Corticosteroids exert markedly diverse effects on development
differentiation
aging and regeneration in the nervous system. These effects are mediated via two receptor system in the brain
glucocorticoid receptor (GR) and mineralocorticoid receptor (MR). The expression of GR occurs in most neurons and glial cells throughout the brain
while MRs are localized mainly in the hippocampus. Although it is mostly accepted that GR is translocated into the nucleus from the cytoplasm only after ligand binding
the subcellular localization of MR is still quite controversial. To elucidate the intracellular trafficking of GR and MR in response to various conditioned in living cells
a chimera construct of a green fluorescent protein (GFP) and rat GR (GFP-GR) and MR (GFP-MR) were prepared. We transiently transfected the chimera construct into primary cultured rat hippocampal neurons
cortical glial cells
and non-neural cells such as COS-1 cells
and examined dynamic changes in subcellular localization of GFP-GR and GFP-MR in these cells. GFP-GR was predominantly localized in the cytoplasm in the absence of ligand
while GRP-MR was distributed in both cytoplasm and nucleus in the majority of the transfected cells without ligand. Corticosterone (CORT)
the principle corticosteroid of the rat
induced a rapid nuclear accumulation of GFP-GR and GFP-MR in all cell types used. Furthermore
we investigated the differential effects of CORT on the nuclear translocation pattern of corticosteroid receptors in single living cells co-transfected with cyan fluorescent protein (CFP)-GR and yellow fluorescent protein (YFP)-MR.Our findings clearly showed that the subcellular distributions of GFP-GR and GFP-MR are dynamically changed in response to extracellular and intracellular conditions
and that there are no conspicuous variations in the manner of trafficking of GFP-GR and GFP-MR between neural cells and non-neural cells. We also demonstrated that CORT-induced nuclear accumulation of CFP-GR and YFP-MR exhibited differential time-course under different ligand concentrations and cell types.
