Identification of known drugs targeting the endoplasmic reticulum stress response.

The endoplasmic reticulum (ER), a multifunctional organelle, plays a central role in cellular signaling, development, and stress response. Dysregulation of ER homeostasis has been associated with human diseases, such as cancer, inflammation, and diabetes. A broad spectrum of stressful stimuli including hypoxia as well as a variety of pharmacological agents can lead to the ER stress response. In this study, we have developed a stable ER stress reporter cell line that stably expresses a ß-lactamase reporter gene under the control of the ER stress response element (ESRE) present in the glucose-regulated protein, 78 kDa (GRP78) gene promoter. This assay has been optimized and miniaturized into a 1536-well plate format. In order to identify clinically used drugs that induce ER stress response, we screened approximately 2800 drugs from the NIH Chemical Genomics Center Pharmaceutical Collection (NPC library) using a quantitative high-throughput screening (qHTS) platform. From this study, we have identified several known ER stress inducers, such as 17-AAG (via HSP90 inhibition), as well as several novel ER stress inducers such as AMI-193 and spiperone. The confirmed drugs were further studied for their effects on the phosphorylation of eukaryotic initiation factor 2α (eIF2α), the X-box-binding protein (XBP1) splicing, and GRP78 gene expression. These results suggest that the ER stress inducers identified from the NPC library using the qHTS approach could shed new lights on the potential therapeutic targets of these drugs.

Pharmacological inhibition of LRRK2 cellular phosphorylation sites provides insight into LRRK2 biology.

Mutations in LRRK2 (leucine-rich repeat kinase 2) have been linked to inherited forms of PD (Parkinson's disease). Substantial pre-clinical research and drug discovery efforts have focused on LRRK2 with the hope that small-molecule inhibitors of the enzyme may be valuable for the treatment or prevention of the onset of PD. The pathway to develop therapeutic or neuroprotective agents based on LRRK2 function (i.e. kinase activity) has been facilitated by the development of both biochemical and cell-based assays for LRRK2. LRRK2 is phosphorylated on Ser910, Ser935, Ser955 and Ser973 in the N-terminal domain of the enzyme, and these sites of phosphorylation are likely to be regulated by upstream enzymes in an LRRK2 kinase-activity-dependent manner. Knowledge of these phosphorylation sites and their regulation can be adapted to high-throughput-screening-amenable platforms. The present review describes the utilization of LRRK2 phosphorylation as indicators of enzyme inhibition, as well as how such assays can be used to deconvolute the pathways in which LRRK2 plays a role.

WNT5A mutations in patients with autosomal dominant Robinow syndrome.

Robinow syndrome is a skeletal dysplasia with both autosomal dominant and autosomal recessive inheritance patterns. It is characterized by short stature, limb shortening, genital hypoplasia, and craniofacial abnormalities. The etiology of dominant Robinow syndrome is unknown; however, the phenotypically more severe autosomal recessive form of Robinow syndrome has been associated with mutations in the orphan tyrosine kinase receptor, ROR2, which has recently been identified as a putative WNT5A receptor. Here, we show that two different missense mutations in WNT5A, which result in amino acid substitutions of highly conserved cysteines, are associated with autosomal dominant Robinow syndrome. One mutation has been found in all living affected members of the original family described by Meinhard Robinow and another in a second unrelated patient. These missense mutations result in decreased WNT5A activity in functional assays of zebrafish and Xenopus development. This work suggests that a WNT5A/ROR2 signal transduction pathway is important in human craniofacial and skeletal development and that proper formation and growth of these structures is sensitive to variations in WNT5A function.

Gene-breaking transposon mutagenesis reveals an essential role for histone H2afza in zebrafish larval development.

We report a novel gene tagging, identification and mutagenicity ('gene-breaking') method for the zebrafish, Danio rerio. This modular approach consists of two distinct and separable molecular cassettes. The first is a gene-finding cassette. In this study, we employed a 3' gene-tagging approach that selectively 'traps' transcripts regardless of expression status, and we show that this cassette identifies both known and novel endogenous transcripts in transgenic zebrafish. The second is a transcriptional termination mutagenicity cassette assembled from a combination of a splice acceptor and polyadenylation signal to disrupt tagged transcripts upon integration into intronic sequence. We identified both novel and conserved loci as linked phenotypic mutations using this gene-breaking strategy, generating molecularly null mutations in both larval lethal and adult viable loci. We show that the Histone 2a family member z (H2afza) variant is essential for larval development through the generation of a lethal locus with a truncation of conserved carboxy-terminal residues in the protein. In principle this gene-breaking strategy is scalable for functional genomics screens and can be used in Sleeping Beauty transposon and other gene delivery systems in the zebrafish.

