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JAK1 N‐terminus binds to conserved box 1 and box 2 motifs of cytokine receptor common β subunit but signal activation requires JAK1 C‐terminus
Author(s) -
Huang HueiMei,
Lee YaLi,
Chang TingWei
Publication year - 2006
Publication title -
journal of cellular biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.028
H-Index - 165
eISSN - 1097-4644
pISSN - 0730-2312
DOI - 10.1002/jcb.20942
Subject(s) - fusion protein , janus kinase 1 , janus kinase , transmembrane protein , microbiology and biotechnology , transmembrane domain , cytokine receptor , signal transduction , protein subunit , receptor , chemistry , biology , biochemistry , gene , recombinant dna
The human interleukin‐3 receptor (hIL‐3R) consists of a unique α subunit (hIL‐3Rα) and a common β subunit (βc). Binding of IL‐3 to IL‐3R activates Janus kinases JAK1 and JAK2. Our previously study showed that JAK2 and JAK1 were constitutively associated with the hIL‐3Rα and βc subunits, respectively. In this study, we further demonstrate that JAK2 binds to the intracellular domain of hIL‐3Rα and JAK1 binds to the Box 1 and Box 2 motifs of βc using GST‐hIL‐3R fusion proteins in pull‐down assays. JAK1 mutational analysis revealed that its JH7‐3 domains bound directly to the Box 1 and Box 2 motifs of βc. We further examined the role of JAK1 JH7‐3 domains in JAK1 and JAK2‐mediated signaling using the CDJAKs fusion proteins, which consisted of a CD16 extracellular domain, a CD7 transmembrane domain, and either JAK1 (CDJAK1), JAK2 (CDJAK2), or JAK1‐JH7‐3 domains (CDJAK1‐JH7‐3) as intracellular domains. Anti‐CD16 antibody crosslinking of wild type fusion proteins CDJAK1 with CDJAK2 could mimic IL‐3 signaling, however, the crosslinking of fusion proteins CDJAK1‐JH7‐3 with CDJAK2 failed to activate downstream proteins. These results suggest that the JAK1‐JH7‐3 domains are required for βc interaction and abolish wild type JAK1 and JAK2‐mediated signaling. J. Cell. Biochem. 99: 1078–1084, 2006. © 2006 Wiley‐Liss, Inc.