Toll-like receptor 8 (TLR8) recognizes viral or bacterial single-stranded RNA (ssRNA) and activates innate immune systems. TLR8 is activated by uridine- and guanosine-rich ssRNA as well as by certain ...synthetic chemicals; however, the molecular basis for ssRNA recognition has remained unknown. In this study, to elucidate the recognition mechanism of ssRNA, we determined the crystal structures of human TLR8 in complex with ssRNA. TLR8 recognized two degradation products of ssRNA—uridine and a short oligonucleotide—at two distinct sites: uridine bound the site on the dimerization interface where small chemical ligands are recognized, whereas short oligonucleotides bound a newly identified site on the concave surface of the TLR8 horseshoe structure. Site-directed mutagenesis revealed that both binding sites were essential for activation of TLR8 by ssRNA. These results demonstrate that TLR8 is a sensor for both uridine and a short oligonucleotide derived from RNA.
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DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SBMB, UILJ, UKNU, UL, UM, UPUK
Toll-like receptor 7 (TLR7) is a single-stranded RNA (ssRNA) sensor in innate immunity and also responds to guanosine and chemical ligands, such as imidazoquinoline compounds. However, TLR7 ...activation mechanism by these ligands remain largely unknown. Here, we generated crystal structures of three TLR7 complexes, and found that all formed an activated m-shaped dimer with two ligand-binding sites. The first site conserved in TLR7 and TLR8 was used for small ligand-binding essential for its activation. The second site spatially distinct from that of TLR8 was used for a ssRNA-binding that enhanced the affinity of the first-site ligands. The first site preferentially recognized guanosine and the second site specifically bound to uridine moieties in ssRNA. Our structural, biochemical, and mutagenesis studies indicated that TLR7 is a dual receptor for guanosine and uridine-containing ssRNA. Our findings have important implications for understanding of TLR7 function, as well as for therapeutic manipulation of TLR7 activation.
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•Determined three crystal structures of activated forms of TLR7•TLR7 harbors two binding sites, first site for small ligands and second site for ssRNA•TLR7 is a dual sensor for guanosine and uridine-containing ssRNA•TLR7 is synergistically activated by guanosine and ssRNA
TLR7 is a ssRNA sensor that also responds to guanosine and chemical ligands, but how these ligands activate TLR7 remains largely unknown. Zhang et al. determined the tertiary structure of TLR7 in its activated form induced by guanosine and ssRNA and reveal the ligand specificity and activation mechanism of TLR7.
Diffusion-sensitized driven equilibrium preparation (DSDE) is a gradient echo (GRE) diffusion-weighted imaging (DWI) sequence that employs a motion-probing gradient (MPG) preparation pulse and phase ...cycling. In DSDE, several scan parameters of the MPG preparation pulse and the GRE sequence affect diffusion sensitivity. Our investigation of the relationship between these scan parameters and the diffusion emphasis effect revealed the importance of “prep.TE” in the MPG preparation pulse and “TFE shot interval” in the gradient echo sequence. Appropriate choice of these parameters allows DSDE to provide a similar DWI to that of conventional single-shot SEEPI DWI. We therefore concluded DSDE to be a useful DWI method.
We have designed and synthesized various mass probes, which enable us to effectively ionize various molecules to be detected with mass spectrometry. We call the ionization method using mass probes ...the “MPAI (mass probes aided ionization)” method. We aim at the sensitive detection of various biological molecules, and also the detection of bio-molecules by a single mass spectrometry serially without changing the mechanical settings. Here, we review mass probes for small molecules with various functional groups and mass probes for proteins. Further, we introduce newly developed mass probes for proteins for highly sensitive detection.
The electron-beam-induced-current (EBIC) technique using scanning transmission electron microscopy (STEM) has been applied to the observation of grain boundaries in polycrystalline Si. It was shown ...that defects in thin regions can disappear or give bright contrast in EBIC images, but are distinct in STEM images. For the sample with a high carrier concentration, the surface effect was shown to dominate the EBIC current for a thin region. The bright contrast of the defects observed for the sample with a low carrier concentration can be attributed to the combination of the diffraction effect and the built-in electric field induced by the depletion of the entire thickness.
Novel labeling reagents, called MS probes, which possess a positively charged quaternary amine moiety and can transform a neutral analyte into a charged compound by simply mixing with the analyte and ...allowing the mixture to stand from several minutes to 30 min at room temperature or while heating to 50°C, were designed and synthesized for the highly sensitive detection of carbonyl, alcohol, carboxylic acid and primary amine samples by electrospray ionization mass spectrometry (ESI-MS). The positively charged products can be detected with high sensitivity in an ESI-MS system, which is the most popular liquid MS instrument. All of the labeled products showed a remarkably large increase in the molecular-ion peak abundance detection sensitivity of over 500-fold at picomolar concentration levels compared to that of unlabeled analytes in an ESI-MS system. These MS probes, used together with liquid MS detection, are widely applicable as a convenient method for the highly sensitive detection of less than picomolar levels of analytes, and therefore greatly enhance the power of ESI-MS analysis.
We have investigated the morphology of the high-temperature-grown AlN nucleation layer and its role in the early stage of GaN growth, by means of transmission electron microscopy. The nitride was ...selectively grown on a 7-degree off-oriented (0
0
1) patterned Si substrate by metalorganic vapor phase epitaxy. AlN was deposited on the inclined unmasked (1
1
1) facet in the form of islands. The size of the islands varied along the slope, which is attributable to the diffusion of the growth species in the vapor phase. The GaN nucleation occurred at the region where rounded AlN islands formed densely. The threading dislocations were observed to generate in the GaN nucleated region.
Authors studied the microstructure in a (1-101) GaN triangular bar and an AlGaN/GaN heterostructure formed on top of it by TEM. The nitride triangular bar was selectively grown on a 7-degree ...off-oriented (001) Si substrate by MOVPE. Convergent beam electron diffraction was used to determine lattice polarity. Threading dislocations were generated near the interface between the unmasked (111) facet of the Si and the nitride. These dislocations bend toward either the (1-101) facet or the interface between the GaN and masked (-1-11) Si, and thread through to the facet or the interface. Dislocations were observed at the AlGaN/GaN interface. Growth proceeded predominantly in the 0001 direction of the nitride with Ga-terminated polarity. 18 refs.
A 56-year-old Japanese female simultaneously developed thrombocytopenia, sicca symptoms, and an elevation of transaminase. Antiphospholipid antibodies were detected in her serum. The presence of ...anti-SS-A antibodies in the serum and sialectasis, disclosed by sialography, suggested the presence of primary Sjögren's syndrome (SjS). The laboratory data and the biopsy of the liver showed compatible findings with autoimmune hepatitis (AIH). Thrombocytopenia and liver dysfunction satisfactorily responded to corticosteroid. To our knowledge, this is the first reported case of SjS with AIH and antiphospholipid antibody syndrome (APAS). Analysis of serum cytokine levels showed a predominance of Th0-Th1 response, which is not compatible with AIH, in this complicated autoimmune state. (Internal Medicine 39: 73-76, 2000)
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