Mass spectrometric analysis of change in phospholipids in biological membrane by external environmental effects

Abstract

Phospholipids are significant and major components of the cell membrane in living organisms. Some phospholipids participate in cellular signal transduction processes as second messenger molecules. Previously, the analysis of biological lipids was performed mostly by GC-MS. But three steps-extraction, hydrolysis, and derivatization-are required before injection into the gas chromatograph/mass spectrometer. Various classes of phospholipids were investigated with electrospray ionization mass spectrometry, as well as matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). The optimal matrix concentration for MALDI-MS is 50 mM 2,5-dyhyroxybenzoic acid. The method using an internal standard allows qualitative and quantitative analysis of complex membrane lipids. This is the first report of the identification of phospholipids in biological membranes by MALDI-MS. This technique was exploited to detect the changes in individual classes of phospholipids with various phorbol 12-myristate 13-acetate (PMA) treatment times; PMA is a known tumor promoter. Here, we compared PMA-treated cells with nontreated cells. The change in amount of phosphatidylcholines indicated that the major mechanism is activation of phospholipase D (PLD) yielding phospatidic acid (PA), and large amount of diacylglycerol arises due to the action of phosphatidic acid phosphorylase on PA. (C) 1999 Academic Press.