The molecular mechanism(s) by which Toll-like receptors become activated are not well understood. For the majority of TLR receptors, dimerization is a prerequisite to facilitate MyD88-TLR complex formation and subsequent cellular signaling to activate NF-κB. However, the parameters controlling interactions between the receptors and their ligands still remain poorly defined. Previous reports have identified that neuraminidase-1 (NEU1) is an important intermediate in the initial process of TLR ligand induced receptor activation and subsequent cell function. What we do not yet understand is how NEU1 is activated following TLR ligand binding. In this thesis, the findings disclose a receptor signaling paradigm involving a process of receptor ligand-induced GPCR-signaling via neuromedin-B (NMBR) Gα-proteins, matrix metalloproteinase-9 (MMP-9) activation, and the induction of Neu1 activation. Central to this process is that NEU1–MMP-9-NMBR complex is associated with TLR-4 receptors on the cell surface of naive primary macrophages and TLR-expressing cell lines. Ligand binding to the receptor initiate GPCR-signaling via GPCR Gα subunit proteins and MMP-9 activation to induce NEU1. Activated NEU1 targets and hydrolyzes sialyl α-2-3-linked to β-galactosyl residues at the ectodomain of TLRs, enabling the removal of steric hindrance to receptor association, activation of receptors and cellular signaling. Furthermore, a novel glycosylation model is uncovered for the activation of nucleic acid sensing intracellular TLR-7 and TLR-9 receptors. It discloses an identical signaling paradigm as described for the cell-surface TLRs. NEU1 and MMP9 cross-talk in alliance with neuromedin-B receptors tethered to TLR-7 and -9 receptors at the ectodomain is essential for ligand activation of the TLRs and pro-inflammatory responses. However, the mechanism(s) behind this GPCR and TLR cross-talk has not been fully defined. Here, GPCR agonists mediate GPCR-signaling via membrane Gα subunit proteins to induce NEU1 and MMP-9 cross-talk at the TLR ectodomain on the cell surface. This molecular organizational GPCR signaling platform is proposed to be an initial processing stage for GPCR agonist-induced transactivation of TLRs and subsequent cellular signaling. Collectively, these novel findings radically redefine the current dogma(s) governing the mechanism(s) of the interaction of TLRs and their ligands, which may provide important pioneering approaches to disease intervention strategies. / Thesis (Ph.D, Microbiology & Immunology) -- Queen's University, 2013-04-30 12:23:42.429

Dissertation (Ph.D.)--Auburn University, 2006. / Abstract. Vita. Includes bibliographic references.

Burns often leads to infection, due to damage to the skin's protective barrier. Burn injury has been repeatedly shown to induce considerable inflammatory and immune dysfunction. The innate immune system is a universal and ancient form of host defense against infection. Activation of innate immunity constitutes the first line of host defense against infection. Neutrophils are white blood cells and part of the immune system. They are the most common PMN (polymorphonuclear neutrophils) and accounted for 70% of all leukocytes. Neutrophils provided the first line of defense of the innate immune system by phagocytosing, killing, and digesting bacteria and fungi. Priming means a process whereby the response of neutrophils to an activating stimulus is potentiated, sometimes greatly, by prior to exposure to priming agents such as tumor necrosis factor-alpha(TNF-alpha), platelet-activating factor (PAF). Neutrophil priming causes a dramatic increase in the response of these cells to an activating agent; this process has been shown to be critical for neutrophil-mediated tissue injury both in vitro and in vivo. However, the intracellular signaling pathways used by neutrophil in response to pro-inflammatory stimuli have not been elucidated. The discovery of TLRs has made us understanding of the mechanisms of innate immune recognition. The innate immune system detectes the invasion of microorganism through TLRs, which recognize microbial components and trigger inflammatory responses. Severe burn injury produces shock and induces acute gastrointestinal derangement that may disrupt gastrointestinal mucosa integrity and facilitate the bacterial translocation (BT) to Mesenteric lymph node (MLN), liver, and spleen. Hypertonic saline (HTS) has been advocated in thermal injury resuscitation because of the possibility of giving less total volume of resuscitation fluid, with a resulting decrease in edema and the need for escharotomy. In this study, I found that priming effect of BM neutrophils is TNF-alpha and p38 dependent and TLRs play a critical role to the innate immunity by recognizing bacteria and HTS enhance host response to bacterial challenge by increasing TLRs of inflammatory cells.

