Interleukin 1 alpha and interleukin 1 beta bind to the same receptor on T cells.
Pure, E. coli-derived recombinant murine interleukin 1 alpha (IL 1 alpha) was labeled with 125I and used for receptor binding studies. The 125I-IL 1 binds to murine EL-4 thymoma cells in a specific and saturable manner. Scatchard plot analysis for binding studies carried out at 4 degrees C reveals a single type of high affinity binding site with an apparent dissociation constant of approximately 2.6 X 10(-10) M and the presence of approximately 1200 binding sites per cell. The rate of association of the 125I-IL 1 with EL-4 cells is slow, requiring more than 3 h to reach apparent steady state at 4 degrees C. Cell-bound 125I-IL 1 cannot be dissociated from EL-4 cells upon removal of unbound 125I-IL 1 and incubation of the cells at 4 degrees C in the presence or absence of unlabeled IL 1. Unlabeled recombinant murine IL 1 competes for 125I-IL 1 binding in a dose-dependent manner, whereas interferon-alpha A, interleukin 2 (IL 2), epidermal growth factor, and nerve growth factor have no effect. The 125I-IL 1 binding site is sensitive to trypsin, suggesting that it is localized on the cell surface. We have also examined the ability of purified recombinant human IL 1 alpha and IL 1 beta to compete for binding of the radiolabeled murine IL 1 to its receptor and to stimulate IL 2 production by EL-4 cells. Previous reports have shown that human IL 1 alpha is approximately 60% homologous in amino acid sequence with murine IL 1, but that human IL 1 beta is only about 25% homologous with either murine IL 1 or human IL 1 alpha. Despite these marked differences, however, we report here that both human IL 1 proteins are able to recognize the same binding site as mouse IL 1. In addition, murine as well as both human IL 1 proteins stimulate IL 2 production by EL-4 cells.
D000818:Animals; D001667:Binding, Competitive; D006801:Humans; D007375:Interleukin-1 / Q000378:metabolism* / Q000502:physiology; D007700:Kinetics; D051379:Mice; D011948:Receptors, Antigen, T-Cell / Q000032:analysis / Q000187:drug effects / Q000378:metabolism*; D011971:Receptors, Immunologic / Q000032:analysis / Q000187:drug effects / Q000378:metabolism*; D017472:Receptors, Interleukin-1; D011994:Recombinant Proteins / Q000378:metabolism; D013601:T-Lymphocytes / Q000378:metabolism*
D007375:Interleukin-1; D011948:Receptors, Antigen, T-Cell; D011971:Receptors, Immunologic; D017472:Receptors, Interleukin-1; D011994:Recombinant Proteins