Name: a semi-quantitative drug affinity responsive target stability (darts) assay for studying rapamycin/mtor interaction
Uploaded: 2019-08-27T14:00:00
Description: Watch this Scientific Journal Video about A Semi-Quantitative Drug Affinity Responsive Target Stability DARTS assay for studying Rapamycin/mTOR interaction at JoVE.com

This work was supported partly by NIH research grants R01NS103931, R01AR062207, R01AR061484, and a DOD research grant W81XWH-16-1-0482.

1. Collect and lyse cells
<ol>
	<li>Grow 293T cells using Dulbecco&#39;s modified Eagle medium (DMEM) with 10% fetal bovine serum, 2 mM glutamine and 1% antibiotics. Incubate cultures at 37 &#176;C under 5% CO2. 
	NOTE: The growth state of the cells may affect the stability of subsequent experiments.</li>
	<li>Expand cells in culture until reaching 80&#8210;90% confluence.</li>
	<li>Mix 345 &#956;L of cell lysis reagent (see the Table of Materials) with 25 &#956;L of 20x protease inhibi...

<ol>
	<li>Rask-Andersen, M., Masuram, S., Schioth, H. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+druggable+genome:+Evaluation+of+drug+targets+in+clinical+trials+suggests+major+shifts+in+molecular+class+and+indication.">The druggable genome: Evaluation of drug targets in clinical trials suggests major shifts in molecular class and indication.</a> Annual Review of Pharmacology and Toxicology. 54, 9-26 (2014).</li><li>O'Connor, C. J., Laraia, L., Spring, D. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chemical+genetics.">Chemical genetics.</a> Chemical Society Reviews. 40 (8), 4332-4345 (2011).</li><li>McFedries, A., Schwaid, A., Saghatelian, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Methods+for+the+elucidation+of+protein-small+molecule+interactions.">Methods for the elucidation of protein-small molecule interactions.</a> Chemistry &amp; Biology. 20 (5), 667-673 (2013).</li><li>Sato, S., Murata, A., Shirakawa, T., Uesugi, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Biochemical+target+isolation+for+novices:+affinity-based+strategies.">Biochemical target isolation for novices: affinity-based strategies.</a> Chemistry &amp; Biology. 17 (6), 616-623 (2010).</li><li>Sleno, L., Emili, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Proteomic+methods+for+drug+target+discovery.">Proteomic methods for drug target discovery.</a> Current Opinion in Chemical Biology. 12 (1), 46-54 (2008).</li><li>Lomenick, B., 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=Target+identification+using+drug+affinity+responsive+target+stability+(DARTS).">Target identification using drug affinity responsive target stability (DARTS).</a> Proceedings of the National Academy of Sciences of the United States of America. 106 (51), 21984-21989 (2009).</li><li>Strickland, E. C., 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=Thermodynamic+analysis+of+protein-ligand+binding+interactions+in+complex+biological+mixtures+using+the+stability+of+proteins+from+rates+of+oxidation.">Thermodynamic analysis of protein-ligand binding interactions in complex biological mixtures using the stability of proteins from rates of oxidation.</a> Nature Protocols. 8 (1), 148-161 (2013).</li><li>Jafari, 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=The+cellular+thermal+shift+assay+for+evaluating+drug+target+interactions+in+cells.">The cellular thermal shift assay for evaluating drug target interactions in cells.</a> Nature Protocols. 9 (9), 2100-2122 (2014).</li><li>Martinez Molina, 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=Monitoring+drug+target+engagement+in+cells+and+tissues+using+the+cellular+thermal+shift+assay.">Monitoring drug target engagement in cells and tissues using the cellular thermal shift assay.</a> Science. 341 (6141), 84-87 (2013).</li><li>Savitski, M. 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=Tracking+cancer+drugs+in+living+cells+by+thermal+profiling+of+the+proteome.">Tracking cancer drugs in living cells by thermal profiling of the proteome.</a> Science. 346 (6205), 1255784 (2014).</li><li>Chang, J., Kim, Y., Kwon, H. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Advances+in+identification+and+validation+of+protein+targets+of+natural+products+without+chemical+modification.">Advances in identification and validation of protein targets of natural products without chemical modification.</a> Natural Product Reports. 33 (5), 719-730 (2016).</li><li>Pai, M. Y., 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=Drug+affinity+responsive+target+stability+(DARTS)+for+small-molecule+target+identification.">Drug affinity responsive target stability (DARTS) for small-molecule target identification.</a> Methods in Molecular Biology. 1263, 287-298 (2015).