Development of a high-throughput scintillation proximity assay for the identification of C-domain translational initiation factor 2 inhibitors

Translational initiation factor 2 (IF2) is the largest of the 3 factors required for translation initiation in prokaryotes and has been shown to be essential in Escherichia coli. It stimulates the binding of fMet-tRNA(f)(Met) to the 30S ribosomal subunit in the presence of GTP. The selectivity is achieved through specific recognition of the tRNA(f)(Met) blocked alpha-amino group. IF2 is composed of 3 structural domains: N-domain, whose function is not known; G-domain, which contains the GTP/GDP binding site and the GTPase catalytic center; and C-domain, which recognizes and binds fMet-tRNA(f)(Met). Its activity is strictly bacteria specific and highly conserved among prokaryotes. So far, antibiotics targeting IF2 function are not known, and this makes it an ideal target for new drugs with mechanisms of resistance not yet developed. A few assays have been developed in the past, which allow the detection of IF2 activity either directly or indirectly. In both instances, the assays are based on radioactive detection and do not allow for high throughput because of the need for separation or solvent extraction steps. The authors describe a novel biochemical assay for IF2 that exploits the molecular recognition of fMet-tRNA(f)(Met) by the C-domain. The assay is based on the incubation of biotinyl-IF2 with fMet-tRNA(f)(Met) and the subsequent capture of the radiolabeled complex by streptavidin-coated beads, exploiting the scintillation proximity assay (SPA) technology. The assay has been designed in an automatable, homogeneous, miniaturized fashion suitable for high-throughput screening and is rapid, sensitive, and robust to dimethyl sulfoxide (DMSO) up to 10% v/v. The assay, used to screen a limited chemical collection of about 5000 compounds and a subset of compounds originated by a 2-D substructural search, has shown to be able to detect potential IF2 inhibitors.     

Three anthrones from Rubus ulmifolius

From the aerial parts of Rubus ulmifolius Schott three new anthrones, rubanthrone A, B and C, have been isolated. Their structures were established by spectral procedures including 1D and 2D NMR techniques and chemical derivatization. Rubanthrone A showed antimicrobial activity against Staphylococcus aureus at 4.5 mg/ml.     

A role for calcium in sphingosine 1-phosphate-induced phospholipase D activity in C2C12 myoblasts

Receptor-regulated phospholipase D (PLD) is a key signaling pathway implicated in the control of fundamental biological processes. Here evidence is presented that in addition to protein kinase C (PKC) and Rho GTPases, Ca(2+) response evoked by sphingosine 1-phosphate (S1P) also participates to the enzyme regulation. Ca(2+) was found critical for PKC(alpha)-mediated PLD activation. Moreover, S1P-induced PLD activity resulted diminished by calmodulin inhibitors such as W-7 and CGS9343B implicating its involvement in the process. A plausible candidate for Ca(2+)-dependent PLD regulation by S1P was represented by calcineurin, in view of the observed reduction of the stimulatory effect by cyclosporin A. In contrast, monomeric GTP-binding protein Ral was translocated to membranes by S1P in a Ca(2+)-independent manner, ruling out its possible role in agonist-mediated regulation of PLD.     

Keratinocytes enriched for stem cells are protected from anoikis via an integrin signaling pathway in a Bcl-2 dependent manner

In zebrafish, the basic helix-loop-helix (bHLH) gene neuroD specifies distinct neurons in the spinal cord. A preliminary experiment indicated that a related bHLH gene, ndr1a, normally expressed only in the olfactory organ in late embryos, also functions as neuroD to induce ectopic formation of spinal cord neurons in early embryos after introduction of its mRNA into early embryos. To define the functional specificity of these bHLH proteins, several mutant forms with selected point mutations in the basic domain were constructed and tested for inducing sensory neurons in the spinal cord. Our data indicate that the functional specificity of NeuroD to define sensory neurons is mainly due to a single residue (asparagine 11) in its basic domain.     

Homozygosity and linkage disequilibrium

We illustrate how homozygosity of haplotypes can be used to measure the level of disequilibrium between two or more markers. An excess of either homozygosity or heterozygosity signals a departure from the gametic phase equilibrium: We describe the specific form of dependence that is associated with high (low) homozygosity and derive various linkage disequilibrium measures. They feature a clear biological interpretation, can be used to construct tests, and are standardized to allow comparison across loci and populations. They are particularly advantageous to measure linkage disequilibrium between highly polymorphic markers.     

Inhibition of cGMP-dependent protein kinases potently decreases neutrophil spontaneous apoptosis

The signalling pathways mediating neutrophil spontaneous apoptosis are still largely unknown. We report that the indolocarbazole compound KT5823, a specific inhibitor of cGMP-dependent protein kinases (cGK), dose-dependently inhibited spontaneous apoptosis of neutrophils. At the concentration eliciting the maximum effect (8 microM), it decreased apoptosis from 72.42+/-12.79% to 45.86+/-7.22% (p=0.0002, n=6). Similarly, the isoquinoline sulfonamide compound H89, another cGK inhibitor, prevented neutrophil apoptosis. At the concentration eliciting the maximum effect (20 microM), it decreased apoptosis from 72.42+/-12.79% to 31.84+/-10.70% (p=0.0004, n=6). The maximum effect of KT5823 and H89 was comparable to that of GM-CSF and LPS, respectively. Moreover, YC-1, a soluble guanylate cyclase activator, and 4-([3',4',-(methylenedioxy)benzyl]amino)-6-methoxyquinazoline, a specific phosphodiesterase 5 inhibitor, enhanced neutrophil apoptosis, and their effect was antagonised by KT5823. Taken together, these observations highlight a new role of cGK as important mediators of neutrophil spontaneous apoptosis.     

