INTESTINAL FATTY-ACID-BINDING PROTEIN EXPRESSION STIMULATES FIBROBLAST FATTY-ACID ESTERIFICATION

The effect of intestinal fatty acid binding protein (I-FABP) expressio n on cell growth and cell lipid content is not known. Therefore, mouse L-cell fibroblasts were transfected with the cDNA encoding for I-FABP . The high expression clones expressed 0.35% of the total cytosolic pr oteins as I-FABP. Mock transfected L-cells did not differ from control L-cells in any properties tested. Neither the growth rate, maximal ce ll density, nor [H-3]oleic acid uptake differed in I-FABP expressing a s compared to control cells. In contrast, I-FABP expression increased triacylglycerol and cholesteryl ester mass (nmol/mg protein) by 63% an d 25%, respectively. Phospholipid mass was unchanged in I-FABP express ing cells. The initial [3H]oleic acid esterification into triacylglyce rols and cholesteryl esters was increased 3.9- and 2.5-fold in I-FABP expressing cells. Although, the initial [H-3]oleic acid esterification into total phospholipids was unchanged, within the phospholipid fract ion the initial [H-3]oleic acid esterification into phosphatidylethano lamine was increased 70% and decreased 50% in phosphatidylcholine in I -FABP expressing cells. These observed differences suggest a distinct role for I-FABP in stimulating net formation, and not just turnover, o f triacylglycerides and cholesteryl esters in transfected L-cell fibro blasts.