Novel interleukin-2 receptor subunit detected by cross-linking under high-affinity conditions.
Interleukin-2 (IL-2) binds to both high- and low-affinity classes of IL-2 receptors on activated T lymphocytes. Only the high-affinity receptors are involved in receptor-mediated endocytosis and normally transduce the mitogenic signals of IL-2; however, the structural features distinguishing the high- and low-affinity receptors are unknown. When 125I-labeled IL-2 was chemically cross-linked to activated human T lymphocytes, two major bands were identified. First, as predicted, a 68- to 72-kilodalton band, consisting of IL-2 (15.5 kilodaltons) cross-linked to the IL-2 receptor (55 kilodaltons), was observed. Second, an unpredicted 85- to 92-kilodalton moiety was detected. This band was not present when IL-2 was cross-linked to transfected C127 cells, which exclusively express low-affinity receptors. The data presented are most consistent with the existence of a 70- to 77-kilodalton glycoprotein subunit (p70) which, upon associating with the 55-kilodalton low-affinity receptor (p55), transforms it into a high-affinity site. It is proposed that p55 and p70 be referred to as the alpha and beta subunits, respectively, of the high-affinity IL-2 receptor.
D000818:Animals; D002460:Cell Line; D003432:Cross-Linking Reagents; D006801:Humans; D007163:Immunosorbent Techniques; D007376:Interleukin-2 / Q000378:metabolism; D007945:Leukemia, Lymphoid / Q000378:metabolism; D008213:Lymphocyte Activation; D051379:Mice; D008970:Molecular Weight; D011971:Receptors, Immunologic / Q000378:metabolism*; D015375:Receptors, Interleukin-2; D013388:Succinimides; D013601:T-Lymphocytes / Q000378:metabolism
D003432:Cross-Linking Reagents; D007376:Interleukin-2; D011971:Receptors, Immunologic; D015375:Receptors, Interleukin-2; D013388:Succinimides; C019358:disuccinimidyl suberate