Defining the functional binding sites of interleukin 12 receptor ?1 and interleukin 23 receptor to Janus kinases.

ABSTRACT: The interleukin (IL)-12-type cytokines IL-12 and IL-23 are involved in T-helper (Th) 1 and Th17 immunity, respectively. They share the IL-12 receptor ?1 (IL-12R?1) as one component of their receptor signaling complexes, with IL-12R?2 as second receptor for IL-12 and IL-23R for IL-23 signal transduction. Stimulation with IL-12 and IL-23 results in activation of receptor-associated Janus kinases (Jak) and phosphorylation of STAT proteins in target cells. The Janus kinase tyrosine kinase (Tyk) 2 associates with IL-12R?1, whereas Jak2 binds to IL-23R and also to IL-12R?2. Receptor association of Jak2 is mediated by Box1 and Box2 motifs located within the intracellular domain of the receptor chains. Here we define the Box1 and Box2 motifs in IL-12R?1 and an unusual Jak2-binding site in IL-23R by the use of deletion and site-directed mutagenesis. Our data show that nonfunctional box motifs abolish IL-12- and IL-23-induced STAT3 phosphorylation and cytokine-dependent proliferation of Ba/F3 cells. Coimmunoprecipitation of Tyk2 by IL-12R?1 and Jak2 by IL?23R supported these findings. In addition, our data demonstrate that association of Jak2 with IL-23R is mandatory for IL-12 and/or IL-23 signaling, whereas Tyk2 seems to be dispensable.

SUBMITTER: Floss DM 

PROVIDER: S-EPMC4945146 | biostudies-literature | 2016 Jul

REPOSITORIES: biostudies-literature