Formation of high affinity IL-2 receptors is dependent on a nonligand binding region of the alpha subunit.
The IL-2R is composed of three subunits, alpha, beta, and gamma, each of which individually contributes to binding IL-2 in the high affinity IL-2R. The molecular mechanism by which the high affinity IL-2R assembles has not been established. Previous studies have shown that human IL-2R subunits form high affinity hybrid IL-2R when mixed with appropriate mouse IL-2R subunits, but the efficiency of this process is not known. In this study, we produced stable cell lines that expressed hybrid human/mouse IL-2R, comprised of heterologous alpha- and beta-chains, to determine the contribution of individual receptor subunits in stabilizing the high affinity IL-2R. Quantitative ligand binding studies and FACS analysis were performed for EL4J cells that expressed hybrid mouse/human IL-2R, and these data were compared with those of cells that expressed homologous mouse IL-2R subunits. EL4J cells that expressed human beta/mouse alpha formed high affinity IL-2R, comparable with cells that express homologous mouse alpha and beta subunits. In contrast, EL4J cells that expressed homologous mouse IL-2R contained an approximately 10-fold higher level of high affinity IL-2R than did EL4J cells that expressed heterologous human alpha/mouse beta IL-2R. This difference was not accounted for by lower levels of human alpha-chains in these cell lines or lower expression of the mouse IL-2R beta or gamma subunits. These results suggest that amino acid sequences within the alpha subunit, distinct from the IL-2 binding site, are important in the assembly and stabilization of the high affinity IL-2R.
Gutgsell
N S
NS
Department of Microbiology and Immunology, University of Miami School of Medicine, FL 33101.
Malek
T R
TR
D000818:Animals; D000911:Antibodies, Monoclonal; D001665:Binding Sites / Q000276:immunology; D005434:Flow Cytometry; D006801:Humans; D007376:Interleukin-2 / Q000378:metabolism*; D051379:Mice; D015375:Receptors, Interleukin-2 / Q000096:biosynthesis / Q000737:chemistry* / Q000378:metabolism*; D011994:Recombinant Proteins / Q000096:biosynthesis; D014162:Transfection / Q000235:genetics; D014407:Tumor Cells, Cultured
D000911:Antibodies, Monoclonal; D007376:Interleukin-2; D015375:Receptors, Interleukin-2; D011994:Recombinant Proteins