CIS associates with the interleukin-2 receptor beta chain and inhibits interleukin-2-dependent signaling

CIS is a cytokine-induced SH2-containing protein that was originally cloned as an interleukin (IL)-3-inducible gene. CIS is known to associate with th e IL-3 receptor beta chain and erythropoietin receptor and to inhibit signa ling mediated by IL-3 and erythropoietin. We now demonstrate that CLS also interacts with the IL-2 receptor beta chain (IL-2R beta), This interaction requires the A region of IL-2R beta (residues 313-382), which also mediates the association of IL-2R beta with Lck and Jak3. Correspondingly, CIS inhi bits functions associated with both of these kinases: Lck-mediated phosphor ylation of IL-2R beta and IL-2-mediated activation of Stat5. Thus, we demon strate that CIS can negatively control at least two independent IL-2 signal ing pathways. Although a functional SH2 binding domain of CIS was not requi red for its interaction with IL-2R beta in vitro, its phosphotyrosine bindi ng capability was essential for the inhibitory action of CIS. On this basis , we have generated a mutant form of CIS protein with an altered SH2 domain that acts as a dominant negative and should prove useful in further unders tanding CIS action.