ag-490 and 1-2-3-4-5-6-hexabromocyclohexane

Type I interferon responses are considered the primary means by which viral infections are controlled in mammals. Despite this view, several pathogens activate antiviral responses in the absence of type I interferons. The mechanisms controlling type I interferon-independent responses are undefined. We found that RIG-I like receptors (RLRs) induce type III interferon expression in a variety of human cell types, and identified factors that differentially regulate expression of type I and type III interferons. We identified peroxisomes as a primary site of initiation of type III interferon expression, and revealed that the process of intestinal epithelial cell differentiation upregulates peroxisome biogenesis and promotes robust type III interferon responses in human cells. These findings highlight the importance of different intracellular organelles in specific innate immune responses.

Topics: Animals; Antineoplastic Agents; Benzimidazoles; Cell Differentiation; Cell Line; Cyclohexanes; DEAD Box Protein 58; DEAD-box RNA Helicases; Enzyme Inhibitors; Humans; Immunity, Innate; Interferons; Intestinal Mucosa; Janus Kinase 2; Mice; p38 Mitogen-Activated Protein Kinases; Peroxisomes; Pyridones; Receptors, Immunologic; Reoviridae; Reoviridae Infections; RNA Interference; RNA, Small Interfering; Signal Transduction; STAT1 Transcription Factor; Tyrphostins; Vidarabine

Chronic myelogenous leukemia (CML) patients treated with imatinib mesylate (IM) become drug resistant by mutations within the kinase domain of Bcr-Abl, and by other changes that cause progression to advanced stage (blast crisis) and increased expression of the Lyn tyrosine kinase, the regulation of which is not understood yet. In Bcr-Abl+ cells inhibition of Jak2, a downstream target of Bcr-Abl, by either Jak2 inhibitors or Jak2-specific short interfering RNA (siRNA) reduced the level of the SET protein, and increased PP2A Ser/Thr phosphatase and Shp1 tyrosine phosphatase activities, which led to decreased levels of activated Lyn. Activation of PP2A combined with Jak2 inhibition enhanced the reduction of activated Lyn kinase compared with Jak2 inhibition alone. In contrast, inhibition of either PP2A or Shp1 combined with Jak2 inhibition interfered with the loss of Lyn kinase activation more so than Jak2 inhibition alone, indicating the involvement of PP2A and Shp1 in the inactivation of the Lyn kinase caused by Jak2 inhibition. Inhibition of Jak2 induced apoptosis and reduced colony formation in IM-sensitive and -resistant Bcr-Abl mutant cell lines. Jak2 inhibition also induced apoptosis in CML cells from blast crisis patients but not in normal hematopoietic cells. These results indicate that Lyn is downstream of Jak2, and Jak2 maintains activated Lyn kinase in CML through the SET-PP2A-Shp1 pathway.

Topics: Animals; Apoptosis; Benzamides; Chromosomal Proteins, Non-Histone; Cyclohexanes; DNA-Binding Proteins; Drug Resistance, Neoplasm; Histone Chaperones; Humans; Imatinib Mesylate; Janus Kinase 2; Leukemia, Myelogenous, Chronic, BCR-ABL Positive; Mice; Phosphorylation; Piperazines; Protein Phosphatase 2; Protein Tyrosine Phosphatase, Non-Receptor Type 6; Proto-Oncogene Proteins c-akt; Pyrimidines; src-Family Kinases; Transcription Factors; Tyrphostins