</li><li>Lomenick, B., Jung, G., Wohlschlegel, J. A., Huang, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Target+identification+using+drug+affinity+responsive+target+stability+(DARTS).">Target identification using drug affinity responsive target stability (DARTS).</a> Current Protocols in Chemical Biology. 3 (4), 163-180 (2011).</li><li>Xu, L., 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=Precision+therapeutic+targeting+of+human+cancer+cell+motility.">Precision therapeutic targeting of human cancer cell motility.</a> Nature Communications. 9 (1), 2454 (2018).</li><li>Lim, H., 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+autophagy+enhancer+as+a+therapeutic+agent+against+metabolic+syndrome+and+diabetes.">A novel autophagy enhancer as a therapeutic agent against metabolic syndrome and diabetes.</a> Nature Communications. 9 (1), 1438 (2018).</li><li>Schulte, M. L., 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=Pharmacological+blockade+of+ASCT2-dependent+glutamine+transport+leads+to+antitumor+efficacy+in+preclinical+models.">Pharmacological blockade of ASCT2-dependent glutamine transport leads to antitumor efficacy in preclinical models.</a> Nature Medicine. 24 (2), 194-202 (2018).</li><li>Skrott, Z., 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=Alcohol-abuse+drug+disulfiram+targets+cancer+via+p97+segregase+adaptor+NPL4.">Alcohol-abuse drug disulfiram targets cancer via p97 segregase adaptor NPL4.</a> Nature. 552 (7684), 194-199 (2017).</li><li>Zhang, C., 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=Endosidin2+targets+conserved+exocyst+complex+subunit+EXO70+to+inhibit+exocytosis.">Endosidin2 targets conserved exocyst complex subunit EXO70 to inhibit exocytosis.</a> Proceedings of the National Academy of Sciences of the United States of America. 113 (1), 41-50 (2016).</li><li>Chin, R. 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=The+metabolite+alpha-ketoglutarate+extends+lifespan+by+inhibiting+ATP+synthase+and+TOR.">The metabolite alpha-ketoglutarate extends lifespan by inhibiting ATP synthase and TOR.</a> Nature. 510 (7505), 397-401 (2014).</li><li>Robinson, T. J., 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+screen+identifies+disulfiram+as+a+potential+therapeutic+for+triple-negative+breast+cancer+cells:+interaction+with+IQ+motif-containing+factors.">High-throughput screen identifies disulfiram as a potential therapeutic for triple-negative breast cancer cells: interaction with IQ motif-containing factors.</a> Cell Cycle. 12 (18), 3013-3024 (2013).</li><li>Aghajan, 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=Chemical+genetics+screen+for+enhancers+of+rapamycin+identifies+a+specific+inhibitor+of+an+SCF+family+E3+ubiquitin+ligase.">Chemical genetics screen for enhancers of rapamycin identifies a specific inhibitor of an SCF family E3 ubiquitin ligase.</a> Nature Biotechnology. 28 (7), 738-742 (2010).</li><li>Brunelle, J. L., Green, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Coomassie+blue+staining.">Coomassie blue staining.</a> Methods in Enzymology. 541, 161-167 (2014).</li><li>Domon, B., Aebersold, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mass+spectrometry+and+protein+analysis.">Mass spectrometry and protein analysis.</a> Science. 312 (5771), 212-217 (2006).</li><li>Hnasko, T. S., Hnasko, R. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Western+Blot.">The Western Blot.</a> Methods in Molecular Biology. 1318, 87-96 (2015).</li><li>Van Duyne, G. D., Standaert, R. F., Karplus, P. A., Schreiber, S. L., Clardy, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Atomic+structures+of+the+human+immunophilin+FKBP-12+complexes+with+FK506+and+rapamycin.">Atomic structures of the human immunophilin FKBP-12 complexes with FK506 and rapamycin.</a> Journal of Molecular Biology. 229 (1), 105-124 (1993).</li><li>Lomenick, B., Olsen, R. W., Huang, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Identification+of+direct+protein+targets+of+small+molecules.">Identification of direct protein targets of small molecules.</a> ACS Chemical Biology. 6 (1), 34-46 (2011).</li><li>Park, Y. 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=Identification+of+Multiple+Cryptococcal+Fungicidal+Drug+Targets+by+Combined+Gene+Dosing+and+Drug+Affinity+Responsive+Target+Stability+Screening.">Identification of Multiple Cryptococcal Fungicidal Drug Targets by Combined Gene Dosing and Drug Affinity Responsive Target Stability Screening.</a> MBio. 7 (4), (2016).</li><li>Qu, Y., 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=Small+molecule+promotes+beta-catenin+citrullination+and+inhibits+Wnt+signaling+in+cancer.">Small molecule promotes beta-catenin citrullination and inhibits Wnt signaling in cancer.</a> Nature Chemical Biology. 14 (1), 94-101 (2018).</li></ol>

