STEROL CARRIER PROTEIN-2 EXPRESSION INCREASES NBD-STEARATE UPTAKE ANDCYTOPLASMIC DIFFUSION IN L-CELLS

The effects of sterol carrier protein-2 (SCP-2) expression on fatty ac id uptake and cytoplasmic diffusion were determined using L cell fibro blasts transfected with cDNA encoding either the 15- or 13.2-kDa form of SCP-2. Cis-parinarate and methyl-(7-nitrobenz-2-oxa-1,3-diazol)amin ostearate (NBD-stearate) were used as nonesterifiable fluorescent fatt y acid probes. NBD-stearate and cis-parinarate uptake was rapid and sa turable. In 15-kDa SCP-2-expressing cells, the extent of NBD-stearate and cis-parinarate uptake was increased 1.4- and 1.2-fold, respectivel y, compared with control. In the 13.2-kDa SCP-2-expressing cells, the extent of NBD-stearate and cis-parinarate uptake was increased 1.3- an d 1.1-fold, respectively, compared with control cells. NBD-stearate cy toplasmic diffusion was increased 1.5-fold in 15-kDa SCP-2-expressing cells, but not in 13.2-kDa SCP-2-expressing cells, compared with contr ol cells. After incubation with NBD-stearate for 30 min at 37 degrees C, fluorescence imaging indicated that NBD-stearate was localized prim arily in lipid droplets in all cell lines. These results suggest that SCP-2 may be involved not only in fatty acid uptake but also in intrac ellular fatty acid trafficking.