Lateral line, nervous system, and maternal expression of Frizzled 7a during zebrafish embryogenesis.

We have isolated and mapped a new wnt receptor frizzled family member, zebrafish frizzled 7a. Fz7a and a previously reported zebrafish fz7 (El-Messaoudi and Renucci, 2001) make an orthologous gene pair, however, they display distinct expression patterns. Fz7a shows strong maternal as well as zygotic expression. Fz7a transcript is enriched dorsally starting with the shield stage. At the end of gastrulation, Fz7a is abundantly expressed within anterior neuroectoderm and expressed more weakly within lateral mesoderm. Fz7a is detected during somitogenesis within the central nervous system, somatic and posterior lateral mesoderm. At 24hpf, fz7a is expressed in migrating lateral line primordium. At 48hpf, fz7a is detected in the ear, pectoral fin bud, and within neuromasts, which had originated from the lateral line primordium. Radiation hybrid mapping using panel LN54 (Hukriede et al., 1999) places fz7a on linkage group 6, linked to the marker fi11h08 (distance 0.00cR, LOD score 14.1). To prove that fz7 and fz7a are indeed different genes we mapped fz7 as well using the same LN54 panel. Fz7 mapped to linkage group 9 with a LOD of 12.5, 27.31 cR from wnt 10a in between markers IBD2759 and fb50e04.

An evaluation of the PowerSeq™ Auto System: A multiplex short tandem repeat marker kit compatible with massively parallel sequencing.

Capillary electrophoresis (CE) and multiplex amplification with fluorescent tagging have been routinely used for STR typing in forensic genetics. However, CE-based methods restrict the number of markers that can be multiplexed simultaneously and cannot detect any intra-repeat variations within STRs. Several studies already have indicated that massively parallel sequencing (MPS) may be another potential technology for STR typing. In this study, the prototype PowerSeq(™) Auto System (Promega) containing the 23 STR loci and amelogenin was evaluated using Illumina MiSeq. Results showed that single source complete profiles could be obtained using as little as 62 pg of input DNA. The reproducibility study showed that the profiles generated were consistent among multiple typing experiments for a given individual. The mixture study indicated that partial STR profiles of the minor contributor could be detected up to 19:1 mixture. The mock forensic casework study showed that full or partial profiles could be obtained from different types of single source and mixture samples. These studies indicate that the PowerSeq Auto System and the Illumina MiSeq can generate concordant results with current CE-based methods. In addition, MPS-based systems can facilitate mixture deconvolution with the detection of intra-repeat variations within length-based STR alleles.

Enhancer trapping in zebrafish using the Sleeping Beauty transposon.

BACKGROUND: Among functional elements of a metazoan gene, enhancers are particularly difficult to find and annotate. Pioneering experiments in Drosophila have demonstrated the value of enhancer "trapping" using an invertebrate to address this functional genomics problem. RESULTS: We modulated a Sleeping Beauty transposon-based transgenesis cassette to establish an enhancer trapping technique for use in a vertebrate model system, zebrafish Danio rerio. We established 9 lines of zebrafish with distinct tissue- or organ-specific GFP expression patterns from 90 founders that produced GFP-expressing progeny. We have molecularly characterized these lines and show that in each line, a specific GFP expression pattern is due to a single transposition event. Many of the insertions are into introns of zebrafish genes predicted in the current genome assembly. We have identified both previously characterized as well as novel expression patterns from this screen. For example, the ET7 line harbors a transposon insertion near the mkp3 locus and expresses GFP in the midbrain-hindbrain boundary, forebrain and the ventricle, matching a subset of the known FGF8-dependent mkp3 expression domain. The ET2 line, in contrast, expresses GFP specifically in caudal primary motoneurons due to an insertion into the poly(ADP-ribose) glycohydrolase (PARG) locus. This surprising expression pattern was confirmed using in situ hybridization techniques for the endogenous PARG mRNA, indicating the enhancer trap has replicated this unexpected and highly localized PARG expression with good fidelity. Finally, we show that it is possible to excise a Sleeping Beauty transposon from a genomic location in the zebrafish germline. CONCLUSIONS: This genomics tool offers the opportunity for large-scale biological approaches combining both expression and genomic-level sequence analysis using as a template an entire vertebrate genome.

A quantitative TR-FRET plate reader immunoassay for measuring autophagy.

