Name: an iodide-yellow fluorescent protein-gap junction-intercellular communication assay
Uploaded: 2019-02-01T14:00:00
Description: Watch this Scientific Journal Video about An Iodide-Yellow Fluorescent Protein-Gap Junction-Intercellular Communication Assay at JoVE.com

This research was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (2011-0023701, 2016R1D1A1A02937397, and 2018R1A6A1A03023718).

1. Generation of lentiviruses expressing YFPQL and SLC26A4
<ol>
	<li>Grow HEK293T human embryonic kidney cells to 80% confluency on 100 mm culture plates. Dulbecco&#39;s Modified Eagle Medium (DMEM) supplemented with 10% fetal bovine serum, 100 U/mL penicillin, and 100 &#181;g/mL streptomycin is the culture medium used throughout the protocol to maintain HEK293T and other cells mentioned below.</li>
	<li>Coat 6-well culture plates by adding 2 mL of 0.005% of sterile poly-L-lysine (PLL) solution to each well ...

<ol>
	<li>Goodenough, D. a., Goliger, J. a., Paul, D. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Connexins,+connexons,+and+Intercellular+Communication.">Connexins, connexons, and Intercellular Communication.</a> Annual Review of Biochemistry. 65, 475-502 (1996).</li><li>Upham, B. L., Weis, L. M., Trosko, J. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Modulated+Gap+Junctional+Intercellular+Communication+as+a+Biomarker+of+PAH+Epigenetic+Toxicity:+Structure-Function+Relationship.">Modulated Gap Junctional Intercellular Communication as a Biomarker of PAH Epigenetic Toxicity: Structure-Function Relationship.</a> Environmental Health Perspectives. 106, 975 (1998).</li><li>U, J. E. T., Chang, C., Upham, B., Wilson, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Epigenetic+toxicology+as+toxicant-induced+changes+in+intracellular+signalling+leading+to+altered+gap+junctional+intercellular+communication.">Epigenetic toxicology as toxicant-induced changes in intracellular signalling leading to altered gap junctional intercellular communication.</a> Toxicology Letters. , 71-78 (1998).</li><li>Yamasaki, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Role+of+disrupted+gap+junctional+intercellular+communications+in+detection+and+characterization+of+carcinogens.">Role of disrupted gap junctional intercellular communications in detection and characterization of carcinogens.</a> Mutation Research - Reviews in Genetic Toxicology. , (1996).</li><li>Yamasaki, 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=Gap+junctional+intercellular+communication+and+cell+proliferation+during+rat+liver+carcinogenesis.">Gap junctional intercellular communication and cell proliferation during rat liver carcinogenesis.</a> Environmental Health Perspectives. 101, 191-197 (1993).</li><li>Vinken, 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=Gap+junctional+intercellular+communication+as+a+target+for+liver+toxicity+and+carcinogenicity.">Gap junctional intercellular communication as a target for liver toxicity and carcinogenicity.</a> Critical Reviews in Biochemistry and Molecular Biology. 44, 201-222 (2009).</li><li>Fonseca, C. G., Green, C. R., Nicholson, L. F. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Upregulation+in+astrocytic+connexin+43+gap+junction+levels+may+exacerbate+generalized+seizures+in+mesial+temporal+lobe+epilepsy.">Upregulation in astrocytic connexin 43 gap junction levels may exacerbate generalized seizures in mesial temporal lobe epilepsy.</a> Brain Research. 929 (1), 105-116 (2002).</li><li>Garbelli, 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=Expression+of+connexin+43+in+the+human+epileptic+and+drug-resistant+cerebral+cortex.">Expression of connexin 43 in the human epileptic and drug-resistant cerebral cortex.</a> Neurology. 76 (10), 895-902 (2011).</li><li>Schulz, 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=Connexin+43+is+an+emerging+therapeutic+target+in+ischemia/reperfusion+injury,+cardioprotection+and+neuroprotection.">Connexin 43 is an emerging therapeutic target in ischemia/reperfusion injury, cardioprotection and neuroprotection.</a> Pharmacology and Therapeutics. 153, 90-106 (2015).</li><li>Sarrouilhe, D., Dejean, C., Mesnil, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Involvement+of+gap+junction+channels+in+the+pathophysiology+of+migraine+with+aura.">Involvement of gap junction channels in the pathophysiology of migraine with aura.</a> Frontiers in Physiology. , (2014).