Abstract
Purpose:
Importins and exportins are proteins that carry out nuclear import and export of many proteins and RNA. However, their role in steroid-induced gene expression has yet to be characterized in the human trabecular meshwork. In the current study, we investigated the effects of dexamethasone treatment on importins a1, a7, b1, 2, 3, 5, 7, 8, and 13 and exportins 1, 4, 5, 6, and T.
Methods:
Stably-transduced RFP-GRalpha, human and bovine primary TM cell-lines were developed. Levels of importins and exportins in cells trated overnight with vehicle (ethanol) or DEX were studied using western blot in isolated nuclear and cytosolic fractions.
Results:
Bovine TM cell-lines have identical GRalpha and beta receptors to human TM cell-lines. DEX increased protein levels of importin b1 (involved in Smad import and ERAD retro-translocation for protein degradation), importin-3 (involved in mRNA transport), and Importin-7 (involved in Smad nuclear import). Also, DEX increased exportin-4 (involved in Smad export), Exportin-5 (involved in pre-miRNA export for maturation in the cytosol), and Exportin-6 (involved in export of actin).
Conclusions:
Mechanism of steroid-regulated gene expression is partially mediated through the importin/exportin network in the trabecular meshwork