scholarly journals The TLR signalling adaptor TRIF/TICAM-1 has an N-terminal helical domain with structural similarity to IFIT proteins

2013 ◽  
Vol 69 (12) ◽  
pp. 2420-2430 ◽  
Author(s):  
M. Obayed Ullah ◽  
Thomas Ve ◽  
Matthew Mangan ◽  
Mohammed Alaidarous ◽  
Matthew J. Sweet ◽  
...  
Keyword(s):  
Interleukin 1 ◽  
Functional Characterization ◽  
Self Regulation ◽  
Adaptor Protein ◽  
Structural Similarity ◽  
Interferon Β ◽  
Tetratricopeptide Repeats ◽  
Tir Domain ◽  
Signalling Molecules ◽  
Selective Targeting

TRIF/TICAM-1 (TIR domain-containing adaptor inducing interferon-β/TIR domain-containing adaptor molecule 1) is the adaptor protein in the Toll-like receptor (TLR) 3 and 4 signalling pathway that leads to the production of type 1 interferons and cytokines. The signalling involves TIR (Toll/interleukin-1 receptor) domain-dependent TRIF oligomerization. A protease-resistant N-terminal region is believed to be involved in self-regulation of TRIF by interacting with its TIR domain. Here, the structural and functional characterization of the N-terminal domain of TRIF (TRIF-NTD) comprising residues 1–153 is reported. The 2.22 Å resolution crystal structure was solved by single-wavelength anomalous diffraction (SAD) using selenomethionine-labelled crystals of TRIF-NTD containing two additional introduced Met residues (TRIF-NTDA66M/L113M). The structure consists of eight antiparallel helices that can be divided into two subdomains, and the overall fold shares similarity to the interferon-induced protein with tetratricopeptide repeats (IFIT) family of proteins, which are involved in both the recognition of viral RNA and modulation of innate immune signalling. Analysis of TRIF-NTD surface features and the mapping of sequence conservation onto the structure suggest several possible binding sites involved in either TRIF auto-regulation or interaction with other signalling molecules or ligands. TRIF-NTD suppresses TRIF-mediated activation of the interferon-β promoter, as well as NF-κB-dependent reporter-gene activity. These findings thus identify opportunities for the selective targeting of TLR3- and TLR4-mediated inflammation.

scholarly journals TIRAP in the Mechanism of Inflammation

2021 ◽  
Vol 12 ◽  
Author(s):  
Sajjan Rajpoot ◽  
Kishore K. Wary ◽  
Rachel Ibbott ◽  
Dongfang Liu ◽  
Uzma Saqib ◽  
...  
Keyword(s):  
Immune Responses ◽  
Protein Interactions ◽  
Inflammatory Diseases ◽  
Interleukin 1 ◽  
Adaptor Protein ◽  
Intracellular Signalling ◽  
Tir Domain ◽  
Signalling Molecules ◽  
Inflammatory Conditions ◽  
Signalling Molecule

The Toll-interleukin-1 Receptor (TIR) domain-containing adaptor protein (TIRAP) represents a key intracellular signalling molecule regulating diverse immune responses. Its capacity to function as an adaptor molecule has been widely investigated in relation to Toll-like Receptor (TLR)-mediated innate immune signalling. Since the discovery of TIRAP in 2001, initial studies were mainly focused on its role as an adaptor protein that couples Myeloid differentiation factor 88 (MyD88) with TLRs, to activate MyD88-dependent TLRs signalling. Subsequent studies delineated TIRAP’s role as a transducer of signalling events through its interaction with non-TLR signalling mediators. Indeed, the ability of TIRAP to interact with an array of intracellular signalling mediators suggests its central role in various immune responses. Therefore, continued studies that elucidate the molecular basis of various TIRAP-protein interactions and how they affect the signalling magnitude, should provide key information on the inflammatory disease mechanisms. This review summarizes the TIRAP recruitment to activated receptors and discusses the mechanism of interactions in relation to the signalling that precede acute and chronic inflammatory diseases. Furthermore, we highlighted the significance of TIRAP-TIR domain containing binding sites for several intracellular inflammatory signalling molecules. Collectively, we discuss the importance of the TIR domain in TIRAP as a key interface involved in protein interactions which could hence serve as a therapeutic target to dampen the extent of acute and chronic inflammatory conditions.

