Name: high-throughput screening for small-molecule modulators of inward rectifier potassium channels
Uploaded: 2013-01-27T14:00:00
Description: Watch this Scientific Journal Video about High-throughput Screening for Small-molecule Modulators of Inward Rectifier Potassium Channels at JoVE.com

This work was supported by funding from National Institutes of Health grants 1R21NS073097-01 and 1R01DK082884 (J.S.D.) and Foundation for the National Institutes grant PIER11VCTR.

1. Generation of Stable Polyclonal Cell Lines
<ol>
	<li>The establishment of a high quality stable cell line expressing the Kir channel of interest is an important first step toward developing a robust high-throughput screening assay. Constitutive K+ channel overexpression can lead to activation of cell death pathways, stable cell line degeneration and loss of assay performance. To avoid these potential problems and provide a convenient internal control for assay development (see below), a tetracycline-ind...

<ol>
	<li>Ehrlich, J. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Inward+rectifier+potassium+currents+as+a+target+for+atrial+fibrillation+therapy.">Inward rectifier potassium currents as a target for atrial fibrillation therapy.</a> J. Cardiovasc. Pharmacol. 52 (2), 129 (2008).</li><li>Bhave, G., Lonergan, D., Chauder, B. A., Denton, J. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Small-molecule+modulators+of+inward+rectifier+K++channels:+recent+advances+and+future+possibilities.">Small-molecule modulators of inward rectifier K+ channels: recent advances and future possibilities.</a> Future Med. Chem. 2 (5), 757 (2010).</li><li>Swartz, K. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tarantula+toxins+interacting+with+voltage+sensors+in+potassium+channels.">Tarantula toxins interacting with voltage sensors in potassium channels.</a> Toxicon. 49 (2), 213 (2007).</li><li>Jin, W., Lu, Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+novel+high-affinity+inhibitor+for+inward-rectifier+K++channels.">A novel high-affinity inhibitor for inward-rectifier K+ channels.</a> Biochemistry. 37 (38), 13291 (1998).</li><li>Jin, W., Lu, Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synthesis+of+a+stable+form+of+tertiapin:+a+high-affinity+inhibitor+for+inward-rectifier+K++channels.">Synthesis of a stable form of tertiapin: a high-affinity inhibitor for inward-rectifier K+ channels.</a> Biochemistry. 38 (43), 14286 (1999).</li><li>Roy, A., McDonald, P. R., Sittampalam, S., Chaguturu, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Open+access+high+throughput+drug+discovery+in+the+public+domain:+a+Mount+Everest+in+the+making.">Open access high throughput drug discovery in the public domain: a Mount Everest in the making.</a> Curr. Pharm. Biotechnol. 11 (7), 764 (2010).</li><li>Weaver, C. D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+thallium-sensitive,+fluorescence-based+assay+for+detecting+and+characterizing+potassium+channel+modulators+in+mammalian+cells.">A thallium-sensitive, fluorescence-based assay for detecting and characterizing potassium channel modulators in mammalian cells.</a> J. Biomol. Screen. 9 (8), 671 (2004).</li><li>Lewis, L. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High-throughput+screening+reveals+a+small-molecule+inhibitor+of+the+renal+outer+medullary+potassium+channel+and.">High-throughput screening reveals a small-molecule inhibitor of the renal outer medullary potassium channel and.</a> 76 (5), 1094 (2009).</li><li>Bhave, G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+of+a+selective+small-molecule+inhibitor+of+Kir1.1,+the+renal+outer+medullary+potassium+channel.">Development of a selective small-molecule inhibitor of Kir1.1, the renal outer medullary potassium channel.</a> Mol. Pharmacol. 79 (1), 42 (2011).</li><li>Raphemot, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Discovery,+characterization,+and+structure-activity+relationships+of+an+inhibitor+of+inward+rectifier+potassium+(Kir)+channels+with+preference+for+Kir2.3,+Kir3.x,+and+Kir7.1.">Discovery, characterization, and structure-activity relationships of an inhibitor of inward rectifier potassium (Kir) channels with preference for Kir2.3, Kir3.x, and Kir7.1.</a> Front Pharmacol. 2, 75 (2012).</li><li>Niswender, C. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+novel+assay+of+Gi/o-linked+G+protein-coupled+receptor+coupling+to+potassium+channels+provides+new+insights+into+the+pharmacology+of+the+group+III+metabotropic+glutamate+receptors.">A novel assay of Gi/o-linked G protein-coupled receptor coupling to potassium channels provides new insights into the pharmacology of the group III metabotropic glutamate receptors.</a> Mol. Pharmacol. 73 (4), 1213 (2008).</li></ol>

