Characterization of the heterodimeric complex of human IL-2 receptor alpha.beta chains reconstituted in a mouse fibroblast cell line, L929.
The receptor for IL-2 has been known to exist in three forms on the basis of their affinities to IL-2: high, intermediate, and low affinity forms. Two IL-2R components have been identified as IL-2R alpha (p55, Tac Ag) and IL-2R beta (p70-75) chains, both bind IL-2 with low and intermediate affinities, respectively. Recently, we cloned human IL-2R beta chain cDNA and demonstrated that the cDNA product binds IL-2 with intermediate affinity and forms high affinity IL-2R with coexpressed IL-2R alpha chain in a human T cell line, Jurkat. In this study, we report the establishment of the mouse fibroblast transformants expressing either the IL-2R beta chain alone or both the IL-2R alpha and IL-2R beta chains. In contrast to lymphoid cells, significant IL-2 binding was not detected in the transformants expressing the IL-2R beta chain alone at IL-2 concentrations (50 pM to 10 nM) generally utilized. Nonetheless, the transformants expressing both IL-2R alpha and IL-2R beta chains displayed two forms of the IL-2R with high and low affinities to IL-2. However, neither IL-2 internalization nor signal transduction via the high affinity IL-2R complex were observed in the L929 transformants. Those findings suggest that the interaction of the IL-2R beta chain with the IL-2R alpha chain occurs in the absence of additional lymphoid specific component(s) to form high affinity IL-2R, but that this interaction is insufficient for IL-2 internalization and signal transduction just as observed in lymphoid cells. The experimental approach described here may allow further dissection of the molecular architecture of the IL-2R complex in the ligand binding, internalization, and signal transduction.
Institute for Molecular and Cellular Biology, Osaka University, Japan.
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S
Minamoto
H
H
Mori
M
M
Hatakeyama
T
T
Kono
T
T
Doi
T
T
Ide
T
T
Uede
T
T
Taniguchi
D000818:Animals; D002460:Cell Line; D003432:Cross-Linking Reagents; D004705:Endocytosis; D015870:Gene Expression; D007376:Interleukin-2 / Q000378:metabolism; D046911:Macromolecular Substances; D051379:Mice; D015375:Receptors, Interleukin-2 / Q000235:genetics / Q000502:physiology*; D013329:Structure-Activity Relationship; D014162:Transfection
D003432:Cross-Linking Reagents; D007376:Interleukin-2; D046911:Macromolecular Substances; D015375:Receptors, Interleukin-2