Structure of a TCR with high affinity for self-antigen reveals basis for escape from negative selection

The failure to eliminate self-reactive T cells during negative selection is a prerequisite for autoimmunity. To escape deletion, autoreactive T-cell receptors (TCRs) may form unstable complexes with self-peptide-MHC by adopting suboptimal binding topologies compared with anti-microbial TCRs. Alternatively, escape can occur by weak binding between self-peptides and MHC. We determined the structure of a human autoimmune TCR (MS2-3C8) bound to a self-peptide from myelin basic protein (MBP) and the multiple sclerosis-associated MHC molecule HLA-DR4. MBP is loosely accommodated in the HLA-DR4-binding groove, accounting for its low affinity. Conversely, MS2-3C8 binds MBP-DR4 as tightly as the most avid anti-microbial TCRs. MS2-3C8 engages self-antigen via a docking mode that resembles the optimal topology of anti-foreign TCRs, but is distinct from that of other autoreactive TCRs. Combined with a unique CDR3β conformation, this docking mode compensates for the weak binding of MBP to HLA-DR4 by maximizing interactions between MS2-3C8 and MBP. Thus, the MS2-3C8-MBP-DR4 complex reveals the basis for an alternative strategy whereby autoreactive T cells escape negative selection, yet retain the ability to initiate autoimmunity.     

Changes in the composition of an acid mine drainage microbial community upon successive transfers in medium containing low-grade copper sulfide

A consortium of microorganisms from acid mine drainage samples was cultured in modified 9 K medium containing low-grade copper sulfide. The culture was maintained for sixty days and then transferred to fresh medium. This process was repeated three more times and a final consortium exhibiting a copper extraction rate of 89.3% was obtained. RFLP and microarrays analysis of 16S rRNA sequences retrieved from the consortia showed that Acidithiobacilluscaldus, Leptospirillumferriphilum, Sulfobacillus sp., Acidiphilium sp., and Sulfolobus spp. were represented in higher numbers in the consortia obtained in the copper-containing medium than in the original consortium. In contrast, a decrease in Acidithiobacillus ferrooxidans, Alicyclobacillus sp., Pseudomonas sp., and Sulfobacillus thermosulfidooxidans was observed. The abundance of genes related to sulfur metabolism from At. caldus and Sulfolobus spp., iron oxidation from Leptospirillum sp. and metal resistance from most of the detected microorganisms increased as the consortium was successively transferred into fresh medium.     

Novel thiazolones as HCV NS5B polymerase allosteric inhibitors: Further designs, SAR, and X-ray complex structure

Structure-activity relationships (SAR) of 1 against HCV NS5B polymerase were described. SAR explorations and further structure-based design led to the identifications of 2 and 3 as novel HCV NS5B inhibitors. X-ray structure of 3 in complex with NS5B polymerase was obtained at a resolution of 2.2A, and confirmed the design.     

Aberrant Expression of RCAN1 in Alzheimer’s Pathogenesis: A New Molecular Mechanism and a Novel Drug Target

AD, a devastating neurodegenerative disorder, is the most common cause of dementia in the elderly. Patients with AD are characterized by three hallmarks of neuropathology including neuritic plaque deposition, neurofibrillary tangle formation, and neuronal loss. Growing evidences indicate that dysregulation of regulator of calcineurin 1 (RCAN1) plays an important role in the pathogenesis of AD. Aberrant RCAN1 expression facilitates neuronal apoptosis and Tau hyperphosphorylation, leading to neuronal loss and neurofibrillary tangle formation. This review aims to describe the recent advances of the regulation of RCAN1 expression and its physiological functions. Moreover, the AD risk factors-induced RCAN1 dysregulation and its role in promoting neuronal loss, synaptic impairments and neurofibrillary tangle formation are summarized. Furthermore, we provide an outlook into the effects of RCAN1 dysregulation on APP processing, Aβ generation and neuritic plaque formation, and the possible underlying mechanisms, as well as the potential of targeting RCAN1 as a new therapeutic approach.     

Surface display of the HPV L1 capsid protein by the autotransporter Shigella IcsA

Autotransporters have become attractive tools for surface expression of foreign proteins in Gram-negative bacteria. In this study, the Shigella autotransporter IcsA, has been exploited to express the human papillomavirus (HPV) type 16 L1 capsid protein in Shigella sonnei and Escherichia coli. The L1 gene was fused in-frame to replace the coding sequence of the IcsA passenger domain that is responsible for actin-based motility. The resultant hybrid protein could be detected by an anti-L1 antibody on the surface of S. sonnei and E. coli. In E. coli, the protein was expressed on the entire surface of the bacterium. In contrast, the protein was detected mainly at one pole of the Shigella bacterium. However, the protein became evenly distributed on the surface of the Shigella bacterium when the icsP gene was removed. Our study demonstrated the possibility of exploiting autotransporters for surface expression of large, heterologous viral proteins, which may be a useful strategy for vaccine development.     

