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 ha ve been identified by molecular cloning, the biochemical identity of t hese 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 th e 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, ga mma(c), and truncated beta subunits or mutant EL4 cells, which selecti vely lacked cell surface gamma(c), revealed that no other material mig rated 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 be ta and gamma(c) subunits appear to be the sole IL-2R constituents of t hese 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-polyac rylamide gel electrophoresis under nonreducing conditions, suggesting a more compact structure for gamma(c) as a result of intrachain disulf ide bonds. The primary posttranslational modification of the mouse bet a and gamma(c) subunits is N-linked glycosylation. These biochemical s tudies reconcile past uncertainties concerning the subunit composition of the mouse IL-2R and are consistent with a model of the IL-2R conta ining only three subunits.