Mechanism and consequences for paralog-specific sumoylation of ubiquitin-specific protease 25

Vertebrates express two distinct families of SUMO proteins (SUMO1 and SUMO2/3) that serve distinct functions as posttranslational modifiers. Many proteins are modified specifically with SUMO1 or SUMO2/3, but the mechanisms for paralog selectivity are poorly understood. In a screen for SUMO2/3 binding proteins, we identified Ubiquitin Specific Protease 25 (USP25). USP25 turned out to also be a target for sumoylation, being more efficient with SUMO2/3. Sumoylation takes place within USP25's two ubiquitin interaction motifs (UIMs) that are required for efficient hydrolysis of ubiquitin chains. USP25 sumoylation impairs binding to and hydrolysis of ubiquitin chains. Both SUMO2/3-specific binding and sumoylation depend on a SUMO interaction motif (SIM/SBM). Seven amino acids in the SIM of USP25 are sufficient for SUMO2/3-specific binding and conjugation, even when taken out of structural context. One mechanism for paralog-specific sumoylation may, thus, involve SIM-dependent recruitment of SUMO1 or SUMO2/3 thioester-charged Ubc9 to targets.     

Non-homologous sex chromosomes in two species of the genus Eigenmannia (Teleostei: Gymnotiformes)

The Neotropical genus Eigenmannia is a fish group with unknown species diversity where representatives possess a broad range of chromosomal sex determining systems namely XY/XX, X(1)X(2)Y/X(1)X(1)X(2)X(2), ZZ/ZW as well as homomorphic sex chromosomes. To test the homology of two heteromorphic XY sex chromosome systems present in two sympatric populations, reciprocal cross-species FISH experiments were performed using probes derived by microdissection of X and Y chromosomes present in analyzed specimens of Eigenmannia virescens and Eigenmannia sp.2, respectively. While X and Y paint probes hybridized to species-specific sex chromosomes, in reciprocal cross-FISH both probes hybridized exclusively to autosomes. The result suggests multiple independent origins of the XY systems in the analyzed populations.     

Cell-wall structural changes in wheat straw pretreated for bioethanol production

Background  

Pretreatment is an essential step in the enzymatic hydrolysis of biomass and subsequent production of bioethanol. Recent results indicate that only a mild pretreatment is necessary in an industrial, economically feasible system. The Integrated Biomass Utilisation System hydrothermal pretreatment process has previously been shown to be effective in preparing wheat straw for these processes without the application of additional chemicals. In the current work, the effect of the pretreatment on the straw cell-wall matrix and its components are characterised microscopically (atomic force microscopy and scanning electron microscopy) and spectroscopically (attenuated total reflectance Fourier transform infrared spectroscopy) in order to understand this increase in digestibility.     

Auditory cortical contrast enhancing by global winner-take-all inhibitory interactions

Brains decompose the world into discrete objects of perception, thereby facing the problem of how to segregate and selectively address similar objects that are concurrently present in a scene. Theoretical models propose that this could be achieved by neuronal implementations of so-called winner-take-all algorithms where neuronal representations of objects or object features interact in a competitive manner. Here we present evidence for the existence of such a mechanism in an animal species. We present electrophysiological, neuropharmacological and neuroanatomical data which suggest a novel view of the role of GABA(A)-mediated inhibition in primary auditory cortex (AI), where intracortical GABA(A)-mediated inhibition operates on a global scale within a circular map of sound periodicity representation in AI, with functionally inhibitory projections of similar effect from any location throughout the whole map. These interactions could underlie the proposed competitive "winner-take-all" algorithm to support object segregation, e.g., segregation of different speakers in cocktail-party situations.     

