Expression of liver fatty acid binding protein in L-cells: plasma membrane response to ethanol.
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abstract
Expression of liver fatty acid binding protein (L-FABP) in transfected L-cell fibroblasts modifies plasma membrane structure and function [Incerpi et al., 1992, Arch. Biochem. Biophys. 298, 35-42]. The effect of L-FABP expression on ethanol induced fluidization of plasma membranes was examined. Ethanol in vitro selectively fluidized the exofacial leaflet of the plasma membranes from L-cells expressing low amounts of L-FABP. In contrast, the plasma membranes from L-cells expressing high amounts of L-FABP were resistant to the actions of ethanol. Furthermore, diphenylhexatriene lifetime distributional analysis demonstrated that the plasma membrane exofacial leaflet had a lower range of apparent dielectric constants than the cytofacial leaflet for both low- and high-expression cells. Both the center of lifetime and the lifetime distributional width of diphenylhexatriene in the bulk plasma membrane versus the cytofacial leaflet were consistent with significantly lower apparent dielectric constant in the exofacial leaflet of high-expression versus low-expression cells. Ethanol in vitro preferentially increased the exofacial leaflet apparent dielectric properties of the plasma membranes from low-expression but not high-expression cells. In conclusion, ethanol appears to dehydrate the lipid headgroups of plasma membranes from high-expression cells, thereby conferring resistance to ethanol fluidization. In contrast, ethanol may not dehydrate the plasma membrane lipid head groups of low-expression cells, resulting in ethanol fluidizing the outer leaflet of the plasma membrane.
