Abstract
BackgroundStAR-related lipid transfer domain containing 7 (StarD7) is a member of the START-domain protein family whose function still remains unclear. Our data from an explorative microarray assay performed with mRNAs from StarD7 siRNA-transfected JEG-3 cells indicated that ABCG2 (ATP-binding cassette sub-family G member 2) was one of the most abundantly downregulated mRNAs.Methodology/Principal FindingsHere, we have confirmed that knocking down StarD7 mRNA lead to a decrease in the xenobiotic/lipid transporter ABCG2 at both the mRNA and protein levels (−26.4% and −41%, p<0.05, at 48 h of culture, respectively). Also a concomitant reduction in phospholipid synthesis, bromodeoxyuridine (BrdU) uptake and 3H-thymidine incorporation was detected. Wound healing and transwell assays revealed that JEG-3 cell migration was significantly diminished (p<0.05). Conversely, biochemical differentiation markers such as human chorionic gonadotrophin β-subunit (βhCG) protein synthesis and secretion as well as βhCG and syncytin-1 mRNAs were increased approximately 2-fold. In addition, desmoplakin immunostaining suggested that there was a reduction of intercellular desmosomes between adjacent JEG-3 cells after knocking down StarD7.Conclusions/SignificanceAltogether these findings provide evidence for a role of StarD7 in cell physiology indicating that StarD7 modulates ABCG2 multidrug transporter level, cell migration, proliferation, and biochemical and morphological differentiation marker expression in a human trophoblast cell model.
Highlights
StAR-related lipid transfer domain containing 7 (StarD7) belongs to the family of START proteins ubiquitously expressed, which are implicated in lipid transport, metabolism, and signaling [1,2,3]
We demonstrated that the regulation of StarD7 gene expression in JEG-3 cells occurs through a steroidogenic transcription factor 1 (SF-1) and b-catenin-mediated activation mechanism that synergistically activate StarD7 promoter [9,10]
StarD7 siRNA Decreases ABCG2 mRNA and Protein Levels To elucidate the impact of StarD7 siRNA on ABCG2 expression, JEG-3 cells were transfected with two different sets of double-stranded siRNA designed against different sequences of the StarD7 mRNA (Table 1)
Summary
StarD7 belongs to the family of START proteins ubiquitously expressed, which are implicated in lipid transport, metabolism, and signaling [1,2,3]. In order to get insight into the function of StarD7 in cell physiology, exploratory differential gene expression analysis of JEG-3 cells transfected with StarD7 siRNA was performed by microarray experiments. Data analysis indicated that ABCG2 was one of the most abundantly downregulated mRNAs [11]. StAR-related lipid transfer domain containing 7 (StarD7) is a member of the START-domain protein family whose function still remains unclear. Our data from an explorative microarray assay performed with mRNAs from StarD7 siRNA-transfected JEG-3 cells indicated that ABCG2 (ATP-binding cassette sub-family G member 2) was one of the most abundantly downregulated mRNAs
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