Global Functional Analyses of Cellular Responses to Pore-Forming Toxins

Here we present the first global functional analysis of cellular responses to pore-forming toxins (PFTs). PFTs are uniquely important bacterial virulence factors, comprising the single largest class of bacterial protein toxins and being important for the pathogenesis in humans of many Gram positive and Gram negative bacteria. Their mode of action is deceptively simple, poking holes in the plasma membrane of cells. The scattered studies to date of PFT-host cell interactions indicate a handful of genes are involved in cellular defenses to PFTs. How many genes are involved in cellular defenses against PFTs and how cellular defenses are coordinated are unknown. To address these questions, we performed the first genome-wide RNA interference (RNAi) screen for genes that, when knocked down, result in hypersensitivity to a PFT. This screen identifies 106 genes (∼0.5% of genome) in seven functional groups that protect Caenorhabditis elegans from PFT attack. Interactome analyses of these 106 genes suggest that two previously identified mitogen-activated protein kinase (MAPK) pathways, one (p38) studied in detail and the other (JNK) not, form a core PFT defense network. Additional microarray, real-time PCR, and functional studies reveal that the JNK MAPK pathway, but not the p38 MAPK pathway, is a key central regulator of PFT-induced transcriptional and functional responses. We find C. elegans activator protein 1 (AP-1; c-jun, c-fos) is a downstream target of the JNK-mediated PFT protection pathway, protects C. elegans against both small-pore and large-pore PFTs and protects human cells against a large-pore PFT. This in vivo RNAi genomic study of PFT responses proves that cellular commitment to PFT defenses is enormous, demonstrates the JNK MAPK pathway as a key regulator of transcriptionally-induced PFT defenses, and identifies AP-1 as the first cellular component broadly important for defense against large- and small-pore PFTs

A Systematic Study of Molecular Interactions of Anionic Drugs with a Dimethylaminoethyl Methacrylate Copolymer Regarding Solubility Enhancement

The methacrylate-copolymer Eudragit EPO (EPO) has raised interest in solubility enhancement of anionic drugs. Effects on aqueous drug solubility at rather low polymer concentrations are barely known despite their importance upon dissolution and dilution of oral dosage forms. We provide evidence for substantial enhancement (factor 4–230) of aqueous solubility of poorly water-soluble anionic drugs induced by low (0.1–5% (w/w)) concentration of EPO for a panel of seven acidic crystalline drugs. Diffusion data (determined by ¹H nuclear magnetic resonance spectroscopy) indicate that the solubility increasing effect monitored by quantitative ultraperformance liquid chromatography was caused primarily by molecular API polymer interactions in the bulk liquid phase. Residual solid API remained unaltered as tested by X-ray powder diffraction. The solubility enhancement (SE) revealed a significant rank correlation (<i>r</i>_Spearman = −0.83) with rDiff_API, where SE and rDiff_API are defined ratios of solubility and diffusion coefficient in the presence and absence of EPO. SE decreased in the order of indomethacin, mefenamic acid, warfarin, piroxicam, furosemide, bezafibrate, and tolbutamide. The solubilizing effect was attributed to both ionic and hydrophobic interactions between drugs and EPO. The excellent solubilizing properties of EPO are highly promising for pharmaceutical development, and the data set provides first steps toward an understanding of drug–excipient interaction mechanisms

Early transcriptional changes linked to naturally occurring Huntington's disease mutations in neural derivatives of human embryonic stem cells

Huntington's disease (HD) is characterized by a late clinical onset despite ubiquitous expression of the mutant gene at all developmental stages. How mutant huntingtin impacts on signalling pathways in the pre-symptomatic period has remained essentially unexplored in humans due to a lack of appropriate models. Using multiple human embryonic stem cell lines derived from blastocysts diagnosed as carrying the mutant huntingtin gene by pre-implantation genetic diagnosis, we explored early developmental changes in gene expression using differential transcriptomics, combined with gain and loss of function strategies. We demonstrated a down-regulation of the HTT gene itself in HD neural cells and identified three genes, the expression of which differs significantly in HD cells when compared with wild-type controls, namely CHCHD2, TRIM4 and PKIB. Similar dysregulation had been observed previously for CHCDH2 and TRIM4 in blood cells from patients. CHCHD2 is involved in mitochondrial function and PKIB in protein kinase A-dependent pathway regulation, which suggests that these functions may be precociously impacted in HD