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1.
J Biol Chem ; 2020 Feb 28.
Artigo em Inglês | MEDLINE | ID: mdl-32111741

RESUMO

Leucine-rich repeat kinase 2 (LRRK2) encodes a complex protein that includes both kinase and GTPase domains. Genome-wide association studies have identified dominant LRRK2 alleles that predispose their carriers to late-onset idiotypic Parkinson's disease (PD) and also to autoimmune disorders such as Crohn's disease. Considerable evidence indicates that PD initiation and progression involve the activation of innate immune functions in microglia, which are brain-resident macrophages. Here, we asked whether LRRK2 modifies inflammatory signaling and how this modification might contribute to PD and Crohn's disease. We used RNA-Seq-based high-resolution transcriptomics to compare gene expression in activated primary macrophages derived from wild-type and Lrrk2-knockout mice. Remarkably, expression of a single gene, Rap guanine nucleotide exchange factor 3 (Rapgef3), was strongly up-regulated in the absence of LRRK2 and down-regulated in its presence. We observed a similar regulation of Rapgef3 expression in cells treated with a highly specific inhibitor of LRRK2 protein kinase activity. Rapgef3 encodes an exchange protein, activated by cAMP 1 (EPAC-1), a guanine nucleotide exchange factor that activates the small GTPase Rap-1. Rap-1 mediates cell adhesion, polarization, and directional motility, and our results indicate that LRRK2 modulates chemotaxis of microglia and macrophages. Dominant PD-associated LRRK2 alleles may suppress EPAC-1 activity, further restricting motility and preventing efficient migration of microglia to sites of neuronal damage. Functional analysis in vivo in a sub-clinical infection model also indicated that LRRK2 subtly modifies the inflammatory response. These results indicate that LRRK2 modulates the expression of genes involved in murine immune cell chemotaxis.

2.
J Immunol ; 2020 Mar 20.
Artigo em Inglês | MEDLINE | ID: mdl-32198144

RESUMO

The B cell adaptor protein (BCAP) is a multimodular regulator of inflammatory signaling in diverse immune system cells. BCAP couples TLR signaling to phosphoinositide metabolism and inhibits MyD88-directed signal transduction. BCAP is recruited to the TLR signalosome forming multitypic interactions with the MAL and MyD88 signaling adaptors. In this study, we show that indirect dimerization of BCAP TIR is required for negative regulation of TLR signaling. This regulation is mediated by a transcription factor Ig (TIG/IPT) domain, a fold found in the NF-κB family of transcription factors. We have solved the crystal structure of the BCAP TIG and find that it is most similar to that of early B cell factor 1 (EBF1). In both cases, the dimer is stabilized by a helix-loop-helix motif at the C terminus and interactions between the ß-sheets of the Ig domains. BCAP is exclusively localized in the cytosol and is unable to bind DNA. Thus, the TIG domain is a promiscuous dimerization module that has been appropriated for a range of regulatory functions in gene expression and signal transduction.

3.
Structure ; 28(3): 281-289.e3, 2020 Mar 03.
Artigo em Inglês | MEDLINE | ID: mdl-31995744

RESUMO

Toll-like receptors (TLRs) are pivotal in triggering the innate immune response to pathogen infection. Ligand binding induces receptor dimerization which facilitates the recruitment of other post-receptor signal transducers into a complex signalosome, the Myddosome. Central to this process is Myeloid differentiation primary response 88 (MyD88), which is required by almost all TLRs, and signaling is thought to proceed via the stepwise, sequential assembly of individual components. Here, we show that the death domains of human MyD88 spontaneously and reversibly associate to form helical filaments in vitro. A 3.1-Å cryoelectron microscopy structure reveals that the architecture of the filament is identical to that of the 6:4 MyD88-IRAK4-IRAK2 hetero-oligomeric Myddosome. Additionally, the death domain of IRAK4 interacts with the filaments to reconstitute the non-stoichiometric 6:4 MyD88-IRAK4 complex. Together, these data suggest that intracellularly, the MyD88 scaffold may be pre-formed and poised for recruitment of IRAKs on receptor activation and TIR engagement.

