Measurement of Ensemble TRPV1 Ion Channel Currents Using Droplet Bilayers

Electrophysiological characterization of ion channels is useful for elucidation of channel function as well as quantitative assessment of pharmaceutical effects on ion channel conductance. We used droplet bilayers to measure ensemble ion channel currents from membrane preparations made from TRPV1-expressing HEK cells. Conductance measurements showed rectification, activation by acid and capsaicin, and inhibition by capsazepine, SB 452533, and JNJ 17293212. We also quantitatively measured concentration-dependent inhibition of channel conductance through determination of capsazepine IC₅₀ in agreement with previously published studies using patch clamp. These results, combined with the reduced apparatus and material requirements of droplet bilayers, indicate that this platform could be used for study of other physiologically relevant ion channels.     

Sequencing Reactions Using 6-Thio-2′-Deoxyguanosine-5′-triphosphate

Abstract

6-Thio-2′-Deoxyguanosine-5′-Triphosphate (6SdGTP) was employed as a substrate replacing dGTP in sequencing reactions with Sequenase? and Thermo Sequenase?.     

A Serendipitous Synthesis of 8-Dimsyl-2′-deoxyguanosine

Abstract

A serendipitous synthesis of 8-dimsyl-dG (2) has been achieved along with the known 8-benzyloxy-dG (3) in a nucleophilic substitution reaction of 8-bromo-dG (1) with in situ generated dimsyl and benzyloxy sodium. Compound 3 was directly converted into the mutagenic oxidative DNA damage product, 8-oxo-dGTP (4).     

Flow cytometry-based characterization of label-retaining stem cells following transplacental BrdU labelling

A method to characterize and culture stem cells from neonate mouse epidermis after transplacental BrdU (bromo-deoxyuridine) administration is described. We have characterized stem cells by their properties viz. to retain BrdU label, adhere rapidly onto collagen-fibronectin substratum and express a specific biomarker beta-1-integrin. BrdU-labelled cells (detected using monoclonal antibody) constituted a sum of 18% of the total number of cells. The ability of freshly isolated keratinocytes [LRCs (label-retaining cells)] to bind to primary BrdU antibody or to pick up PI (propidium iodide) stain was distinguishable. Viable LRCs did not retain PI. Such cells, termed EpSC (epidermis stem cell), were PI negative and BrdU positive. EpSC constituted 6% of the total cell yield. Culture in low Ca2+ medium and susceptibility to differentiation in the presence of high Ca2+ levels further characterized the stem cells. This protocol is useful for studying transplacental carcinogenesis.     

Entry of oomycete and fungal effectors into plant and animal host cells

Fungal and oomycete pathogens cause many destructive diseases of plants and important diseases of humans and other animals. Fungal and oomycete plant pathogens secrete numerous effector proteins that can enter inside host cells to condition susceptibility. Until recently it has been unknown if these effectors enter via pathogen-encoded translocons or via pathogen-independent mechanisms. Here we review recent evidence that many fungal and oomycete effectors enter via receptor-mediated endocytosis, and can do so in the absence of the pathogen. Surprisingly, a large number of these effectors utilize cell surface phosphatidyinositol-3-phosphate (PI-3-P) as a receptor, a molecule previously known only inside cells. Binding of effectors to PI-3-P appears to be mediated by the cell entry motif RXLR in oomycetes, and by diverse RXLR-like variants in fungi. PI-3-P appears to be present on the surface of animal cells also, suggesting that it may mediate entry of effectors of fungal and oomycete animal pathogens, for example, RXLR effectors found in the oomycete fish pathogen, Saprolegnia parasitica. Reagents that can block PI-3-P-mediated entry have been identified, suggesting new therapeutic strategies.     

Lipoglycans contribute to innate immune detection of mycobacteria

Innate immune recognition is based on the detection, by pattern recognition receptors (PRRs), of molecular structures that are unique to microorganisms. Lipoglycans are macromolecules specific to the cell envelope of mycobacteria and related genera. They have been described to be ligands, as purified molecules, of several PRRs, including the C-type lectins Mannose Receptor and DC-SIGN, as well as TLR2. However, whether they are really sensed by these receptors in the context of a bacterium infection remains unclear. To address this question, we used the model organism Mycobacterium smegmatis to generate mutants altered for the production of lipoglycans. Since their biosynthesis cannot be fully abrogated, we manipulated the biosynthesis pathway of GDP-Mannose to obtain some strains with either augmented (～1.7 fold) or reduced (～2 fold) production of lipoglycans. Interestingly, infection experiments demonstrated a direct correlation between the amount of lipoglycans in the bacterial cell envelope on one hand and the magnitude of innate immune signaling in TLR2 reporter cells, monocyte/macrophage THP-1 cell line and human dendritic cells, as revealed by NF-κB activation and IL-8 production, on the other hand. These data establish that lipoglycans are bona fide Microbe-Associated Molecular Patterns contributing to innate immune detection of mycobacteria, via TLR2 among other PRRs.     

Genetic polymorphisms of CYP2E1 and DNA repair genes HOGG1 and XRCC1: Association with hepatitis B related advanced liver disease and cancer

A population based case–control study was designed to explore the genetic risk factors for hepatitis B virus (HBV) related liver disease susceptibility. A total of 424 subjects comprising 210 controls, 50 acute HBV (AVH), 84 chronic HBV (CHBV), 25 HBV related cirrhosis and 55 HBV related hepatocellular carcinoma (HCC) cases were included in the study. PCR-RFLP was used for the genotyping of Cyp2E1*5B, hOGG1 codon 326 and XRCC1 codon 399. Compared to controls, Cyp2E1 rsaI variant c2 genotype increased the risk of HBV related liver disease severity by 2.68 fold, the highest for HCC cases (3.981 folds, p = 0.106); and was associated with higher histology activity index (HAI) (p < 0.001) in CHBV patients. Cyp2E1 and hOGG1 variants were independently associated with a significantly higher fibrosis score in CHBV group. Analysis of gene–gene interaction studies showed an increased risk of HCC, cirrhosis and CHBV in a Cyp2E1 variant + XRCC1 variant combination (p < 0.001); and hOGG1 variants + XRCC1 variants. A mutually independent heterozygous hOGG1 and XRCC1 combination resulted in a decreased risk of HBV related liver disease. On the other hand, a wild-type hOGG1 and XRCC1 combination was associated with a significantly higher risk of AVH (p = 0.010) but a lower risk of CHBV (p = 0.032) and HCC (p = 0.006). The gene–gene interactions were also associated with a significant increase in HAI and fibrosis score in CHBV patients. Cyp2E1, hOGG1 and XRCC1 genotypes significantly alter the risk of HBV related liver disease susceptibility and severity, independently or through gene–gene interaction.