As shown in Physique 3, the CK2 inhibitors TBB and emodin suppressed IFN-Cinduced tyrosine phosphorylation of both STAT-1 and STAT-3, and GH-induced tyrosine phosphorylation of STAT-5

As shown in Physique 3, the CK2 inhibitors TBB and emodin suppressed IFN-Cinduced tyrosine phosphorylation of both STAT-1 and STAT-3, and GH-induced tyrosine phosphorylation of STAT-5. and PV cells. Our data provide evidence for novel cross-talk between CK2 and JAK-STAT signaling, with implications for therapeutic intervention in JAK2V617F-positive MPDs. Introduction The JAK-STAT pathway is crucial in transmitting signals from many cytokines and growth factors into the nucleus, regulating gene expression. Cytokines of the IL-6 family, type I and II IFNs, and growth GW 9662 factors such as growth hormone (GH) activate the JAK-STAT signaling pathway. Oncostatin M (OSM), a cytokine belonging to the IL-6 family, is usually a potent activator of the JAK-STAT signaling pathway.1 Binding of OSM induces heterodimerization of its receptors, gp130 and OSMR, and the receptor-associated JAKs, JAK1 and JAK2, become activated, leading to phosphorylation of gp130 tyrosine residues. The phosphorylated residues direct the recruitment of STAT proteins, including STAT-3, STAT-1, and STAT-5, which in turn become JAK substrates. Activated tyrosineCphosphorylated STATs form homodimers or heterodimers, translocate to the nucleus, and bind to consensus sequences in the promoters of OSM-responsive genes, inducing transcription.2 The JAK tyrosine kinase family comprises 4 mammalian members: JAK1, JAK2, JAK3, and TYK2. JAK2 is essential in erythropoiesis,3 and its dysfunction has been implicated in myeloproliferative disorders (MPDs) and leukemias.4 MPDs are a group of clonal hematopoietic disorders including polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF).4 Recent studies have revealed that JAK2V617F, a somatic, activating point mutation, occurs in most PV patients and in 50% of ET and PMF patients, GW 9662 and is involved in the pathogenesis of MPDs.5C8 Overexpression of JAK2V617F in murine Ba/F3 cells leads to cytokine-independent growth,5 and expression of JAK2V617F in mice recapitulates many pathologic characteristics observed in PV, ET, and PMF patients.9C11 Among the signaling pathways activated by JAK2V617F are the STATs, predominantly STAT-5.12 Therefore, JAK2V617F represents an ideal target for therapeutic intervention, especially in JAK2V617F-positive MPDs. Protein kinase CK2 (formerly known as casein kinase 2 or II) is usually a ubiquitous, highly conserved serine/threonine kinase, and recent studies have shown that it can also phosphorylate tyrosine residues.13 CK2 phosphorylates 300 substrates involved in DNA replication, gene transcription, signal transduction, and cell growth and GW 9662 apoptosis.14,15 CK2 presents as a tetramer composed of 2 catalytic subunits ( or ) and 2 regulatory subunits. CK2 is essential for cell viability, because disruption of either CK2 or CK2 is usually embryonically lethal.16,17 CK2 Rabbit polyclonal to UBE3A expression and activity are up-regulated in blood tumors, including multiple myeloma18 and GW 9662 leukemia,19 and in solid tumors, including kidney, mammary gland, lung, prostate, and head and neck cancers.20 In mouse models, CK2 cooperatively promotes oncogenesis and tumor progression with overexpression of other oncogenes such as c-myc,21 or with loss of tumor suppressors such as p53.22 Prosurvival genes such as -test distribution. .05 was considered statistically significant. All experiments were performed a minimum of 3 times. Results CK2 is required for cytokine-induced STAT activation and downstream gene expression Previous studies in our laboratory identified the tumor suppressor PML as a regulator of GW 9662 the JAK-STAT pathway.31 Furthermore, PML was shown to be a substrate of CK2 and targeted for degradation by the proteosome.32 Therefore, we were interested in determining whether the JAK-STAT pathway.