Huey P U, Marcell T, Owens G C, Etienne J, Eckel R H
Department of Medicine, University of Colorado Health Sciences Center, 4200 E. 9th Avenue, Denver, CO 80262, USA.
J Lipid Res. 1998 Nov;39(11):2135-42.
We have previously demonstrated that lipoprotein lipase (LPL; triacylglycero-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 be the site of expression in the peripheral nervous system as well. We investigated the expression of LPL in cultured 1. 17 cells, an immortalized rat sciatic nerve Schwann cell line. The 1. 17 cells were shown to express LPL mRNA by reverse transcriptase-polymerase chain reaction analysis. The 1.17 Schwann cells demonstrated heparin-releasable lipolytic activity that was inhibited by the lipase inhibitor tetrahydrolipstatin in a dose-dependent manner. Preincubation of 1.17 cells with an anti-rat LPL antiserum reduced the heparin-releasable lipolytic activity to <10% of that measured in untreated cells. To investigate the role of LPL in Schwann cell lipid metabolism, 1.17 cells were incubated for up to 24 h with an emulsified [14C]triolein substrate and the incorporation of [14C]triolein radioactivity into various cellular lipids was examined in the presence of either anti-rat LPL antiserum or preimmune serum. Inhibiting LPL activity reduced the incorporation of 14C 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 14C incorporation into polar lipids was still reduced by >60%. Separation of the polar lipids into individual lipid species revealed no specific changes in triolein-derived radioactivity incorporation across the phospholipid species examined. These results suggest that LPL-mediated 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.
我们之前已经证明，脂蛋白脂肪酶（LPL；三酰甘油 - 蛋白酰基水解酶，EC 3.1.1.34）很可能在脊髓的非神经元细胞中表达，因此神经胶质细胞也可能是其在外周神经系统中的表达位点。我们研究了LPL在培养的1.17细胞（一种永生化的大鼠坐骨神经雪旺细胞系）中的表达。通过逆转录 - 聚合酶链反应分析表明，1.17细胞表达LPL mRNA。1.17雪旺细胞表现出可被肝素释放的脂解活性，该活性可被脂肪酶抑制剂四氢脂抑素以剂量依赖的方式抑制。用抗大鼠LPL抗血清预孵育1.17细胞后，可被肝素释放的脂解活性降低至未处理细胞中测得活性的<10%。为了研究LPL在雪旺细胞脂质代谢中的作用，将1.17细胞与乳化的[14C]三油精底物孵育长达24小时，并在存在抗大鼠LPL抗血清或免疫前血清的情况下，检测[14C]三油精放射性掺入各种细胞脂质中的情况。在添加放射性标记底物后2小时和6小时，抑制LPL活性使14C掺入细胞极性脂质、二酰甘油和胆固醇酯中的量减少>80%。在24小时时，用抗LPL抗血清或免疫前血清处理的细胞中，二酰甘油和胆固醇酯中的放射性相似，而14C掺入极性脂质中的量仍减少>60%。将极性脂质分离为单个脂质种类后发现，在所检测的磷脂种类中，三油精衍生的放射性掺入没有特定变化。这些结果表明，LPL介导的外源性三酰甘油水解是雪旺细胞游离脂肪酸的重要来源，因此可能在外周神经系统的髓鞘生物合成中起关键作用。
