出版社：American Society for Biochemistry and Molecular Biology
摘要：Placenta expresses various lipase activities. However, a detailedcharacterization 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 proteinextracts were separated by heparin-Sepharose affinity chromatography,the EL protein eluted as a single peak without detectable phospholipidor triglyceride (TG) lipase activity. The major portion of LPLprotein eluted slightly after EL. This peak also had no lipaseactivity and most likely contained monomeric LPL. Fractionseluting at a higher NaCl concentration contained small amountsof LPL protein (most likely dimeric LPL) and had substantialTG lipase activity. In situ hybridization studies showed ELmRNA expression in syncytiotrophoblasts and endothelial cellsand LPL mRNA in syncytiotrophoblasts. In contrast, immunohistochemistryshowed EL and LPL protein associated with both cell types. Inmouse placentas, lack of LPL expression resulted in increasedEL mRNA expression.
These results suggest that the cellular expression of EL andLPL in human placenta is different. Nevertheless, the two lipasesmight have overlapping functions in the mouse placenta. Ourdata also suggest that the major portions of both proteins arestored in an inactive form in human term placenta.Abbreviations: DIG, digoxigenin; EL, endothelial lipase; TG, triglyceride
Supplementary key words lipid transport • in situ hybridization • immunohistochemistry • lipase activity • lipoprotein lipase deficiency