Receptor glycosylation is critical in receptor-ligand interactions in immune cells, but the exact role of glycosylation in receptor activation upon ligand binding has not been elucidated. In neuronal cells, we have shown that when neurotrophic factors bind their respective Trk tyrosine kinase receptors, receptor activation and subsequent neurotrophin-mediated signaling is dependent upon the induction and activity of an endogenous sialidase enzyme. In this thesis, we report that toll-like receptor (TLR) activation upon ligand binding is similarly dependent on the induction of a cellular sialidase, which we have identified as Neu1 sialidase, which specifically targets and hydrolyses alpha-2,3-linked sialic acid residues on the receptor. Blocking Neu1 sialidase activity with specific inhibitor Tamiflu detrimentally impacts ligand-induced TLR4/MyD88 interaction, NFkappaB activation and TLR-mediated effector responses like nitric oxide and pro-inflammatory cytokine production. Diminished cytokine production is also seen in vivo in Neu1-deficient mice. We propose a mechanism for the induction of Neu1 sialidase, upon ligand binding to TLR, that involves the activation of heterotrimeric G-alpha protein-dependent G-protein coupled receptor (GPCR) signaling to activate a matrix metalloproteinase (MMP) enzyme, likely MMP-9. It is suggested that MMP-(9) targets the cell surface elastin receptor complex of Neu1/protective protein cathepsinA/elastin binding protein (EBP), which potentially catalytically activates Neu1. In addition, we report an association between Neu1 and TLR2, TLR3 and TLR4 on the plasma membrane that has not previously been described. The idea that the multiple functionality and diversity of TLRs and TLR-mediated signaling may be an immunologic paradigm capable of explaining all human disease is provocative but plausible. Certainly, the structural integrity of TLRs, their ligand interactions and activation are essential for immunological protection. Thus, understanding the molecular mechanism of Neu1 sialidase regulation of TLR activation will provide important opportunities for disease control through TLR manipulation. The future directions of this research will also open a new area of glycobiology research (the glycomics of innate immune responses) and will widen the scope for the development of novel therapeutic drugs to combat infections and inflammatory diseases. / Thesis (Ph.D, Microbiology & Immunology) -- Queen's University, 2009-01-26 12:33:32.743

Thesis (Ph. D.)--Case Western Reserve University, 2007. / [School of Medicine] Department of Pathology. Includes bibliographical references.

Submitted by Isaac Francisco de Souza Dias (isaac.souzadias@ufpe.br) on 2015-05-19T16:34:38Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) DISSERTAÇÃO Carolina da Rocha Simões.pdf: 2694652 bytes, checksum: 6446d4fa347e53fe42ce7e769f745124 (MD5) / Made available in DSpace on 2015-05-19T16:34:38Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) DISSERTAÇÃO Carolina da Rocha Simões.pdf: 2694652 bytes, checksum: 6446d4fa347e53fe42ce7e769f745124 (MD5) Previous issue date: 2014-02-20 / CAPES / O aumento da informação proveniente do sequenciamento de alta performance (NGS), e de projetos como o 1000 genomas e HapMap, permitiram a descoberta de milhões de variações. Entretanto, o maior desafio é a identificação da relação entre o genótipo e o fenótipo, proporcionando informações que possam ajudar a definir os polimorfismos que podem ou não causar doenças. Ferramentas computacionais tem auxiliado na predição das modificações estruturais geradas pelos polimorfismos, e as consequentes alterações funcionais sofridas pelas proteínas. Os receptores Toll Like (TLR) são proteínas do sistema imunológico que estão envolvidas na regulação da inflamação e em alguns casos no desenvolvimento do câncer. O objetivo deste projeto foi analisar, através de ferramentas in silico, os polimorfismos de base única nos genes das TLRs, buscando por polimorfismos que possam estar relacionados com a predisposição ao câncer e com alterações da via de sinalização das TLRs. Foram encontrados 37 genes que estão envolvidos na via de sinalização e podem ser utilizados como marcadores genéticos (biomarcadores) para o diagnóstico e predição das alterações na expressão dos genes relacionados à esta via. Estes genes, se regulados, podem ser utilizados como inibidores. Em relação aos polimorfismos foram coletados no banco de dados dbSNP/NCBI 5.839 SNPs entre os 10 genes das TLRs. Destes, 1.017 variações foram classificadas como missense e analisadas para avaliar as consequências estruturais pela troca dos aminoácidos. Para isso quatro ferramentas preditoras (SIFT, Polyphen, MutationAssessor e SDM) foram utilizadas gerando informações sobre as modificações e associando-as com possíveis danos nas proteínas. Dos polimorfismos analisados 223 foram classificados como danosos baseados na troca de aminoácido e podem causar uma desregulação funcional na proteína. Entre eles está o rs5743708 (TLR2), rs3775291, (TLR3) e rs11466653 (TLR10) que já foi estudado in vitro e tiveram associação com câncer colorectal (TLR2 e 3) e carcinoma da tireóide (TLR10). A predição prévia, in silico, das alterações funcionais pode auxiliar na interpretação das variações gênicas, neste caso associadas com o câncer, e também na caracterização precisa dos fatores que levam a estas alterações, contribuindo no diagnóstico, na prevenção e em melhores respostas aos tratamentos oferecidos.

