Internalization of interleukin 2 is mediated by the beta chain of the high-affinity interleukin 2 receptor.
High-affinity IL-2-R correspond to a membrane receptor complex composed of two different IL-2-binding proteins, the Tac antigen (alpha chain) and a 70-75 kD beta chain. Using cell lines that express either the alpha or the beta protein, we demonstrate that IL-2 internalization occurs when ligand is bound to the isolated beta chain, but not when it is bound to the isolated alpha chain. The kinetics of IL-2 internalization mediated by the intermediate-affinity beta chain were nearly identical to those of the high-affinity alpha/beta heterodimer (t1/2 of 10-15 min), and each type of receptor targeted the bound IL-2 for intracellular degradation in lysosomes. The beta chain thus appeared to provide the essential element necessary for ligand internalization by both types of IL-2-R.
D000818:Animals; D000954:Antigens, Surface / Q000378:metabolism*; D004705:Endocytosis; D006801:Humans; D006922:Hylobates; D007376:Interleukin-2 / Q000378:metabolism*; D007700:Kinetics; D011485:Protein Binding; D011971:Receptors, Immunologic / Q000378:metabolism*; D015375:Receptors, Interleukin-2; D018127:Tumor Necrosis Factor Receptor Superfamily, Member 7
D000954:Antigens, Surface; D007376:Interleukin-2; D011971:Receptors, Immunologic; D015375:Receptors, Interleukin-2; D018127:Tumor Necrosis Factor Receptor Superfamily, Member 7