The structural basis of flagellin detection by NAIP5 Tenthorey, Jeannette L.; Haloupek, Nicole; López-Blanco, José Ramón ...
Science (American Association for the Advancement of Science),
11/2017, Letnik:
358, Številka:
6365
Journal Article
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Robust innate immune detection of rapidly evolving pathogens is critical for host defense. Nucleotide-binding domain leucine-rich repeat (NLR) proteins function as cytosolic innate immune sensors in ...plants and animals. However, the structural basis for ligand-induced NLR activation has so far remained unknown. NAIP5 (NLR family, apoptosis inhibitory protein 5) binds the bacterial protein flagellin and assembles with NLRC4 to form amultiprotein complex called an inflammasome. Here we report the cryo–electron microscopy structure of the assembled ~1.4-megadalton flagellin-NAIP5-NLRC4 inflammasome, revealing how a ligand activates an NLR. Six distinct NAIP5 domains contact multiple conserved regions of flagellin, prying NAIP5 into an open and active conformation. We show that innate immune recognition of multiple ligand surfaces is a generalizable strategy that limits pathogen evolution and immune escape.
Objective The purpose of this study is to investigate apoptosis of hippocampal neurons and the expression of glial cell line ⁃derived neurotrophic factor (GDNF) and brain⁃derived neurotrophic factor ...(BDNF) in neonatal pups with EDNRB gene deficiency. Methods The infant rats (2-3 d after birth) with EDNRB gene defect caused by congenital base deletion were divided into wild (+/+), heterozygous (+/sl) and homozygous (sl/sl), 6-8 rats were included in each group. Apoptosis of hippocampal nerve cells was detected by TUNEL staining. The number of apoptotosic cells was calculated by confocal fluorescence microscopy, and the levels of GDNF and BDNF in hippocampus was determined by enzyme⁃linked immunsorbent assay (ELISA). Results The number of apoptotic cells in hippocampus of the three genotypes was significantly different (F=24.315, P=0.000), the number of apoptotic cells in sl/sl was higher than that in +/+ (t=⁃6.780, P=0.000) and +/sl (t=4.801, P=0.000). The number of apoptotic cells was the highest in hippocamp
Tumor necrosis factor (TNF)‑related apoptosis‑inducing ligand (TRAIL), a type II transmembrane protein, is a part of the TNF superfamily of cytokines. Cantharidin, a type of terpenoid, is extracted ...from the blister beetles (Mylabris genus) used in Traditional Chinese Medicine. Cantharidin elicits antibiotic, antiviral and antitumor effects, and can affect the immune response. The present study demonstrated that a cantharidin and TRAIL combination treatment regimen elicited a synergistic outcome in TRAIL‑resistant DU145 cells. Notably, it was also identified that cantharidin treatment initiated the downregulation of cellular FLICE‑like inhibitory protein (c‑FLIP) and upregulation of death receptor 5 (DR‑5), and sensitized cells to TRAIL‑mediated apoptosis by initiating autophagy flux. In addition, cantharidin treatment increased lipid‑modified microtubule‑associated proteins 1A/1B light chain 3B expression and significantly attenuated sequestosome 1 expression. Attenuation of autophagy flux by a specific inhibitor such as chloroquine and genetic modification using ATG5 small interfering RNA abrogated the cantharidin‑mediated TRAIL‑induced apoptosis. Overall, the results of the present study revealed that cantharidin effectively sensitized cells to TRAIL‑mediated apoptosis and its effects are likely to be mediated by autophagy, the downregulation of c‑FLIP and the upregulation of DR‑5. They also suggested that the combination of cantharidin and TRAIL may be a successful therapeutic strategy for TRAIL‑resistant prostate cancer.
Ferroptosis is a form of non-apoptotic cell death originally identified in cancer cells. However, the key regulator of ferroptosis in mitochondria remains unknown. Here, we show that CDGSH iron ...sulfur domain 1 (CISD1, also termed mitoNEET), an iron-containing outer mitochondrial membrane protein, negatively regulates ferroptotic cancer cell death. The classical ferroptosis inducer erastin promotes CISD1 expression in an iron-dependent manner in human hepatocellular carcinoma cells (e.g., HepG2 and Hep3B). Genetic inhibition of CISD1 increased iron-mediated intramitochondrial lipid peroxidation, which contributes to erastin-induced ferroptosis. In contrast, stabilization of the iron sulfur cluster of CISD1 by pioglitazone inhibits mitochondrial iron uptake, lipid peroxidation, and subsequent ferroptosis. These findings indicate a novel role of CISD1 in protecting against mitochondrial injury in ferroptosis.