</li><li>Patel, S. 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=Gap+junction+inhibition+prevents+drug-induced+liver+toxicity+and+fulminant+hepatic+failure.">Gap junction inhibition prevents drug-induced liver toxicity and fulminant hepatic failure.</a> Nature Biotechnology. 30 (2), 179-183 (2012).</li><li>Kandyba, E. E., Hodgins, M. B., Martin, P. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+murine+living+skin+equivalent+amenable+to+live-cell+imaging:+analysis+of+the+roles+of+connexins+in+the+epidermis.">A murine living skin equivalent amenable to live-cell imaging: analysis of the roles of connexins in the epidermis.</a> Journal of Investigative Dermatology. 128 (4), 1039-1049 (2008).</li><li>Upham, B. 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=Differential+roles+of+2+,+6+,+and+8+carbon+ceramides+on+the+modulation+of+gap+junctional+communication+and+apoptosis+during+carcinogenesis.">Differential roles of 2 , 6 , and 8 carbon ceramides on the modulation of gap junctional communication and apoptosis during carcinogenesis.</a> Cancer Letters. 191, 27-34 (2003).</li><li>Upham, B. 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=Structure-activity-dependent+regulation+of+cell+communication+by+perfluorinated+fatty+acids+using+in+vivo+and+in+vitro+model+systems.">Structure-activity-dependent regulation of cell communication by perfluorinated fatty acids using in vivo and in vitro model systems.</a> Environmental Health Perspectives. 117 (4), 545-551 (2009).</li><li>Weis, 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=Bay+or+Baylike+Regions+of+Polycyclic+Aromatic+Hydrocarbons+Were+Potent+Inhibitors+of+Gap+Intercellular+Communication.">Bay or Baylike Regions of Polycyclic Aromatic Hydrocarbons Were Potent Inhibitors of Gap Intercellular Communication.</a> Environmental Health Perspectives. 106 (1), 17-22 (1998).</li><li>el-Fouly, M. H., Trosko, J. E., Chang, C. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Scrape-Loading+and+Dye+Transfer:+A+Rapid+and+Simple+Technique+to+Study+Gap+Junctional+Intercellular+Communication.">Scrape-Loading and Dye Transfer: A Rapid and Simple Technique to Study Gap Junctional Intercellular Communication.</a> Experimental Cell Research. 168 (2), 422-430 (1987).</li><li>Wade, M. H., Trosko, J. E., Schindler, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Photobleaching+Assay+of+Gap+Junction-+Mediated+Communication+Between+Human+Cells.">Photobleaching Assay of Gap Junction- Mediated Communication Between Human Cells.</a> Advancement of Science. 232 (4749), 525-528 (2010).</li><li>Abbaci, 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=In+vitro+characterization+of+gap+junctional+intercellular+communication+by+gap-FRAP+technique.">In vitro characterization of gap junctional intercellular communication by gap-FRAP technique.</a> Proceedings of SPIE. , 585909 (2005).</li><li>Neyton, J., Trautmann, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Single-channel+currents+of+an+intercellular+junction.">Single-channel currents of an intercellular junction.</a> Nature. 317 (6035), 331-335 (1985).</li><li>Wilders, R., Jongsma, 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=Limitations+of+the+dual+voltage+clamp+method+in+assaying+conductance+and+kinetics+of+gap+junction+channels.">Limitations of the dual voltage clamp method in assaying conductance and kinetics of gap junction channels.</a> Biophysical Journal. 63 (4), 942-953 (1992).</li><li>Lee, J. Y., Choi, E. J., Lee, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+new+high-throughput+screening-compatible+gap+junctional+intercellular+communication+assay.">A new high-throughput screening-compatible gap junctional intercellular communication assay.</a> BMC Biotechnology. 15 (1), 1-9 (2015).</li><li>Galietta, L. J. V., Haggie, P. M., Verkman, A. 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The I-YFP-GJIC assay can be used for HTS because it is robust, rapid, and inexpensive. An HTS assay is considered robust if the Z&#39;-factor is above 0.525. See Zhang et al. for a description of the statistical analysis used to assessing the suitability of HTS assays25. When LN215 cells were used, the Z&#39;-factor was &#62;0.5 without any assay optimization. If other cell types are used in the assay and its Z&#39;-factor is &#60;0.5, the robustness can be improved by exte...