Data treatment: Once the data are collected, a common step in the analysis involves normalizing each well's fluorescence response, F, to its initial value at the beginning of the experiment, F0. This is commonly referred to as the "static ratio" and symbolized "F/F0". In cases where F0 is dominated by the indicator dye the static ratio operation will substantially correct for many factors such as disuniformities in illumination, signal collection, an...

An erratum was issued for: <a href="https://www.jove.com/video/4209/high-throughput-screening-for-small-molecule-modulators-inward">High-throughput Screening for Small-molecule Modulators of Inward Rectifier Potassium Channels</a>. The Protocol section has been updated.
The formula in step 7.1 of the Protocol has been updated from:
Z prime = 1- (3SDp + 3SDn)/|meanp + meann |
to:
Z prime = 1- (3SDp + 3SDn)/|meanp - meann |

An erratum was issued for: <a href="https://www.jove.com/video/4209/high-throughput-screening-for-small-molecule-modulators-inward">High-throughput Screening for Small-molecule Modulators of Inward Rectifier Potassium Channels</a>. The Protocol section has been updated.

Erratum: High-throughput Screening for Small-molecule Modulators of Inward Rectifier Potassium Channels

<table border="1">
 <tbody>
 <tr>
 <td>Name of the reagent</td>
 <td>Company</td>
 <td>Catalog number</td>
 <td>Comments</td>
 </tr>
 <tr>
 <td>pcDNA5/TO</td>
 <td>Invitrogen</td>
 <td>V1033-20</td>
 <td>Tetracycline-inducible expression vector</td>
 </tr>
 <tr>
 <td>T-REx-HEK293 cells</td>
 <td>Invitrogen</td>
 <td>R71007</td>
 <td>Tetracycline-inducible cell line</td>
 </tr>
 <tr>
 <td>Lipofectamine LTX/Plus Reagent</td>
 <td>Invitrogen</td>
 <td>15338100</td>
 <td>Transfection reagent</td>
 </tr>
 <tr>
 <td>FBS</td>
 <td>ATLANTA Biologicals</td>
 <td>S11550</td>
 <td>Cell culture media</td>
 </tr>
 <tr>
 <td>DMEM</td>
 <td>Invitrogen</td>
 <td>11965</td>
 <td>Cell culture media</td>
 </tr>
 <tr>
 <td>Hygromycin B</td>
 <td>Invitrogen</td>
 <td>10687-010</td>
 <td>Cell culture media</td>
 </tr>
 <tr>
 <td>Blasticidin S</td>
 <td>Invitrogen</td>
 <td>R210-01</td>
 <td>Cell culture media</td>
 </tr>
 <tr>
 <td>Penicillin/Streptomycin</td>
 <td>Invitrogen</td>
 <td>15140</td>
 <td>Cell culture media</td>
 </tr>
 <tr>
 <td>HBSS-divalent free</td>
 <td>Mediatech</td>
 <td>21022CV</td>
 <td>Cell washing</td>
 </tr>
 <tr>
 <td>Trypsin-0.25%</td>
 <td>Mediatech</td>
 <td>25053CI</td>
 <td>Cell dissociation</td>
 </tr>
 <tr>
 <td>Tetracycline-HCl</td>
 <td>Sigma</td>