Early stages of Human Immunodeficiency Virus-1 (HIV-1) infection are associated with local recruitment and activation of important effectors of innate immunity, i.e. natural killer (NK) cells and ...dendritic cells (DCs). Immature DCs (iDCs) capture HIV-1 through specific receptors and can disseminate the infection to lymphoid tissues following their migration, which is associated to a maturation process. This process is dependent on NK cells, whose role is to keep in check the quality and the quantity of DCs undergoing maturation. If DC maturation is inappropriate, NK cells will kill them ("editing process") at sites of tissue inflammation, thus optimizing the adaptive immunity. In the context of a viral infection, NK-dependent killing of infected-DCs is a crucial event required for early elimination of infected target cells. Here, we report that NK-mediated editing of iDCs is impaired if DCs are infected with HIV-1. We first addressed the question of the mechanisms involved in iDC editing, and we show that cognate NK-iDC interaction triggers apoptosis via the TNF-related apoptosis-inducing ligand (TRAIL)-Death Receptor 4 (DR4) pathway and not via the perforin pathway. Nevertheless, once infected with HIV-1, DC(HIV) become resistant to NK-induced TRAIL-mediated apoptosis. This resistance occurs despite normal amounts of TRAIL released by NK cells and comparable DR4 expression on DC(HIV). The escape of DC(HIV) from NK killing is due to the upregulation of two anti-apoptotic molecules, the cellular-Flice like inhibitory protein (c-FLIP) and the cellular inhibitor of apoptosis 2 (c-IAP2), induced by NK-DC(HIV) cognate interaction. High-mobility group box 1 (HMGB1), an alarmin and a key mediator of NK-DC cross-talk, was found to play a pivotal role in NK-dependent upregulation of c-FLIP and c-IAP2 in DC(HIV). Finally, we demonstrate that restoration of DC(HIV) susceptibility to NK-induced TRAIL killing can be obtained either by silencing c-FLIP and c-IAP2 by specific siRNA, or by inhibiting HMGB1 with blocking antibodies or glycyrrhizin, arguing for a key role of HMGB1 in TRAIL resistance and DC(HIV) survival. These findings provide evidence for a new strategy developed by HIV to escape immune attack, they challenge the question of the involvement of HMGB1 in the establishment of viral reservoirs in DCs, and they identify potential therapeutic targets to eliminate infected DCs.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Constitutive activation of the Janus kinase (JAK)/signal transducer and activator of transcription (STAT) axis is fundamental to the molecular pathogenesis of a host of hematological disorders, ...including acute leukemias and myeloproliferative neoplasms (MPN). We demonstrate here that the major JAK2 mutation observed in these diseases (JAK2.sup.V617F) enforces Mcl-1 transcription via STAT3 signaling. Targeting this lesion with JAK inhibitor I (JAKi-I) attenuates STAT3 binding to the Mcl-1 promoter and suppresses Mcl-1 transcript and protein expression. The neutralization of Mcl-1 in JAK2.sup.V617F -harboring myelodyssplastic syndrome cell lines sensitizes them to apoptosis induced by the BH3-mimetic and Bcl-xL/Bcl-2 inhibitor, ABT-263. Moreover, simultaneously targeting JAK and Bcl-xL/-2 is synergistic in the presence of the JAK2.sup.V617F mutation. These findings suggest that JAK/Bcl-xL/-2 inhibitor combination therapy may have applicability in a range of hematological disorders characterized by activating JAK2 mutations.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Summary Tumour necrosis factor-related apoptosis-inducing ligand or Apo2 ligand (TRAIL/Apo2L) is a member of the tumour necrosis factor (TNF) superfamily of cytokines that induces apoptosis upon ...binding to its death domain-containing transmembrane receptors, death receptors 4 and 5 (DR4, DR5). Importantly, TRAIL preferentially induces apoptosis in cancer cells while exhibiting little or no toxicity in normal cells. To date, research has focused on the mechanism of apoptosis induced by TRAIL and the processes involved in the development of TRAIL resistance. TRAIL-resistant tumours can be re-sensitized to TRAIL by a combination of TRAIL with chemotherapeutics or irradiation. Studies suggest that in many cancer cells only one of the two death-inducing TRAIL receptors is functional. These findings as well as the aim to avoid decoy receptor-mediated neutralization of TRAIL led to the development of receptor-specific TRAIL variants and agonistic antibodies. These molecules are predicted to be more potent than native TRAIL in vivo and may be suitable for targeted treatment of particular tumours. This review focuses on the current status of TRAIL receptor-targeting for cancer therapy, the apoptotic signalling pathway induced by TRAIL receptors, the prognostic implications of TRAIL receptor expression and modulation of TRAIL sensitivity of tumour cells by combination therapies. The mechanisms of TRAIL resistance and the potential measures that can be taken to overcome them are also addressed. Finally, the status of clinical trials of recombinant TRAIL and DR4-/DR5-specific agonistic antibodies as well as the pre-clinical studies of receptor-selective TRAIL variants is discussed including the obstacles facing the use of these molecules as anti-cancer therapeutics.
Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has received attention as an anticancer therapy because it mediates apoptosis of several cancer cell types but not normal human cell ...types. In this study, we implemented genome editing techniques to upregulate DR5 and downregulate cFLIP in HeLa cells to stimulate TRAIL-induced apoptosis. We designed and validated sgRNAs to enrich the endogenous level of DR5 by dead Cas9 (dCas9). Similarly, we designed two sgRNAs to disrupt the cFLIP gene by CRISPR/Cas9. We analyzed the effect of TRAIL on tumor cells by co-transfecting HeLa cells with the best combinations of sgRNAs regulating DR5 and cFLIP genes. TRAIL-induced apoptosis in HeLa cells was evaluated by the γH2AX foci formation assay to check for double-strand break and propidium iodide and Annexin V staining to quantify apoptotic cells. Viable cells were identified by CCK-8 assay, and cleaved-PARP level was evaluated by Western blot. This is the first study to demonstrate that genome editing techniques can be used as an effective combinatorial treatment strategy to induce apoptosis of cancer cells. In particular, enhancement of DR5 expression and inhibition of cFLIP expression by genome editing had a synergistic effect of inhibiting proliferation and inducing apoptosis in TRAIL-resistant HeLa cells. These results suggest that combinatorial treatment strategies mediated by the CRISPR/Cas9 system may be effective for design of other human TRAIL-resistant cell types.
•First time to implement genome editing techniques in TRAIL therapy for cancer cells.•Endogenous DR5 gene activation by dead Cas9 sensitize HeLa cells to TRAIL treatment.•Gene disruption of cFLIP by CRISPR/Cas9 sensitize HeLa cells to TRAIL treatment.•DR5 and cFLIP synergistically sensitize HeLa cells to TRAIL-mediated apoptosis.
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