scholarly journals Cytosolic Sensors for Pathogenic Viral and Bacterial Nucleic Acids in Fish

2020 ◽  
Vol 21 (19) ◽  
pp. 7289
Author(s):  
Miriam Mojzesz ◽  
Krzysztof Rakus ◽  
Magdalena Chadzinska ◽  
Kentaro Nakagami ◽  
Gouranga Biswas ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Nucleic Acids ◽  
Current Knowledge ◽  
Innate Immune ◽  
Rna Helicases ◽  
Protein Kinase R ◽  
Evolutionarily Conserved ◽  
Different Types ◽  
Molecular Patterns ◽  
Inducible Gene

Recognition of the non-self signature of invading pathogens is a crucial step for the initiation of the innate immune mechanisms of the host. The host response to viral and bacterial infection involves sets of pattern recognition receptors (PRRs), which bind evolutionarily conserved pathogen structures, known as pathogen-associated molecular patterns (PAMPs). Recent advances in the identification of different types of PRRs in teleost fish revealed a number of cytosolic sensors for recognition of viral and bacterial nucleic acids. These are DExD/H-box RNA helicases including a group of well-characterized retinoic acid inducible gene I (RIG-I)-like receptors (RLRs) and non-RLR DExD/H-box RNA helicases (e.g., DDX1, DDX3, DHX9, DDX21, DHX36 and DDX41) both involved in recognition of viral RNAs. Another group of PRRs includes cytosolic DNA sensors (CDSs), such as cGAS and LSm14A involved in recognition of viral and intracellular bacterial dsDNAs. Moreover, dsRNA-sensing protein kinase R (PKR), which has a role in antiviral immune responses in higher vertebrates, has been identified in fish. Additionally, fish possess a novel PKR-like protein kinase containing Z-DNA binding domain, known as PKZ. Here, we review the current knowledge concerning cytosolic sensors for recognition of viral and bacterial nucleic acids in teleosts.

scholarly journals The NLRP3 Inflammasome and Its Role in the Pathogenicity of Leukemia

2021 ◽  
Vol 22 (3) ◽  
pp. 1271
Author(s):  
Laura Urwanisch ◽  
Michela Luciano ◽  
Jutta Horejs-Hoeck
Keyword(s):  
Nlrp3 Inflammasome ◽  
Innate Immune System ◽  
Inflammatory Cell ◽  
Current Knowledge ◽  
Innate Immune ◽  
Leukemic Cells ◽  
Different Types ◽  
Molecular Patterns ◽  
Damage Associated Molecular Patterns

Chronic inflammation contributes to the development and progression of various tumors. Especially where the inflammation is mediated by cells of the innate immune system, the NLRP3 inflammasome plays an important role, as it senses and responds to a variety of exogenous and endogenous pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs). The NLRP3 inflammasome is responsible for the maturation and secretion of the proinflammatory cytokines interleukin-1β (IL-1β) and IL-18 and for the induction of a type of inflammatory cell death known as pyroptosis. Overactivation of the NLRP3 inflammasome can be a driver of various diseases. Since leukemia is known to be an inflammation-driven cancer and IL-1β is produced in elevated levels by leukemic cells, research on NLRP3 in the context of leukemia has increased in recent years. In this review, we summarize the current knowledge on leukemia-promoting inflammation and, in particular, the role of the NLRP3 inflammasome in different types of leukemia. Furthermore, we examine a connection between NLRP3, autophagy and leukemia.

scholarly journals NOD-Like Receptors: Guards of Cellular Homeostasis Perturbation during Infection

2021 ◽  
Vol 22 (13) ◽  
pp. 6714
Author(s):  
Gang Pei ◽  
Anca Dorhoi
Keyword(s):  
Immune System ◽  
Innate Immune System ◽  
Current Knowledge ◽  
Protein Translation ◽  
Innate Immune ◽  
Cellular Homeostasis ◽  
Translation Block ◽  
Cytoskeleton Disruption ◽  
Molecular Patterns ◽  
Fine Tune