Autophagy involves the isolation and targeting of unwanted cellular components to lysosomes for their digestion and reuse. Autophagic dysregulation has recently been implicated in a wide range of disease processes, yet facile methods for quantifying autophagy have been lacking in the field. Here we describe the generation of a quantitative plate reader assay for measuring the autophagic activity of cells. One of the best characterized autophagy markers is the protein LC3B, which normally resides in the cytosol (LC3B-I) but upon induction of autophagy becomes lipidated and embedded in autophagosomal membranes (LC3B-II). To quantify autophagy, we reasoned that GFP-tagged LC3B could serve as a time-resolved fluorescence resonance energy transfer (TR-FRET) acceptor upon cell lysis in the presence of terbium-labeled LC3B antibodies. Using this TR-FRET immunoassay approach, we screened a panel of LC3B antibodies and identified an antibody that exhibits strong preferential affinity toward autophagosome-associated LC3B-II and thereby facilitates specific detection of autophagic activity. The plate reader format provides both a quantitative and an objective result, thus overcoming some of the key limitations of the traditional immunoblotting and imaging approaches used to monitor autophagy. Moreover, since the assay step requires only a single addition of cell lysis buffer containing the detection antibody its simple workflow is both automation-friendly and scalable, which renders it suitable for high-throughput screening. We demonstrate how this TR-FRET immunoassay for GFP-tagged LC3B-II can be applied to quantitatively detect changes in the autophagy activity of cells, including estimating effects on autophagic flux.

Screening for novel LRRK2 inhibitors using a high-throughput TR-FRET cellular assay for LRRK2 Ser935 phosphorylation.

BACKGROUND: Mutations in the leucine-rich repeat kinase-2 (LRRK2) have been linked to Parkinson's disease. Recent studies show that inhibition of LRRK2 kinase activity decreased the level of phosphorylation at its own Ser910 and Ser935, indicating that these sites are prime targets for cellular readouts of LRRK2 inhibition. METHODOLOGY/PRINCIPAL FINDINGS: Using Time-Resolved Förster Resonance Energy Transfer (TR-FRET) technology, we developed a high-throughput cellular assay for monitoring LRRK2 phosphorylation at Ser935. LRRK2-Green Fluorescence Protein (GFP) fusions were expressed in cells via BacMam. Phosphorylation at Ser935 in these cells is detected using a terbium labeled anti-phospho-Ser935 antibody that generates a TR-FRET signal between terbium and GFP. LRRK2 wild-type and G2019S are constitutively phosphorylated at Ser935 in cells as measured by TR-FRET. The phosphorylation level is reduced for the R1441C mutant and little could be detected for the kinase-dead mutant D1994A. The TR-FRET cellular assay was further validated using reported LRRK2 inhibitors including LRRK2-IN-1 and our results confirmed that inhibition of LRRK2 can reduce the phosphorylation level at Ser935. To demonstrate the utility of this assay for screening, we profiled a small library of 1120 compounds. Three known LRRK2 inhibitors were identified and 16 hits were followed up in the TR-FRET and a cytotoxicity assay. Interestingly, out of the top 16 hits, five are known inhibitors of IκB phosphorylation, two CHK1 and two CDC25 inhibitors. Thirteen hits were further tested in a biochemical LRRK2 kinase activity assay and Western blot analysis for their effects on the phosphorylation of Ser910, Ser935, Ser955 and Ser973. CONCLUSIONS/SIGNIFICANCE: We developed a TR-FRET cellular assay for LRRK2 Ser935 phosphorylation that can be applied to the screening for LRRK2 inhibitors. We report for the first time that several compounds such as IKK16, CHK1 inhibitors and GW441756 can inhibit LRRK2 Ser935 phosphorylation in cells and LRRK2 kinase activity in vitro.

Development and validation of a cell-based assay for the nuclear receptor retinoid-related orphan receptor gamma.

The nuclear receptor retinoid-related orphan receptor gamma (RORγ) has become an attractive target for drug discovery due to its important role in the development and differentiation of Th17 cells, a subset of T cells that produce interleukin-17 and are involved in the pathogenesis of human inflammatory and autoimmune diseases. To facilitate the drug discovery efforts in this area, we have developed a cellular assay for screening for RORγ inverse agonists. We stably engineered a tetracycline-inducible Gal4 DNA-binding domain/RORγ ligand-binding domain fusion protein into an upstream activation sequence driven-beta-lactamase reporter gene cell line. Due to its constitutive activity, the induced Gal4-RORγ expression leads to increased reporter activity, which can be knocked down using RORγ ligand-binding domain-specific RNA interference oligos. Using this assay, we tested several recently reported ligands for RORγ and observed varying levels of partial inverse agonist activity at µM concentrations. Additionally, we screened a small library of biologically active compounds with this assay and demonstrated its robustness and usefulness in high-throughput screening and follow-up studies for this emerging drug target.

