The tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) caused a marked stimulation of inorganic [32P]orthophosphate incorporation into HeLa-cell phosphatidylcholine (PC), phosphatidylethanolamine (PE), and lysophosphatidylethanolamine. The increased incorporation of inorganic [32P]orthophosphate into PE and lysophosphatidylethanolamine in the presence of TPA was not associated with an increase in PE synthesis as detected by the incorporation of [3H]serine or [3H]ethanolamine. The PC-specific exchange protein from beef liver was used to insert PC labeled with [3H]choline, inorganic [32P]orthophosphate, or [14C]arachidonic acid plus [3H]palmitic acid into the outer monolayer of intact HeLa cell membranes. Radioactivity from the latter two compounds was rapidly incorporated into PE and lysophosphatidylethanolamine; the incorporation was stimulated by TPA. It was concluded that TPA stimulated the formation of PE by base exchange between ethanolamine and PC.
This study was supported by the Australian Research Grants Committee, the National Health and Medical Research Council, and the Universities of South Australia Anti-Cancer Foundation.