DARTS allows for identification of small molecule targets by exploiting the protective effect of protein binding against degradation. DARTS does not require any chemical modification or immobilization of the small molecule26. This allows small molecules to be used to determine their direct binding protein targets. Standard assessment criteria for the classical DARTS method include gel staining, mass spectrometry and western blotting12,13. ...

Identifying small molecule target proteins is essential to the mechanistic understanding and development of potential therapeutic drugs1,2,3. Affinity chromatography, as a classical method for identifying the target proteins of small molecules, has yielded good results4,5. However, this method has limitations, in that chemical modification of small molecules often results in reduced or altered binding specificity or affinity. To overcome these limitations, several new strategies have recently been developed and applied to identify the small molecule targets without chemical modification of the small molecules. These direct methods for target identification of label-free small molecules include drug affinity responsive target stability (DARTS)6, stability of proteins from rates of oxidation (SPROX)7, cellular thermal shift assay (CETSA)8,9, and thermal proteome profiling (TPP)10. These methods are highly advantageous because they use natural, unmodified small molecules and rely only on direct binding interactions to find target proteins11.
Among these new methods, DARTS is a comparatively simple methodology that can easily be adopted by most labs12,13. DARTS depends on the concept that ligand-bound proteins demonstrate modified susceptibility to enzymatic degradation relative to unbound proteins. The new target protein can be detected by examination of the altered band in SDS-PAGE gel through liquid chromatography-mass spectrometry (LC-MS/MS). This approach has been successfully implemented for identification of previously unknown targets of natural products and drugs14,15,16,17,18,19. It is also powerful as a means to screen or validate binding of compounds to a specific protein20,21. In this study, we present an improvement to the experiment by monitoring the changes in protein stability with small molecules and identifying protein-ligand binding affinities. We use mTOR- rapamycin interaction as an example to demonstrate our approach.