TR-FRET cellular assays for interrogating posttranslational modifications of histone H3.

Posttranslational modifications such as phosphorylation, acetylation, and methylation play important roles in regulating the structures and functions of histones, which in turn regulate gene expression and DNA repair and replication. Histone-modifying enzymes, such as deacetylases, methyltransferases and demethylases, have been pursued as therapeutic targets for various diseases. However, detection of the activities of these enzymes in high-throughput cell-based formats has remained challenging. The authors have developed high-throughput LanthaScreen cellular assays for Histone H3 site-specific modifications. These assays use cells expressing green fluorescence protein-tagged Histone H3 transiently delivered via BacMam and terbium-labeled anti-Histone H3 modification-specific antibodies. Robust time-resolved Förster resonance energy transfer signals were detected for H3 lysine-9 acetylation and dimethylation (H3K9me2), serine-10 phosphorylation, K4 di- and trimethylation, and K27 trimethylation. Consistent with previous reports, hypoxic stress increased K4 methylation levels, and methyltransferase G9a inhibitor UNC-0638 decreased K9me2 levels significantly, with little effects on other modifications. To demonstrate the utility of this assay platform in screening, the K9 acetylation assay was used to profile the Enzo Epigenetics Library. Twelve known HDAC inhibitors were identified as hits and followed up in a dose-response format. In conclusion, this assay platform enables high-throughput cell-based analysis of diverse types of posttranslational modifications of Histone H3.

Measurement of the cellular deacetylase activity of SIRT1 on p53 via LanthaScreen® technology.

Upon genomic insult, the tumor suppressor p53 is phosphorylated and acetylated at specific serine and lysine residues, increasing its stability and transactivation function. Deacetylases, including the type III histone deacetylase SIRT1, remove acetyl groups from p53 and counterbalance acetyltransferase activity during a DNA damage response. This report describes a series of high-throughput LanthaScreen® time-resolved Förster resonance energy transfer (TR-FRET) immunoassays for detection of intracellular p53 phosphorylation of Ser15 and acetylation of Lys382 upon treatment with DNA damage agents, such as etoposide. These assays were used to measure the deacetylase activity of SIRT1 and/or Type I/II Histone deacetylases (HDACs). First, BacMam-mediated overexpression of SIRT1 resulted in dose-dependent deacetylation of GFP-p53 following etoposide treatment of U-2 OS cells, confirming that GFP-p53 serves as a SIRT1 substrate in this assay format. Further, overexpression of the acetyltransferase p300 via BacMam increased the acetylation of GFP-p53 at Lys382. Next, siRNA-mediated knockdown of SIRT1 resulted in increased GFP-p53 acetylation, indicating that endogenous SIRT1 activity can also be measured in U-2 OS cells. Consistent with these results, GFP-p53 acetylation was also increased upon treatment of cells with a small-molecule inhibitor of SIRT1, EX-527. The effect of this compound was dramatically increased when used in combination with chemotherapeutic drug and/or the HDAC inhibitor Trichostatin A, confirming a proposed synergistic mechanism of p53 deacetylation by SIRT1 and Type I/II HDACs. Taken together, the cellular assays described here can be used as high-throughput alternatives to traditional immunoassays such as western blotting for identifying pharmacological modulators of specific p53-modifying enzymes.

Mining Dictyoglomus turgidum for enzymatically active carbohydrases.

The genome of Dictyoglomus turgidum was sequenced and analyzed for carbohydrases. The broad range of carbohydrate substrate utilization is reflected in the high number of glycosyl hydrolases, 54, and the high percentage of CAZymes present in the genome, 3.09% of its total genes. Screening a random clone library generated from D. turgidum resulted in the discovery of five novel biomass-degrading enzymes with low homology to known molecules. Whole genome sequencing of the organism followed by bioinformatics-directed amplification of selected genes resulted in the recovery of seven additional novel enzyme molecules. Based on the analysis of the genome, D. turgidum does not appear to degrade cellulose using either conventional soluble enzymes or a cellulosomal degradation system. The types and quantities of glycosyl hydrolases and carbohydrate-binding modules present in the genome suggest that D. turgidum degrades cellulose via a mechanism similar to that used by Cytophaga hutchinsonii and Fibrobacter succinogenes.

Hemicellulases and auxiliary enzymes for improved conversion of lignocellulosic biomass to monosaccharides.

