Pan-Vertebrate Toll-Like Receptors During Evolution

Human toll-like receptors (TLRs) recognize pathogen-associated molecular patterns (PAMPs) to raise innate immune responses. The human TLR family was discovered because of its sequence similarity to fruit fly (Drosophila) Toll, which is involved in an anti-fungal response. In this review, we focus on the origin of the vertebrate TLR family highlighted through functional and phylogenetic analyses of TLRs in non-mammalian vertebrates. Recent extensive genome projects revealed that teleosts contain almost all subsets of TLRs that correspond to human TLRs (TLR1, 2, 3, 4, 5, 7, 8, and 9), whereas the urochordate Ciona intestinalis contains only a few TLR genes. Therefore, mammals likely obtained almost all TLR family members at the beginning of vertebrate evolution. This premise is further supported by several functional analyses of non-mammalian TLRs. We have summarized several teleost TLRs with unique properties distinct from mammalian TLRs to outline their specific roles. According to Takifugu rubripes genome project, the puffer fish possesses fish-specific TLR21 and 22. Surprisingly, phylogenetic analyses indicate that TLR21 and 22 emerged during an early period of vertebrate evolution in parallel with other TLRs and that the mammalian ancestor lost TLR21 and 22 during evolution. Our laboratory recently revealed that TLR22 recognizes double-strand RNA and induces interferon production through the TICAM-1 adaptor, as in TLR3, but unlike TLR3, TLR22 localizes to the cell surface. Therefore, differential expression of TLR3 and TLR22, rather than simple redundancy of RNA sensors, may explain the effective protection of fish from RNA virus infection in the water. In this review, we summarize the similarities and differences of the TLR family in various vertebrates and introduce these unique TLRs for a possible application to the field of clinical practices for cancer or virus infection

2D Particle Simulation of Liver Cell Proliferation with Angiogenesis - Hepatic Lobule Formation

The liver has the ability to reform and regenerate in our body. However, the mechanisms of reformation or regeneration of the liver have not been elucidated. In this study, we propose an analysis model using a Particle Model to elucidate the mechanism of liver formation. The object of analysis is a hepatic lobule, which is the basic component of the liver. First, a 2-dimensional cell proliferation around one blood vessel was modeled. Second, angiogenesis was added and considered. And finally, the model was applied to the hepatic lobule and the 2D formation of the hepatic lobule was revealed. We used experimentally derived parameters such as diffusivity, oxygen concentration, and oxygen consumption of a cell. The model will be expected to facilitate in developing tissue-engineered liver using regenerative medicine technology.2nd Conference on Advances in Prevention and Treatment of Cancer (CAPTC 2016), March 18-20, 2016, Los Angeles, US

Cross-priming for antitumor CTL induced by soluble Ag + polyI:C depends on the TICAM-1 pathway in mouse CD11c+ /CD8α+ dendritic cells

PolyI:C is a nucleotide pattern molecule that induces cross-presentation of foreign Ag in myeloid dendritic cells (DC) and MHC Class I-dependent proliferation of cytotoxic T lymphocytes (CTL). DC (BM or spleen CD8α(+)) have sensors for dsRNA including polyI:C to signal facilitating cross-presentation. Endosomal TLR3 and cytoplasmic RIG-I/MDA5 are reportedly responsible for polyI:C sensing and presumed to deliver signal for cross-presentation via TICAM-1 (TRIF) and IPS-1 (MAVS, Cardif, VISA) adaptors, respectively. In fact, when tumor-associated Ag (TAA) was simultaneously taken up with polyI:C in DC, the DC cross-primed CTL specific to the TAA in a syngenic mouse model. Here we tested which of the TICAM-1 or IPS-1 pathway participate in cross-presentation of tumor-associated soluble Ag and retardation of tumor growth in the setting with a syngeneic tumor implant system, EG7/C57BL6, and exogenously challenged soluble Ag (EG7 lysate) and polyI:C. When EG7 lysate and polyI:C were subcutaneously injected in tumor-bearing mice, EG7 tumor growth retardation was observed in wild-type and to a lesser extent IPS-1(−/−) mice, but not TICAM-1(−/−) mice. IRF-3/7 were essential but IPS-1 and type I IFN were minimally involved in the polyI:C-mediated CTL proliferation. Although both TICAM-1 and IPS-1 contributed to CD86/CD40 upregulation in CD8α(+) DC, H2K(b)-SL8 tetramer and OT-1 proliferation assays indicated that OVA-recognizing CD8 T cells predominantly proliferated in vivo through TICAM-1 and CD8α(+) DC is crucial in ex vivo analysis. Ultimately, tumor regresses > 8 d post polyI:C administration. The results infer that soluble tumor Ag induces tumor growth retardation, i.e., therapeutic potential, if the TICAM-1 signal coincidentally occurs in CD8α(+) DC around the tumor

TICAM-1/TRIF associates with Act1 and suppresses IL-17 receptor–mediated inflammatory responses

TICAM-1 (also called TRIF) is the sole adaptor of TLR3 that recognizes double-stranded RNA. Here, we report that TICAM-1 is involved not only in TLR3 signaling but also in the cytokine receptor IL-17RA signaling. We found that TICAM-1 bound to IL-17R adaptor Act1 to inhibit the interaction between IL-17RA and Act1. Interestingly, TICAM-1 knockout promoted IL-17RA/Act1 interaction and increased IL-17A–mediated activation of NF-κB and MAP kinases, leading to enhanced expression of inflammatory cytokines and chemokines upon IL-17A stimulation. Moreover, Ticam-1 knockout augmented IL-17A–mediated CXCL1 and CXCL2 expression in vivo, resulting in accumulation of myeloid cells. Furthermore, Ticam-1 knockout enhanced delayed type hypersensitivity and exacerbated experimental autoimmune encephalomyelitis. Ticam-1 knockout promoted accumulation of myeloid and lymphoid cells in the spinal cord of EAE-induced mice. Collectively, these data indicate that TICAM-1 inhibits the interaction between IL-17RA and Act1 and functions as a negative regulator in IL-17A–mediated inflammatory responses

