Absence in glucocorticoid-resistant mouse lymphoma P1798 of a glucocorticoid receptor domain responsible for biological effects.

Glucocorticoid-resistant (CR), in contrast to glucocorticoid-sensitive (CS), mouse lymphoma P1798 was shown to lack antiglucocorticoid receptor immunoactivity. Antibodies raised against the purified rat liver glucocorticoid receptor (GR) cross-reacted with the GR from CS, but not with the GR from CR, P1798 lymphoma. Using highly specific antisera against the GR in an indirect competitive enzyme-linked immunosorbent assay, it was demonstrated that alpha-chymotrypsin digestion of the GR from CS P1798 lymphoma caused a separation of a "resistant-like" nonimmunogenic steroid and DNA-binding domain (Stokes' radius, 3.3 nm) from an immunoactive domain (Stokes' radius, 2.6 nm). In contrast to CS P1798 lymphoma, neither before nor after alpha-chymotrypsin digestion, immunoactivity could be found in the cytosol from CR P1798 lymphoma. This was assayed after chromatography on DNA-cellulose or gel filtration on Agarose A (0.5 m). These results suggest that the domain of the CS GR containing the immunoactive determinant(s), normally removed by limited proteolysis by alpha-chymotrypsin, appears to be missing in CR P1798 lymphoma cytosol. It seems that this domain plays an important role in the mechanism of action of glucocorticoids. This might suggest that a mutation has occurred affecting the genome resulting in defective transcription of the receptor gene(s) in CR P1798 lymphoma.