Genome-wide scan on total serum IgE levels identifies FCER1A as novel susceptibility locus

High levels of serum IgE are considered markers of parasite and helminth exposure. In addition, they are associated with allergic disorders, play a key role in anti-tumoral defence, and are crucial mediators of autoimmune diseases. Total IgE is a strongly heritable trait. In a genome-wide association study (GWAS), we tested 353,569 SNPs for association with serum IgE levels in 1,530 individuals from the population-based KORA S3/F3 study. Replication was performed in four independent population-based study samples (total n = 9,769 individuals). Functional variants in the gene encoding the alpha chain of the high affinity receptor for IgE (FCER1A) on chromosome 1q23 (rs2251746 and rs2427837) were strongly associated with total IgE levels in all cohorts with P values of 1.85 x 10(-20) and 7.08 x 10(-19) in a combined analysis, and in a post-hoc analysis showed additional associations with allergic sensitization (P = 7.78 x 10(-4) and P = 1.95 x 10(-3)). The "top" SNP significantly influenced the cell surface expression of FCER1A on basophils, and genome-wide expression profiles indicated an interesting novel regulatory mechanism of FCER1A expression via GATA-2. Polymorphisms within the RAD50 gene on chromosome 5q31 were consistently associated with IgE levels (P values 6.28 x 10(-7)-4.46 x 10(-8)) and increased the risk for atopic eczema and asthma. Furthermore, STAT6 was confirmed as susceptibility locus modulating IgE levels. In this first GWAS on total IgE FCER1A was identified and replicated as new susceptibility locus at which common genetic variation influences serum IgE levels. In addition, variants within the RAD50 gene might represent additional factors within cytokine gene cluster on chromosome 5q31, emphasizing the need for further investigations in this intriguing region. Our data furthermore confirm association of STAT6 variation with serum IgE levels.     

Directional and non‐directional vegetation changes in a temperate salt marsh in relation to biotic and abiotic factors

Abstract. The effects of reduction and cessation of sheep grazing on salt‐marsh vegetation were studied on a formerly intensively grazed salt marsh in northern Germany. Plant species cover was recorded in 45 permanent plots from 1992 to 2000. In 1995, physical and chemical soil parameters were analysed. Results of Redundancy Analysis (RDA) indicated that salinity and the depth of anoxic conditions below the surface were the most important soil factors related to the spatial vegetation pattern. Furthermore, plant species distribution was influenced by present and past grazing intensity, by soil grain size and nitrogen content. Vegetation changes over 9 yr were analysed by non‐linear regression. The cover of Aster tripolium, Atriplex portulacoides, and, to a lesser extent, Artemisia maritima and Elymus athericus increased due to reduced grazing pressure, whereas the cover of Salicornia europaea decreased. After a strong increase in the first years Aster decreased 2 to 6 yr after abandonment. In the mid salt‐marsh zone Puccinellia maritima was replaced by Festuca rubra. The cover of Puccinellia, Festuca, Suaeda maritima, Glaux maritima and Salicornia fluctuated strongly, probably due to differences in weather conditions and inundation frequency. Species richness per 4 m² generally increased while vegetation evenness decreased during the study period. Only in the high salt marsh abandoned for 9 yr did the number of species decrease slightly. Thus far, cessation of grazing did not lead to large‐scale dominance of single plant species.     

Differential roles of PKCalpha and PKCepsilon in controlling the gene expression of Nox4 in human endothelial cells

NADPH oxidases are major sources of superoxide in the vascular wall. This study investigates the role of protein kinase C (PKC) in regulating gene expression of NADPH oxidases. Treatment of human umbilical vein endothelial cells (HUVEC) and HUVEC-derived EA.hy 926 endothelial cells with phorbol 12-myristate 13-acetate (PMA) or phorbol 12,13-dibutyrate led to a PKC-dependent biphasic expression of the gp91phox homolog Nox4. A downregulation of Nox4 was observed at 6 h and an upregulation at 48 h after phorbol ester treatment. The early Nox4 downregulation was associated with a reduced superoxide production, whereas the late Nox4 upregulation was accompanied by a clear enhancement of superoxide. PMA activated the PKC isoforms alpha and epsilon in HUVEC and EA.hy 926 cells. Knockdown of PKCepsilon by siRNA prevented the early downregulation of Nox4, whereas knockdown of PKCalpha selectively abolished the late Nox4 upregulation. Vascular endothelial growth factor (VEGF), which activates PKCalpha but not PKCepsilon in HUVEC, increased Nox4 expression without the initial downregulation. VEGF-induced Nox4 upregulation was associated with an enhanced proliferation and angiogenesis of HUVEC. Both effects could be reduced by inhibition of NADPH oxidase. Thus, a selective inhibition/knockdown of PKCalpha may represent a novel therapeutic strategy for vascular disease.     