4.
Sci Rep ; 9(1): 13168, 2019 Sep 11.
Artigo em Inglês | MEDLINE | ID: mdl-31511529

RESUMO

Toll-like receptors (TLRs) are important sentinels of bacterial and viral infection and thus fulfil a critical sensory role in innate immunity. Polo-like kinases (PLKs), a five membered family of Ser/Thr protein kinases, have long been studied for their role in mitosis and thus represent attractive therapeutic targets in cancer therapy. Recently, PLKs were implicated in TLR signaling in mice but the role of PLKs in TLR signaling in untransformed primary immune cells has not been addressed, even though PLK inhibitors are in clinical trials. We here identified several phospho-serine and phospho-threonine residues in the known TLR pathway kinases, Interleukin-1 receptor-associated kinase (IRAK) 2 and IRAK4. These sites lie in canonical polo-box motifs (PBM), sequence motifs known to direct recruitment of PLKs to client proteins. Interestingly, PLK1 was phosphorylated and PLK 2 and 3 mRNA induced upon TLR stimulation in primary immune cells, respectively. In whole blood, PLK inhibition disparately affected TLR mediated cytokine responses in a donor- and inhibitor-dependent fashion. Collectively, PLKs may thus potentially interface with TLR signaling in humans. We propose that temporary PLK inhibitor-mediated blockade of TLR-signaling in certain patients receiving such inhibitors during cancer treatment may cause adverse effects such as an increased risk of infections due to a then compromised ability of the TLR recognition system to sense and initiate cytokine responses to invading microbes.

5.
J Biol Chem ; 294(52): 19852-19861, 2019 Dec 27.
Artigo em Inglês | MEDLINE | ID: mdl-31527084

RESUMO

B-cell adaptor protein (BCAP) is a multimodular, multifunctional signal transducer that regulates signal transduction pathways in leukocytes, including macrophages, B-cells, and T-cells. In particular, BCAP suppresses inflammatory signaling by Toll-like receptors (TLRs). However, how BCAP itself is regulated and what its interaction partners are is unclear. Here, using human immune cell lines, including THP-1 cells, we characterized the complex phosphorylation patterns of BCAP and used a novel protein complex trapping strategy, called virotrap, to identify its interaction partners. This analysis identified known interactions of BCAP with phosphoinositide 3-kinase (PI3K) p85 subunit and NCK adaptor protein (NCK), together with previously unknown interactions of BCAP with Src homology 2 (SH2) and SH3 domain-containing adaptor proteins, notably growth factor receptor-bound protein 2 (GRB2) and CRK-like proto-oncogene, adaptor protein (CRKL). We show that the SH3 domain of GRB2 can bind to BCAP independently of BCAP phosphorylation status, suggesting that the SH2 domains mediate interactions with activated receptor tyrosine kinase complexes including the CD19 subunit of the B-cell receptor. Our results also suggested that the PI3K p85 subunit binds to BCAP via SH3 domains forming an inactive complex that is then activated by sequential binding with the SH2 domains. Taken together, our results indicate that BCAP is a complex hub that processes signals from multiple pathways in diverse cell types of the immune system.

7.
PLoS Pathog ; 15(6): e1007871, 2019 06.
Artigo em Inglês | MEDLINE | ID: mdl-31226171

RESUMO

Infection of host cells by Toxoplasma gondii is an active process, which is regulated by secretion of microneme (MICs) and rhoptry proteins (ROPs and RONs) from specialized organelles in the apical pole of the parasite. MIC1, MIC4 and MIC6 assemble into an adhesin complex secreted on the parasite surface that functions to promote infection competency. MIC1 and MIC4 are known to bind terminal sialic acid residues and galactose residues, respectively and to induce IL-12 production from splenocytes. Here we show that rMIC1- and rMIC4-stimulated dendritic cells and macrophages produce proinflammatory cytokines, and they do so by engaging TLR2 and TLR4. This process depends on sugar recognition, since point mutations in the carbohydrate-recognition domains (CRD) of rMIC1 and rMIC4 inhibit innate immune cells activation. HEK cells transfected with TLR2 glycomutants were selectively unresponsive to MICs. Following in vitro infection, parasites lacking MIC1 or MIC4, as well as expressing MIC proteins with point mutations in their CRD, failed to induce wild-type (WT) levels of IL-12 secretion by innate immune cells. However, only MIC1 was shown to impact systemic levels of IL-12 and IFN-γ in vivo. Together, our data show that MIC1 and MIC4 interact physically with TLR2 and TLR4 N-glycans to trigger IL-12 responses, and MIC1 is playing a significant role in vivo by altering T. gondii infection competency and murine pathogenesis.