<table>
	<tbody>
		<tr>
			<td>100X Protease inhibitor cocktail</td>
			<td>Sigma-Aldrich</td>
			<td>P8340</td>
			<td>Dilute to 20X with ultrapure water</td>
		</tr>
		<tr>
			<td>293T cell line</td>
			<td>ATCC</td>
			<td>CRL-3216</td>
			<td>DMEM medium with 10% FBS</td>
		</tr>
		<tr>
			<td>Acetic acid</td>
			<td>Sigma-Aldrich</td>
			<td>A6283</td>
			<td></td>
		</tr>
		<tr>
			<td>BCA Protein Assay Kit</td>
			<td>Thermo Fisher</td>
			<td>23225</td>
			<td></td>
		</tr>
		<tr>
			<td>Calcium chloride</td>
			<td>Sigma-Aldrich</td>
			<td>C1016</td>
			<td></td>
		</tr>
		<tr>
			<td>Cell scraper</td>
			<td>Thermo Fisher</td>
			<td>179693</td>
			<td></td>
		</tr>
		<tr>
			<td>Coomassie Brilliant Blue R-250 Staining Solution</td>
			<td>Bio-Rad</td>
			<td>1610436</td>
			<td></td>
		</tr>
		<tr>
			<td>Dimethyl sulfoxide(DMSO)</td>
			<td>Sigma-Aldrich</td>
			<td>D2650</td>
			<td></td>
		</tr>
		<tr>
			<td>GraphPad Prism</td>
			<td>GraphPad Software</td>
			<td>Version 6.0</td>
			<td>statistical analysis and drawing software</td>
		</tr>
		<tr>
			<td>Hydrochloric acid</td>
			<td>Sigma-Aldrich</td>
			<td>H1758</td>
			<td></td>
		</tr>
		<tr>
			<td>ImageJ</td>
			<td>National Institutes of Health</td>
			<td>Version 1.52</td>
			<td>image processing and analysis software</td>
		</tr>
		<tr>
			<td>M-PER Cell Lysis Reagent</td>
			<td>Thermo Fisher</td>
			<td>78501</td>
			<td></td>
		</tr>
		<tr>
			<td>Phosphate-buffered saline (PBS)</td>
			<td>Corning</td>
			<td>R21-040-CV</td>
			<td></td>
		</tr>
		<tr>
			<td>Pronase</td>
			<td>Roche</td>
			<td>PRON-RO</td>
			<td>10 mg/ml</td>
		</tr>
		<tr>
			<td>Sodium chloride</td>
			<td>Sigma-Aldrich</td>
			<td>S7653</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium fluoride</td>
			<td>Sigma-Aldrich</td>
			<td>S7920</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium orthovanadate</td>
			<td>Sigma-Aldrich</td>
			<td>450243</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium pyrophosphate</td>
			<td>Sigma-Aldrich</td>
			<td>221368</td>
			<td></td>
		</tr>
		<tr>
			<td>Trizma base</td>
			<td>Sigma-Aldrich</td>
			<td>T1503</td>
			<td>adjust to pH 8.0</td>
		</tr>
		<tr>
			<td>&#946;-glycerophosphate</td>
			<td>Sigma-Aldrich</td>
			<td>G9422</td>
			<td></td>
		</tr>
	</tbody>
</table>

a semi-quantitative drug affinity responsive target stability (darts) assay for studying rapamycin/mtor interaction

Drug Affinity Responsive Target Stability (DARTS) is a robust method for detection of novel small molecule protein targets. It can be used to verify known small molecule-protein interactions and to find potential protein targets for natural products. Compared with other methods, DARTS uses native, unmodified, small molecules and is simple and easy to operate. In this study, we further enhanced the data analysis capabilities of the DARTS experiment by monitoring the changes in protein stability and estimating the affinity of protein-ligand interactions. The protein-ligand interactions can be plotted into two curves: a proteolytic curve and a dose-dependence curve. We have used the mTOR-rapamycin interaction as an exemplary case for establishment of our protocol. From the proteolytic curve we saw that the proteolysis of mTOR by pronase was inhibited by the presence of rapamycin. The dose-dependency curve allowed us to estimate the binding affinity of rapamycin and mTOR. This method is likely to be a powerful and simple method for accurately identifying novel target proteins and for the optimization of drug target engagement.

