Charge heterogeneity in wildtype and variant glucocorticoid receptors.
Two-dimensional electrophoresis was used to examine charge heterogeneity in glucocorticoid receptors (GCRs) from sublines of the thymic-derived, mouse P1798 lymphosarcoma which were sensitive (S) or resistant (R) to glucocorticoid-mediated apoptosis. Previous work had identified the 97 kDa wildtype GCR (WT-GCR) in S cells and two variant GCRs in R cells: a 45 kDa, steroid-binding truncated GCR (TR-GCR), and a 97 kDa non steroid-binding GCR (NSB-GCR). Using denaturing isoelectric focusing, we now show that S cells as well as adult mouse thymus gland also express the NSB-GCR at pI 5.6 in addition to the WT-GCR which resolves between pH 5.9-7.1. Thus, the NSB-GCR is detected in steroid-sensitive cells and is not unique to R cells. Separation of receptors by native isoelectric focusing suggested that the TR-GCR in R cells resolved at a single, high pI (8.1) relative to the WT-GCR which resolved in a broad range (pI 5.8-8.0). The high pI of the TR-GCR may alter its functional activity thereby contributing to the resistance phenotype.
Rowan
B G
BG
Department of Experimental Therapeutics, Roswell Park Cancer Institute, Buffalo, NY 14263, USA.
Ip
M M
MM
D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D003907:Dexamethasone / Q000378:metabolism / Q000494:pharmacology; D004351:Drug Resistance; D015180:Electrophoresis, Gel, Two-Dimensional; D007525:Isoelectric Focusing; D008228:Lymphoma, Non-Hodgkin / Q000473:pathology; D051379:Mice; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009363:Neoplasm Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D011965:Receptors, Glucocorticoid / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D014407:Tumor Cells, Cultured / Q000187:drug effects
D009363:Neoplasm Proteins; D011965:Receptors, Glucocorticoid; D003907:Dexamethasone