Fine-tuning of the binding and dissociation of CO by the amino acids of the heme pocket of Coprinus cinereus peroxidase

Resonance Raman and infrared spectra and the CO dissociation rates (k(off)) were measured in Coprinus cinereus peroxidase (CIP) and several mutants in the heme binding pocket. These mutants included the Asp245Asn, Arg51Leu, Arg51Gln, Arg51Asn, Arg51Lys, Phe54Trp, and Phe54Val mutants. Binding of CO to CIP produced different CO adducts at pH 6 and 10. At pH 6, the bound CO is H-bonded to the protonated distal His55 residue, whereas at alkaline pH, the vibrational signatures and the rate of CO dissociation indicate a distal side which is more open or flexible than in other plant peroxidases. The distal Arg51 residue is important in determining the rate of dissociation in the acid form, increasing by 8-17-fold in the Arg51 mutants compared to that for the wild-type protein. Replacement of the distal Phe with Trp created a new acid form characterized by vibrational frequencies and k(off) values very similar to those of cytochrome c peroxidase.     

Flurbiprofen release from eudragit RS and RL aqueous nanosuspensions: a kinetic study by DSC and dialysis experiments

The present work investigated the release of Flurbiprofen (FLU) from Eudragit RS100 (RS) and Eudragit RL100 (RL) nanosuspensions to a biological model membrane consisting of Dimyristoylphosphatidylcholine (DMPC) multilamellar vesicles (MLV). This release was compared with those observed from solid drug particles as well as with dialysis experiments. Nanosuspensions were prepared by a modification of Quasi-Emulsion Solvent Diffusion technique. Drug release was monitored by the Differential Scanning Calorimetry (DSC). FLU dispersed in MLV affects the transition temperature (T(m)) of DMPC liposomes, causing a shift towards lower values. The temperature shift is modulated by the drug fraction present in the aqueous lipid bilayer suspension. DSC was also performed, after increasing incubation periods at 37 degrees C, on suspensions of blank liposomes added to fixed amounts of unloaded and FLU-loaded nanosuspensions, as well as to powdered free drug. T(m) shifts, caused by the drug released from the polymeric system or by free-drug dissolution during incubation cycles, were compared with those caused by free drug increasing molar fractions dispersed directly in the membrane during their preparation. These results were compared with the drug release and were followed by a classical dialysis technique. Comparing the suitability of the 2 different techniques in order to follow the drug release as well as the differences between the 2 RL and RS polymer systems, it is possible to confirm the efficacy of DSC in studying the release from polymeric nanoparticulate systems compared with the "classical" release test by dialysis. The different rate of kinetic release could be due to void liposomes, which represent a better uptaking system than aqueous solution in dialysis experiments.     

Antibody detection in human serum using a versatile protein chip platform constructed by applying nanoscale self-assembled architectures on gold

We report a novel high-throughput (HTP) protein chip platform, constructed on gold using self-assembly techniques, for conducting high quality antigen-antibody interactions. Biotinylated monolayers were used to immobilize a streptavidin surface with high packing density. This biocompatible platform was then used for detection of serum IgM antibodies. Serum samples of patients suspected to suffer from Lyme borreliosis were used to validate the protein chip platform using biotinylated peptide AAOspC8 molecules as the test probes. Various experimental parameters such as the effect of concentration of probes, targets, temperature of incubation, and their effect on the resulting signal-to-noise ratio are described in detail. Highly specific protein interaction data with a high signal-to-noise ratio were obtained with serum sample solutions as low as 1 microL/spot (1/10 diluted).     

Nicotine Prevents Experimental Parkinsonism in Rodents and Induces Striatal Increase of Neurotrophic Factors

Abstract: The repeated finding of an apparent protective effect of cigarette smoking on the risk of Parkinson's disease is one of the few consistent results in the epidemiology of this disorder. Among the numerous substances that originate from tobacco smoke, nicotine is by far the most widely studied. Nicotine is a natural alkaloid that has considerable stimulatory effects on the CNS. Its effects on the CNS are mediated by the activation of neuronal heteromeric acetylcholine-gated ion channel receptors (nAChRs, also termed nicotinic acetylcholine receptors). In the present study, we describe the neuroprotective effects of (−)-nicotine in two animal models of parkinsonism: diethyldithiocarbamate-induced enhancement of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine toxicity in mice and methamphetamine-induced neurotoxicity in rats and mice. The neuroprotective effect of (−)-nicotine was very similar to that of the noncompetitive NMDA receptor antagonist (+)-MK-801. In parallel experiments, we found that (−)-nicotine induces the basic fibroblast growth factor-2 (FGF-2) and the brain-derived neurotrophic factor in rat striatum. The effect of (−)-nicotine on the induction of FGF-2 was prevented by the nAChR antagonist mecamylamine. We also found that (+)-MK-801 was able to induce FGF-2 in the striatum. As trophic factors have been reported to be neuroprotective for dopaminergic cells, our data suggest that the increase in neurotrophic factors is a possible mechanism by which (−)-nicotine protects from experimental parkinsonisms.