Pococurante (Poc): An ENU-Induced Missense Mutation of MyD88 with Selective Effects on TLR Signal Transduction.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 649-649
Author(s):  
Zhengfan Jiang ◽  
Chenglong Li ◽  
Louis Shamel ◽  
Arthur Olson ◽  
Bruce Beutler
Keyword(s):  
Signal Transduction ◽  
Interleukin 1 ◽  
Adaptor Protein ◽  
Structural Diversity ◽  
Lipoteichoic Acid ◽  
Protein Docking ◽  
Structural Basis ◽  
Cpg Dna ◽  
Cpg Dinucleotides ◽  
Tir Domain

Abstract Toll-like receptors (TLRs) are key sensors of the innate immune system, and individual TLRs respond to specific molecules derived from microbes. MyD88 is a Toll/Interleukin-1/Resistance (TIR) domain-containing adaptor protein required for signaling by all TLRs except TLR3. While the structural basis of association between MyD88 and TIR-domain receptors is obscure, MyD88-deficient mice show no responses to bacterial flagellin, peptidoglycan (PGN), lipoteichoic acid (LTA), bacterial lipopeptides such as PAM2CSK4, PAM3CSK4 and R- or S-MALP-2, DNA bearing unmethylated CpG dinucleotides (CpG DNA), or Resiquimod (RSQ). Using germline ENU mutagenesis, we have produced a large number of phenotypic variants that have abnormal TLR signaling. We now report the identification of a new mutation called Pococurante (Poc), originally detected in screening because macrophages from this mouse showed no response to the tri-acylated lipopeptide PAM3CSK4, the di-acylated lipopeptide S-MALP-2, LTA, CpG DNA, RSQ, and a markedly reduced response to LPS: the ligands for TLRs 2/1, 2/6, 9, 7 and 4 respectively. They also had no response to interleukin-1, a cytokine that signals by way of a MyD88-dependent TIR domain receptor. However, Poc mice showed a normal response to PGN, as well as R-MALP-2 and PAM2CSK4 lipopeptides. The latter three ligands are sensed in a TLR2-dependent, MyD88-dependent fashion. The Poc phenotype was ascribed to a point mutation of MyD88 affecting a surface residue (I179N). Because the mutation is discriminatory, permitting MyD88 to carry a signal from some TIR domain receptors but not others, we infer that it resides at the receptor:adaptor signaling interface. A new model of TIR receptor:adaptor interaction is proposed on the basis of docking studies that take account of the Poc phenotype, made using the protein-protein docking program SURFDOCK. We note that S-MALP-2 is dependent upon TLR2/6 heterodimers, while PAM3CSK4 sensing depends upon TLR2/1 heterodimers. Since the Poc mutation forbids detection of both these ligands while it allows detection of PAM2CSK4 and R-MALP-2, it may be inferred that TLR2 signal transduction entails greater structural diversity than was previously supposed. The involvement of TLR2 homodimers, or the incorporation of subunits yet unknown into the receptor complex, cannot be excluded.

scholarly journals Central role of the TIR-domain-containing adaptor-inducing interferon-β (TRIF) adaptor protein in murine sterile liver injury

Hepatology ◽  
2017 ◽  
Vol 65 (4) ◽  
pp. 1336-1351 ◽  
Author(s):  
Katherine J. Brempelis ◽  
Sebastian Y. Yuen ◽  
Nicole Schwarz ◽  
Isaac Mohar ◽  
Ian N. Crispe
Keyword(s):  
Liver Injury ◽  
Adaptor Protein ◽  
Interferon Β ◽  
Tir Domain

scholarly journals The SARM1 TIR NADase: Mechanistic Similarities to Bacterial Phage Defense and Toxin-Antitoxin Systems

2021 ◽  
Vol 12 ◽  
Author(s):  
Aaron DiAntonio ◽  
Jeffrey Milbrandt ◽  
Matthew D. Figley
Keyword(s):  
Defense Mechanisms ◽  
Interleukin 1 ◽  
Innate Immune ◽  
Activation Mechanism ◽  
Bacterial Toxin ◽  
Axon Degeneration ◽  
Tir Domain ◽  
Immune Mechanisms ◽  
Signalling Molecules ◽  
Tir Domains

