DEAD-box RNA helicase 18 disrupts IRF3-binding to the interferon-β promoter

The production of type I interferons (IFN-α/β) requires strict control to avoid excessive activation during viral infections. The binding of interferon regulatory factor 3 (IRF3) to the IFN-β promoter region in the nucleus is essential for IFN-β transcription; however, whether nuclear factors have important negative-regulatory roles in this process is largely unknown. By screening for IRF3-interacting partners in the nucleus, we identified DEAD-box RNA helicase 18 (DDX18) as an important negative regulator of intranuclear IRF3. Overexpression of DDX18 suppressed virus- and IRF3-induced IFN-β production, whereas knockdown of DDX18 expression or knockout of the DDX18 gene had opposite effects. Mechanistically, DDX18 interacts with IRF3 and decreases the binding of IRF3 to the IFN-β promoter after viral infection. DDX18 knockdown mice (Ddx18+/-) further demonstrated that DDX18 suppressed antiviral innate immunity in vivo. Thus, despite many members of the DDX family act as important positive regulators in the cytoplasm, DDX18 plays a unique "braking" role in balancing virus-induced type I IFN production.

The overexpression of Tipe2 in CRC cells suppresses survival while endogenous Tipe2 accelerates AOM/DSS induced-tumor initiation

Aging is a natural and progressive process characterized by an increased frequency of age-related diseases such as cancer. But its mechanism is unclear. TNFAIP8L2 (Tipe2) is an important negative regulator for homeostasis through inhibiting TLR and TCR signaling. Our work reveals that Tipe2 might have dual function by regulating senescence. One side, the overexpression of Tipe2 in CRC cells could induce typical senescent phenotype, especially exposure to oxidative stress. Tipe2 inhibits telomerase activity by regulating c-Myc and c-Est-2 binding to the hTERT promotor. Interestingly, Tipe2 KO mice treated with D-Gal showed a less serious inverse of CD4:CD8 ratio, a lower percentage of Treg compared to WT. Besides, Tipe2 KO mice were more tolerant to the initiation of AOM/DSS-induced CRC, accompanied by a lower level of Treg within IEL. Therefore, specific antibodies against CD25 effectively ameliorate tumorigenesis. These data suggest strongly that the overexpressed Tipe2 suppresses tumor cells proliferation and survival, but endogenous Tipe2 promotes the initiation of tumorigenesis when exposure to dangerous environment such as AOM/DSS-related inflammation.

Role of the transcriptional regulator SP140 in resistance to bacterial infections via repression of type I interferons

Type I interferons (IFNs) are essential for anti-viral immunity, but often impair protective immune responses during bacterial infections. An important question is how type I IFNs are strongly induced during viral infections, and yet are appropriately restrained during bacterial infections. The Super susceptibility to tuberculosis 1 (Sst1) locus in mice confers resistance to diverse bacterial infections. Here we provide evidence that Sp140 is a gene encoded within the Sst1 locus that represses type I IFN transcription during bacterial infections. We generated Sp140-/- mice and find they are susceptible to infection by Legionella pneumophila and Mycobacterium tuberculosis. Susceptibility of Sp140-/- mice to bacterial infection was rescued by crosses to mice lacking the type I IFN receptor (Ifnar-/-). Our results implicate Sp140 as an important negative regulator of type I IFNs that is essential for resistance to bacterial infections.

Effect of TRAF1 on phenotypic changes of Kupffer cells in liver transplantation ischemic-reperfusion

Objective: The purpose of this study was to explore the effect of TRAF1 on phenotypic changes of KCs in I/R in liver transplantation. Methods: SD rats were randomly divided into sham group and liver transplantation I/R group. KCs were extracted from rat livers in each group. KCs were transfected by lentivirus of si-TRAF1 or si-HOIP, and induced by lipopolysaccharide (LPS). Flow cytometry was used to detect cell apoptosis. Western blot and RT-PCR were used to detect the protein and mRNA expression levels. Results: Compared with sham group, the expression levels of TRAF1, TNF-α and IL-1β were significantly increased in I/R group (P<0.05). In addition, compared with control group, the expression levels of NF-κB (P65 and p-P65) and M1 phenotype (TNF-α and IL-1β) were notably increased in si-TRAF1 and si-HOIP group (all P<0.05). Furthermore, the levels of linear ubiquitin complex (LUBAC) were markedly increased in LPS-induced KCs in comparison with control group (P<0.05). Moreover, compared with control group, the expression levels of P65, p-P65, TNF-α and IL-1β were notably decreased in si-TRAF1 and si-HOIP group (P<0.05). The expression levels of P65, p-P65, TNF-α and IL-1β were significantly increased in si-TRAF1 and si-HOIP group when compared to control group (P<0.05). Conclusion: TRAF1 was an important negative regulator of liver transplantation I/R by inhibiting the activation of NF-κB in KCs and preventing its M1 phenotype transformation.

Discovery, X-ray structure and CPP-conjugation enabled uptake of p53/MDM2 macrocyclic peptide inhibitors

Mouse double minute 2 homolog (MDM2, Hdm2) is an important negative regulator of the tumor suppressor p53. Using a mRNA based display technique to screen a library of >1012 in...