The flow chart of the experiment is outlined in Figure 1. The result of Coomassie blue staining is shown in Figure 2. Incubation with the small molecule confers protection against proteolysis. Three bands that appear to be protected by incubation with rapamycin over vehicle control are found. The expected results from proteolytic curve experiment are shown in Figure 3. As a proof-of-principle, we examined the well-studied protein mT...

Watch this Scientific Journal Video about A Semi-Quantitative Drug Affinity Responsive Target Stability DARTS assay for studying Rapamycin/mTOR interaction at JoVE.com

A Semi-Quantitative Drug Affinity Responsive Target Stability DARTS assay for studying Rapamycin/mTOR interaction

In this study, we enhanced the data analysis capabilities of the DARTS experiment by monitoring the changes in protein stability and estimating the affinity of protein-ligand interactions. The interactions can be plotted into two curves: a proteolytic curve and a dose-dependence curve. We have used mTOR-rapamycin interaction as an exemplary case.

A Semi-Quantitative Drug Affinity Responsive Target Stability (DARTS) assay for studying Rapamycin/mTOR interaction

Drug Affinity Responsive Target Stability (DARTS) is a robust method for detection of novel small molecule protein targets. It can be used to verify known ...

Research

JoVE Journal

Biochemistry

Method for Identifying Small Molecule Inhibitors of the Protein-protein Interaction Between HCN1 and TRIP8b

Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels are expressed ubiquitously throughout the brain, where they function to regulate the ...

Differential Scanning Calorimetry &#8212; A Method for Assessing the Thermal Stability and Conformation of Protein Antigen

Differential Scanning Calorimetry ÃƒÆ’Ã‚Â¢ÃƒÂ¢Ã¢â‚¬Å¡Ã‚Â¬ÃƒÂ¢Ã¢â€šÂ¬Ã‚Â A Method for Assessing the Thermal Stability and Conformation of Protein Antigen

Differential scanning calorimetry (DSC) is an analytical technique that measures the molar heat capacity of samples as a function of temperature. In the ...

Time-resolved ElectroSpray Ionization Hydrogen-deuterium Exchange Mass Spectrometry for Studying Protein Structure and Dynamics

Intrinsically disordered proteins (IDPs) have long been a challenge to structural biologists due to their lack of stable secondary structure elements. ...

A G-quadruplex DNA-affinity Approach for Purification of Enzymatically Active G4 Resolvase1

Higher-order nucleic acid structures called G-quadruplexes (G4s, G4 structures) can form in guanine-rich regions of both DNA and RNA and are highly ...

A Simple, Robust, and High Throughput Single Molecule Flow Stretching Assay Implementation for Studying Transport of Molecules Along DNA

We describe a simple, robust and high throughput single molecule flow-stretching assay for studying 1D diffusion of molecules along DNA. In this assay, ...

Semi-automated Biopanning of Bacterial Display Libraries for Peptide Affinity Reagent Discovery and Analysis of Resulting Isolates

Biopanning bacterial display libraries is a proven technique for peptide affinity reagent discovery for recognition of both biotic and abiotic targets. ...

A Modified Yeast-one Hybrid System for Heteromeric Protein Complex-DNA Interaction Studies

Over the years, the yeast one-hybrid assay has proven to be an important technique for the identification and validation of physical interactions between ...

Benchtop Immobilized Metal Affinity Chromatography, Reconstitution and Assay of a Polyhistidine Tagged Metalloenzyme for the Undergraduate Laboratory

Benchtop immobilized metal affinity chromatography (IMAC), of polyhistidine tagged proteins is easily mastered by undergraduate students and has become ...

Native Cell Membrane Nanoparticles System for Membrane Protein-Protein Interaction Analysis

Protein-protein interactions in cell membrane systems play crucial roles in a wide range of biological processes- from cell-to-cell interactions to signal ...