LIPOPROTEIN-LIPASE IS EXPRESSED IN CULTURED SCHWANN-CELLS AND FUNCTIONS IN LIPID-SYNTHESIS AND UTILIZATION

We have previously demonstrated that lipoprotein lipase (LPL; triacylg lycero-protein acylhydrolase, EC 3.1.1.34) is most likely expressed in the non-neuronal cells of the spinal cord, and glial cells may thus b e the site of expression in the peripheral nervous system as well. We investigated the expression of LPL in cultured 1.17 cells, an immortal ized rat sciatic nerve Schwann cell line. The 1.17 cells were shown to express LPL mRNA by reverse transcriptase-polymerase chain reaction a nalysis. The 1.17 Schwann cells demonstrated heparin-releasable lipoly tic activity that was inhibited by the lipase inhibitor tetrahydrolips tatin in a dose-dependent manner. Preincubation of 1.17 cells with an anti-rat LPL antiserum reduced the heparin-releasable lipolytic activi ty to <10% of that measured in untreated cells. To investigate the rol e of LPL in Schwann cell lipid metabolism, 1.17 cells were incubated f or up to 24 h with an emulsified [C-14]triolein substrate and the inco rporation of [C-14]triolein radioactivity into various cellular lipids was examined in the presence of either anti-rat LPL antiserum or prei mmune serum. Inhibiting LPL activity reduced the incorporation of C-14 into cellular polar lipids, diacylglycerol, and cholesteryl esters by >80% at 2 and 6 h after addition of the radiolabeled substrate. At 24 h, radioactivity in diacylglycerol and cholesteryl esters was similar in cells treated with anti-LPL antiserum or preimmune serum, whereas C-14 incorporation into polar lipids was still reduced by >60%, Separa tion of the polar lipids into individual lipid species revealed no spe cific changes in triolein-derived radioactivity incorporation across t he phospholipid species examined.jlr These results suggest that LPL-me diated hydrolysis of exogenous triacylglycerol is an important source of free fatty acids for the Schwann cell and thus may play a critical role in myelin biosynthesis in the peripheral nervous system.