The Toll/interleukin-1 receptor (TIR) domain is the signature signalling motif of innate immunity, with essential roles in innate immune signalling in bacteria, plants, and animals. TIR domains canonically function as scaffolds, with stimulus-dependent multimerization generating binding sites for signalling molecules such as kinases and ligases that activate downstream immune mechanisms. Recent studies have dramatically expanded our understanding of the TIR domain, demonstrating that the primordial function of the TIR domain is to metabolize NAD+. Mammalian SARM1, the central executioner of pathological axon degeneration, is the founding member of the TIR-domain class of NAD+ hydrolases. This unexpected NADase activity of TIR domains is evolutionarily conserved, with archaeal, bacterial, and plant TIR domains all sharing this catalytic function. Moreover, this enzymatic activity is essential for the innate immune function of these proteins. These evolutionary relationships suggest a link between SARM1 and ancient self-defense mechanisms that has only been strengthened by the recent discovery of the SARM1 activation mechanism which, we will argue, is strikingly similar to bacterial toxin-antitoxin systems. In this brief review we will describe the regulation and function of SARM1 in programmed axon self-destruction, and highlight the parallels between the SARM1 axon degeneration pathway and bacterial innate immune mechanisms.

scholarly journals Common and distinct features of TIR domain function

2014 ◽  
Vol 70 (a1) ◽  
pp. C242-C242
Author(s):  
Simon Williams ◽  
Mohammed Alaidarous ◽  
Thomas Ve ◽  
Xiaoxiao Zhang ◽  
Eugene Valkov ◽  
...  
Keyword(s):  
Fungal Pathogens ◽  
Paracoccus Denitrificans ◽  
Brucella Melitensis ◽  
Interleukin 1 ◽  
Adaptor Protein ◽  
Site Directed Mutagenesis ◽  
Tir Domain ◽  
Common Features ◽  
Self Association ◽  
Tir Domains

TIR (Toll/interleukin-1 receptor, resistance protein) domains feature in diverse proteins with functions in the immune system, such as animal TLRs (Toll-like receptors), plant NLRs (nucleotide binding, leucine-rich repeat) and bacterial virulence factors. It has been well established, especially through the work on TLRs, that signalling depends on regulated self-association of TIR domains. However, every single TIR domain structure has revealed a different association mode [1]. In the search for common features, we have targeted a number of TIR domains from mammals, plants and bacteria to characterize structurally. We have determined the crystal structures of the TIR domains from the human TLR adaptor protein MAL [1], the bacterial protein TcpB from Brucella melitensis [2] and the plant immune proteins L6 from flax [3] and SNC1, RPS4 and RRS1 from Arabidopsis (unpublished). In the case of the proteins RPS4 and RRS1, which work together as a protein complex to confer resistance to three different bacterial and fungal pathogens, we have determined, using linker-assisted crystallization, the first structure of a hetero-dimeric complex of TIR domains (Fig. 1). The association interface in this complex is conserved in the crystals of the TIR domains of RPS4 and RRS1 on their own, as well as in those of SNC1 and another Arabidopsis protein AT1G72930. Similarly, the dimerization interface observed in the structure of TcpB is conserved in the structure of the TIR domain-containing protein from Paracoccus denitrificans. We validated the association interfaces by site-directed mutagenesis coupled with a variety of cellular assays. As self-association is key to TIR domain function, our studies are finally revealing common features of the molecular function of TIR domains across phyla.

scholarly journals Inhibition of TLR4 Signalling-Induced Inflammation Attenuates Secondary Injury after Diffuse Axonal Injury in Rats

2016 ◽  
Vol 2016 ◽  
pp. 1-16 ◽  
Author(s):  
Yonglin Zhao ◽  
Yahui Zhao ◽  
Ming Zhang ◽  
Junjie Zhao ◽  
Xudong Ma ◽  
...  
Keyword(s):  
Interleukin 1 ◽  
Axonal Injury ◽  
Critical Role ◽  
Diffuse Axonal Injury ◽  
Adaptor Protein ◽  
Signalling Pathway ◽  
Inflammatory Factors ◽  
Secondary Injury ◽  
Neuroprotective Effects ◽  
Signalling Molecules

