No effect of retinoic acid on either phospholipase activity could be observed in nonnuclear membranes. The stimulation of these enzymes may be i nvolved in the generation and regulation of arachidonic acid and its metabo lites during differentiation.