The innate immune system relies on families of pattern recognition receptors (PRRs) that detect distinct conserved molecular motifs from microbes to initiate antimicrobial responses. Activation of PRRs triggers a series of signaling cascades, leading to the release of pro-inflammatory cytokines, chemokines and antimicrobials, thereby contributing to the early host defense against microbes and regulating adaptive immunity. Additionally, PRRs can detect perturbation of cellular homeostasis caused by pathogens and fine-tune the immune responses. Among PRRs, nucleotide binding oligomerization domain (NOD)-like receptors (NLRs) have attracted particular interest in the context of cellular stress-induced inflammation during infection. Recently, mechanistic insights into the monitoring of cellular homeostasis perturbation by NLRs have been provided. We summarize the current knowledge about the disruption of cellular homeostasis by pathogens and focus on NLRs as innate immune sensors for its detection. We highlight the mechanisms employed by various pathogens to elicit cytoskeleton disruption, organelle stress as well as protein translation block, point out exemplary NLRs that guard cellular homeostasis during infection and introduce the concept of stress-associated molecular patterns (SAMPs). We postulate that integration of information about microbial patterns, danger signals, and SAMPs enables the innate immune system with adequate plasticity and precision in elaborating responses to microbes of variable virulence.

scholarly journals The Stress Granule Protein G3BP1 Recruits Protein Kinase R To Promote Multiple Innate Immune Antiviral Responses

2014 ◽  
Vol 89 (5) ◽  
pp. 2575-2589 ◽  
Author(s):  
Lucas C. Reineke ◽  
Richard E. Lloyd
Keyword(s):  
Protein Kinase ◽  
Antiviral Activity ◽  
Cellular Stress ◽  
Stress Granules ◽  
Innate Immune ◽  
Stress Granule ◽  
Productive Infection ◽  
Antiviral Protein ◽  
Protein Kinase R ◽  
Transcriptional Responses

ABSTRACTStress granules (SGs) are cytoplasmic storage sites containing translationally silenced mRNPs that can be released to resume translation after stress subsides. We previously showed that poliovirus 3C proteinase cleaves the SG-nucleating protein G3BP1, blocking the ability of cells to form SGs late in infection. Many other viruses also target G3BP1 and inhibit SG formation, but the reasons why these functions evolved are unclear. Previously, we also showed a link between G3BP1-induced SGs and protein kinase R (PKR)-mediated translational control, but the mechanism of PKR interplay with SG and the antiviral consequences are unknown. Here, we show that G3BP1 exhibits antiviral activity against several enteroviruses, whereas truncated G3BP1 that cannot form SGs does not. G3BP1-induced SGs are linked to activation of innate immune transcriptional responses through NF-κB and JNK. The G3BP1-induced SGs also recruit PKR and other antiviral proteins. We show that the PXXP domain within G3BP1 is essential for the recruitment of PKR to SGs, for eIF2α phosphorylation driven by PKR, and for nucleating SGs of normal composition. We also show that deletion of the PXXP domain in G3BP1 compromises its antiviral activity. These findings tie PKR activation to its recruitment to SGs by G3BP1 and indicate that G3BP1 promotes innate immune responses at both the transcriptional and translational levels and integrates cellular stress responses and innate immunity.IMPORTANCEStress granules appear during virus infection, and their importance is not well understood. Previously, it was assumed that they were nonfunctional artifacts associated with cellular stress. PKR is a well-known antiviral protein; however, its regulation in cells is not well understood. Our work links cellular stress granules with activation of PKR and other innate immune pathways through the activity of G3BP1, a critical stress granule component. The ability of stress granules and G3BP1 to activate PKR and other innate immune transcriptional responses indicates that G3BP1 is an antiviral protein. This work helps to refine a longstanding paradigm indicating stress granules are inert structures and explains why G3BP1 is subverted by many viruses to promote a productive infection.

