Expression of the human IL-2 receptor on lymphocytes involves rapid turnover of its p55 alpha-subunit (Tac).
Upon mitogenic stimulation, both mRNA encoding the p55 alpha-subunit (Tac) of the human IL-2R alpha and IL-2R alpha protein are induced and expressed in tonsil lymphocyte populations over several days. Using a quantitative dot-blot immunoassay for the IL-2R alpha subunit, a rapid disappearance of this polypeptide from cells is demonstrated in the presence of the translation inhibitor, cycloheximide. The half-life of IL-2R alpha subunit protein is 2 to 3 h. This decline in cell-associated IL-2R alpha subunit is matched by a rapid decline in IL-2R alpha on the cell surface and is not accompanied by any increase in soluble IL-2R alpha protein. Long term expression of the IL-2R on the cell surface is thus the result of continual synthesis and rapid breakdown of IL-2R alpha chains in the cell. Steady state expression of the IL-2R after an immune stimulus hence depends upon continuous expression of the IL-2R alpha subunit gene. Rapid turnover of the unstable alpha-subunit on the cell surface provides a novel mechanism for sensitive control of functional IL-2R expression.
Department of Molecular Virology, Hebrew University-Hadassah Medical School, Jerusalem, Israel.
D
D
Sayar
M
M
Ketzinel
L
L
Gerez
C
C
Silberberg
A
A
Reshef
R
R
Kaempfer
D015152:Blotting, Northern; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D006801:Humans; D066298:In Vitro Techniques; D008214:Lymphocytes / Q000378:metabolism*; D046911:Macromolecular Substances; D012333:RNA, Messenger / Q000235:genetics; D015375:Receptors, Interleukin-2 / Q000235:genetics / Q000378:metabolism*; D013997:Time Factors
D046911:Macromolecular Substances; D012333:RNA, Messenger; D015375:Receptors, Interleukin-2