B. Gametchu et al., Plasma membrane-resident glucocorticoid receptors in rodent lymphoma and human leukemia models, STEROIDS, 64(1-2), 1999, pp. 107-119
The presence of the glucocorticoid (GC) receptor is required for GC-evoked
apoptosis. However, the explicit mechanism of involvement of this receptor
continues to be debated. Employing the murine (S-49) and human (CCRF-CEM) l
ymphoid cell lines, we demonstrated that this response requires a specializ
ed form of the glucocorticoid receptor (GR) that resides in the plasma memb
rane (mGR). Our studies of mGR have been done in our stable mGR-enriched (b
y sequential cell separation-immunopanning, fluorescent cell sorting, soft
agar cloning) S-49 and CCRF-CEM cells. Direct and indirect immunofluorescen
t studies of live intact cells showed GR-specific periplasma membrane stain
ing. Immunoanalysis by Flow cytometry demonstrated abundant mGR in mGR(++)
cells, but only barely detectable mGR in mGR(--) cells. Western blot and au
toradiographic analyses of immunoprecipitated membrane extracts from these
cells show they contain Immunoreactive and competitively labeled high M-r,
receptor ranging from 94 to 150 kDa. Using mGR(++) CCRF-CEM cells and three
synchronization procedures (double thymidine, thymidine/colcemid, and colc
emid blocks), we have investigated the influence of cell cycle on regulatio
n and function of mGR. Both mGR expression and GC-mediated lymphocytolysis
appear highest at late S-G2/M. Analysis of mGR in lymphocytes of several le
ukemic patients indicated differences in the levels of receptor expression.
These findings might provide diagnostic clues about patients' differential
response to steroid therapy and potential therapeutic avenues for effectiv
e treatment of hormone-responsive leukemic patients. (C) 1999 Elsevier Scie
nce Inc. All rights reserved.