BIOCHEMICAL IDENTITY AND CHARACTERIZATION OF THE MOUSE INTERLEUKIN-2 RECEPTOR-BETA AND GAMMA(C) SUBUNITS

Although the mouse IL-2 receptor (IL-2R) beta and gamma(c) subunits have been identified by molecular cloning, the biochemical identity of these subunits has not yet been established. In the present study, the mouse IL-2R was biochemically characterized from cell lines expressing normal and aberrant IL-2R. Using novel monoclonal antibodies specific for the beta or gamma(c) subunits, we established that the M(r) of the beta chain is 90,000-100,000 and that of the gamma(c) subunit is 75,000-80,000. Analysis of transfected EL4 cells that expressed alpha, gamma(c), and truncated beta subunits or mutant EL4 cells, which selectively lacked cell surface gamma(c), revealed that no other material migrated to a position on SDS-PAGE characteristic of IL-2/IL-2R beta and IL-2/IL-2R gamma(c) cross-linked complexes, respectively. Thus, the beta and gamma(c) subunits appear to be the sole IL-2R constituents of these IL-2 cross-linked complexes. The IL-2/IL-2R gamma(c), but not the IL-2/IL-2R beta, complex exhibited enhanced mobility after SDS-polyacrylamide gel electrophoresis under nonreducing conditions, suggesting a more compact structure for gamma(c) as a result of intrachain disulfide bonds. The primary posttranslational modification of the mouse beta and gamma(c) subunits is N-linked glycosylation. These biochemical studies reconcile past uncertainties concerning the subunit composition of the mouse IL-2R and are consistent with a model of the IL-2R containing only three subunits.