Alterations of new methylated phospholipid synthesis in the plasma membranes of macrophages exposed to chemoattractants.

Abstract

Chemotactic factors inhibit the methylation of phosphatidylethanolamine in macrophages without affecting total phospholipid synthesis. Newly synthesized membranes of [guinea pig] macrophages exposed to chemoattractants would therefore have an increased ratio of phosphatidylethanolamine to its methylated derivatives. These ratios were measured directly in newly synthesized phospholipids of plasma membranes isolated from guinea pig peritoneal macrophages. The phosphatidylethanolamine:methylated phospholipid ratio in such plasma membranes was increased by 53-111% upon exposure of the cells to chemotactic factors. This increase was due to decreased synthesis of methylated phospholipids and not to altered formation of phosphatidylethanolamine or activation of phospholipases. Methylated phospholipid ratios were studied in the leading front lamellipodia isolated from macrophages migrating under chemotactic and nonchemotactic conditions. The phosphatidylethanolamine:methylated phospholipid ratios were increased up to 4-fold in lamellipodia of macrophages migrating towards chemotactic agents when compared to those from cells migrating randomly. Biophysical changes in the plasma membrane produced by an increase in the ratio of phosphatidylethanolamine:methylated phospholipids as a result of exposure of cells to chemoattractants may be required for sustained directed migration.