Gap junctions (GJs) act as intercellular channels to allow the diffusion of small molecules of &#60;1 kDa such as nutrients, metabolites, and signaling molecules between adjacent cells. The junctional elements include a hemichannel or connexon in each cell, and each connexon constitutes six connexins (Cxs)1. GJs and Cxs have been used in toxicology assays of carcinogens such as polycyclic aromatic hydrocarbons (PAH), which are GJ inhibitors2,3,4. Disrupted GJIC has been associated with nongenotoxic carcinogenesis5,6. As a potential therapeutic target, GJ involvement has been reported in particular subtypes of seizures7,8, protection from cardiac and brain ischemia/reperfusion injury9, migraine with aura10, drug-induced liver injury6,11, and wound healing12. High-throughput screening (HTS) assays are required to identify GJ-modulating chemicals or antibodies for drug discovery, for toxicology assays, and to identify novel cellular regulators of GJ activity. HTS assays can also be used to investigate structure-activity relationships of GJ modulators2,13,14,15.
Some GJIC assays include dye transfer or dual patch clamp techniques. Lucifer yellow CH (LY) and calcein acetoxymethyl ester (calcein-AM) have been used in dye-transfer assays. Cells are not permeable to LY, which is introduced by microinjection, scrape loading, or electroporation. Once inside the cell, LY spreads into neighboring cells via GJs and GJ activity is assayed by the extent of the LY migration16. Calcein-AM assays usually involve gap-fluorescence recovery after photobleaching17,18. Calcein-AM is a cell-permeant dye that is converted intracellularly into impermeable calcein by an intrinsic esterase. The assay requires a confocal microscope to observe the transfer of calcein-AM into a cell from those surrounding it following laser photobleaching. If functional GJs are present, calcein-AM in adjacent cells enters the photobleached cells and the fluorescence is recovered. GJ activity is assayed by the extent of fluorescence recovery of the photobleached cells. Dye-transfer assays are laborious and time consuming or have low sensitivities. Dual patch clamping is an electrophysiological method that measures junctional conductance. It is relatively sensitive, with a direct dependence of conductance on the number of open GJs19; however, it is technically demanding, time consuming, and expensive20. The I-YFP-GJIC assay was developed for use in HTS.
Figure 1 illustrates the components and steps of the I-YFP GJIC assay, which utilizes acceptor cells expressing an iodide-sensitive YFP variant bearing H148Q and I152L (YFPQL) and donor cells expressing an iodide transporter (SLC26A4)21. The two mutations carried by YFPQL allow quenching of fluorescence by iodide22. Iodides are added to co-cultured acceptor and donor cells; they do not enter the acceptor cells, but are taken up by the SLC26A4 transporters present on the donor cells. Iodides in the donor cells diffuse through functioning GJs into adjacent acceptor cells where they quench the YFPQL fluorescence. If GJs are closed or blocked by inhibitors, iodide cannot enter the acceptor cells to quench the fluorescence. The YFPQL quenching rate reflects GJ activity. The I-YFP GJIC assay procedure is neither complicated nor time consuming. It is compatible with HTS and can be used to test the effects of a large number of compounds on GJ activity in a relatively short period. It requires only acceptor and donor cells, and two balanced salt solutions. The protocol described below is based on LN215 cells whose major Cx is Cx4321. The LN215-YFPQL receptor and LN215-I&#8722; donor cells were generated by transduction with lentiviruses expressing YFPQL or SLC26A421,23.

