ABSTRACT
The composition and physical state of membrane lipids determine the dynamic nature of membranes, which in turn, could directly be linked to the activity of various membrane-associated cellular functions. To better understand the molecular basis of different membrane-related phenomena we established a novel strategy to alter unsaturation of mammalian cell membranes with an identical genetic background. We transfected L929 mouse fibroblastoid cells with DNA constructs containing the Delta9-fatty acid desaturase gene (Ole1) of S. cerevisiae under the control of desaturase promoters derived either from wild type or mutant strains of the dimorphic fungus H. capsulatum.
Subject(s)
Fatty Acid Desaturases/genetics , Lipid Metabolism , Membrane Fluidity , Saccharomyces cerevisiae/genetics , Transformation, Genetic , Animals , Cell Line, Transformed , DNA, Fungal , Mice , Saccharomyces cerevisiae/enzymology , Stearoyl-CoA DesaturaseABSTRACT
L929 and WEHI tumor cell lines were genetically modified to constitutively express the Saccharomyces cerevisiae Ole 1 gene, coding for the delta 9-desaturase enzyme. These cells exhibit an increased ratio of monounsaturated fatty acids in their membrane phospholipids paralleled by an overall decrease in the membrane molecular order and a highly increased tumor necrosis factor-alpha (TNF) sensitivity. The TNF-alpha signaling cascade involves events, like receptor clustering and cleavage of membrane constituent lipid molecules by phospholipases, which are influenced by the physical state of cellular membranes. We discuss the possible involvement of non-bilayer forming lipids in the control of signaling mechanisms leading to TNF cytotoxicity.