Previous results using 293-EcR cells with ecdysone-inducible 15-LOX-1, when supplemented with an appropriate substrate, like arachidonate, show an inhibition of the selenoprotein thioredoxin reductase activity by ~50% (Yu et al. 2004). This raised the question of whether other selenoenzymes might demonstrate altered expression under similar conditions. Quantitative PCR experiments performed using 293-EcR cells with stable, ecdysone-inducible 15-LOX-1, as well as the control cell lines with inducible ΔIle662 15-LOX-1, and β-galactosidase, demonstrated enhanced expression of SEPP1 following ponasterone A treatment (Figure 1). Since SEPP1 demonstrated increased expression in all these cell lines, even without substrate for the 15-LOX-1, it is likely that the changes in SEPP1 expression resulted from components of the ecdysone-inducible system rather than a response to 15-LOX-1 catalysis.