<table border="0" cellpadding="0" cellspacing="0" style="width:629px;" width="630">
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	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:268px;">96-well plate</td>
			<td style="width:72px;">SPL</td>
			<td style="width:123px;">30096</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:268px;">Calcium chloride (CaCl2)</td>
			<td style="width:72px;">Sigma</td>
			<td style="width:123px;">C5670</td>
			<td>I-solution</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:268px;">D-(+)-Glucose</td>
			<td style="width:72px;">Sigma</td>
			<td style="width:123px;">G7021</td>
			<td>C-solution, I-solution</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:268px;">Dimethyl sulfoxide (DMSO)</td>
			<td style="width:72px;">sigma</td>
			<td style="width:123px;">276855</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:268px;">HEPES</td>
			<td style="width:72px;">Sigma</td>
			<td style="width:123px;">RES6003H-B7</td>
			<td>C-solution, I-solution</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:268px;">Lipofectamine 2000</td>
			<td style="width:72px;">Invitrogen</td>
			<td style="width:123px;">11668-027</td>
			<td>transfection reagent</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:268px;">Magnesium chloride hexahydrate (MgCl2 6H2O)</td>
			<td style="width:72px;">Sigma</td>
			<td style="width:123px;">M2393</td>
			<td>C-solution</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:268px;">Microplate reader&#160;</td>
			<td style="width:72px;">BMG LabTech&#160;</td>
			<td style="width:123px;">POLARstar Omega 415-1618</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">pMD2.G&#160;</td>
			<td style="width:72px;">Addgene</td>
			<td>#12259</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:268px;">Polybrene</td>
			<td style="width:72px;">sigma</td>
			<td style="width:123px;">H9268</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:268px;">Poly-L-lysine solution</td>
			<td style="width:72px;">sigma</td>
			<td style="width:123px;">P4707</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:268px;">Potassium chloride (KCl)</td>
			<td style="width:72px;">Sigma</td>
			<td style="width:123px;">P5405</td>
			<td>C-solution, I-solution</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">psPAX2&#160;</td>
			<td style="width:72px;">Addgene</td>
			<td style="width:123px;">&#160;#12260</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:268px;">Puromycin Dihydrochloride</td>
			<td style="width:72px;">sigma</td>
			<td style="width:123px;">P8833</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:268px;">Sodium chloride (NaCl)</td>
			<td style="width:72px;">Sigma</td>
			<td style="width:123px;">S5886</td>
			<td>C-solution, I-solution</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:268px;">Sodium hyroxide (NaOH)</td>
			<td style="width:72px;">Sigma</td>
			<td style="width:123px;">S2770</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:268px;">Sodium Iodide (NaI)</td>
			<td style="width:72px;">Sigma</td>
			<td style="width:123px;">383112</td>
			<td>I-solution</td>
		</tr>
	</tbody>
</table>

an iodide-yellow fluorescent protein-gap junction-intercellular communication assay

Gap junctions (GJs) are cell membrane channels that allow diffusion of molecules smaller than 1 kDa between adjacent cells. As they have physiological and pathological roles, there is need of high-throughput screening (HTS) assays to identify GJ modulators in drug discovery and toxicology assays. A novel iodide-yellow fluorescent protein-gap junction-intercellular communication (I-YFP-GJIC) assay fulfills this need. It is a cell-based assay including acceptor and donor cells that are engineered to stably express a yellow fluorescent protein (YFP) variant, whose fluorescence is sensitively quenched by iodide, or SLC26A4, an iodide transporter, respectively. When iodide is added to a mixed culture of the two cell types, they enter the donor cells via the SLC26A4 transporter and diffuse to the adjacent acceptor cells via GJs where they quench the YFP fluorescence. YFP fluorescence is measured well by well in a kinetic mode. The YFP quenching rate reflects GJ activity. The assay is reliable and rapid enough to be used for HTS. The protocol for the I-YFP-GJIC assay using the LN215 cells, human glioma cells, is described.

Twenty-nine 96-well culture plates were used to screen 2,320 chemicals to identify novel GJIC modulators by I-YFP GJIC assay using the LN215-YFPQL and LN215-I&#8722; cells. The results obtained with a representative plate are shown in Figure 2. The percentage of YFP fluorescence in each well is shown as a line graph in Figure 2A and the percentage of GJIC activity in each well is shown in th...

Watch this Scientific Journal Video about An Iodide-Yellow Fluorescent Protein-Gap Junction-Intercellular Communication Assay at JoVE.com

An Iodide-Yellow Fluorescent Protein-Gap Junction-Intercellular Communication Assay

Here, we present a protocol for a novel gap junction intercellular communication assay designed for the high-throughput screening of gap junction-modulating chemicals for drug discovery and toxicological assessment.

Gap junctions (GJs) are cell membrane channels that allow diffusion of molecules smaller than 1 kDa between adjacent cells. As they have physiological and ...