Pathogen recognition in the innate immune response

2009 ◽  
Vol 420 (1) ◽  
pp. 1-16 ◽  
Author(s):  
Himanshu Kumar ◽  
Taro Kawai ◽  
Shizuo Akira
Keyword(s):  
Immune Responses ◽  
Germ Line ◽  
Innate Immune ◽  
Microbial Pathogens ◽  
Signalling Pathways ◽  
Pathogen Recognition ◽  
Adaptive Immune ◽  
Evolutionarily Conserved ◽  
Cellular Compartments ◽  
Inducible Gene

Immunity against microbial pathogens primarily depends on the recognition of pathogen components by innate receptors expressed on immune and non-immune cells. Innate receptors are evolutionarily conserved germ-line-encoded proteins and include TLRs (Toll-like receptors), RLRs [RIG-I (retinoic acid-inducible gene-I)-like receptors] and NLRs (Nod-like receptors). These receptors recognize pathogens or pathogen-derived products in different cellular compartments, such as the plasma membrane, the endosomes or the cytoplasm, and induce the expression of cytokines, chemokines and co-stimulatory molecules to eliminate pathogens and instruct pathogen-specific adaptive immune responses. In the present review, we will discuss the recent progress in the study of pathogen recognition by TLRs, RLRs and NLRs and their signalling pathways.

Role of Toll-like receptors in liver health and disease

2011 ◽  
Vol 121 (10) ◽  
pp. 415-426 ◽  
Author(s):  
Ruth Broering ◽  
Mengji Lu ◽  
Joerg F. Schlaak
Keyword(s):  
Immune System ◽  
Liver Disease ◽  
Innate Immune System ◽  
Innate Immune ◽  
Toll Like Receptors ◽  
Evolutionarily Conserved ◽  
Liver Health ◽  
Health And Disease ◽  
Molecular Patterns

TLRs (Toll-like receptors), as evolutionarily conserved germline-encoded pattern recognition receptors, have a crucial role in early host defence by recognizing so-called PAMPs (pathogen-associated molecular patterns) and may serve as an important link between innate and adaptive immunity. In the liver, TLRs play an important role in the wound healing and regeneration processes, but they are also involved in the pathogenesis and progression of various inflammatory liver diseases, including autoimmune liver disease, alcoholic liver disease, non-alcoholic steatohepatitis, fibrogenesis, and chronic HBV (hepatitis B virus) and HCV (hepatitis C virus) infection. Hepatitis viruses have developed different evading strategies to subvert the innate immune system. Thus recent studies have suggested that TLR-based therapies may represent a promising approach in the treatment in viral hepatitis. The present review focuses on the role of the local innate immune system, and TLRs in particular, in the liver.

scholarly journals Regulation of Actin Dynamics by Protein Kinase R Control of Gelsolin Enforces Basal Innate Immune Defense

Immunity ◽  
2012 ◽  
Vol 36 (5) ◽  
pp. 795-806 ◽  
Author(s):  
Aaron T. Irving ◽  
Die Wang ◽  
Oliver Vasilevski ◽  
Olivier Latchoumanin ◽  
Noga Kozer ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Immune Defense ◽  
Innate Immune ◽  
Actin Dynamics ◽  
Protein Kinase R ◽  
Innate Immune Defense

scholarly journals CD14 is a coreceptor of Toll-like receptors 7 and 9

2010 ◽  
Vol 207 (12) ◽  
pp. 2689-2701 ◽  
Author(s):  
Christoph L. Baumann ◽  
Irene M. Aspalter ◽  
Omar Sharif ◽  
Andreas Pichlmair ◽  
Stephan Blüml ◽  
...  
Keyword(s):  
Nucleic Acid ◽  
Nucleic Acids ◽  
Innate Immune ◽  
Confocal Imaging ◽  
Acid Uptake ◽  
Innate Immune Responses ◽  
Toll Like Receptors ◽  
Molecular Patterns ◽  
Cluster Of Differentiation

Recognition of pathogens by the innate immune system requires proteins that detect conserved molecular patterns. Nucleic acids are recognized by cytoplasmic sensors as well as by endosomal Toll-like receptors (TLRs). It has become evident that TLRs require additional proteins to be activated by their respective ligands. In this study, we show that CD14 (cluster of differentiation 14) constitutively interacts with the MyD88-dependent TLR7 and TLR9. CD14 was necessary for TLR7- and TLR9-dependent induction of proinflammatory cytokines in vitro and for TLR9-dependent innate immune responses in mice. CD14 associated with TLR9 stimulatory DNA in precipitation experiments and confocal imaging. The absence of CD14 led to reduced nucleic acid uptake in macrophages. Additionally, CD14 played a role in the stimulation of TLRs by viruses. Using various types of vesicular stomatitis virus, we showed that CD14 is dispensable for viral uptake but is required for the triggering of TLR-dependent cytokine responses. These data show that CD14 has a dual role in nucleic acid–mediated TLR activation: it promotes the selective uptake of nucleic acids, and it acts as a coreceptor for endosomal TLR activation.

scholarly journals Protein Kinase R in Bacterial Infections: Friend or Foe?

