Metalloprotease meprin beta in rat kidney: glomerular localization and differential expression in glomerulonephritis

Meprin (EC 3.4.24.18) is an oligomeric metalloendopeptidase found in microvillar membranes of kidney proximal tubular epithelial cells. Here, we present the first report on the expression of meprin beta in rat glomerular epithelial cells and suggest a potential involvement in experimental glomerular disease. We detected meprin beta in glomeruli of immunostained rat kidney sections on the protein level and by quantitative RT-PCR of laser-capture microdissected glomeruli on the mRNA level. Using immuno-gold staining we identified the membrane of podocyte foot processes as the main site of meprin beta expression. The glomerular meprin beta expression pattern was altered in anti-Thy 1.1 and passive Heymann nephritis (PHN). In addition, the meprin beta staining pattern in the latter was reminiscent of immunostaining with the sheep anti-Fx1A antiserum, commonly used in PHN induction. Using Western blot and immunoprecipitation assays we demonstrated that meprin beta is recognized by Fx1A antiserum and may therefore represent an auto-antigen in PHN. In anti-Thy 1.1 glomerulonephritis we observed a striking redistribution of meprin beta in tubular epithelial cells from the apical to the basolateral side and the cytosol. This might point to an involvement of meprin beta in this form of glomerulonephritis.     

Caspase-12 modulates NOD signaling and regulates antimicrobial peptide production and mucosal immunity

Bacterial sensing by intracellular Nod proteins and other Nod-like receptors (NLRs) activates signaling pathways that mediate inflammation and pathogen clearance. Nod1 and Nod2 associate with the kinase Rip2 to stimulate NF-kappaB signaling. Other cytosolic NLRs assemble caspase-1-activating multiprotein complexes termed inflammasomes. Caspase-12 modulates the caspase-1 inflammasome, but unlike other NLRs, Nod1 and Nod2 have not been linked to caspases, and mechanisms regulating the Nod-Rip2 complex are less clear. We report that caspase-12 dampens mucosal immunity to bacterial infection independent of its effects on caspase-1. Caspase-12 deficiency enhances production of antimicrobial peptides, cytokines, and chemokines to entric pathogens, an effect dependent on bacterial type III secretion and the Nod pathway. Mechanistically, caspase-12 binds to Rip2, displacing Traf6 from the signaling complex, inhibiting its ubiquitin ligase activity, and blunting NF-kappaB activation. Nod activation and resulting antimicrobial peptide production constitute an early innate defense mechanism, and caspase-12 inhibits this mucosal antimicrobial response.     

The VIL gene CRAWLING ELEPHANT controls maturation and differentiation in tomato via polycomb silencing

VERNALIZATION INSENSITIVE 3-LIKE (VIL) proteins are PHD-finger proteins that recruit the repressor complex Polycomb Repressive Complex 2 (PRC2) to the promoters of target genes. Most known VIL targets are flowering repressor genes. Here, we show that the tomato VIL gene CRAWLING ELEPHANT (CREL) promotes differentiation throughout plant development by facilitating the trimethylation of Histone H3 on lysine 27 (H3K27me3). We identified the crel mutant in a screen for suppressors of the simple-leaf phenotype of entire (e), a mutant in the AUX/IAA gene ENTIRE/SlIAA9, involved in compound-leaf development in tomato. crel mutants have increased leaf complexity, and suppress the ectopic blade growth of e mutants. In addition, crel mutants are late flowering, and have delayed and aberrant stem, root and flower development. Consistent with a role for CREL in recruiting PRC2, crel mutants show drastically reduced H3K27me3 enrichment at approximately half of the 14,789 sites enriched in wild-type plants, along with upregulation of many underlying genes. Interestingly, this reduction in H3K27me3 across the genome in crel is also associated with gains in H3K27me3 at a smaller number of sites that normally have modest levels of the mark in wild-type plants, suggesting that PRC2 activity is no longer limiting in the absence of CREL. Our results uncover a wide role for CREL in plant and organ differentiation in tomato and suggest that CREL is required for targeting PRC2 activity to, and thus silencing, a specific subset of polycomb targets.     

Spatial distribution, connectivity, and the influence of scale: habitat availability for the endangered Mona Island rock iguana

The Caribbean region is one of the five leading biodiversity hotspots in the world. Analysis of the spatial structure of critical habitats and how it affects endemic species in this region is essential baseline information for biodiversity monitoring and management. We quantified and evaluated the spatial structure and connectivity of depression forests on Mona Island and their potential impact on Mona Island rock iguana habitat, as a framework to assess spatial distribution, connectivity, and the issue of scale in small and widely dispersed habitats. Using IKONOS imagery, we mapped and delineated depression forests at four different scales (minimum mapping units: <100, 100, 500, and 1,000 m), and calculated landscape metrics describing their spatial structure, and connectivity, for each map resolution. Our approach resulted in a more detailed map than previously described maps, providing better information on habitat connectivity for iguanas. The comparison of the island landscape mapped at different scales provided evidence on how changing scales affect the output of spatial metrics and may have a significant impact when planning decisions and assigning conservation priorities. It also highlighted the importance of adequate ecological scales when addressing landscape management and conservation priorities. The analysis of landscapes at multiple scales provided a mechanism to evaluate the role of patch detection and its effect on the interpretation of connectivity and spatial structure of suitable areas for species with small and widely dispersed habitats. These methodologies can be applied other species, in different environments, with similar limitations related to connectivity and habitat availability.     

Marine bacteria associated with sponge as source of cyclic peptides

Two bacteria associated with the marine sponge Ircinia variabilis were isolated using commercial and experimental media. The use of media containing marine derived proteins improved the growth of both isolated bacteria, showing that marine bacteria need of marine derived proteins for a better growth. The composition of free and total fatty acids of both strains cultivated under different carbon source was investigated. Several diketopiperazines were isolated from both bacteria and the hypothesis of their role in the bacterial-spongy interaction is discussed.     