Assuntos
Moléculas de Adesão Celular/imunologia , Células Dendríticas/imunologia , Imunidade Inata , Macrófagos/imunologia , Proteínas de Protozoários/imunologia , Ácidos Siálicos/imunologia , Receptor 2 Toll-Like/imunologia , Receptor 4 Toll-Like/imunologia , Toxoplasma/imunologia , Toxoplasmose Animal/imunologia , Animais , Interleucina-12/imunologia , Camundongos , Camundongos Knockout , Receptor 2 Toll-Like/genética , Receptor 4 Toll-Like/genética , Toxoplasmose Animal/genética
8.
Cell Mol Life Sci ; 76(18): 3667-3678, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31062071

RESUMO

Cardiolipins (CLs) are tetra-acylated diphosphatidylglycerols found in bacteria, yeast, plants, and animals. In healthy mammals, CLs are unsaturated, whereas saturated CLs are found in blood cells from Barth syndrome patients and in some Gram-positive bacteria. Here, we show that unsaturated but not saturated CLs block LPS-induced NF-κB activation, TNF-α and IP-10 secretion in human and murine macrophages, as well as LPS-induced TNF-α and IL-1ß release in human blood mononuclear cells. Using HEK293 cells transfected with Toll-like receptor 4 (TLR4) and its co-receptor Myeloid Differentiation 2 (MD2), we demonstrate that unsaturated CLs compete with LPS for binding TLR4/MD2 preventing its activation, whereas saturated CLs are TLR4/MD2 agonists. As a consequence, saturated CLs induce a pro-inflammatory response in macrophages characterized by TNF-α and IP-10 secretion, and activate the alternative NLRP3 inflammasome pathway in human blood-derived monocytes. Thus, we identify that double bonds discriminate between anti- and pro-inflammatory properties of tetra-acylated molecules, providing a rationale for the development of TLR4 activators and inhibitors for use as vaccine adjuvants or in the treatment of TLR4-related diseases.


Assuntos
Cardiolipinas/farmacologia , Macrófagos/efeitos dos fármacos , Receptor 4 Toll-Like/metabolismo , Animais , Anti-Infecciosos/química , Anti-Infecciosos/metabolismo , Anti-Infecciosos/farmacologia , Ligação Competitiva , Cardiolipinas/química , Cardiolipinas/metabolismo , Sobrevivência Celular/efeitos dos fármacos , Quimiocina CXCL10/metabolismo , Células HEK293 , Humanos , Receptores de Lipopolissacarídeos/metabolismo , Lipopolissacarídeos/metabolismo , Lipopolissacarídeos/farmacologia , Antígeno 96 de Linfócito/genética , Antígeno 96 de Linfócito/metabolismo , Macrófagos/citologia , Macrófagos/metabolismo , Camundongos , Monócitos/citologia , Monócitos/metabolismo , NF-kappa B/metabolismo , Proteína 3 que Contém Domínio de Pirina da Família NLR/metabolismo , Ligação Proteica , Transdução de Sinais/efeitos dos fármacos , Receptor 4 Toll-Like/agonistas , Receptor 4 Toll-Like/antagonistas & inibidores , Receptor 4 Toll-Like/genética , Fator de Necrose Tumoral alfa/metabolismo
9.
BMC Biol ; 17(1): 15, 2019 02 20.
Artigo em Inglês | MEDLINE | ID: mdl-30786893

RESUMO

A paper published in BMC Biology characterises biophysically oligomeric and filamentous structures formed spontaneously by the Toll-like receptor signalling adaptor MyD88. Naturally occurring mutants of MyD88 that cause immunodeficiency are unable to form these structures. By contrast a somatic mutant that promotes the survival of tumour cells forms oligomers much more readily than the wild-type protein. These findings suggest that assembly of oligomeric MyD88 is critical for the regulation of inflammatory signalling.


