Endocrinology, Vol 113, 1528-1530, Copyright © 1983 by Endocrine Society

ARTICLES

Characterization of the glucocorticoid receptor translocated to the nucleus in intact AtT-20 mouse pituitary tumor cells at low temperatures

F Svec and J Williams

Although low temperatures retard the nuclear translocation of glucocorticoid-receptor complexes, they do not completely inhibit it. To gain insight into the mechanism of nuclear translocation, we determined the Stokes radius and surface charge density of the receptors bound to the nucleus at 0 C and compared them with the values obtained from standard preparations of activated and unactivated glucocorticoid receptors. Specifically, intact, viable AtT-20 cells were incubated at 0 C for 3 h with 10 nM tritiated triamcinolone acetonide and the nuclear receptor extracted with 0.3 M KCl/20 mM sodium molybdate. These nuclear receptors were found to elute from an Agarose A 1.5 m column with a Stokes radius identical to that of an "activated" receptor (6.4 nm) but eluted from a DEAE column at the same position as an "unactivated" species (0.17 M KCl). From these results we hypothesize that the change in receptor structure that leads to nuclear binding is a multistep process, and although the change in molecular size may be a prerequisite for nuclear binding, the change in surface charge is not.