 <td>T9823</td>
 <td>Induction reagent</td>
 </tr>
 <tr>
 <td>Dialyzed FBS</td>
 <td>ATLANTA Biologicals</td>
 <td>S12650</td>
 <td>Plating media</td>
 </tr>
 <tr>
 <td>FluoZin-2</td>
 <td>Invitrogen</td>
 <td>F24189</td>
 <td>Fluorescent dye</td>
 </tr>
 <tr>
 <td>Pluronic F-127</td>
 <td>Invitrogen</td>
 <td>P-3000MP</td>
 <td>Dye loading</td>
 </tr>
 <tr>
 <td>HBSS</td>
 <td>Invitrogen</td>
 <td>14175</td>
 <td>Assay buffer</td>
 </tr>
 <tr>
 <td>HEPES</td>
 <td>Invitrogen</td>
 <td>15630</td>
 <td>Assay buffer</td>
 </tr>
 <tr>
 <td>NaHCO3</td>
 <td>Sigma</td>
 <td>S6297</td>
 <td>Tl+ stimulus buffer</td>
 </tr>
 <tr>
 <td>MgSO4</td>
 <td>Sigma</td>
 <td>M2643</td>
 <td>Tl+ stimulus buffer</td>
 </tr>
 <tr>
 <td>CaSO4&bull;2H2O</td>
 <td>Sigma</td>
 <td>C3771</td>
 <td>Tl+ stimulus buffer</td>
 </tr>
 <tr>
 <td>D-Glucose</td>
 <td>Sigma</td>
 <td>G7528</td>
 <td>Tl+ stimulus buffer</td>
 </tr>
 <tr>
 <td>Thallium sulfate</td>
 <td>Aldrich</td>
 <td>204625</td>
 <td>Tl+ stimulus buffer</td>
 </tr>
 <tr>
 <td>HEPES</td>
 <td>Sigma</td>
 <td>H4034</td>
 <td>Tl+ stimulus buffer</td>
 </tr>
 <tr>
 <td>DMSO</td>
 <td>Sigma</td>
 <td>D4540</td>
 <td>Solvent</td>
 </tr>
 <tr>
 <td>Eight-channel electronic pipettor</td>
 <td>Biohit</td>
 <td>E300</td>
 <td>Cell plating in 384-well plates</td>
 </tr>
 <tr>
 <td>BD PureCoat amine-coated 384-well plates</td>
 <td>BD Biosciences</td>
 <td>356719</td>
 <td>Assay microplates</td>
 </tr>
 <tr>
 <td>Echo qualified 384-Well polypropylene microplate (384PP)</td>
 <td>Labcyte</td>
 <td>P-05525</td>
 <td>Compound source microplates</td>
 </tr>
 <tr>
 <td>384-well polypropylene microplates</td>
 <td>Greiner Bio-One</td>
 <td>781280</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Multidrop Combi reagent dispenser</td>
 <td>Thermo Scientific</td>
 <td>5840300</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>ELx405 microplate washer</td>
 <td>BioTek</td>
 <td>ELx405HT</td>
 <td>Automated cell washing</td>
 </tr>
 <tr>
 <td>Echo liquid handler</td>
 <td>Labcyte</td>
 <td>Labcyte Echo 550</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Bravo automated liquid handling platform</td>
 <td>Agilent Technologies</td>
 <td>Standard model</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Hamamatsu FDSS 6000</td>
 <td>Hamamatsu</td>
 <td>&nbsp;</td>
 <td>Kinetic imaging plate reader</td>
 </tr>
 </tbody>
</table>
Table 1. List of Materials and Reagents.

high-throughput screening for small-molecule modulators of inward rectifier potassium channels