Assuntos
Fator 88 de Diferenciação Mieloide/química , Receptores Toll-Like/genética , Sistema Imunitário , Mutação , Transdução de Sinais/imunologia
10.
Neuropharmacology ; 135: 1-10, 2018 06.
Artigo em Inglês | MEDLINE | ID: mdl-29505789

RESUMO

Toll like receptor 3 (TLR3) belongs to a family of pattern recognition receptors that recognise molecules found on pathogens referred to as pathogen associated molecular patterns (PAMPs). Its involvement in innate immunity is well known but despite its presence in the central nervous system (CNS), our knowledge of its function is limited. Here, we have investigated whether TLR3 activation modulates synaptic activity in primary hippocampal cultures and induced pluripotent stem cell (iPSC)-derived neurons. Synaptically driven spontaneous action potential (AP) firing was significantly reduced by the TLR3 specific activator, poly I:C, in a concentration-dependent manner following both short (5 min) and long exposures (1h) in rat hippocampal cultures. Notably, the consequence of TLR3 activation on neuronal function was reproduced in iPSC-derived cortical neurons, with poly I:C (25 µg/ml, 1h) significantly inhibiting sAP firing. We examined the mechanisms underlying these effects, with poly I:C significantly reducing peak sodium current, an effect dependent on the MyD88-independent TRIF dependent pathway. Furthermore, poly I:C (25 µg/ml, 1h) resulted in a significant reduction in miniature excitatory postsynaptic potential (mEPSC) frequency and amplitude and significantly reduced surface AMPAR expression. These novel findings reveal that TLR3 activation inhibits neuronal excitability and synaptic activity through multiple mechanisms, with this being observed in both rat and human iPSC-derived neurons. These data might provide further insight into how TLR3 activation may contribute to neurodevelopmental disorders following maternal infection and in patients with increased susceptibility to herpes simplex encephalitis.


Assuntos
Potenciais de Ação/fisiologia , Potenciais Pós-Sinápticos Excitadores/fisiologia , Neurônios/fisiologia , Transdução de Sinais , Transmissão Sináptica/fisiologia , Receptor 3 Toll-Like/fisiologia , Proteínas Adaptadoras de Transporte Vesicular/genética , Animais , Córtex Cerebral/fisiologia , Relação Dose-Resposta a Droga , Hipocampo/fisiologia , Humanos , Potenciais Pós-Sinápticos em Miniatura/fisiologia , Poli I-C/farmacologia , Cultura Primária de Células , Ratos , Ratos Transgênicos , Receptores de Glutamato/biossíntese , Transdução de Sinais/efeitos dos fármacos , Bloqueadores dos Canais de Sódio/farmacologia , Receptor 3 Toll-Like/agonistas
11.
Elife ; 72018 01 24.
Artigo em Inglês | MEDLINE | ID: mdl-29368691

RESUMO

Infection and tissue damage induces assembly of supramolecular organizing centres (SMOCs)), such as the Toll-like receptor (TLR) MyDDosome, to co-ordinate inflammatory signaling. SMOC assembly is thought to drive digital all-or-none responses, yet TLR activation by diverse microbes induces anything from mild to severe inflammation. Using single-molecule imaging of TLR4-MyDDosome signaling in living macrophages, we find that MyDDosomes assemble within minutes of TLR4 stimulation. TLR4/MD2 activation leads only to formation of TLR4/MD2 heterotetramers, but not oligomers, suggesting a stoichiometric mismatch between activated receptors and MyDDosomes. The strength of TLR4 signalling depends not only on the number and size of MyDDosomes formed but also how quickly these structures assemble. Activated TLR4, therefore, acts transiently nucleating assembly of MyDDosomes, a process that is uncoupled from receptor activation. These data explain how the oncogenic mutation of MyD88 (L265P) assembles MyDDosomes in the absence of receptor activation to cause constitutive activation of pro-survival NF-κB signalling.


