[Structure and function of IL-2 receptor subunits].

IL-2 regulates growth and differentiation of various types of cells in the immune system via its interaction with IL-2 receptor (IL-2R). The high and intermediate-affinity IL-2Rs, which consist of the alpha beta gamma heterotrimer complex and the beta gamma heterodimer complex, respectively, harbor the function of the intracellular signal transduction, indicating that the beta and gamma chains are indispensable for the signal transduction but not the alpha chain. The reconstitution studies of IL-2Rs with alpha, beta and gamma chain genes demonstrated that each subunit has potential for altering the affinity of the receptor, and the cytoplasmic domains of the beta and gamma chains participate in signal transduction in terms of cell growth, activation of alpha tyrosine kinase and enhancement of c-myc, c-fos and c-jun transcription. The region containing the SH2 homologous sequence of the gamma chain should have a critical function for signal transduction. On the other hand, common subunits are known to be shared among receptors for IL-3, IL-5 and GM-CSF, and receptors for IL-6, LIF, OSM and LIF. We have demonstrated that the monoclonal antibody specific for the IL-2R gamma chain completely inhibited not only IL-2-dependent cell growth but also IL-4-dependent, IL-7-dependent, and IL-9-dependent cell growth, suggesting that the gamma chain is possibly shared among receptors for IL-2, IL-4, IL-7 and IL-9. Impairment of the gamma chain function is considered to be closely related to human XSCID characterized by profound T cell defect.(ABSTRACT TRUNCATED AT 250 WORDS)