title: Phospholipid scramblase 1 (PLSCR1) in villous trophoblast of the human placenta.
abstract: A crucial factor for effective villous trophoblast fusion in the human placenta is the transient deregulation of plasma membrane phospholipid asymmetry leading to externalization of phosphatidylserine to the outer membrane leaflet. Screening of scramblase family members implicated in the collapse of phospholipid asymmetry revealed that phospholipid scramblase 1 (PLSCR1) is strongly expressed in villous trophoblast. Therefore, we assessed the putative role of PLSCR1 in villous trophoblast fusion. Spatio-temporal analysis in first trimester and term placenta showed abundant expression of PLSCR1 in syncytiotrophoblast, macrophages and endothelial cells, while it was virtually absent in villous cytotrophoblasts. For functional studies, BeWo cells, isolated primary term trophoblasts and first trimester villous explants were used. During forskolin-mediated BeWo cell differentiation, neither PLSCR1 mRNA nor protein levels showed significant changes. In contrast, when primary trophoblasts were stimulated with Br-cAMP, a decrease in PLSCR1 mRNA and protein expression was observed. To elucidate a role for PLSCR1 in syncytialization, we used RNA interference and a chemical scramblase inhibitor, R5421 (ethanedioic acid). Silencing of PLSCR1 using siRNA had no effects while inhibition of scramblase activity by R5421 increased GCM-1 mRNA expression, beta-hCG protein secretion and fusion rates of BeWo cells. In primary trophoblasts and villous explants, no effects of siRNA or R5421 treatment on fusion were detected. This study provides data on PLSCR1 localization and general expression in the human placenta. The data make it tempting to speculate on a role of PLSCR1 in negatively regulating trophoblast fusion.
authors.affiliation: Institute of Cell Biology, Histology and Embryology, Medical University of Graz, Harrachgasse 21/VII, 8010, Graz, Austria.
authors.forename: Veronika M
authors.initials: VM
authors.lastname: Berghold
authors.forename: Martin
authors.initials: M
authors.lastname: Gauster
authors.forename: Denise G
authors.initials: DG
authors.lastname: Hemmings
authors.forename: Gerit
authors.initials: G
authors.lastname: Moser
authors.forename: Julia
authors.initials: J
authors.lastname: Kremshofer
authors.forename: Monika
authors.initials: M
authors.lastname: Siwetz
authors.forename: Monika
authors.initials: M
authors.lastname: Sundl
authors.forename: Berthold
authors.initials: B
authors.lastname: Huppertz
mesh_terms: D002454:Cell Differentiation; D002459:Cell Fusion; D002460:Cell Line; D006063:Chorionic Gonadotropin / Q000378:metabolism; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D018507:Gene Expression Regulation, Developmental; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D049294:Phospholipid Transfer Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D034622:RNA Interference; D015398:Signal Transduction; D013997:Time Factors; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014162:Transfection; D014327:Trophoblasts / Q000187:drug effects / Q000201:enzymology*
chemical_list: D006063:Chorionic Gonadotropin; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; C491089:GCM1 protein, human; D009687:Nuclear Proteins; C493422:PLSCR1 protein, human; D049294:Phospholipid Transfer Proteins; D014157:Transcription Factors