Increasing evidence suggests that secondary injury after diffuse axonal injury (DAI) damages more axons than the initial insult, but the underlying mechanisms of this phenomenon are not fully understood. Recent studies show that toll-like receptor 4 (TLR4) plays a critical role in promoting adaptive immune responses and have been shown to be associated with brain damage. The purpose of this study was to investigate the role of the TLR4 signalling pathway in secondary axonal injury in the cortices of DAI rats. TLR4 was mainly localized in microglial cells and neurons, and the levels of TLR4 downstream signalling molecules, including TLR4, myeloid differentiation primary response gene 88, toll/IR-1-(TIR-) domain-containing adaptor protein inducing interferon-beta, interferon regulatory factor 3, interferonβ, nuclear factorκB (NF-κB) p65, and phospho-NF-κB p65, significantly increased and peaked at 1 d after DAI. Inhibition of TLR4 by TAK-242 attenuated apoptosis, neuronal and axonal injury, and glial responses. The neuroprotective effects of TLR4 inhibition were associated with decreases in the levels of TLR4 downstream signalling molecules and inflammatory factors, including interleukin-1β, interleukin-6, and tumour necrosis factor-α. These results suggest that the TLR4 signalling pathway plays an important role in secondary injury and may be an important therapeutic target following DAI.

Insights into the biochemical and functional characterization of sortase E transpeptidase of Corynebacterium glutamicum

2019 ◽  
Vol 476 (24) ◽  
pp. 3835-3847 ◽  
Author(s):  
Aliyath Susmitha ◽  
Kesavan Madhavan Nampoothiri ◽  
Harsha Bajaj
Keyword(s):  
Protein Engineering ◽  
Cell Attachment ◽  
Functional Characterization ◽  
Protein Structures ◽  
Structural Similarity ◽  
Surface Proteins ◽  
Sortase A ◽  
Peptide Cleavage ◽  
New Findings

Most Gram-positive bacteria contain a membrane-bound transpeptidase known as sortase which covalently incorporates the surface proteins on to the cell wall. The sortase-displayed protein structures are involved in cell attachment, nutrient uptake and aerial hyphae formation. Among the six classes of sortase (A–F), sortase A of S. aureus is the well-characterized housekeeping enzyme considered as an ideal drug target and a valuable biochemical reagent for protein engineering. Similar to SrtA, class E sortase in GC rich bacteria plays a housekeeping role which is not studied extensively. However, C. glutamicum ATCC 13032, an industrially important organism known for amino acid production, carries a single putative sortase (NCgl2838) gene but neither in vitro peptide cleavage activity nor biochemical characterizations have been investigated. Here, we identified that the gene is having a sortase activity and analyzed its structural similarity with Cd-SrtF. The purified enzyme showed a greater affinity toward LAXTG substrate with a calculated KM of 12 ± 1 µM, one of the highest affinities reported for this class of enzyme. Moreover, site-directed mutation studies were carried to ascertain the structure functional relationship of Cg-SrtE and all these are new findings which will enable us to perceive exciting protein engineering applications with this class of enzyme from a non-pathogenic microbe.

scholarly journals Modulation of microtubule dynamics by a TIR domain protein from the intracellular pathogen Brucella melitensis

2011 ◽  
Vol 439 (1) ◽  
pp. 79-83 ◽  
Author(s):  
Girish K. Radhakrishnan ◽  
Jerome S. Harms ◽  
Gary A. Splitter
Keyword(s):  
Brucella Melitensis ◽  
Interleukin 1 ◽  
Nuclear Factor Κb ◽  
Microtubule Dynamics ◽  
Innate Immune Responses ◽  
Tir Domain ◽  
Microtubule Stabilization ◽  
Loop Region ◽  
Microtubule Formation ◽  
Domain Protein

TIR (Toll/interleukin-1 receptor) domain-containing proteins play a crucial role in innate immunity in eukaryotes. Brucella is a highly infectious intracellular bacterium that encodes a TIR domain protein (TcpB) to subvert host innate immune responses to establish a beneficial niche for pathogenesis. TcpB inhibits NF-κB (nuclear factor κB) activation and pro-inflammatory cytokine secretions mediated by TLR (Toll-like receptor) 2 and TLR4. In the present study, we have demonstrated that TcpB modulates microtubule dynamics by acting as a stabilization factor. TcpB increased the rate of nucleation as well as the polymerization phases of microtubule formation in a similar manner to paclitaxel. TcpB could efficiently inhibit nocodazole- or cold-induced microtubule disassembly. Microtubule stabilization by TcpB is attributed to the BB-loop region of the TIR domain, and a point mutation affected the microtubule stabilization as well as the TLR-suppression properties of TcpB.

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