2021 ◽  
Vol 12 ◽  
Author(s):  
Robin Smyth ◽  
Jim Sun
Keyword(s):  
Immune Response ◽  
Protein Kinase ◽  
Bacterial Infections ◽  
Current Knowledge ◽  
Bacterial Pathogens ◽  
Treatment Strategies ◽  
Protein Translation ◽  
Protein Kinase R ◽  
Cell Functions ◽  
Pharmacological Modulators

The global antimicrobial resistance crisis poses a significant threat to humankind in the coming decades. Challenges associated with the development of novel antibiotics underscore the urgent need to develop alternative treatment strategies to combat bacterial infections. Host-directed therapy is a promising new therapeutic strategy that aims to boost the host immune response to bacteria rather than target the pathogen itself, thereby circumventing the development of antibiotic resistance. However, host-directed therapy depends on the identification of druggable host targets or proteins with key functions in antibacterial defense. Protein Kinase R (PKR) is a well-characterized human kinase with established roles in cancer, metabolic disorders, neurodegeneration, and antiviral defense. However, its role in antibacterial defense has been surprisingly underappreciated. Although the canonical role of PKR is to inhibit protein translation during viral infection, this kinase senses and responds to multiple types of cellular stress by regulating cell-signaling pathways involved in inflammation, cell death, and autophagy – mechanisms that are all critical for a protective host response against bacterial pathogens. Indeed, there is accumulating evidence to demonstrate that PKR contributes significantly to the immune response to a variety of bacterial pathogens. Importantly, there are existing pharmacological modulators of PKR that are well-tolerated in animals, indicating that PKR is a feasible target for host-directed therapy. In this review, we provide an overview of immune cell functions regulated by PKR and summarize the current knowledge on the role and functions of PKR in bacterial infections. We also review the non-canonical activators of PKR and speculate on the potential mechanisms that trigger activation of PKR during bacterial infection. Finally, we provide an overview of existing pharmacological modulators of PKR that could be explored as novel treatment strategies for bacterial infections.

scholarly journals Sin1-mediated mTOR signaling in cell growth, metabolism and immune response

2019 ◽  
Vol 6 (6) ◽  
pp. 1149-1162
Author(s):  
Chun Ruan ◽  
Xinxing Ouyang ◽  
Hongzhi Liu ◽  
Song Li ◽  
Jingsi Jin ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Current Knowledge ◽  
Mammalian Target Of Rapamycin ◽  
Adaptor Protein ◽  
Interaction Network ◽  
Mitogen Activated Protein Kinase ◽  
Cellular Functions ◽  
Evolutionarily Conserved ◽  
Mitogen Activated Protein ◽  
Growth Metabolism

Abstract The mammalian target of rapamycin (mTOR) is an evolutionarily conserved Ser/Thr protein kinase with essential cellular function via processing various extracellular and intracellular inputs. Two distinct multi-protein mTOR complexes (mTORC), mTORC1 and mTORC2, have been identified and well characterized in eukaryotic cells from yeast to human. Sin1, which stands for Sty1/Spc1-interacting protein1, also known as mitogen-activated protein kinase (MAPK) associated protein (MAPKAP)1, is an evolutionarily conserved adaptor protein. Mammalian Sin1 interacts with many cellular proteins, but it has been widely studied as an essential component of mTORC2, and it is crucial not only for the assembly of mTORC2 but also for the regulation of its substrate specificity. In this review, we summarize our current knowledge of the structure and functions of Sin1, focusing specifically on its protein interaction network and its roles in the mTOR pathway that could account for various cellular functions of mTOR in growth, metabolism, immunity and cancer.

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