Complex human glucocorticoid receptor dim mutations define glucocorticoid induced apoptotic resistance in bone cells.

A mutation in the D-loop of the second zinc finger of the DNA-binding domain of the human glucocorticoid receptor (hGR), A458T (GR(dim)), has been suggested to be essential for dimerization and DNA binding of the GR, and genetically altered GR(dim) mice survive, whereas murine GR knockout mice die. Interestingly, thymocytes isolated from the GR(dim) mice were reported to be resistant to glucocorticoid-induced apoptosis. To further evaluate the dim mutations in glucocorticoid-induced apoptosis, we stably expressed either the hGR(dim) (A458T) or the hGR(dim4) (A458T, R460D, D462C, and N454D) mutant receptors in human osteosarcoma (U-2 OS) cells that are devoid of hGR and unresponsive to glucocorticoids.