The Xenopus TRPV6 homolog encodes a Mg2+‐permeant channel that is inhibited by interaction with TRPC1

The TRP gene family encodes primarily cation non‐selective, Ca²⁺ permeant channels that are involved in a dizzying array of sensory mechanisms. Two channels in this large family TRPV5 and TRPV6 are highly Ca²⁺ selective and are expressed in epithelia where they are important in Ca²⁺ uptake. TRPV5/6 are constitutively active, yet the mechanisms regulating their activation in native tissue remains elusive. Here we functionally characterize the Xenopus TRPV6 homolog. xTRPV6 is expressed in the oocyte and encodes a channel that is permeant to divalents including Ca²⁺, and displays a high permeability to Mg²⁺. The oocyte does not exhibit functional TRPV6‐like current at rest, showing that the endogenous channel is somehow maintained in an inactive state. We show that endogenous as well as overexpressed xTRPV6 interacts with xTRPC1 and that this interaction inhibits xTRPV6 currents. As such TRPC1 is likely to regulate the activity of TRPV6 under physiological conditions. J. Cell. Physiol. 228: 2386–2398, 2013. © 2013 The Authors. Journal of Cellular Physiology Published by Wiley Periodicals, Inc.     

Immobilization of β-glucosidase on Eupergit C for Lignocellulose Hydrolysis

β-Glucosidase is frequently used to supplement cellulase preparations for hydrolysis of cellulosic and lignocellulosic substrates in order to accelerate the conversion of cellobiose to glucose. Typically, commercial cellulase preparations are deficient in this enzyme and accumulation of cellobiose leads to product inhibition. This study evaluates the potential for recycling β-glucosidase by immobilization on a methacrylamide polymer carrier, Eupergit C. The immobilized β-glucosidase had improved stability at 65 °C, relative to the free enzyme, while the profile of activity versus pH was unchanged. Immobilization resulted in an increase in the apparent K_m from 1.1 to 11 mm and an increase in V_max from 296 to 2430 μmol mg⁻¹ min⁻¹. The effect of immobilized β-glucosidase on the hydrolysis of cellulosic and lignocellulosic substrates was comparable to that of the free enzyme when used at the same level of protein. Operational stability of the immobilized β-glucosidase was demonstrated during six rounds of lignocellulose hydrolysis. Received 22 August 2005; Revisions requested 20 September 2005; Revisions received 8 November 2005; Accepted 10 November 2005     

Activation of the pyrin inflammasome by intracellular Burkholderia cenocepacia

Burkholderia cenocepacia is an opportunistic pathogen that causes chronic infection and induces progressive respiratory inflammation in cystic fibrosis patients. Recognition of bacteria by mononuclear cells generally results in the activation of caspase-1 and processing of IL-1β, a major proinflammatory cytokine. In this study, we report that human pyrin is required to detect intracellular B. cenocepacia leading to IL-1β processing and release. This inflammatory response involves the host adapter molecule ASC and the bacterial type VI secretion system (T6SS). Human monocytes and THP-1 cells stably expressing either small interfering RNA against pyrin or YFP-pyrin and ASC (YFP-ASC) were infected with B. cenocepacia and analyzed for inflammasome activation. B. cenocepacia efficiently activates the inflammasome and IL-1β release in monocytes and THP-1. Suppression of pyrin levels in monocytes and THP-1 cells reduced caspase-1 activation and IL-1β release in response to B. cenocepacia challenge. In contrast, overexpression of pyrin or ASC induced a robust IL-1β response to B. cenocepacia, which correlated with enhanced host cell death. Inflammasome activation was significantly reduced in cells infected with T6SS-defective mutants of B. cenocepacia, suggesting that the inflammatory reaction is likely induced by an as yet uncharacterized effector(s) of the T6SS. Together, we show for the first time, to our knowledge, that in human mononuclear cells infected with B. cenocepacia, pyrin associates with caspase-1 and ASC forming an inflammasome that upregulates mononuclear cell IL-1β processing and release.     

Pangenomic study of Corynebacterium diphtheriae that provides insights into the genomic diversity of pathogenic isolates from cases of classical diphtheria, endocarditis, and pneumonia

Corynebacterium diphtheriae is one of the most prominent human pathogens and the causative agent of the communicable disease diphtheria. The genomes of 12 strains isolated from patients with classical diphtheria, endocarditis, and pneumonia were completely sequenced and annotated. Including the genome of C. diphtheriae NCTC 13129, we herewith present a comprehensive comparative analysis of 13 strains and the first characterization of the pangenome of the species C. diphtheriae. Comparative genomics showed extensive synteny and revealed a core genome consisting of 1,632 conserved genes. The pangenome currently comprises 4,786 protein-coding regions and increases at an average of 65 unique genes per newly sequenced strain. Analysis of prophages carrying the diphtheria toxin gene tox revealed that the toxoid vaccine producer C. diphtheriae Park-Williams no. 8 has been lysogenized by two copies of the ω(tox)(+) phage, whereas C. diphtheriae 31A harbors a hitherto-unknown tox(+) corynephage. DNA binding sites of the tox-controlling regulator DtxR were detected by genome-wide motif searches. Comparative content analysis showed that the DtxR regulons exhibit marked differences due to gene gain, gene loss, partial gene deletion, and DtxR binding site depletion. Most predicted pathogenicity islands of C. diphtheriae revealed characteristics of horizontal gene transfer. The majority of these islands encode subunits of adhesive pili, which can play important roles in adhesion of C. diphtheriae to different host tissues. All sequenced isolates contain at least two pilus gene clusters. It appears that variation in the distributed genome is a common strategy of C. diphtheriae to establish differences in host-pathogen interactions.     