TRPC3 channels are required for synaptic transmission and motor coordination

In the mammalian central nervous system, slow synaptic excitation involves the activation of metabotropic glutamate receptors (mGluRs). It has been proposed that C1-type transient receptor potential (TRPC1) channels underlie this synaptic excitation, but our analysis of TRPC1-deficient mice does not support this hypothesis. Here, we show unambiguously that it is TRPC3 that is needed for mGluR-dependent synaptic signaling in mouse cerebellar Purkinje cells. TRPC3 is the most abundantly expressed TRPC subunit in Purkinje cells. In mutant mice lacking TRPC3, both slow synaptic potentials and mGluR-mediated inward currents are completely absent, while the synaptically mediated Ca2+ release signals from intracellular stores are unchanged. Importantly, TRPC3 knockout mice exhibit an impaired walking behavior. Taken together, our results establish TRPC3 as a new type of postsynaptic channel that mediates mGluR-dependent synaptic transmission in cerebellar Purkinje cells and is crucial for motor coordination.     

A novel physiological property of snake bradykinin-potentiating peptides-reversion of MK-801 inhibition of nicotinic acetylcholine receptors

The first naturally occurring angiotensin-converting enzyme (ACE) inhibitors described are pyroglutamyl proline-rich oligopeptides, found in the venom of the viper Bothrops jararaca, and named as bradykinin-potentiating peptides (BPPs). Biochemical and pharmacological properties of these peptides were essential for the development of Captopril, the first active site-directed inhibitor of ACE, currently used for the treatment of human hypertension. However, a number of data have suggested that the pharmacological activity of BPPs could not only be explained by their inhibitory action on enzymatic activity of somatic ACE. In fact, we showed recently that the strong and long-lasting anti-hypertensive effect of BPP-10c [相似文献   

Dinucleotides as growth-promoting extracellular mediators. Presence of dinucleoside diphosphates Ap2A, Ap2G, and Gp2G in releasable granules of platelets

Dinucleoside diphosphates, Ap(2)A, Ap(2)G, and Gp(2)G represent a new class of growth-promoting extracellular mediators, which are released from granules after activation of platelets. The presence of theses substances was shown after purification from a platelet concentrate. The substances were identified by UV spectrometry, retention time comparison with authentic substances, matrix-assisted laser desorption/ionization mass spectrometry, post-source-decay matrix-assisted laser desorption/ionization mass spectrometry, and enzymatic analysis. Ap(2)A, Ap(2)G, and Gp(2)G have growth-stimulating effects on vascular smooth muscle cells in nanomolar concentrations as shown by [(3)H]thymidine incorporation measurements. The calculated EC(50) (log m; mean +/- S.E.) values were -6.07 +/- 0.14 for Ap(2)A, -6.27 +/- 0.25 for Ap(2)G, and -6.91 +/- 0.44 for Gp(2)G. At least 61.5 +/- 4.3% of the dinucleoside polyphosphates are released by platelet activation. The intraplatelet concentrations suggest that, in the close environment of a platelet thrombus, similar dinucleoside polyphosphate concentrations can be found as in platelets. Intraplatelet concentration can be estimated in the range of 1/20 to 1/100 of the concentration of ATP. In conclusion, Ap(2)A, Ap(2)G, and Gp(2)G derived from releasable granules of human platelets may play a regulatory role in vascular smooth muscle growth as growth-promoting mediators.