Cloning of a unique lipase from endothelial cells extends the lipase gene family

A new lipoprotein lipase-like gene has been cloned from endothelial cells t hrough a subtraction methodology aimed at characterizing genes that are exp ressed with in vitro differentiation of this cell type. The conceptual endo thelial cell-derived lipase protein contains 500 amino acids, including an 18-amino acid hydrophobic signal sequence, and is 44% identical to lipoprot ein lipase and 41% identical to hepatic lipase. Comparison of primary seque nce to that of lipoprotein and hepatic lipase reveals conservation of the s erine, aspartic acid, and histidine catalytic residues as well as the 10 cy steine residues involved in disulfide bond formation. Expression was identi fied in cultured human umbilical vein endothelial cells, human coronary art ery endothelial cells, and murine endothelial-like yolk sac cells by Northe rn blot. In addition, Northern blot and in situ hybridization analysis reve aled expression of the endothelial-derived lipase in placenta, liver, lung, ovary, thyroid gland, and testis. A c-Myc-tagged protein secreted from tra nsfected COS7 cells had phospholipase Al activity but no triglyceride lipas e activity. Its tissue-restricted pattern of expression and its ability to be expressed by endothelial cells, suggests that endothelial cell-derived l ipase may have unique functions in lipoprotein metabolism and in vascular d isease.