Specific members of the inward rectifier potassium (Kir) channel family are postulated drug targets for a variety of disorders, including hypertension, atrial fibrillation, and pain1,2. For the most part, however, progress toward understanding their therapeutic potential or even basic physiological functions has been slowed by the lack of good pharmacological tools. Indeed, the molecular pharmacology of the inward rectifier family has lagged far behind that of the S4 superfamily of voltage-gated potassium (Kv) channels, for which a number of nanomolar-affinity and highly selective peptide toxin modulators have been discovered3. The bee venom toxin tertiapin and its derivatives are potent inhibitors of Kir1.1 and Kir3 channels4,5, but peptides are of limited use therapeutically as well as experimentally due to their antigenic properties and poor bioavailability, metabolic stability and tissue penetrance. The development of potent and selective small-molecule probes with improved pharmacological properties will be a key to fully understanding the physiology and therapeutic potential of Kir channels.
The Molecular Libraries Probes Production Center Network (MLPCN) supported by the National Institutes of Health (NIH) Common Fund has created opportunities for academic scientists to initiate probe discovery campaigns for molecular targets and signaling pathways in need of better pharmacology6. The MLPCN provides researchers access to industry-scale screening centers and medicinal chemistry and informatics support to develop small-molecule probes to elucidate the function of genes and gene networks. The critical step in gaining entry to the MLPCN is the development of a robust target- or pathway-specific assay that is amenable for high-throughput screening (HTS).
Here, we describe how to develop a fluorescence-based thallium (Tl+) flux assay of Kir channel function for high-throughput compound screening7,8,9,10.The assay is based on the permeability of the K+ channel pore to the K+ congener Tl+. A commercially available fluorescent Tl+ reporter dye is used to detect transmembrane flux of Tl+ through the pore. There are at least three commercially available dyes that are suitable for Tl+ flux assays: BTC, FluoZin-2, and FluxOR7,8. This protocol describes assay development using FluoZin-2. Although originally developed and marketed as a zinc indicator, FluoZin-2 exhibits a robust and dose-dependent increase in fluorescence emission upon Tl+ binding. We began working with FluoZin-2 before FluxOR was available7,8 and have continued to do so9,10. However, the steps in assay development are essentially identical for all three dyes, and users should determine which dye is most appropriate for their specific needs. We also discuss the assay's performance benchmarks that must be reached to be considered for entry to the MLPCN. Since Tl+ readily permeates most K+ channels, the assay should be adaptable to most K+ channel targets.

The use of a tetracycline-inducible expression system provides a convenient internal control for distinguishing Tl+ flux through endogenous pathways and the Kir channel of interest. Figure 1 shows some examples of cell plating maps used in different types of experiments. The positions of wells containing uninduced or tetracycline-induced cells are indicated with different colors. Figure 2A shows the source plate map used to determine the optimal Tl+ concentration fo...

Watch this Scientific Journal Video about High-throughput Screening for Small-molecule Modulators of Inward Rectifier Potassium Channels at JoVE.com

High-throughput Screening for Small-molecule Modulators of Inward Rectifier Potassium Channels

Methods for developing and validating a quantitative fluorescence assay for measuring the activity of inward rectifier potassium (Kir) channels for high-throughput compound screening is presented.

Specific members of the inward rectifier potassium (Kir) channel family are postulated drug targets for a variety of disorders, including hypertension, ...

high-throughput-screening-for-small-molecule-modulators-inward

Research

JoVE Journal

Biology

High-throughput Screening and Biosensing with Fluorescent C. elegans Strains

High-throughput screening (HTS) is a powerful approach for identifying chemical modulators of biological processes. However, many compounds identified in screens using cell culture models are often found to be toxic or pharmacologically inactive in vivo1-2. Screening in whole animal models can help avoid these pitfalls and streamline the path to drug development.
C. elegans is a multicellular model organism well suited for HTS. It is small (&lt;1 mm) and can be economically cultured and dispensed in liquids. C. elegans is also one of the most experimentally tractable animal models permitting rapid and detailed identification of drug mode-of-action3.
We describe a protocol for culturing and dispensing fluorescent strains of C. elegans for high-throughput screening of chemical libraries or detection of environmental contaminants that alter the expression of a specific gene. Large numbers of developmentally synchronized worms are grown in liquid culture, harvested, washed, and suspended at a defined density. Worms are then added to black, flat-bottomed 384-well plates using a peristaltic liquid dispenser. Small molecules from a chemical library or test samples (e.g., water, food, or soil) can be added to wells with worms. In vivo, real-time fluorescence intensity is measured with a fluorescence microplate reader. This method can be adapted to any inducible gene in C. elegans for which a suitable reporter is available. Many inducible stress and developmental transcriptional pathways are well defined in C. elegans and GFP transgenic reporter strains already exist for many of them4. When combined with the appropriate transgenic reporters, our method can be used to screen for pathway modulators or to develop robust biosensor assays for environmental contaminants. 
We demonstrate our C. elegans culture and dispensing protocol with an HTS assay we developed to monitor the C. elegans cap &#x2018;n&#x2019; collar transcription factor SKN-1. SKN-1 and its mammalian homologue Nrf2 activate cytoprotective genes during oxidative and xenobiotic stress5-10. Nrf2 protects mammals from numerous age-related disorders such as cancer, neurodegeneration, and chronic inflammation and has become a major chemotherapeutic target11-13.Our assay is based on a GFP transgenic reporter for the SKN-1 target gene gst-414, which encodes a glutathione-s transferase6. The gst-4 reporter is also a biosensor for xenobiotic and oxidative chemicals that activate SKN-1 and can be used to detect low levels of contaminants such as acrylamide and methyl-mercury15-16.