The CD8+ T-cell response to lymphocytic choriomeningitis virus involves the L antigen: uncovering new tricks for an old virus

CD8(+) T-cell responses control lymphocytic choriomeningitis virus (LCMV) infection in H-2(b) mice. Although antigen-specific responses against LCMV infection are well studied, we found that a significant fraction of the CD8(+) CD44(hi) T-cell response to LCMV in H-2(b) mice was not accounted for by known epitopes. We screened peptides predicted to bind major histocompatibility complex class I and overlapping 15-mer peptides spanning the complete LCMV proteome for gamma interferon (IFN-gamma) induction from CD8(+) T cells derived from LCMV-infected H-2(b) mice. We identified 19 novel epitopes. Together with the 9 previously known, these epitopes account for the total CD8(+) CD44(hi) response. Thus, bystander T-cell activation does not contribute appreciably to the CD8(+) CD44(hi) pool. Strikingly, 15 of the 19 new epitopes were derived from the viral L polymerase, which, until now, was not recognized as a target of the cellular response induced by LCMV infection. The L epitopes induced significant levels of in vivo cytotoxicity and conferred protection against LCMV challenge. Interestingly, protection from viral challenge was best correlated with the cytolytic potential of CD8(+) T cells, whereas IFN-gamma production and peptide avidity appear to play a lesser role. Taken together, these findings illustrate that the LCMV-specific CD8(+) T-cell response is more complex than previously appreciated.     

Assessing mitochondrial outer membrane permeabilization during apoptosis

Mitochondria play a pivotal role in the regulation of apoptosis. An imbalance in apoptosis can lead to disease. Unscheduled apoptosis has been linked to neurodegeneration while inhibition of apoptosis can cause cancer. An early and key event during apoptosis is the release of factors from mitochondria. In apoptosis the mitochondrial outer membrane becomes permeable, leading to release of apoptogenic factors into the cytosol. One such factor, cytochrome c, is an electron carrier of the respiratory chain normally trapped within the mitochondrial intermembrane space. Many apoptotic studies investigate mitochondrial outer membrane permeabilization (MOMP) by monitoring the release of cytochrome c. Here, we describe three reliable techniques that detect cytochrome c release from mitochondria, through subcellular fractionation or immunocytochemistry and fluorescence microscopy, or isolated mitochondria and recombinant Bax and t-Bid proteins in vitro. These techniques will help to identify mechanisms and characterize factors regulating MOMP.     

Attenuation of AD‐like neuropathology by harnessing peripheral immune cells: local elevation of IL‐10 and MMP‐9

Immunization with an altered myelin‐derived peptide (MOG45D) improves recovery from acute CNS insults, partially via recruitment of monocyte‐derived macrophages that locally display a regulatory activity. Here, we investigated the local alterations in the cellular and molecular immunological milieu associated with attenuation of Alzheimer’s disease‐like pathology following immunotherapy. We found that immunization of amyloid precursor protein/presenilin 1 double‐transgenic mice with MOG45D peptide, loaded on dendritic cells, led to a substantial reduction of parenchymal and perivascular amyloid beta (Aβ)‐plaque burden and soluble Aβ_(1–42) peptide levels as well as reduced astrogliosis and levels of a key glial scar protein (chondroitin sulphate proteoglycan). These changes were associated with a shift in the local innate immune response, manifested by increased Iba1⁺/CD45^high macrophages that engulfed Aβ, reduced pro‐inflammatory (tumor necrosis factor‐α) and increased anti‐inflammatory (interleukin‐10) cytokines, as well as a significant increase in growth factors (IGF‐1 and TGFβ) in the brain. Furthermore, the levels of matrix metalloproteinase‐9, an enzyme shown to degrade Aβ and is associated with glial scar formation, were significantly elevated in the brain following immunization. Altogether, these results indicate that boosting systemic immune cells leads to a local immunomodulation manifested by elevated levels of anti‐inflammatory cytokines and metalloproteinases that contribute to ameliorating Alzheimer’s disease pathology.     

Distinct bacterial communities exist beneath a high Arctic polythermal glacier

Bacterial communities reside in basal ice, sediment, and meltwater in the supra-, sub-, and proglacial environments of John Evans Glacier, Nunavut, Canada. We examined whether the subglacial bacterial community shares common members with the pro- and supraglacial communities, and by inference, whether it could be derived from communities in either of these environments (e.g., by ice overriding proglacial sediments or by in-wash of surface meltwaters). Terminal restriction fragment length polymorphism analysis of bacterial 16S rRNA genes amplified from these environments revealed that the subglacial water, basal ice, and sediment communities were distinct from those detected in supraglacial meltwater and proglacial sediments, with 60 of 142 unique terminal restriction fragments (T-RFs) detected exclusively in subglacial samples and only 8 T-RFs detected in all three environments. Supraglacial waters shared some T-RFs with subglacial water and ice, likely reflecting the seasonal flow of surface meltwater into the subglacial drainage system, whereas supraglacial and proglacial communities shared the fewest T-RFs. Thus, the subglacial community at John Evans Glacier appears to be predominantly autochthonous rather than allochthonous, and it may be adapted to subglacial conditions. Chemical analysis of water and melted ice also revealed differences between the supraglacial and proglacial environments, particularly regarding electrical conductivity and nitrate, sulfate, and dissolved organic carbon concentrations. Whereas the potential exists for common bacterial types to be broadly distributed throughout the glacial system, we have observed distinct bacterial communities in physically and chemically different glacial environments.