title: Conditional activation of Janus kinase (JAK) confers factor independence upon interleukin-3-dependent cells. Essential role of Ras in JAK-triggered mitogenesis.
abstract: Cytokines play crucial roles in the growth and differentiation of hematopoietic cells. They bind to specific cell membrane receptors that usually do not possess intrinsic protein-tyrosine kinase activity. Janus kinases (JAKs) are cytoplasmic protein-tyrosine kinases that physically interact with intracellular domains of the cytokine receptors and have been implicated in playing important roles in signal transduction triggered by the cytokine-cytokine receptor interaction. However, it is still uncertain whether JAK activation alone suffices to induce cell proliferation. In this work, we modified Tyk2, a member of the JAK family, by adding a membrane localization sequence and a chemical dimerizer (coumermycin)-dependent dimerization sequence. The modified Tyk2 was activated in a coumermycin-dependent manner, and the activated Tyk2 conferred cytokine independence upon interleukin-3-dependent pro-B lymphoid cells. This cytokine-independent proliferation was completely inhibited by dominant-negative Ras. These results indicate that activation of JAK through membrane-proximal dimerization is sufficient to induce cell cycle progression and that Ras is essentially involved in JAK-triggered mitogenesis.
authors.affiliation: Department of Viral Oncology, Cancer Institute, Japanese Foundation for Cancer Research, 1-37-1 Kami-Ikebukuro, Toshima-ku, Tokyo 170-8455, Japan.
authors.forename: R
authors.initials: R
authors.lastname: Mizuguchi
authors.forename: M
authors.initials: M
authors.lastname: Hatakeyama
mesh_terms: D049933:Aminocoumarins; D000818:Animals; D001402:B-Lymphocytes; D002455:Cell Division / Q000187:drug effects / Q000502:physiology*; D002460:Cell Line; D002462:Cell Membrane / Q000502:physiology; D003374:Coumarins / Q000494:pharmacology; D019281:Dimerization; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007377:Interleukin-3 / Q000494:pharmacology / Q000502:physiology*; D053613:Janus Kinase 1; D053614:Janus Kinase 2; D053616:Janus Kinase 3; D051379:Mice; D008954:Models, Biological; D011401:Promoter Regions, Genetic; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism*; D011518:Proto-Oncogene Proteins; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D053634:TYK2 Kinase; D014162:Transfection
chemical_list: D049933:Aminocoumarins; D003374:Coumarins; D004791:Enzyme Inhibitors; D007377:Interleukin-3; D011506:Proteins; D011518:Proto-Oncogene Proteins; D011993:Recombinant Fusion Proteins; D011505:Protein-Tyrosine Kinases; C507905:Jak1 protein, mouse; C507926:Jak2 protein, mouse; C507935:Jak3 protein, mouse; D053613:Janus Kinase 1; D053614:Janus Kinase 2; D053616:Janus Kinase 3; D053634:TYK2 Kinase; C499356:Tyk2 protein, mouse; C004628:coumermycin