BPIFB3 interacts with ARFGAP1 and TMED9 to regulate non-canonical autophagy and RNA virus infection

Autophagy is a degradative cellular pathway that targets cytoplasmic contents and organelles for turnover by the lysosome. Various autophagy pathways play key roles in the clearance of viral infections, and many families of viruses have developed unique methods for avoiding degradation. Some positive stranded RNA viruses, such as enteroviruses and flaviviruses, usurp the autophagic pathway to promote their own replication. We previously identified the endoplasmic reticulum-localized protein BPIFB3 as an important negative regulator of non-canonical autophagy that uniquely impacts the replication of enteroviruses and flaviviruses. Here, we find that many components of the canonical autophagy machinery are not required for BPIFB3 depletion induced autophagy and identify the host factors that facilitate its role in the replication of enteroviruses and flaviviruses. Using proximity-dependent biotinylation (BioID) followed by mass spectrometry, we identify ARFGAP1 and TMED9 as two cellular components that interact with BPIFB3 to regulate autophagy and viral replication. Importantly, our data demonstrate that non-canonical autophagy in mammalian cells can be controlled outside of the traditional pathway regulators and define the role of two proteins in BPIFB3 depletion mediated non-canonical autophagy.

Recent Advances in Signaling Pathways Comprehension as Carcinogenesis Triggers in Basal Cell Carcinoma

Basal cell carcinoma (BCC) is the most common malignant skin tumor. BCC displays a different behavior compared with other neoplasms, has a slow evolution, and metastasizes very rarely, but sometimes it causes an important local destruction. Chronic ultraviolet exposure along with genetic factors are the most important risk factors involved in BCC development. Mutations in the PTCH1 gene are associated with Gorlin syndrome, an autosomal dominant disorder characterized by the occurrence of multiple BCCs, but are also the most frequent mutations observed in sporadic BCCs. PTCH1 encodes for PTCH1 protein, the most important negative regulator of the Hedgehog (Hh) pathway. There are numerous studies confirming Hh pathway involvement in BCC pathogenesis. Although Hh pathway has been intensively investigated, it remains incompletely elucidated. Recent studies on BCC tumorigenesis have shown that in addition to Hh pathway, there are other signaling pathways involved in BCC development. In this review, we present recent advances in BCC carcinogenesis.

Dkk1 is a negative regulator for the pathogenesis of ossification of the posterior longitudinal ligament

PurposeOssification of the posterior longitudinal ligament (OPLL) is an osteogenic disorder characterized by ectopic bone formation in the posterior longitudinal ligament of the spine. dinkkopf 1 (Dkk1) is a secreted inhibitor of the Wnt pathway, which negatively regulates bone formation during skeletal development. However, whether Dkk1 impacts the pathogenesis of OPLL has not been reported. This study is to investigate the implication of Dkk1 in the pathogenesis of OPLL.MethodsThe serum level of Dkk1 in OPLL patients was determined using ELISA. The expression of Dkk1 and activation of the Wnt/β-catenin signaling were examined in OPLL ligament-derived fibroblasts. The modulation of Dkk1 on OPLL cell proliferation, apoptosis, as well as BMP2-induced osteogenic differentiation was also investigated.ResultsThe serum level of Dkk1 is decreased in OPLL patients as compared to non-OPLL patients. The expression of Dkk1 is also reduced in OPLL fibroblasts. Downregulation of Dkk1 in OPLL cells is associated with stabilized β-catenin and increased TCF-dependent transcriptional activity, indicating an activation of the Wnt/β-catenin signaling pathway. Functionally, Dkk1 exerts a growth-inhibitory effect by repressing proliferation but promoting apoptosis of OPLL fibroblasts. Dkk1 also suppresses BMP2-induced entire osteogenic differentiation of OPLL cells and this suppression is mediated via its inhibition of the Wnt pathway.ConclusionDkk1 acts as an important negative regulator in the pathogenesis of OPLL. Targeting the Wnt pathway using Dkk1 or small molecule inhibitors may represent a potential therapeutic strategy for the treatment of OPLL.

Accelerated cell cycles enable organ regeneration under developmental time constraints in the Drosophila hindgut

SummaryIndividual organ development must be temporally coordinated with development of the rest of the organism. As a result, cell division in a developing organ occurs on a relatively fixed time scale. Despite this, many developing organs can regenerate cells lost to injury. How organs regenerate within the time constraints of organism development remains unclear. Here, we show the developing Drosophila hindgut regenerates by accelerating the mitotic cell cycle. This process requires JAK/STAT signaling and is achieved by decreasing G1 length during the normal period of developmental mitoses. Mitotic capacity is then terminated by the steroid hormone ecdysone receptor. This receptor activates a hindgut-specific enhancer of fizzy-related, a negative regulator of mitotic cyclins. We further identify the Sox transcription factor Dichaete as an important negative regulator of injury-induced mitotic cycles. Our findings reveal how mitotic cell cycle entry mechanisms can be adapted to accomplish developmental organ regeneration.

Role of C1858T Polymorphism of Lymphoid Tyrosine Phosphatase in Egyptian Children and Adolescents with Type 1 Diabetes

Background: Type 1 Diabetes Mellitus (T1DM) is a multifactorial autoimmune disease. The Protein Tyrosine Phosphatase Non-receptor 22 (PTPN22) gene is an important negative regulator of signal transduction through the T-cell Receptors (TCR). A PTPN22 polymorphism, C1858T, has been found to be a risk determinant for several autoimmune diseases, including T1DM, in different populations. Objective: The present study was aimed to analyze a possible association between the C1858T polymorphism in Egyptian children with T1DM. Methods: This case-control study included 240 children divided evenly between T1DM patients and controls. The PTPN22 C1858T polymorphism was genotyped using polymerase chain reaction with Restriction Fragment Length Polymorphism (RFLP). Results: Both the 1858CΤ and 1858ΤΤ genotypes and the 1858T allele were found more frequently in patients (32.5% and 18.7%, respectively) than in controls (10% and 5.0%, respectively), P=0.013 and P=0.007, respectively. Among females, the 1858T allele was more common in patients (18%) than in controls (2.6%), P=0.014. Conclusion: These findings suggest that the PTPN22 1858T allele could be a T1DM susceptibility factor in the Egyptian population and that it might play a different role in susceptibility to T1DM according to gender in T1DM patients.