Seminar on Innate Immunity

Viral components induce strong type I IFN responses through the activation of toll-like receptors (TLRs) and intracellular cytoplasmic receptors such as an RNA helicase RIG-I and/or MDA5. According to recent studies, the NF-κB essential modulator NEMO (also called IKKγ) is crucial for this virus-induced antiviral response. However, the precise roles of signal activation by NEMO adaptor have not been elucidated. Here, we show that virusinduced IRF3 and NF-κB activation depends on the K(lys)-27-linked polyubiquitination to NEMO by the novel ubiquitin E3 ligase TRIM23 (Triparite motif protein 23). Virus-induced IRF3 and NF-κB activation, as well as K27-linked NEMO polyubiquitination, were abrogated in TRIM23 knockdown cells, while TRIM23 knockdown had no effect on TNFα-mediated NF-κB activation. Furthermore, in NEMO-deficient mouse embryo fibroblast cells, interferon-stimulated response element (ISRE)-driven reporter activity was restored by ectopic expression of wild-type NEMO. From these results, we conclude that TRIM23mediated ubiquitin conjugation to NEMO is essential for TLR3and RIG-I/MDA5-mediated antiviral innate and inflammatory responses. “Trypsinogen 5 is under the control of interferon regulatory factors” Professor Toshifumi Matsuyama Division of Cytokine Signaling Nagasaki University Graduate School of Biomedical Sciences, JAPAN Abstract Interferons (IFNs) render cells resistant to viral infection and regulate cell growth and differentiation. They elicit the pleiotropic biological effects mainly by regulating the expressions of many interferon-stimulated genes (ISGs) mainly via interferon regulatory factors (IRFs). We have analyzed the roles of IRFs in vivo using the knock-out mice, and found that IRF2-deficient (IRF2-/-) mice showed early death compared to normal mice after lymphocytic choriomeningitis virus (LCMV) infection, with severe inflammation in the pancreas. The lethal acute pancreatitis is also induced by intra-peritoneal poly(I:C) challenge. The pancreatitis was abolished by further knocking-out IFNα receptor1 (IFNαR1) gene, indicating the importance of type1 IFN signaling via IFNAR1 to develop the poly(I:C)induced panreatitis in IRF2-/mice. To identify the molecules involved in the poly(I:C)induced panreatitis in IRF2-/mice, we thoroughly examined the gene expression levels in the pancreas using Affymetrix DNA microarray system covering 35,000 gene probes, before and after 250 μg poly(I:C) injection to IRF2-/mice and wild-type mice. Fourteen annotated genes were up-regulated more than 10-fold in IRF2-/mouse, and nine genes were downregulated more than 10-fold, compare to the wild-type mouse. The up-regulation of trypsinogen 5, but not other trypsinogen family members 1 and 2, by inactivating IRF2 gene was noteworthy and it reached about thousand-fold. From enzymatic analysis, trypsinogen5 was resistant to Spink3, a major endogenous trypsin inhibitor in the pancreas, compared to the two major pancreatic trypsinogen genes. Furthermore, trypsinogen 5 is directly regulated by IRF family members. Possible role of IFN-stimulated genes in the pancreatitis model will be discussed. Department of Microbiology Seminar Series .... November 2010Interferons (IFNs) render cells resistant to viral infection and regulate cell growth and differentiation. They elicit the pleiotropic biological effects mainly by regulating the expressions of many interferon-stimulated genes (ISGs) mainly via interferon regulatory factors (IRFs). We have analyzed the roles of IRFs in vivo using the knock-out mice, and found that IRF2-deficient (IRF2-/-) mice showed early death compared to normal mice after lymphocytic choriomeningitis virus (LCMV) infection, with severe inflammation in the pancreas. The lethal acute pancreatitis is also induced by intra-peritoneal poly(I:C) challenge. The pancreatitis was abolished by further knocking-out IFNα receptor1 (IFNαR1) gene, indicating the importance of type1 IFN signaling via IFNAR1 to develop the poly(I:C)induced panreatitis in IRF2-/mice. To identify the molecules involved in the poly(I:C)induced panreatitis in IRF2-/mice, we thoroughly examined the gene expression levels in the pancreas using Affymetrix DNA microarray system covering 35,000 gene probes, before and after 250 μg poly(I:C) injection to IRF2-/mice and wild-type mice. Fourteen annotated genes were up-regulated more than 10-fold in IRF2-/mouse, and nine genes were downregulated more than 10-fold, compare to the wild-type mouse. The up-regulation of trypsinogen 5, but not other trypsinogen family members 1 and 2, by inactivating IRF2 gene was noteworthy and it reached about thousand-fold. From enzymatic analysis, trypsinogen5 was resistant to Spink3, a major endogenous trypsin inhibitor in the pancreas, compared to the two major pancreatic trypsinogen genes. Furthermore, trypsinogen 5 is directly regulated by IRF family members. Possible role of IFN-stimulated genes in the pancreatitis model will be discussed. Department of Microbiology Seminar Series .... November 2010