title: JAK2 tyrosine kinase phosphorylates and is negatively regulated by centrosomal protein Ninein.
abstract: JAK2 is a cytoplasmic tyrosine kinase critical for cytokine signaling. In this study, we have identified a novel centrosome-associated complex containing ninein and JAK2. We have found that active JAK2 localizes around the mother centrioles, where it partly colocalizes with ninein, a protein involved in microtubule (MT) nucleation and anchoring. We demonstrated that JAK2 is an important regulator of centrosome function. Depletion of JAK2 or use of JAK2-null cells causes defects in MT anchoring and increased numbers of cells with mitotic defects; however, MT nucleation is unaffected. We showed that JAK2 directly phosphorylates the N terminus of ninein while the C terminus of ninein inhibits JAK2 kinase activity in vitro. Overexpressed wild-type (WT) or C-terminal (amino acids 1179 to 1931) ninein inhibits JAK2. This ninein-dependent inhibition of JAK2 significantly decreases prolactin- and interferon gamma (IFN-γ)-induced tyrosyl phosphorylation of STAT1 and STAT5. Downregulation of ninein enhances JAK2 activation. These results indicate that JAK2 is a novel member of centrosome-associated complex and that this localization regulates both centrosomal function and JAK2 kinase activity, thus controlling cytokine-activated molecular pathways.
authors.affiliation: Department of Biological Sciences, University of Toledo, Toledo, Ohio, USA.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Jay
authors.affiliation: Department of Biological Sciences, University of Toledo, Toledo, Ohio, USA.
authors.forename: Alan
authors.initials: A
authors.lastname: Hammer
authors.affiliation: Advanced Microscopy & Imaging Center, University of Toledo, Toledo, Ohio, USA.
authors.forename: Andrea
authors.initials: A
authors.lastname: Nestor-Kalinoski
authors.affiliation: Department of Biological Sciences, University of Toledo, Toledo, Ohio, USA mdiakon@utnet.utoledo.edu.
authors.forename: Maria
authors.initials: M
authors.lastname: Diakonova
mesh_terms: D000818:Animals; D019556:COS Cells; D002502:Centrioles / Q000648:ultrastructure; D018385:Centrosome / Q000378:metabolism / Q000648:ultrastructure*; D002522:Chlorocebus aethiops; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic; D020868:Gene Silencing; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D007371:Interferon-gamma / Q000378:metabolism; D053614:Janus Kinase 2 / Q000378:metabolism*; D008870:Microtubules / Q000648:ultrastructure; D008938:Mitosis; D009687:Nuclear Proteins / Q000378:metabolism*; D010766:Phosphorylation; D011388:Prolactin / Q000378:metabolism; D017434:Protein Structure, Tertiary
chemical_list: D003598:Cytoskeletal Proteins; C512806:NIN protein, human; D009687:Nuclear Proteins; D007371:Interferon-gamma; D011388:Prolactin; C507924:JAK2 protein, human; D053614:Janus Kinase 2