FATP1 channels exogenous FA into 1,2,3-triacyl-sn-glycerol and down-regulates sphingomyelin and cholesterol metabolism in growing 293 cells

Biosynthesis of lipids was investigated in growing 293 cells stably expressing fatty acid (FA) transport protein 1 (FATP1), a bifunctional polypeptide with FA transport as well as fatty acyl-CoA synthetase activity. In short-term (30 s) incubations, FA uptake was increased in FATP1 expressing cells (C8 cells) compared with the vector (as determined by BODIPY 3823 staining and radioactive FA uptake). In long-term (4 h) incubations, incorporation of [¹⁴C]acetate, [3H]oleic acid, or [¹⁴C]lignoceric acid into 1,2,3-triacyl-snglycerol (TG) was elevated in C8 cells compared with vector, whereas incorporation of radiolabel into glycerophospholipids was unaltered. The increase in TG biosynthesis correlated with an increase in 1,2-diacyl-sn-glycerol acyltransferase activity in C8 cells compared with vector. In contrast, incorporation of [¹⁴C]acetate into sphingomyelin (SM) and cholesterol, and [3H]oleic acid or [¹⁴C]lignoceric acid into SM was reduced due to a reduction in de novo biosynthesis of these lipids in C8 cells compared with vector. The results indicate that exogenously supplied FAs, and their subsequently produced acyl-CoAs, are preferentially channeled by an FATP1 linked mechanism into the TG biosynthetic pathway and that such internalized lipids down-regulate de novo SM and cholesterol metabolism in actively growing 293 cells.