Assuntos
Antígeno 96 de Linfócito/metabolismo , Multimerização Proteica , Transdução de Sinais , Receptor 4 Toll-Like/metabolismo , Animais , Camundongos , Células RAW 264.7 , Imagem Individual de Molécula
12.
PLoS Genet ; 13(8): e1006968, 2017 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-28846707

RESUMO

Neurotrophism, structural plasticity, learning and long-term memory in mammals critically depend on neurotrophins binding Trk receptors to activate tyrosine kinase (TyrK) signaling, but Drosophila lacks full-length Trks, raising the question of how these processes occur in the fly. Paradoxically, truncated Trk isoforms lacking the TyrK predominate in the adult human brain, but whether they have neuronal functions independently of full-length Trks is unknown. Drosophila has TyrK-less Trk-family receptors, encoded by the kekkon (kek) genes, suggesting that evolutionarily conserved functions for this receptor class may exist. Here, we asked whether Keks function together with Drosophila neurotrophins (DNTs) at the larval glutamatergic neuromuscular junction (NMJ). We tested the eleven LRR and Ig-containing (LIG) proteins encoded in the Drosophila genome for expression in the central nervous system (CNS) and potential interaction with DNTs. Kek-6 is expressed in the CNS, interacts genetically with DNTs and can bind DNT2 in signaling assays and co-immunoprecipitations. Ligand binding is promiscuous, as Kek-6 can also bind DNT1, and Kek-2 and Kek-5 can also bind DNT2. In vivo, Kek-6 is found presynaptically in motoneurons, and DNT2 is produced by the muscle to function as a retrograde factor at the NMJ. Kek-6 and DNT2 regulate NMJ growth and synaptic structure. Evidence indicates that Kek-6 does not antagonise the alternative DNT2 receptor Toll-6. Instead, Kek-6 and Toll-6 interact physically, and together regulate structural synaptic plasticity and homeostasis. Using pull-down assays, we identified and validated CaMKII and VAP33A as intracellular partners of Kek-6, and show that they regulate NMJ growth and active zone formation downstream of DNT2 and Kek-6. The synaptic functions of Kek-6 could be evolutionarily conserved. This raises the intriguing possibility that a novel mechanism of structural synaptic plasticity involving truncated Trk-family receptors independently of TyrK signaling may also operate in the human brain.


Assuntos
Proteínas de Drosophila/genética , Proteínas de Membrana/genética , Fatores de Crescimento Neural/metabolismo , Plasticidade Neuronal/genética , Receptores Proteína Tirosina Quinases/genética , Animais , Proteína Quinase Tipo 2 Dependente de Cálcio-Calmodulina/genética , Proteínas de Transporte/genética , Sistema Nervoso Central/crescimento & desenvolvimento , Sistema Nervoso Central/metabolismo , Drosophila/genética , Drosophila/fisiologia , Humanos , Larva/metabolismo , Neurônios Motores/metabolismo , Fatores de Crescimento Neural/genética , Junção Neuromuscular , Ligação Proteica , Transdução de Sinais , Transmissão Sináptica
13.
J Cell Biol ; 216(5): 1421-1438, 2017 05 01.
Artigo em Inglês | MEDLINE | ID: mdl-28373203

RESUMO

Cell number plasticity is coupled to circuitry in the nervous system, adjusting cell mass to functional requirements. In mammals, this is achieved by neurotrophin (NT) ligands, which promote cell survival via their Trk and p75NTR receptors and cell death via p75NTR and Sortilin. Drosophila NTs (DNTs) bind Toll receptors instead to promote neuronal survival, but whether they can also regulate cell death is unknown. In this study, we show that DNTs and Tolls can switch from promoting cell survival to death in the central nervous system (CNS) via a three-tier mechanism. First, DNT cleavage patterns result in alternative signaling outcomes. Second, different Tolls can preferentially promote cell survival or death. Third, distinct adaptors downstream of Tolls can drive either apoptosis or cell survival. Toll-6 promotes cell survival via MyD88-NF-κB and cell death via Wek-Sarm-JNK. The distribution of adaptors changes in space and time and may segregate to distinct neural circuits. This novel mechanism for CNS cell plasticity may operate in wider contexts.


