Effects of phospholipid base analogues on the subcellular membrane ether composition of suspension cultured LM cells.
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A strain of mouse fibroblasts, LM cells, was cultured in suspension with a chemically defined medium in the absence of lipid or serum. The subcellular distribution of ether-linked lipids in these cells was determined. O-alkyl and O-alk-1-enyl glycerolipids were found in plasma membranes, microsomes, and mitochondria. The glyceryl ether diesters from all three membrane fractions were devoid of O-alk-1-enyl moieties. Phospholipids contained both O-alkyl and O-alk-1-enyl ether chains. The distribution of these lipids among the subcellular fractions was not uniform. Microsomes contained the largest quantities of O-alkyldiacylglycerols, O-alkylacylphosphatides, and O-alk-1-enylacylphosphatides. Mitochondria were essentially devoid of O-alk-1-enyl phospholipids. The in vivo incorporation of new polar head groups such as N,N-dimethyl-ethanolamine, N-monomethylethanolamine, or ethanolamine instead of N,N,N-trimethylethanolamine (choline) into LM suspension cell membrane phospholipids resulted in increased levels of ether-linked glycerolipids. These increases were inversely proportional to the number of CH3 groups on the nitrogen atom of the base supplement. Both neutral lipids and phospholipids contained increased (2-fold or greater) quantities of O-alkyl moieties, but the levels of O-alk-1-enyl ether moieties in the phospholipids were slightly decreased or unchanged. These alterations in ether lipid content occurred primarily in the microsomes and plasma membranes while mitochondrial ether content or composition was not altered significantly. The chain length composition and degree of unsaturation of the O-alkyl and O-alk-1-enyl side chains from neutral lipids and phospholipids of these membranes were determined. Small (less than 10%) increases in unsaturation of O-alkyl side chains and larger (2-fold) increases in unsaturation of O-alk-1-enyl side chains of plasma membranes and microsomes were noted. These changes were not consistent with developmental alterations during the growth phase since the degree of unsaturation of ether-linked lipids from control LM cells decreased with age of the culture, an affect opposite to that noted in the presence of base analogues. In addition, the increases in levels of ether lipids after base analogue supplementation were much greater than could be accounted for simply by alterations in growth phase of LM suspension cells. 1976.
author list (cited authors)
Schroeder, F., & Vagelos, P. R.
complete list of authors
Schroeder, F||Vagelos, PR