The role of +TIPs in directional tip expansion

Aspergillus nidulans is an ideal model to study nuclear migration and intracellular transport by dynein and kinesin owing to its long neuron‐like hyphae, conserved transport mechanisms, and powerful genetics. In this organism, as in other filamentous fungi, microtubules have been implicated in patterning cell shape through polarized tip growth – the hallmark mode of growth that generates the elongated hyphae. Exactly how microtubules regulate tip growth is incompletely understood and remains a fascinating question for various cell types, such as pollen tubes and root hairs. Zeng et al. (2014) describe important new findings in A. nidulans regarding the role of EBA, the master regulator of microtubule plus end‐tracking proteins, in specifying microtubule dynamics required for directional tip growth at the hyphal tip.     

Discovery of new pyridoacridine alkaloids from Lissoclinum cf. badium that inhibit the ubiquitin ligase activity of Hdm2 and stabilize p53

Compounds that stabilize p53 could suppress tumors providing a additional tool to fight cancer. Mdm2, and the human ortholog, Hdm2 serve as ubiquitin E3 ligases and target p53 for ubiquitylation and degradation. Inhibition of Hdm2 stabilizes p53, inhibits cell proliferation and induces apoptosis. Using HTS to discover inhibitors, we identified three new alkaloids, isolissoclinotoxin B, diplamine B, and lissoclinidine B from Lissoclinum cf. badium. Lissoclinidine B inhibited ubiquitylation and degradation of p53, and selectively killed transformed cells harboring wild-type p53, suggesting this compound could be used to develop new treatments.     

Stable high-level expression of truncated human papillomavirus type 16 L1 protein in Drosophila Schneider-2 cells

To improve the existing human papillomavirus type 16 (HPV16) virus-like particle (VLP) preparation, the Drosophila inducible/secreted expression system, a highly efficient, economical method, was used to produce HPV16 VLPs. Drosophila Schneider-2 cells were cotransfected with pMT/BiP/V5-His expression vector containing the target gene encoding HPV16L1 protein without nucleus localization sequence and the selection vector pCoHygro plasmids at the ratio of 4:1. The stabled hygromycin-resistant cell line was obtained 1 month later, and the protein expression was induced by copper sulfate. The molecular mass of expressed HPV16L1 protein was 66 kDa, as revealed by SDS-PAGE, and confirmed by Western blot analysis. The yield of HPV16L1 protein was 0.554 mg per 1×10⁷ cells. The characteristics of HPV16L1 protein were further analyzed by mouse erythrocyte hemagglutination assay, hemagglutination inhibition assay, and transmission electron microscopy. Results showed that the truncated protein was as biologically active as natural HPVL1 protein, inducing murine erythrocyte agglutination and VLP formation. These findings indicate that the Drosophila inducible/secreted expression system is promising as a convenient and economical method for the preparation of HPV16VLP vaccine.     

Characteristics of the Achnatherum splendens community along the Qinghai-Tibet Railway, China

The Achnatherum splendens community is an important type of warm steppe vegetation which plays a very important role in environmental protection in the area along the Qinghai-Tibet Railway. In order to understand its dynamic features, the characteristics of the A. splendens community, such as spatial distribution pattern, species richness and biomass, were examined near Haiyan County, Qinghai Province. Results showed that the A. splendens community consisted of two types of mosaic patches, the microaggregation dominated by A. splendens and the microaggregation dominated by Stipa sp. The number and size of the two patches showed an interesting distribution pattern. The A. splendens patch decreased with increasing distance away from the railway, while species diversity increased. The total coverage of A. splendens was significantly higher than that of Stipa sp. The number and size of patches may indicate the degradation of the A. splendens community, which could be accelerated by human activities. Based on the characteristics and status quo of the A. splendens community, we suggest that some measures be taken to control human activities and rodents to conserve the A. splendens community. __________ Translated from Acta Ecologica Sinica, 2007, 27(2): 497–503 [译自:生态学报]     

Maize growth responses to soil microbes and soil properties after fertilization with different green manures

The use of green manures in agriculture can provide nutrients, affect soil microbial communities, and be a more sustainable management practice. The activities of soil microbes can effect crop growth, but the extent of this effect on yield remains unclear. We investigated soil bacterial communities and soil properties under four different green manure fertilization regimes (Vicia villosa, common vetch, milk vetch, and radish) and determined the effects of these regimes on maize growth. Milk vetch showed the greatest potential for improving crop productivity and increased maize yield by 31.3 %. This change might be related to changes in soil microbes and soil properties. The entire soil bacterial community and physicochemical properties differed significantly among treatments, and there were significant correlations between soil bacteria, soil properties, and maize yield. In particular, abundance of the phyla Acidobacteria and Verrucomicrobia was positively correlated with maize yield, while Proteobacteria and Chloroflexi were negatively correlated with yield. These data suggest that the variation of maize yield was related to differences in soil bacteria. The results also indicate that soil pH, alkali solution nitrogen, and available potassium were the key environmental factors shaping soil bacterial communities and determining maize yields. Both soil properties and soil microbes might be useful as indicators of soil quality and potential crop yield.