High-throughput Screening and Biosensing with Fluorescent C. elegans Strains

A procedure for liquid-based culturing and dispensing of C. elegans strains expressing fluorescent reporter proteins is described that does not require expensive sorting equipment. This approach can be applied to numerous inducible C. elegans genes for drug discovery or biosensing of contaminants.

High-throughput screening (HTS) is a powerful approach for identifying chemical modulators of biological processes.  However, many compounds identified in ...

High Throughput Screening of Fungal Endoglucanase Activity in Escherichia coli

Cellulase enzymes (endoglucanases, cellobiohydrolases, and &beta;-glucosidases) hydrolyze cellulose into component sugars, which in turn can be converted into fuel alcohols1. The potential for enzymatic hydrolysis of cellulosic biomass to provide renewable energy has intensified efforts to engineer cellulases for economical fuel production2. Of particular interest are fungal cellulases3-8, which are already being used industrially for foods and textiles processing.
Identifying active variants among a library of mutant cellulases is critical to the engineering process; active mutants can be further tested for improved properties and/or subjected to additional mutagenesis. Efficient engineering of fungal cellulases has been hampered by a lack of genetic tools for native organisms and by difficulties in expressing the enzymes in heterologous hosts. Recently, Morikawa and coworkers developed a method for expressing in E. coli the catalytic domains of endoglucanases from H. jecorina3,9, an important industrial fungus with the capacity to secrete cellulases in large quantities. Functional E. coli expression has also been reported for cellulases from other fungi, including Macrophomina phaseolina10 and Phanerochaete chrysosporium11-12. 
We present a method for high throughput screening of fungal endoglucanase activity in E. coli. (Fig 1) This method uses the common microbial dye Congo Red (CR) to visualize enzymatic degradation of carboxymethyl cellulose (CMC) by cells growing on solid medium. The activity assay requires inexpensive reagents, minimal manipulation, and gives unambiguous results as zones of degradation (&#x201C;halos&#x201D;) at the colony site. Although a quantitative measure of enzymatic activity cannot be determined by this method, we have found that halo size correlates with total enzymatic activity in the cell. Further characterization of individual positive clones will determine , relative protein fitness. 
Traditional bacterial whole cell CMC/CR activity assays13 involve pouring agar containing CMC onto colonies, which is subject to cross-contamination, or incubating cultures in CMC agar wells, which is less amenable to large-scale experimentation. Here we report an improved protocol that modifies existing wash methods14 for cellulase activity: cells grown on CMC agar plates are removed prior to CR staining. Our protocol significantly reduces cross-contamination and is highly scalable, allowing the rapid screening of thousands of clones. In addition to H. jecorina enzymes, we have expressed and screened endoglucanase variants from the Thermoascus aurantiacus and Penicillium decumbens (shown in Figure 2), suggesting that this protocol is applicable to enzymes from a range of organisms.

High Throughput Screening of Fungal Endoglucanase Activity in Escherichia coli

We describe a low cost, high throughput method to screen for fungal endoglucanase activity in E. coli. The method relies on a simple visual readout of substrate degradation, does not require enzyme purification, and is highly scalable. This allows for the rapid screening of large libraries of enzyme variants.

Cellulase enzymes (endoglucanases, cellobiohydrolases, and &beta;-glucosidases) hydrolyze cellulose into component sugars, which in turn can be converted ...

