Two Distinct Domains Within the N-Terminal Region of Janus Kinase 1 Intreact with Cytokine Receptors

摘要

The interaction between receptors and kinases of the Janes kinase (Jak) family is critical for signaling by growth factors, cytokines, and IFNs. Therefore, the characterization of the domains involved in these interactions is pivotal not only in understanding kinase activation but also in the development of drugs that mimic or inhibit signaling. In this report, we have characterized the domains of Jak1 required to associate with distinct cytokine receptor subunits: IFN-alphaRbetaL, IFN-gammaRalpha, IL-10Ralpha, IL-2Rbeta, and IL-4Ralpha. We demonstrate that two regions of Jak1 are necessary for the interaction with cytokine receptors. First, a common N-terminal region that includes Jak homology (JH) domain 7 and the first 19 aa of JH6, and, second, a C-terminal region (JH6-3) that was different for distinct receptors. The contribution of the two different regions of Jak1 to cytokine receptor binding was also variable. Deletion of JH7-6 impaired the associated of IL-2Rbeta and IL-4Ralpha chains with Jak1 but did not have a major impact on the binding of Jak1 to IFN-alphaRbetaL or IL-10Ralpha. Interestingly, regardless of the effect on receptor binding removal of JH7-6 completely abrogated kinase activation, indicating that this domain is required for ligand-driven kinase activation and, thus, for proper signaling through cytokine receptors.