Intracytoplasmic detection of the Tac (p55) chain of interleukin-2 receptor in pre-B leukemic cells associated with a constitutive expression of Tac mRNA.
The pre-B Reh-6 leukemic cells do not express membrane interleukin-2 (IL-2)-R alpha (Tac or p55) chain; however, their incubation with PMA induces the expression of both high and low affinity IL-2-R. Northern analysis of nonstimulated Reh-6 as well as leukemic cells from patients with acute B cell precursor lymphoblastic leukemia displayed a constitutive expression of p55 mRNA transcripts, which could be enhanced by PMA. Both actinomycin-D and cycloheximide could abrogate PMA-induced p55 membrane expression, suggesting the need for de novo mRNA and protein synthesis. The increased PMA-induced p55 mRNA accumulation was an early event (4 hr) and could be enhanced, specifically, by rIL-2 because anti-Tac moAb inhibited this rIL-2-mediated effect. Immunofluorescence and cross-linking studies using 125I-rIL-2 failed to reveal membrane-associated p55 protein on both Reh-6 and patients' leukemic cells. Conversely, immunogold staining and electron microscopy studies, revealed p55 immunoreactive molecules in the cytoplasm but not in the nucleus of all Reh-6 cells. Using a sensitive EIA, p55 molecules could be detected in cell lysates but not the culture supernatants of Reh-6 cells, suggesting that p55 was not released into the culture medium. These results indicate that constitutively expressed p55 mRNA on pre-B leukemic cells is translated into a relative immunoreactive protein that cannot be expressed on cell surface for unknown, yet, reasons.
Thanos
D
D
Faculty of Biology, Department of Molecular Biology, University of Crete, Iraklion, Greece.
Allouche
M
M
Sahraoui
Y
Y
Spanakis
E
E
Perraki
M
M
Papadogiorgaki
E
E
Galanopoulos
V
V
Papamatheakis
J
J
Georgoulias
V
V
D015152:Blotting, Northern; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line / Q000187:drug effects; D002462:Cell Membrane / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D015870:Gene Expression / Q000187:drug effects*; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism; D008854:Microscopy, Electron; D015452:Precursor B-Cell Lymphoblastic Leukemia-Lymphoma / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism*; D015375:Receptors, Interleukin-2 / Q000235:genetics* / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D008565:Membrane Proteins; D012333:RNA, Messenger; D015375:Receptors, Interleukin-2; D013755:Tetradecanoylphorbol Acetate