A Fluorescent Screening Assay for Identifying Modulators of GIRK Channels

G protein-gated inward rectifier K+ (GIRK) channels function as cellular mediators of a wide range of hormones and neurotransmitters and are expressed in the brain, heart, skeletal muscle and endocrine tissue1,2. GIRK channels become activated following the binding of ligands (neurotransmitters, hormones, drugs, etc.) to their plasma membrane-bound, G protein-coupled receptors (GPCRs). This binding causes the stimulation of G proteins (Gi and Go) which subsequently bind to and activate the GIRK channel. Once opened the GIRK channel allows the movement of K+ out of the cell causing the resting membrane potential to become more negative. As a consequence, GIRK channel activation in neurons decreases spontaneous action potential formation and inhibits the release of excitatory neurotransmitters. In the heart, activation of the GIRK channel inhibits pacemaker activity thereby slowing the heart rate.
GIRK channels represent novel targets for the development of new therapeutic agents for the treatment neuropathic pain, drug addiction, cardiac arrhythmias and other disorders3. However, the pharmacology of these channels remains largely unexplored. Although a number of drugs including anti-arrhythmic agents, antipsychotic drugs and antidepressants block the GIRK channel, this inhibition is not selective and occurs at relatively high drug concentrations3.
Here, we describe a real-time screening assay for identifying new modulators of GIRK channels. In this assay, neuronal AtT20 cells, expressing GIRK channels, are loaded with membrane potential-sensitive fluorescent dyes such as bis-(1,3-dibutylbarbituric acid) trimethine oxonol [DiBAC4(3)] or HLB 021-152 (Figure 1). The dye molecules become strongly fluorescent following uptake into the cells (Figure 1). Treatment of the cells with GPCR ligands stimulates the GIRK channels to open. The resulting K+ efflux out of the cell causes the membrane potential to become more negative and the fluorescent signal to decrease (Figure 1). Thus, drugs that modulate K+ efflux through the GIRK channel can be assayed using a fluorescent plate reader. Unlike other ion channel screening assays, such atomic absorption spectrometry4 or radiotracer analysis5, the GIRK channel fluorescent assay provides a fast, real-time and inexpensive screening procedure.

A real-time screening procedure for identifying drugs that interact with G protein-gated inward rectifier K+ (GIRK) channels is described. The assay utilizes membrane potential-sensitive fluorescent dyes to measure GIRK channel activity. This technique is adaptable for use on a number of cell lines.

G protein-gated inward rectifier K+ (GIRK) channels function as cellular mediators of a wide range of hormones and neurotransmitters and are expressed in ...

High-throughput Functional Screening using a Homemade Dual-glow Luciferase Assay

We present a rapid and inexpensive high-throughput screening protocol to identify transcriptional regulators of alpha-synuclein, a gene associated with Parkinson&#39;s disease. 293T cells are transiently transfected with plasmids from an arrayed ORF expression library, together with luciferase reporter plasmids, in a one-gene-per-well microplate format. Firefly luciferase activity is assayed after 48 hr to determine the effects of each library gene upon alpha-synuclein transcription, normalized to expression from an internal control construct (a hCMV promoter directing Renilla luciferase). This protocol is facilitated by a bench-top robot enclosed in a biosafety cabinet, which performs aseptic liquid handling in 96-well format. Our automated transfection protocol is readily adaptable to high-throughput lentiviral library production or other functional screening protocols requiring triple-transfections of large numbers of unique library plasmids in conjunction with a common set of helper plasmids. We also present an inexpensive and validated alternative to commercially-available, dual luciferase reagents which employs PTC124, EDTA, and pyrophosphate to suppress firefly luciferase activity prior to measurement of Renilla luciferase. Using these methods, we screened 7,670 human genes and identified 68 regulators of alpha-synuclein. This protocol is easily modifiable to target other genes of interest.

We present a rapid and inexpensive screening method for identifying transcriptional regulators using high-throughput robotic transfections and a homemade dual-glow luciferase assay. This protocol rapidly generates direct side-by-side functional data for thousands of genes and is easily modifiable to target any gene of interest.

We present a rapid and inexpensive high-throughput screening protocol to identify transcriptional regulators of alpha-synuclein, a gene associated with ...

A Method of Permeabilization of Drosophila Embryos for Assays of Small Molecule Activity

The Drosophila embryo has long been a powerful laboratory model for elucidating molecular and genetic mechanisms that control development. The ease of genetic manipulations with this model has supplanted pharmacological approaches that are commonplace in other animal models and cell-based assays. Here we describe recent advances in a protocol that enables application of small molecules to the developing fruit fly embryo. The method details steps to overcome the impermeability of the eggshell while maintaining embryo viability. Eggshell permeabilization across a broad range of developmental stages is achieved by application of a previously described d-limonene embryo permeabilization solvent (EPS1) and by aging embryos at reduced temperature (18 &#176;C) prior to treatments. In addition, use of a far-red dye (CY5) as a permeabilization indicator is described, which is compatible with downstream applications involving standard red and green fluorescent dyes in live and fixed preparations. This protocol is applicable to studies using bioactive compounds to probe developmental mechanisms as well as for studies aimed at evaluating teratogenic or pharmacologic activity of uncharacterized small molecules.

