Differential distribution of arachidonate in nuclear and non-nuclear membranes

The nucleus has recently been recognized as the site to which arachidonate-metabolizing enzymes such as cytosolic phospholipase A2, cyclooxygenases and 5-lipoxygenase associate following cell activation. The present study has focused on identifying the arachidonate-containing phospholipid classes and subclasses in nuclei of human monocyte-like THP-1 cells, murine bone marrow-derived mast cells and liver mast cells CFTL-15. When normalized to DNA content, isolated nuclei contained 1525% of the total cellular arachidonate within these cells. A greater proportion of nuclear arachidonate was associated with phosphatidylinositol species compared to other cellular membranes. In contrast, the proportion of arachidonate in nuclear phosphatidylethanolamine (PE) species was lower in nuclear extracts than other cellular membranes. In addition, the distribution of arachidonate in PE subclasses differed in nuclear and other cell membranes. Nuclear PE was more enriched in 1-acyl linked species while other membranes contained greater proportions of 1-alk-l-enyl-2arachidonoyl-PE molecular species. Although phosphatidylcholine (PC) contained similar proportions of total arachidonate in nuclear and nonnuclear membranes, a greater proportion of arachidonate associated with nuclear PC was associated with 1-acyl-linked species than in other membranes. These results indicate that the class and subclass distribution of arachidonate in nuclear membranes differs from membranes of the rest of the cell.