title: CD45 recruits adapter protein DOK-1 and negatively regulates JAK-STAT signaling in hematopoietic cells.
abstract: It has been extensively documented that CD45 positively regulates T cell receptor-mediated signaling through the activation of Src-family kinases. The mechanism whereby CD45 negatively regulates the JAK/STAT pathway, however, has not been fully elucidated. Here we describe the mechanism by which CD45 negatively regulates the JAK/STAT pathway through the recruitment of the inhibitory molecule Downstream of Kinase 1 (DOK-1) in hematopoietic cells. We present evidences that CD45 recruits DOK-1 to associate with tyrosine-phosphorylated DOK-1, and that the DOK-1-Y296F mutant completely abrogates its interaction with CD45. Moreover, CD45 expression is required for DOK-1 targeting to the plasma membrane in response to anti-CD3 stimulation. Functional studies further showed that stable expression of DOK-1 in K562 cells markedly decreased both JAK-2 and STAT-3/5 phosphorylation following IL-3 and IFN-alpha stimulation. Likewise, stable expression of DOK-1 in Jurkat cells significantly decreased JAK-2 phosphorylation. Similarly, both IL-3 and IFN-alpha-induced JAK-2 phosphorylations were significantly increased in CD45 deficient Jurkat cells. Consistently, silencing of the DOK-1 gene resulted in rescue of MAP kinases and JAKs activities in CD45 positive Jurkat cells. Accordingly, CD45 recruits adaptor DOK-1 to the proximal plasma membrane to serve as a downstream effector, resulting in negative regulation of the JAK/STAT signaling pathway.
authors.affiliation: Department of Medicine, McGill University, Montreal, Quebec, Canada.
authors.forename: Liangtang
authors.initials: L
authors.lastname: Wu
authors.forename: Krikor
authors.initials: K
authors.lastname: Bijian
authors.forename: Shi-Hsiang
authors.initials: SH
authors.lastname: Shen
authors.forename: Shi-Shiang
authors.initials: SS
authors.lastname: Shen
mesh_terms: D002462:Cell Membrane / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D006801:Humans; D016898:Interferon-alpha / Q000378:metabolism / Q000494:pharmacology; D007377:Interleukin-3 / Q000378:metabolism / Q000494:pharmacology; D053614:Janus Kinase 2 / Q000378:metabolism*; D019169:Jurkat Cells; D020014:K562 Cells; D017493:Leukocyte Common Antigens / Q000235:genetics / Q000502:physiology*; D020935:MAP Kinase Signaling System / Q000502:physiology; D009154:Mutation; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D016601:RNA-Binding Proteins / Q000378:metabolism*; D050796:STAT3 Transcription Factor / Q000378:metabolism*; D050799:STAT5 Transcription Factor / Q000378:metabolism*; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000378:metabolism
chemical_list: D004268:DNA-Binding Proteins; C489560:DOK1 protein, human; D016898:Interferon-alpha; D007377:Interleukin-3; D010750:Phosphoproteins; D016601:RNA-Binding Proteins; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D050799:STAT5 Transcription Factor; D053614:Janus Kinase 2; D017493:Leukocyte Common Antigens