BACKGROUND: High enzyme loading is a major economic bottleneck for the commercial processing of pretreated lignocellulosic biomass to produce fermentable sugars. Optimizing the enzyme cocktail for specific types of pretreated biomass allows for a significant reduction in enzyme loading without sacrificing hydrolysis yield. This is especially important for alkaline pretreatments such as Ammonia fiber expansion (AFEX) pretreated corn stover. Hence, a diverse set of hemicellulases supplemented along with cellulases is necessary for high recovery of monosaccharides. RESULTS: The core fungal cellulases in the optimal cocktail include cellobiohydrolase I [CBH I; glycoside hydrolase (GH) family 7A], cellobiohydrolase II (CBH II; GH family 6A), endoglucanase I (EG I; GH family 7B) and ß-glucosidase (ßG; GH family 3). Hemicellulases tested along with the core cellulases include xylanases (LX1, GH family 10; LX2, GH family 10; LX3, GH family 10; LX4, GH family 11; LX5, GH family 10; LX6, GH family 10), ß-xylosidase (LßX; GH family 52), α-arabinofuranosidase (LArb, GH family 51) and α-glucuronidase (LαGl, GH family 67) that were cloned, expressed and/or purified from different bacterial sources. Different combinations of these enzymes were tested using a high-throughput microplate based 24 h hydrolysis assay. Both family 10 (LX3) and family 11 (LX4) xylanases were found to most efficiently hydrolyze AFEX pretreated corn stover in a synergistic manner. The optimal mass ratio of xylanases (LX3 and LX4) to cellulases (CBH I, CBH II and EG I) is 25:75. LßX (0.6 mg/g glucan) is crucial to obtaining monomeric xylose (54% xylose yield), while LArb (0.6 mg/g glucan) and LαGl (0.8 mg/g glucan) can both further increase xylose yield by an additional 20%. Compared with Accellerase 1000, a purified cocktail of cellulases supplemented with accessory hemicellulases will not only increase both glucose and xylose yields but will also decrease the total enzyme loading needed for equivalent yields. CONCLUSIONS: A diverse set of accessory hemicellulases was found necessary to enhance the synergistic action of cellulases hydrolysing AFEX pretreated corn stover. High glucose (around 80%) and xylose (around 70%) yields were achieved with a moderate enzyme loading (~20 mg protein/g glucan) using an in-house developed cocktail compared to commercial enzymes.

Syndecan-2 is essential for angiogenic sprouting during zebrafish development.

We used a morpholino-based gene-targeting screen to identify a novel protein essential for vascular development using the zebrafish, Danio rerio. We show that syndecan-2, a cell-surface heparan sulfate proteoglycan, is essential for angiogenic sprouting during embryogenesis. The vascular function of syndecan-2 is likely conserved, as zebrafish and mouse syndecan-2 show similar expression patterns around major trunk vessels, and human syndecan-2 can restore angiogenic sprouting in syndecan-2 morphants. In contrast, forced expression of a truncated form of syndecan-2 results in embryos with defects in angiogenesis, indicating that the highly conserved cytoplasmic tail is important for the vascular function of syndecan-2. We further show that vascular endothelial growth factor (VEGF) and syndecan-2 genetically interact in vivo using both gain-of-function and loss-of-function studies in zebrafish. VEGF-mediated ectopic signaling is compromised in syndecan-2 morphants, and ectopic syndecan-2 potentiates ectopic VEGF signaling. Syndecan-2 as a novel angiogenic factor is a potential candidate for use in the development of angiogenesis-based therapies.

Efficient gene delivery and gene expression in zebrafish using the Sleeping Beauty transposon.

We used the Tc1/mariner family transposable element Sleeping Beauty (SB) for transgenesis and long-term expression studies in the zebrafish (Danio rerio), a popular organism for clinical disease, vertebrate patterning, and cell biology applications. SB transposase enhanced the transgenesis and expression rate sixfold (from 5 to 31%) and more than doubled the total number of tagged chromosomes over standard, plasmid injection-based transgenesis methods. Molecular analysis of these loci demonstrated a precise integration of these elements into recipient chromosomes with genetic footprints diagnostic of transposition. GFP expression from transposase-mediated integrants was Mendelian through the eighth generation. A blue-shifted GFP variant (BFP) and a red fluorescent protein (DsRed) were also useful transgenesis markers, indicating that multiple reporters are practical for use with SB in zebrafish. We showed that SB is suitable for tissue-specific transgene applications using an abbreviated gamma-crystallin GFP cassette. Finally, we describe a general utility transposon vector for chromosomal engineering and molecular genetics experiments in zebrafish. Together, these data indicate that SB is an efficient tool for transgenesis and expression in zebrafish, and that the transposon will be useful for gene expression in cell biology applications as well as an insertional mutagen for gene discovery during development.