Yes / Alopecia areata (AA) is thought to be an autoimmune process. In other autoimmune diseases, the innate immune system and Toll‐like receptors (TLRs) can play a significant role. Expression of TLR7, TLR9 and associated inducible genes was evaluated by quantitative PCR in peripheral blood mononuclear cells (PBMCs) from 10 healthy individuals and 19 AA patients, categorized according to disease duration, activity and hair loss extent. Microdissected scalp biopsies from five patients and four controls were also assessed by quantitative PCR and immunohistology. TLR9 was significantly upregulated 2.37 fold in AA PBMCs. Notably, TLR9 was most significantly upregulated in patients with active AA, as shown by a positive hair pull test, compared to stable AA patients. In hair follicle bulbs from AA patients, IFNG and TLR7 exhibited statistically significant 3.85 and 2.70 fold increases in mRNA, respectively. Immunohistology revealed TLR7 present in lesional follicles, while TLR9 positive cells were primarily observed peri‐bulbar to AA affected hair follicles. The increased expression of TLR7 and TLR9 suggest components of the innate immune system may be active in AA pathogenesis. / National Alopecia Areata Foundation; Canadian Dermatology Foundation; Michael Smith Foundation for Health Research, Grant/Award Number: CI‐SCH‐00480(06‐1); Canadian Institutes of Health Research, Grant/Award Number: MOP‐167368 and MSH‐192593‐140450

Toll-like receptors (TLRs), named after toll proteins identified in Drosophila melanogaster, are the pattern recognition receptors in the innate immune system that detect microbes. TLRs are mono, membrane-spanning, as well as non-catalytic receptors, which are mainly expressed in sentinel cells, such as the dendritic cells, neutrophils and macrophages. While humans have ten TLRs (TLR 1 to 10), the mouse has another three (TLRs 11, 12, 13). TLRs are made up of glycoproteins, which have luminal ligand-binding sites consisting of leucine-rich repeat (LRR) for detection of pathogens leading to activation of immune cells. TLR1, 2, 4, and 6 are responsible for recognition of lipids (such as triacetylated lipopeptide), peptidoglycan, and lipopolysaccharide (LPS). However, the TLR3, 7, 8, and 9 mainly recognize nucleic acids, such as double-stranded RNA (dsRNA) and CpG DNA, while the TLR13 detects ribosomal RNA sequences. So far, there are no data on the localization and immunological functions of TLR10. I studied the expression, localization and role of TLR10 in S. pneumoniae infection. First, I examined the expression of TLR10 in lungs of pig, cattle, dog, rat, and chickens. The light and electron microscopic data show TLR10 expression in vascular endothelium and smooth muscles in lungs of control and inflamed animals. Further, we found altered basal level of expression and localization of TLR10 in bovine neutrophils treated with E. coli lipopolysaccharide. These data show the expression of TLR10 in the lungs of tested animal species, and its alteration by LPS in bovine neutrophils. The next study was designed to investigate the regulation of TLR10 expression and to address its role in neutrophil chemotaxis. E. coli LPS activated human neutrophils showed temporal and spatial change in TLR10 expression. Confocal microscopy showed cytosolic and nuclear distribution of TLR10 in normal and activated neutrophils. TLR10 in E. coli LPS-activated neutrophils colocalized with flotallin-1, a lipid raft marker, and EEA-1, an early endosomal marker, suggested its endocytosis. Live cell imaging of LPS activated neutrophils showed TLR10 translocation to the leading edge. Neutrophils upon TLR10 knockdown were unable for fMLP-induced migration. TLR10 knockdown reduced the number of membrane pseudopods in activated neutrophils without altering the expression of key proteins of actin nucleation process, ARP-3 and Diap1. These data show TLR4-mediated pathway for regulation of TLR10 expression, and that TLR10 may have a role in neutrophil chemotaxis. Next, I examined the role of TLR10 in innate immune response to S. pneumoniae infection in U937 human macrophage cell line. S. pneumoniae are major causative agents of pneumonia, meningitis and bacteremia. A significant increase in TLR10 mRNA expression was found in S. pneumoniae (107 cfu for 6hr) challenged macrophages. TLR10 knockdown significantly reduced production of IL-1β, IL-8, IL-17 and TNF-α and no significant change in IL-10 expression, and also significantly diminished nuclear translocation of NF-κB but without affecting the phagocytosis of S. pneumoniae. Altogether, I report the that TLR10 is expressed in the normal and inflamed lungs in cattle, pigs, dogs, rats, chickens and humans. The expression of TLR10 is altered in activated neutrophils, and it plays a role in neutrophils chemotaxis and production of pro-inflammatory cytokines in macrophages infected with S. pneumoniae.

