Regulated exocytosis and SNARE function (Review)

The pairing of cognate v- and t-SNAREs between two opposing lipid bilayers drives spontaneous membrane fusion and confers specificity to intracellular membrane trafficking. These fusion events are regulated by a cascade of protein-protein interactions that locally control SNARE activity and complex assembly, determining when and where fusion occurs with high efficiency in vivo. This basic regulation occurs at all transport steps and is mediated by conserved protein families such as Rab proteins and their effectors and Sec1/unc18 proteins. Regulated exocytosis employs auxiliary components that couple the signal (which triggers exocytosis) to the fusion machinery. At the neuronal synapse, munc13 as well as munc18 control SNARE complex assembly. Synaptotagmin and complexin ensure fast synchronous calcium-evoked neurotransmitter release.     

Development of small-molecule P-gp inhibitors of the N-benzyl 1,4-dihydropyridine type: Novel aspects in SAR and bioanalytical evaluation of multidrug resistance (MDR) reversal properties

Novel series of N-benzyl 1,4-dihydropyridines have been prepared by facile syntheses. All relevant substituents of the molecular scaffold have been varied. The resulting compounds were biologically evaluated as P-glycoprotein (P-gp) inhibitors. Substitutions of the N-benzyl residue favour biological activity beside respective 3-ester functions. Most active compounds were further evaluated as multidrug resistance (MDR) modulators to restore the cytotoxic properties of varying daunorubicin applications.     

Improving bioorthogonal protein ubiquitylation by click reaction

Posttranslational modification of proteins with ubiquitin (ubiquitylation) regulates numerous cellular processes. Besides functioning as a signal for proteasomal degradation, ubiquitylation has also non-proteolytic functions by altering the biochemical properties of the modified protein. To investigate the effect(s) of ubiquitylation on the properties of a protein, sufficient amounts of homogenously and well-defined ubiquitylated proteins are required. Here, we report on the elaboration of a method for the generation of high amounts of site-specifically mono-ubiquitylated proteins. Firstly, a one-step affinity purification scheme was developed for ubiquitin containing the unnatural amino acid azidohomoalanine at the C-terminal position. This ubiquitin was conjugated in a click reaction to recombinant DNA polymerase β, equipped with an alkyne function at a distinct position. Secondly, addition of defined amounts of SDS to the reaction significantly improved product formation. With these two technical improvements, we have developed a straight forward procedure for the efficient generation of site-specifically ubiquitylated proteins that can be used to study the effect(s) of ubiquitylation on the activities/properties of a protein.     

Ionenkanalerkrankungen der Niere und Nebenniere

Genetic kidney diseases represent a significant proportion of kidney diseases manifesting in childhood and adolescence, but are also gaining importance in slowly progressive or late-onset adult diseases. A significant portion of kidney diseases particularly in childhood are associated with end stage renal disease and/or other relevant morbidity. An early (molecular) diagnosis can be a prerequisite for a better prognostic assessment and provides opportunities in terms of optimized symptomatic therapy. Mechanistically speaking, mutations in ion channel-associated nephropathy represent—in addition to structural defects of the glomerular filter (e.g., COL4A3, LAMB2, nephrin) and disorders of signaling pathways that are relevant for the development of the urogenital tract (e.g., HNF1B, WT1)—a significant proportion of the group with respect to number and prototypes. Determination of the molecular genetics of (hypokalemic) salt-losing tubulopathies has contributed significantly to our understanding of the central role of the kidney in salt balance. The spectrum of renal ion channelopathies is shown using the example of classical salt-losing tubulopathies (Bartter syndrome and Gitelman syndrome), the transient receptor potential (TRP) channel group and the role of channel changes in aldosteronism and congenital hypertension.     

Growth, regeneration and shade tolerance of the Wild Service Tree (Sorbus torminalis (L.) Crantz) in aged oak coppice forests

Sorbus torminalis L. (Crantz) is a rare species in Central European forests with very limited quantitative information on its regeneration and growth dynamics. Since coppicing is no longer practiced in the most parts of Central Europe, it is unclear whether S. torminalis, which has usually a shorter end height than companion species, can persist in high forest systems. Here, we quantified species frequency on three 1 ha sample plots of former oak coppice forest. To determine whether S. torminalis regenerated continuously and how it might compete with oaks, the age of 80 trees was determined, and diameter and height growth were reconstructed for the 20 largest trees by stem analysis. To assess its shade tolerance, photosynthesis was measured for leaves located in high and low light conditions. Dendrochronological data demonstrated that, over the last 80 years, continuous recruitment of S. torminalis occurred. Growth patterns and photosynthesis measurements suggest that S. torminalis is a highly shade-tolerant species. We conclude that abandonment of coppicing in these forests does not threaten the status of S. torminalis, which can persist beneath the canopy of oaks.     

The occurence of Telescopus nigriceps (Ahl, 1924) in western Iran,with comments on the genus Telescopus (Serpentes: Colubridae)

Telescopus nigriceps, was discovered in the Kermanshah region in Iran, which is the first record of this species in Iran. A comparison is made with the sympatric and parapatric Telescopus tessellatus and T. fallax iberus.     

The architecture of Norway spruce ectomycorrhizae: three-dimensional models of cortical cells, fungal biomass, and interface for potential nutrient exchange

Gathering realistic data on actual fungal biomass in ectomycorrhized fine root systems is still a matter of concern. Thus far, observations on architecture of ectomycorrhizae (ECMs) have been limited to analyses of two-dimensional (2-D) images of tissue sections. This unavoidably causes stereometrical problems that lead to inadequate assumptions about actual size of cells and their arrangement within ECM's functional compartments. Based on extensive morphological investigations of field samples, we modeled the architectural components of an average-sized Norway spruce ECM. In addition to our comprehensive and detailed quantitative data on cell sizes, we studied actual shape and size, in vivo arrangement, and potential nutrient exchange area of plant cortical cells (CCs) using computer-aided three-dimensional (3-D) reconstructions based on semithin serial sections. We extrapolated a factual fungal biomass in ECMs (Hartig net (HN) included) of 1.71 t?ha^?1 FW (0.36 t?ha^?1 DW) for the top 5 cm of soil for an autochthonous, montane, optimum Norway spruce stand in the Tyrolean Alps. The corresponding potential nutrient exchange area in ECMs including main axes of ECM systems, which is defined as the sum of interfaces between plant CCs and the HN, amounts to at least 3.2?×?10⁵?m²?ha^?1. This is the first study that determines the contribution of the HN to the total fungal biomass in ECMs as well as the quantification of its contact area. Our results may stimulate future research on fungal below-ground processes and their impact on the global carbon cycle.