Identification of a polyI:C-inducible membrane protein that participates in dendritic cell–mediated natural killer cell activation

The novel polyI:C-inducible membrane protein INAM triggers dendritic cell–mediated natural killer cell activation

Development of Mouse Hepatocyte Lines Permissive for Hepatitis C Virus (HCV)

The lack of a suitable small animal model for the analysis of hepatitis C virus (HCV) infection has hampered elucidation of the HCV life cycle and the development of both protective and therapeutic strategies against HCV infection. Human and mouse harbor a comparable system for antiviral type I interferon (IFN) induction and amplification, which regulates viral infection and replication. Using hepatocytes from knockout (ko) mice, we determined the critical step of the IFN-inducing/amplification pathways regulating HCV replication in mouse. The results infer that interferon-beta promoter stimulator (IPS-1) or interferon A receptor (IFNAR) were a crucial barrier to HCV replication in mouse hepatocytes. Although both IFNARko and IPS-1ko hepatocytes showed a reduced induction of type I interferons in response to viral infection, only IPS-1-/- cells circumvented cell death from HCV cytopathic effect and significantly improved J6JFH1 replication, suggesting IPS-1 to be a key player regulating HCV replication in mouse hepatocytes. We then established mouse hepatocyte lines lacking IPS-1 or IFNAR through immortalization with SV40T antigen. Expression of human (h)CD81 on these hepatocyte lines rendered both lines HCVcc-permissive. We also found that the chimeric J6JFH1 construct, having the structure region from J6 isolate enhanced HCV replication in mouse hepatocytes rather than the full length original JFH1 construct, a new finding that suggests the possible role of the HCV structural region in HCV replication. This is the first report on the entry and replication of HCV infectious particles in mouse hepatocytes. These mouse hepatocyte lines will facilitate establishing a mouse HCV infection model with multifarious applications

Collaborative Action of Brca1 and CtIP in Elimination of Covalent Modifications from Double-Strand Breaks to Facilitate Subsequent Break Repair

Topoisomerase inhibitors such as camptothecin and etoposide are used as anti-cancer drugs and induce double-strand breaks (DSBs) in genomic DNA in cycling cells. These DSBs are often covalently bound with polypeptides at the 3′ and 5′ ends. Such modifications must be eliminated before DSB repair can take place, but it remains elusive which nucleases are involved in this process. Previous studies show that CtIP plays a critical role in the generation of 3′ single-strand overhang at “clean” DSBs, thus initiating homologous recombination (HR)–dependent DSB repair. To analyze the function of CtIP in detail, we conditionally disrupted the CtIP gene in the chicken DT40 cell line. We found that CtIP is essential for cellular proliferation as well as for the formation of 3′ single-strand overhang, similar to what is observed in DT40 cells deficient in the Mre11/Rad50/Nbs1 complex. We also generated DT40 cell line harboring CtIP with an alanine substitution at residue Ser332, which is required for interaction with BRCA1. Although the resulting CtIPS332A/−/− cells exhibited accumulation of RPA and Rad51 upon DNA damage, and were proficient in HR, they showed a marked hypersensitivity to camptothecin and etoposide in comparison with CtIP+/−/− cells. Finally, CtIPS332A/−/−BRCA1−/− and CtIP+/−/−BRCA1−/− showed similar sensitivities to these reagents. Taken together, our data indicate that, in addition to its function in HR, CtIP plays a role in cellular tolerance to topoisomerase inhibitors. We propose that the BRCA1-CtIP complex plays a role in the nuclease-mediated elimination of oligonucleotides covalently bound to polypeptides from DSBs, thereby facilitating subsequent DSB repair

Regulation of RIG-I Activation by K63-Linked Polyubiquitination

RIG-I is a pattern recognition receptor and recognizes cytoplasmic viral double-stranded RNA (dsRNA). Influenza A virus, hepatitis C virus, and several other pathogenic viruses are mainly recognized by RIG-I, resulting in the activation of the innate immune responses. The protein comprises N-terminal two caspase activation and recruitment domains (2CARDs), an RNA helicase domain, and the C-terminal domain (CTD). The CTD recognizes 5′-triphosphate viral dsRNA. After recognition of viral dsRNA, the protein harbors K63-linked polyubiquitination essential for RIG-I activation. First, it was reported that TRIM25 ubiquitin ligase delivered K63-linked polyubiquitin moiety to the 2CARDs. The polyubiquitin chain stabilizes a structure called the 2CARD tetramer, in which four 2CARDs assemble and make a core that promotes the aggregation of the mitochondrial antiviral-signaling (MAVS) protein on mitochondria. MAVS aggregation then triggers the signal to induce the innate immune responses. However, subsequent studies have reported that Riplet, MEX3C, and TRIM4 ubiquitin ligases are also involved in K63-linked polyubiquitination and the activation of RIG-I. MEX3C and TRIM4 mediate polyubiquitination of the 2CARDs. By contrast, Riplet ubiquitinates the CTD. The physiological significance of each ubiquitin ligases has been shown by knockout and knockdown studies, but there appears to be contradictory to evidence reported in the literature. In this review, we summarize recent findings related to K63-linked polyubiquitination and propose a model that could reconcile current contradictory theories. We also discuss the physiological significance of the ubiquitin ligases in the immune system against viral infection