Cytomegaloviruses (CMV), the prototypical β-herpesviruses, have co-evolved with their hosts and thus acquired multiple strategies for modulation of the immune response. Viral engagement of pattern recognition receptors (PRR), such as toll-like receptors (TLRs) and cytosolic nucleic acids sensors, initiates the host immune response through activation of elaborate signalling programs. The ensuing inflammatory response is further sustained and amplified through cytokines, such as IL-1β, activating signalling pathways greatly overlapping those utilized by TLRs. The central hypothesis of this thesis is that a viral counter-measure by murine CMV (MCMV) involves specific targeting of TLR- and IL-1β-induced signalling along the MyD88 to NF-κB pathway. To test this hypothesis MCMV inhibition of IL-1β signalling was initially investigated in a fibroblast cell line. It was demonstrated that in MCMV infected cells IL-1β-induced IκBα degradation is largely inhibited. Comparison of productive and non-productive infection showed this modulation requires de-novo viral gene expression beyond the immediate early region. Further investigations utilising a ORF M45 deletion mutant identified viral gene M45 as necessary for mediating the observed modulation of IL-1β- induced IκBα degradation. To further test the hypothesis, studies were extended to include TLR stimulation in the context of bone marrow-derived macrophages (BMDM) infection. It was found that TLR7/9-induced NF-κB activation is inhibited in MCMV infected BMDM. Overall, data presented in this study demonstrate a previously unrecognised MCMV inhibition of IL-1β- and TLR7/9-induced NF-κB activation, and indicate a role for viral gene M45 in mediating this effect.

Mutation, whether spontaneous or induced, is the premier tool for understanding gene function. One approach is to create mutations in a specific gene, and then use the resulting cell or organism to search for a phenotype. An alternative is to create mutations at random, and focus first on the identification of phenotypes. The mutation that underlies a phenotype can then be tracked down, forming the foundation of testable hypotheses. Using random chemical mutagenesis in mice, I have identified 20 heritable phenotypes affecting either the innate or adaptive branches of immunity. The genetic basis of 18 of these phenotypes was solved, caused by mutations in at least 16 unique genes. Five of these genes were not previously known to be involved in immunity, and a detailed analysis of four of them is provided in this thesis. These include genes encoding the following proteins: the inactive rhomboid protease iRhom2, which is specifically required for the secretion of tumour necrosis factor alpha; the hypothetical phospholipid flippase ATP11C, required for B cell development in the adult bone marrow; the folliculin-interacting protein FNIP1, also required for B cell development; and the zinc finger transcription factor ZBTB1, essential for the development of all lymphocyte lineages. These findings uncover new entry points for the understanding of mammalian immunity, and highlight the value of mouse forward genetics in the understanding of mammalian phenomena in general.