Corrugation Architecture Enabled Ultraflexible Wafer‐Scale High‐Efficiency Monocrystalline Silicon Solar Cell

Advanced classes of modern application require new generation of versatile solar cells showcasing extreme mechanical resilience, large‐scale, low cost, and excellent power conversion efficiency. Conventional crystalline silicon‐based solar cells offer one of the most highly efficient power sources, but a key challenge remains to attain mechanical resilience while preserving electrical performance. A complementary metal oxide semiconductor‐based integration strategy where corrugation architecture enables ultraflexible and low‐cost solar cell modules from bulk monocrystalline large‐scale (127 × 127 cm²) silicon solar wafers with a 17% power conversion efficiency. This periodic corrugated array benefits from an interchangeable solar cell segmentation scheme which preserves the active silicon thickness of 240 µm and achieves flexibility via interdigitated back contacts. These cells can reversibly withstand high mechanical stress and can be deformed to zigzag and bifacial modules. These corrugation silicon‐based solar cells offer ultraflexibility with high stability over 1000 bending cycles including convex and concave bending to broaden the application spectrum. Finally, the smallest bending radius of curvature lower than 140 µm of the back contacts is shown that carries the solar cells segments.     

Preparation,characterization of silver phyto nanoparticles and their impact on growth potential of Lupinus termis L. seedlings

The current study reports rapid and easy method for synthesis of eco-friendly silver nanoparticles (AgNPs) using Coriandrum sativum leaves extract as a reducing and covering agent. The bio-reductive synthesis of AgNPs was monitored using a scanning double beam UV-vis spectrophotometer. Transmission electron microscopy (TEM) was used to characterize the morphology of AgNPs obtained from plant extracts. X-ray diffraction (XRD) patterns of AgNPs indicate that the structure of AgNPs is the face centered cubic structure of metallic silver. The surface morphology and topography of the AgNPs were examined by scanning electron microscopy and the energy dispersive spectrum revealed the presence of elemental silver in the sample. The silver phyto nanoparticles were collected from plant extract and tested growth potential and metabolic pattern in (Lupinus termis L.) seedlings upon exposure to different concentrations of AgNPs. The seedlings were exposed to various concentrations of (0, 0.1, 0.3 and 0.5 mg L^?1) AgNPs for ten days. Significant reduction in shoot and root elongation, shoot and root fresh weights, total chlorophyll and total protein contents were observed under the higher concentrations of AgNPs. Exposure to 0.5 mg L^?1 of AgNPs decreased sugar contents and caused significant foliar proline accumulation which considered as an indicator of the stressful effect of AgNPs on seedlings. AgNPs exposure resulted in a dose dependent decrease in different growth parameters and also caused metabolic disorders as evidenced by decreased carbohydrates and protein contents. Further studies needed to find out the efficacy, longevity and toxicity of AgNPs toward photosynthetic system and antioxidant parameters to improve the current investigation.     

A Nuclear Localization Signal at the SAM-SAM Domain Interface of AIDA-1 Suggests a Requirement for Domain Uncoupling Prior to Nuclear Import

The neuronal scaffolding protein AIDA-1 is believed to act as a convener of signals arising at postsynaptic densities. Among the readily identifiable domains in AIDA-1, two closely juxtaposed sterile alpha motif (SAM) domains and a phosphotyrosine binding domain are located within the C-terminus of the longest splice variant and exclusively in four shorter splice variants. As a first step towards understanding the possible emergent properties arising from this assembly of ligand binding domains, we have used NMR methods to solve the first structure of a SAM domain tandem. Separated by a 15-aa linker, the two SAM domains are fused in a head-to-tail orientation that has been observed in other hetero- and homotypic SAM domain structures. The basic nuclear import signal for AIDA-1 is buried at the interface between the two SAM domains. An observed disparity between the thermal stabilities of the two SAM domains suggests a mechanism whereby the second SAM domain decouples from the first SAM domain to facilitate translocation of AIDA-1 to the nucleus.     

A Nonquiescent “Idling” Population State in Drug-Treated,BRAF-Mutated Melanoma

Targeted therapy is an effective standard of care in BRAF-mutated malignant melanoma. However, the duration of tumor remission varies unpredictably among patients, and relapse is almost inevitable. Here, we examine the responses of several BRAF-mutated melanoma cell lines (including isogenic subclones) to BRAF inhibitors. We observe complex response dynamics across cell lines, with short-term responses (<100 h) varying from cell line to cell line. In the long term, however, we observe equilibration of all drug-treated populations into a nonquiescent state characterized by a balanced rate of death and division, which we term the “idling” state, and to our knowledge, this state has not been previously reported. Using mathematical modeling, we propose that the observed population-level dynamics are the result of cells transitioning between basins of attraction within a drug-modified phenotypic landscape. Each basin is associated with a drug-induced proliferation rate, a recently introduced metric of an antiproliferative drug effect. The idling population state represents a new dynamic equilibrium in which cells are distributed across the landscape such that the population achieves zero net growth. By fitting our model to experimental drug-response data, we infer the phenotypic landscapes of all considered melanoma cell lines and provide a unifying view of how BRAF-mutated melanomas respond to BRAF inhibition. We hypothesize that the residual disease observed in patients after targeted therapy is composed of a significant number of idling cells. Thus, defining molecular determinants of the phenotypic landscape that idling populations occupy may lead to “targeted landscaping” therapies based on rational modification of the landscape to favor basins with greater drug susceptibility.