Co-internalization of the p55 and p70 subunits of the high-affinity human interleukin 2 receptor. Evidence for a stable ternary receptor complex.
The high-affinity IL-2-R complex is composed of at least two distinct IL-2-binding subunits, including p55 (Tac, IL-2-R alpha) and p70 (IL-2-R beta). Using a radiolabeled mAb specific for the p55 receptor subunit and cells expressing a homogeneous population of high-affinity binding sites, we demonstrate that p55 is co-internalized with p70 after IL-2 binding to the receptor complex. Endocytosis of p55 depends upon the presence of IL-2 in a form capable of effectively interacting with the p70 subunit. Whether IL-2 is required for high-affinity receptor assembly or triggering of the internalization of preassembled receptors remains unresolved. Together, these findings support the existence of a stable, high-affinity human IL-2-R membrane complex composed of at least the p55 and p70 receptor subunits and IL-2.
Fung
M R
MR
Howard Hughes Medical Institute, Duke University Medical Center, Durham, North Carolina 27710.
Ju
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Greene
W C
WC
D001665:Binding Sites; D002460:Cell Line; D004705:Endocytosis; D006801:Humans; D007376:Interleukin-2 / Q000378:metabolism; D046911:Macromolecular Substances; D008970:Molecular Weight; D015375:Receptors, Interleukin-2 / Q000502:physiology* / Q000648:ultrastructure; D013601:T-Lymphocytes / Q000502:physiology*
D007376:Interleukin-2; D046911:Macromolecular Substances; D015375:Receptors, Interleukin-2