title: CD45 is a JAK phosphatase and negatively regulates cytokine receptor signalling.
abstract: The regulation of tyrosine phosphorylation and associated signalling through antigen, growth-factor and cytokine receptors is mediated by the reciprocal activities of protein tyrosine kinases and protein tyrosine phosphatases (PTPases). The transmembrane PTPase CD45 is a key regulator of antigen receptor signalling in T and B cells. Src-family kinases have been identified as primary molecular targets for CD45 (ref. 4). However, CD45 is highly expressed in all haematopoietic lineages at all stages of development, indicating that CD45 could regulate other cell types and might act on additional substrates. Here we show that CD45 suppresses JAK (Janus kinase) kinases and negatively regulates cytokine receptor signalling. Targeted disruption of the cd45 gene leads to enhanced cytokine and interferon-receptor-mediated activation of JAKs and STAT (signal transducer and activators of transcription) proteins. In vitro, CD45 directly dephosphorylates and binds to JAKs. Functionally, CD45 negatively regulates interleukin-3-mediated cellular proliferation, erythropoietin-dependent haematopoieisis and antiviral responses in vitro and in vivo. Our data identify an unexpected and novel function for CD45 as a haematopoietic JAK phosphatase that negatively regulates cytokine receptor signalling.
authors.affiliation: Amgen Institute, Department of Medical Biophysics, University of Toronto, Ontario, Canada.
authors.forename: J
authors.initials: J
authors.lastname: Irie-Sasaki
authors.forename: T
authors.initials: T
authors.lastname: Sasaki
authors.forename: W
authors.initials: W
authors.lastname: Matsumoto
authors.forename: A
authors.initials: A
authors.lastname: Opavsky
authors.forename: M
authors.initials: M
authors.lastname: Cheng
authors.forename: G
authors.initials: G
authors.lastname: Welstead
authors.forename: E
authors.initials: E
authors.lastname: Griffiths
authors.forename: C
authors.initials: C
authors.lastname: Krawczyk
authors.forename: C D
authors.initials: CD
authors.lastname: Richardson
authors.forename: K
authors.initials: K
authors.lastname: Aitken
authors.forename: N
authors.initials: N
authors.lastname: Iscove
authors.forename: G
authors.initials: G
authors.lastname: Koretzky
authors.forename: P
authors.initials: P
authors.lastname: Johnson
authors.forename: P
authors.initials: P
authors.lastname: Liu
authors.forename: D M
authors.initials: DM
authors.lastname: Rothstein
authors.forename: J M
authors.initials: JM
authors.lastname: Penninger
mesh_terms: D000818:Animals; D001665:Binding Sites; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000378:metabolism; D004789:Enzyme Activation; D006410:Hematopoiesis; D007377:Interleukin-3 / Q000378:metabolism; D053614:Janus Kinase 2; D017493:Leukocyte Common Antigens / Q000235:genetics / Q000378:metabolism*; D008407:Mast Cells / Q000378:metabolism; D051379:Mice; D008894:Milk Proteins; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D018121:Receptors, Cytokine / Q000037:antagonists & inhibitors / Q000378:metabolism; D050796:STAT3 Transcription Factor; D050799:STAT5 Transcription Factor; D015398:Signal Transduction; D015534:Trans-Activators / Q000378:metabolism; D014443:Tyrosine / Q000378:metabolism; D019061:src-Family Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D004268:DNA-Binding Proteins; D007377:Interleukin-3; D008894:Milk Proteins; D011518:Proto-Oncogene Proteins; D018121:Receptors, Cytokine; D050796:STAT3 Transcription Factor; D050799:STAT5 Transcription Factor; C494087:Stat3 protein, mouse; D015534:Trans-Activators; D014443:Tyrosine; D011505:Protein-Tyrosine Kinases; C507926:Jak2 protein, mouse; D053614:Janus Kinase 2; D019061:src-Family Kinases; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D020928:Mitogen-Activated Protein Kinases; D017493:Leukocyte Common Antigens