Assuntos
Fatores de Crescimento Neural/metabolismo , Receptores Toll-Like/metabolismo , Animais , Contagem de Células , Morte Celular , Sobrevivência Celular , Drosophila , Plasticidade Neuronal , Transdução de Sinais
14.
J Control Release ; 247: 182-193, 2017 02 10.
Artigo em Inglês | MEDLINE | ID: mdl-28040465

RESUMO

Lipopolyamines (LPAs) are cationic lipids; they interact spontaneously with nucleic acids to form lipoplexes used for gene delivery. The main hurdle to using lipoplexes in gene therapy lies in their immunostimulatory properties, so far attributed to the nucleic acid cargo, while cationic lipids were considered as inert to the immune system. Here we demonstrate for the first time that di-C18 LPAs trigger pro-inflammatory responses through Toll-like receptor 2 (TLR2) activation, and this whether they are bound to nucleic acids or not. Molecular docking experiments suggest potential TLR2 binding modes reminiscent of bacterial lipopeptide sensing. The di-C18 LPAs share the ability of burying their lipid chains in the hydrophobic cavity of TLR2 and, in some cases, TLR1, at the vicinity of the dimerization interface; the cationic headgroups form multiple hydrogen bonds, thus crosslinking TLRs into functional complexes. Unravelling the molecular basis of TLR1 and TLR6-driven heterodimerization upon LPA binding underlines the highly collaborative and promiscuous ligand binding mechanism. The prevalence of non-specific main chain-mediated interactions demonstrates that potentially any saturated LPA currently used or proposed as transfection agent is likely to activate TLR2 during transfection. Hence our study emphasizes the urgent need to test the inflammatory properties of transfection agents and proposes the use of docking analysis as a preliminary screening tool for the synthesis of new non-immunostimulatory nanocarriers.


Assuntos
Inflamação/induzido quimicamente , Lipídeos/imunologia , Poliaminas/imunologia , Receptor 2 Toll-Like/imunologia , Linhagem Celular , Células HEK293 , Humanos , Inflamação/imunologia , Lipídeos/efeitos adversos , Macrófagos/efeitos dos fármacos , Macrófagos/imunologia , Simulação de Acoplamento Molecular , Ácidos Nucleicos/administração & dosagem , Ácidos Nucleicos/genética , Poliaminas/efeitos adversos , Transfecção , Fator de Necrose Tumoral alfa/imunologia
15.
J Biol Chem ; 292(2): 652-660, 2017 Jan 13.
Artigo em Inglês | MEDLINE | ID: mdl-27909057

RESUMO

Ligand binding to Toll-like receptors (TLRs) results in dimerization of their cytosolic Toll/interleukin-1 receptor (TIR) domains and recruitment of post-receptor signal transducers into a complex signalosome. TLR activation leads to the production of transcription factors and pro-inflammatory molecules and the activation of phosphoinositide 3-kinases (PI3K) in a process that requires the multimodular B-cell adaptor for phosphoinositide 3-kinase (BCAP). BCAP has a sequence previously proposed as a "cryptic" TIR domain. Here, we present the structure of the N-terminal region of human BCAP and show that it possesses a canonical TIR fold. Dimeric BCAP associates with the TIR domains of TLR2/4 and MAL/TIRAP, suggesting that it is recruited to the TLR signalosome by multitypic TIR-TIR interactions. BCAP also interacts with the p85 subunit of PI3K and phospholipase Cγ, enzymes that deplete plasma membrane phosphatidylinositol 4,5-bisphosphate (PIP2), and these interactions provide a molecular explanation for BCAP-mediated down-regulation of inflammatory signaling.


Assuntos
Proteínas de Transporte/química , Multimerização Proteica , Transdução de Sinais , Receptor 2 Toll-Like/química , Receptor 4 Toll-Like/química , Proteínas de Transporte/genética , Proteínas de Transporte/metabolismo , Humanos , Glicoproteínas de Membrana/química , Glicoproteínas de Membrana/metabolismo , Proteínas Proteolipídicas Associadas a Linfócitos e Mielina/química , Proteínas Proteolipídicas Associadas a Linfócitos e Mielina/genética , Proteínas Proteolipídicas Associadas a Linfócitos e Mielina/metabolismo , Fosfatidilinositol 3-Quinases , Fosfatidilinositol 4,5-Difosfato/química , Fosfatidilinositol 4,5-Difosfato/genética , Fosfatidilinositol 4,5-Difosfato/metabolismo , Domínios Proteicos , Receptores de Interleucina-1/química , Receptores de Interleucina-1/metabolismo , Receptor 2 Toll-Like/genética , Receptor 2 Toll-Like/metabolismo , Receptor 4 Toll-Like/genética , Receptor 4 Toll-Like/metabolismo
16.
Front Immunol ; 8: 1820, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-29326706