A Method of Permeabilization of Drosophila Embryos for Assays of Small Molecule Activity

Introduction of small molecules to the developing Drosophila embryo offers great potential for characterizing biological activity of novel compounds, drugs, and toxins as well as for probing fundamental developmental pathways. Methods described herein outline steps that overcome natural barriers to this approach, expanding the utility of the Drosophila embryo model.

The Drosophila embryo has long been a powerful laboratory model for elucidating molecular and genetic mechanisms that control development. The ease of ...

A Manual Small Molecule Screen Approaching High-throughput Using Zebrafish Embryos

Zebrafish have become a widely used model organism to investigate the mechanisms that underlie developmental biology and to study human disease pathology due to their considerable degree of genetic conservation with humans. Chemical genetics entails testing the effect that small molecules have on a biological process and is becoming a popular translational research method to identify therapeutic compounds. Zebrafish are specifically appealing to use for chemical genetics because of their ability to produce large clutches of transparent embryos, which are externally fertilized. Furthermore, zebrafish embryos can be easily drug treated by the simple addition of a compound to the embryo media. Using whole-mount in situ hybridization (WISH), mRNA expression can be clearly visualized within zebrafish embryos. Together, using chemical genetics and WISH, the zebrafish becomes a potent whole organism context in which to determine the cellular and physiological effects of small molecules. Innovative advances have been made in technologies that utilize machine-based screening procedures, however for many labs such options are not accessible or remain cost-prohibitive. The protocol described here explains how to execute a manual high-throughput chemical genetic screen that requires basic resources and can be accomplished by a single individual or small team in an efficient period of time. Thus, this protocol provides a feasible strategy that can be implemented by research groups to perform chemical genetics in zebrafish, which can be useful for gaining fundamental insights into developmental processes, disease mechanisms, and to identify novel compounds and signaling pathways that have medically relevant applications.

The zebrafish is an excellent experimental organism to study vertebrate developmental processes and model human disease. Here, we describe a protocol on how to perform a manual high-throughput chemical screen in zebrafish embryos with a whole-mount in situ hybridization (WISH) read-out.

Zebrafish have become a widely used model organism to investigate the mechanisms that underlie developmental biology and to study human disease pathology ...

Recovery of Adult Zebrafish Hearts for High-throughput Applications

Use of the zebrafish model system for studying development, regeneration, and disease is expanding toward use of adult hearts for cell dissociation and purification of RNA, DNA, and proteins. All of these applications demand the rapid recovery of significant numbers of zebrafish hearts to avoid gene regulatory, metabolic, and other changes that begin after death. Adult zebrafish hearts are also required for studying heart structure for a variety of mutants and for studying heart regeneration. However, the traditional zebrafish heart dissection is slow and difficult and requires specialized tools, making large-scale dissection of adult zebrafish hearts tedious. Traditional methods also harbor the risk of damaging the heart during the dissection. Here, we describe a method for dissection of adult zebrafish hearts that is fast, reproducible, and preserves heart architecture. Furthermore, this method does not require specialized tools, is painless for the zebrafish, can be performed on fresh or fixed specimens, and can be performed on zebrafish as young as one month old. The approach described expands the use of adult zebrafish for cardiovascular research.

Use of zebrafish for cardiovascular research is expanding towards research on adult hearts. For these applications, quick and simple isolation of cardiac tissues is key to avoid post-mortem changes and to obtain an adequate number of samples. Here, we describe a fast and reproducible method for dissecting adult zebrafish hearts.

Use of the zebrafish model system for studying development, regeneration, and disease is expanding toward use of adult hearts for cell dissociation and ...

