Lindegaard Marie L S, Olivecrona Gunilla, Christoffersen Christina, Kratky Dagmar, Hannibal Jens, Petersen Bodil L, Zechner Rudolf, Damm Peter, Nielsen Lars B
Department of Clinical Biochemistry, Rigshospitalet, Bispebjerg Hospital, University of Copenhagen, Copenhagen, Denmark.
J Lipid Res. 2005 Nov;46(11):2339-46. doi: 10.1194/jlr.M500277-JLR200. Epub 2005 Sep 8.
Placenta expresses various lipase activities. However, a detailed characterization of the involved genes and proteins is lacking. In this study, we compared the expression of endothelial lipase (EL) and LPL in human term placenta. When placental protein extracts were separated by heparin-Sepharose affinity chromatography, the EL protein eluted as a single peak without detectable phospholipid or triglyceride (TG) lipase activity. The major portion of LPL protein eluted slightly after EL. This peak also had no lipase activity and most likely contained monomeric LPL. Fractions eluting at a higher NaCl concentration contained small amounts of LPL protein (most likely dimeric LPL) and had substantial TG lipase activity. In situ hybridization studies showed EL mRNA expression in syncytiotrophoblasts and endothelial cells and LPL mRNA in syncytiotrophoblasts. In contrast, immunohistochemistry showed EL and LPL protein associated with both cell types. In mouse placentas, lack of LPL expression resulted in increased EL mRNA expression. These results suggest that the cellular expression of EL and LPL in human placenta is different. Nevertheless, the two lipases might have overlapping functions in the mouse placenta. Our data also suggest that the major portions of both proteins are stored in an inactive form in human term placenta.
胎盘表达多种脂肪酶活性。然而，目前尚缺乏对相关基因和蛋白质的详细表征。在本研究中，我们比较了人足月胎盘中内皮脂肪酶（EL）和脂蛋白脂肪酶（LPL）的表达。当胎盘蛋白提取物通过肝素 - 琼脂糖亲和层析分离时，EL蛋白以单一峰洗脱，未检测到磷脂或甘油三酯（TG）脂肪酶活性。LPL蛋白的主要部分在EL之后稍有洗脱。该峰也没有脂肪酶活性，很可能含有单体LPL。在较高NaCl浓度下洗脱的组分含有少量LPL蛋白（很可能是二聚体LPL），并具有大量TG脂肪酶活性。原位杂交研究显示，合体滋养层细胞和内皮细胞中有EL mRNA表达，合体滋养层细胞中有LPL mRNA表达。相比之下，免疫组织化学显示EL和LPL蛋白与这两种细胞类型均相关。在小鼠胎盘中，LPL表达缺失导致EL mRNA表达增加。这些结果表明，人胎盘中EL和LPL的细胞表达不同。然而，这两种脂肪酶在小鼠胎盘中可能具有重叠功能。我们的数据还表明，这两种蛋白质的主要部分在人足月胎盘中以无活性形式储存。