RESUMO

We have reported that some lectins act as agonists of toll-like receptors (TLRs) and have immunomodulatory properties. The plant lectin ArtinM, for example, interacts with N-glycans of TLR2, whereas other lectins of microbial origin interact with TLR2 and TLR4. Expression of the receptors on the surface of antigen-presenting cells exposes N-glycans that may be targeted by lectins of different structures, specificities, and origins. In vitro, these interactions trigger cell signaling that leads to NF-κB activation and production of the Th1 polarizing cytokine IL-12. In vivo, a same sequence of events follows the administration of an active lectin to mice infected with an intracellular pathogen, conferring resistance to the pathogen. The lectins of the human pathogens Toxoplasma gondii (TgMIC1 and TgMIC4) and Paracoccidioides brasiliensis (Paracoccin), by recognition and activation of TLR2 and TLR4, induce cell events and in vivo effects comparable to the promoted by the plant lectin ArtinM. In this article, we highlight these two distinct mechanisms for activating antigen-presenting cells. On the one hand, TLRs act as sensors for the presence of conventional pathogen-associated molecular patterns, such as microbial lipids. On the other hand, we showed that TLR-mediated cell activation might be triggered by an alternative way, in which lectins bind to TLRs N-glycans and stimulate cells to increase the expression of pro-inflammatory cytokines. This process may lead to the development of new pharmaceutical tools that promote protective immune responses directed against intracellular pathogens and tumors.

17.
Sci Rep ; 6: 37267, 2016 11 23.
Artigo em Inglês | MEDLINE | ID: mdl-27876844

RESUMO

Activation of Toll-like receptors induces dimerization and the recruitment of the death domain (DD) adaptor protein MyD88 into an oligomeric post receptor complex termed the Myddosome. The Myddosome is a hub for inflammatory and oncogenic signaling and has a hierarchical arrangement with 6-8 MyD88 molecules assembling with exactly 4 of IRAK-4 and 4 of IRAK-2. Here we show that a conserved motif in IRAK-4 (Ser8-X-X-X-Arg12) is autophosphorylated and that the phosphorylated DD is unable to form Myddosomes. Furthermore a mutant DD with the phospho-mimetic residue Asp at this position is impaired in both signalling and Myddosome assembly. IRAK-4 Arg12 is also essential for Myddosome assembly and signalling and we propose that phosphorylated Ser8 induces the N-terminal loop to fold into an α-helix. This conformer is stabilised by an electrostatic interaction between phospho-Ser8 and Arg12 and would destabilise a critical interface between IRAK-4 and MyD88. Interestingly IRAK-2 does not conserve this motif and has an alternative interface in the Myddosome that requires Arg67, a residue conserved in paralogues, IRAK-1 and 3(M).


Assuntos
Quinases Associadas a Receptores de Interleucina-1/química , Complexos Multiproteicos/química , Fator 88 de Diferenciação Mieloide/química , Transdução de Sinais , Motivos de Aminoácidos , Humanos , Quinases Associadas a Receptores de Interleucina-1/metabolismo , Complexos Multiproteicos/metabolismo , Fator 88 de Diferenciação Mieloide/metabolismo , Estrutura Quaternária de Proteína , Eletricidade Estática
18.
Methods Mol Biol ; 1390: 29-39, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-26803620

RESUMO

Continual advancements in computing power and sophistication, coupled with rapid increases in protein sequence and structural information, have made bioinformatic tools an invaluable resource for the molecular and structural biologist. With the degree of sequence information continuing to expand at an almost exponential rate, it is essential that scientists today have a basic understanding of how to utilise, manipulate and analyse this information for the benefit of their own experiments. In the context of Toll-Interleukin I Receptor domain containing proteins, we describe here a series of the more common and user-friendly bioinformatic tools available as Internet-based resources. These will enable the identification and alignment of protein sequences; the identification of functional motifs; the characterisation of protein secondary structure; the identification of protein structural folds and distantly homologous proteins; and the validation of the structural geometry of modelled protein structures.


