Changes in expression and function of syncytin and its receptor, amino acid transport system B(0) (ASCT2), in human placental choriocarcinoma BeWo cells during syncytialization.

Relative abundance of mRNAs encoding syncytin and its receptor, amino acid transport system B(0), and activity of amino acid transport thought to be through this system have been studied in parallel in a cell model of syncytialization (BeWo cell following forskolin treatment). Relative mRNA abundance (determined by reverse transcription-polymerase chain reaction) for syncytin showed stimulation by forskolin. In contrast, the level of amino acid transporter B(0) mRNA expression was lower in forskolin treated cells. Na(+)-dependent alpha-(methylamino)isobutyric acid insensitive L -alanine transport was similarly decreased significantly in cells treated with forskolin suggesting that there is modulation of cell surface expression of the syncytin receptor associated with syncytialization.