Maximizing Production of Estrogen Receptor β with the Baculovirus Expression System

Abstract

Steroid hormone/nuclear receptor expression in cultured insect cell lines is routinely driven by a baculovirus vector. An advantage of the baculovirus production of these receptors is that large amounts of functional receptors are obtained for subsequent in vitro studies. Most laboratories produce nuclear receptors in Spodoptera frugiperda (Sf)9 cells. However, no one has determined whether this cell line is optimal for the production of any nuclear receptor. We compared the time course and level of estrogen receptor β (ERβ) production from a baculovirus in two S. frugiperda cell lines, IPLB-SF21AE (Sf21) and Sf9, and two Trichloplusia ni cell lines, Tn368 and BTITN5b1-4 (High FiveTM). Cells were harvested at various times (0.5–5 days) after infection. ERβ expression and activity was determined by specific [3H]estradiol (E2) binding, Western blot analysis, and estrogen response element (ERE) binding in vitro. The highest functional, bioactive ERβ expression both at the earliest time after infection and in the amount of ERβ produced/cell was with the Sf21 cell line. Baculovirus expressed ERβ-bound EREs with high affinity in a DNA sequence-dependent manner. We conclude that Sf21 cells are the best-suited cells for ERβ production.