Assuntos
Sequência de Aminoácidos , Biologia Computacional/métodos , Conformação Proteica , Domínios e Motivos de Interação entre Proteínas , Receptores Toll-Like/química , Animais , Bases de Dados Genéticas , Humanos , Modelos Moleculares , Processamento de Proteína Pós-Traducional , Reprodutibilidade dos Testes , Relação Estrutura-Atividade , Receptores Toll-Like/genética , Receptores Toll-Like/metabolismo
19.
Int J Biol Macromol ; 82: 22-30, 2016 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-26433176

RESUMO

Recent advances in glycobiology have revealed the essential role of lectins in deciphering the glycocodes at the cell surface to generate important biological signaling responses. ArtinM, a d-mannose-binding lectin isolated from the seeds of jackfruit (Artocarpus heterophyllus), is composed of 16 kDa subunits that are associated to form a homotetramer. Native ArtinM (n-ArtinM) exerts immunomodulatory and regenerative effects, but the potential pharmaceutical applicability of the lectin is highly limited by the fact that its production is expensive, laborious, and impossible to be scaled up. This led us to characterize a recombinant form of the lectin obtained by expression in Saccharomyces cerevisiae (y-ArtinM). In the present study, we demonstrated that y-ArtinM is similar to n-ArtinM in subunit arrangement, oligomerization and carbohydrate binding specificity. We showed that y-ArtinM can exert n-ArtinM biological activities such as erythrocyte agglutination, stimulation of neutrophil migration and degranulation, mast cell degranulation, and induction of interleukin-12 and interleukin-10 production by macrophages. In summary, the expression of ArtinM in yeast resulted in successful production of an active, recombinant form of ArtinM that is potentially useful for pharmaceutical application.


Assuntos
Carboidratos/química , Lectinas de Ligação a Manose/química , Estrutura Molecular , Proteínas Recombinantes , Animais , Degranulação Celular/efeitos dos fármacos , Degranulação Celular/imunologia , Movimento Celular/efeitos dos fármacos , Movimento Celular/imunologia , Citocinas/biossíntese , Hemaglutinação , Humanos , Macrófagos/efeitos dos fármacos , Macrófagos/imunologia , Macrófagos/metabolismo , Masculino , Lectinas de Ligação a Manose/metabolismo , Lectinas de Ligação a Manose/farmacologia , Mastócitos/efeitos dos fármacos , Mastócitos/imunologia , Mastócitos/metabolismo , Camundongos , Neutrófilos/efeitos dos fármacos , Neutrófilos/imunologia , Neutrófilos/metabolismo , Polissacarídeos/química , Ligação Proteica , Receptor 2 Toll-Like , Leveduras/genética , Leveduras/metabolismo
20.
Mol Immunol ; 63(2): 162-5, 2015 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-25081091

RESUMO

The molecular mechanisms by which pattern recognition receptors (PRRs) signal are increasingly well understood. Toll-like receptor 4 (TLR4) signals through two separate pairs of adaptor proteins Mal/MyD88 and Tram/Trif. Structural studies have revealed a common theme for PRR signalling in that their signalling proteins form large macromolecular complexes which are thought to form the active signalling complex. The first of these to be characterised was the MyD88 signalling complex Myddosome. Many questions remain unanswered however. In particular it is unclear whether these signalling complexes form within the living cell, how many of each signalling protein is within the intracellular Myddosome and whether the stoichiometry can vary in a ligand-dependent manner. In this review we will discuss what is known about the macromolecular complexes thought to be important for TLR4 signalling.


Assuntos
Substâncias Macromoleculares/metabolismo , Transdução de Sinais/imunologia , Receptores Toll-Like/imunologia , Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Animais , Humanos , Inflamação/patologia , Complexos Multiproteicos/metabolismo
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