High-throughput Screening for Chemical Modulators of Post-transcriptionally Regulated Genes

Both transcriptional and post-transcriptional regulation have a profound impact on genes expression. However, commonly adopted cell-based screening assays focus on transcriptional regulation, being essentially aimed at the identification of promoter-targeting molecules. As a result, post-transcriptional mechanisms are largely uncovered by gene expression targeted drug development. Here we describe a cell-based assay aimed at investigating the role of the 3&#39; untranslated region (3&#8217; UTR) in the modulation of the fate of its mRNA, and at identifying compounds able to modify it. The assay is based on the use of a luciferase reporter construct containing the 3&#8217; UTR of a gene of interest stably integrated into a disease-relevant cell line. The protocol is divided into two parts, with the initial focus on the primary screening aimed at the identification of molecules affecting luciferase activity after 24 hr of treatment. The second part of the protocol describes the counter-screening necessary to discriminate compounds modulating luciferase activity specifically through the 3&#8217; UTR. In addition to the detailed protocol and representative results, we provide important considerations about the assay development and the validation of the hit(s) on the endogenous target. The described cell-based reporter gene assay will allow scientists to identify molecules modulating protein levels via post-transcriptional mechanisms dependent on a 3&#8217; UTR.

Here we describe a cell-based reporter gene assay as a valuable tool to screen chemical libraries for compounds modulating post-transcriptional control mechanisms exerted through 3&#8217; UTR.

Both transcriptional and post-transcriptional regulation have a profound impact on genes expression. However, commonly adopted cell-based screening assays ...

Identification of Kinase-substrate Pairs Using High Throughput Screening

We have developed a screening platform to identify dedicated human protein kinases for phosphorylated substrates which can be used to elucidate novel signal transduction pathways. Our approach features the use of a library of purified GST-tagged human protein kinases and a recombinant protein substrate of interest. We have used this technology to identify MAP/microtubule affinity-regulating kinase 2 (MARK2) as the kinase for a glucose-regulated site on CREB-Regulated Transcriptional Coactivator 2 (CRTC2), a protein required for beta cell proliferation, as well as the Axl family of tyrosine kinases as regulators of cell metastasis by phosphorylation of the adaptor protein ELMO. We describe this technology and discuss how it can help to establish a comprehensive map of how cells respond to environmental stimuli.

Protein phosphorylation is a central feature of how cells interpret and respond to information in their extracellular milieu. Here, we present a high throughput screening protocol using kinases purified from mammalian cells to rapidly identify kinases that phosphorylate a substrate(s) of interest.


We have developed a screening platform to identify dedicated human protein kinases for phosphorylated substrates which can be used to elucidate novel ...

Automated Modular High Throughput Exopolysaccharide Screening Platform Coupled with Highly Sensitive Carbohydrate Fingerprint Analysis

Many microorganisms are capable of producing and secreting exopolysaccharides (EPS), which have important implications in medical fields, food applications or in the replacement of petro-based chemicals. We describe an analytical platform to be automated on a liquid handling system that allows the fast and reliable analysis of the type and the amount of EPS produced by microorganisms. It enables the user to identify novel natural microbial exopolysaccharide producers and to analyze the carbohydrate fingerprint of the corresponding polymers within one day in high-throughput (HT). Using this platform, strain collections as well as libraries of strain variants that might be obtained in engineering approaches can be screened. The platform has a modular setup, which allows a separation of the protocol into two major parts. First, there is an automated screening system, which combines different polysaccharide detection modules: a semi-quantitative analysis of viscosity formation via a centrifugation step, an analysis of polymer formation via alcohol precipitation and the determination of the total carbohydrate content via a phenol-sulfuric-acid transformation. Here, it is possible to screen up to 384 strains per run. The second part provides a detailed monosaccharide analysis for all the selected EPS producers identified in the first part by combining two essential modules: the analysis of the complete monomer composition via ultra-high performance liquid chromatography coupled with ultra violet and electrospray ionization ion trap detection (UHPLC-UV-ESI-MS) and the determination of pyruvate as a polymer substituent (presence of pyruvate ketal) via enzymatic oxidation that is coupled to a color formation. All the analytical modules of this screening platform can be combined in different ways and adjusted to individual requirements. Additionally, they can all be handled manually or performed with a liquid handling system. Thereby, the screening platform enables a huge flexibility in order to identify various EPS.

We present an automated modular high-throughput-method for the identification and characterization of microbial exopolysaccharides in small scale. This method combines a fast preselection to analyze the total amount of secreted polysaccharides with a detailed carbohydrate fingerprint to enable the fast screening of newly isolated bacterial strains or entire strain collections.