Gap junctions have been suggested as drug targets. Iodide-YFP-GJIC assay is compatible with high-throughput screening to discover gap junction modulators. It have be used to test the effects of a large number of compounds on gap junction activities in a relatively short period.Iodide-YFP-GJIC assay is simple, robust, repeatable and inexpensive. This assay requires only acceptor and donor cells and two balanced salt solutions. No additional reagents such as Lucifer yellow and Calcein AM are needed.Also it measures total gap junction activities of the cells in a single well which results in low between-well variability. To begin this procedure grow LN215 cells to 80%confluency in supplemented DMEM as outlined in the text protocol. One day before transduction wash the cells twice with 10 milliliters of PBS.Add two milliliters of 0.25%trypsin EDTA to the cells and incubate at 37 degrees Celsius for three minutes. Using a 10-milliliter serological pipette resuspend the cells in five milliliters of culture medium and adjust the cell density to 50, 000 cells per milliliter. Add 400 microliters of media which contains 20, 000 cells to each well of a 24-well culture plate.Incubate at 37 degrees Celsius for 24 hours. The next day transduce two wells by replacing the culture medium with 400 microliters of a one-to-one mixture of a lentivirus and fresh culture medium supplemented with polybrene at a final concentration of four micrograms per milliliter. For the no virus controls replace the culture medium with fresh culture medium supplemented with polybrene at a final concentration of four micrograms per milliliter.Incubate at 37 degrees Celsius for 15 hours. Then aspirate the medium containing lentiviruses, and fresh culture medium. Incubate the cells at 37 degrees Celsius for an additional 72 hours.After this, wash the cells in each well twice with 0.5 milliliters of PBS. Add 300 microliters of 0.25%trypsin EDTA to the cells, and incubate at 37 degrees Celsius for three minutes. Resuspend the cells in two milliliters of culture medium, and then plate them in six-well culture plates with two micrograms per milliliter of puromycin.Culture the cells until all of the cells in the control wells are dead, which usually takes approximately a week. First, separately culture LN215-YFP and LN215-iodide cells in 100-millimeter plates in culture medium to reach the populations required for the assay. One day before the assay, wash each plate with 10 milliliters of PBS.Treat each plate with two milliliters of 0.25%trypsin EDTA solution, and incubate at 37 degrees Celsius for five minutes. Resuspend the cells in four milliliters of culture medium and transfer them to a 15-milliliter conical tubes. Centrifuge at 1, 000 g for three minutes to pellet the cells.Discard the supernatant and resuspend each cell pellet in five milliliters of culture medium. Pipette up and down about 20 times to break up any cell clumps. Use a hemocytometer to count the cells.And then dilute the cells in culture medium to make cell suspension at the densities shown here. Next, mix seven milliliters of each cell suspension together in a reservoir. Use a multichannel pipette to add 100 microliters of this mixture to each well of a 96-well culture plate.Incubate at 37 degrees Celsius with 5%carbon dioxide for 24 hours. First, use a fluorescence microscope with 20X magnification and a GFP filter to check the 96-well plates to be sure there are no clumps of cells, and that the cultures are fully confluent and well distributed. At least 30 minutes before the assay turn on a microplate reader and set it to 37 degrees Celsius.Wash the tubing of an automated injector with three milliliters of 70%ethanol, three milliliters of distilled water, and three milliliters of I-solution. Next, warm the C and I-solutions to 37 degrees Celsius in a water bath. Either aspirate the growth medium or invert the plate to empty it.Tap out any residual medium. Then add the C-solution to a reservoir using a multichannel pipette to add 200 microliters of C-solution to each well of the plate. Either aspirate the solution or invert the plate to empty it, making to tap out any residual solution.Add 50 microliters of C-solution to each well. Then add one microliter of either a 2.5-millimolar chemical stock or DMSO as a vehicle, and add another 50 microliters of C-solution to each well. Incubate the cells at 37 degrees Celsius in air for approximately 10 minutes.During the incubation, begin setting the parameters in the microplate reader program by clicking the Manage Protocols button. Click the New button. Select the Fluorescence Intensity in the Measurement Method section, and Well Mode in the Reading Mode section.Next, click the OK button. A new tab will appear. In the Basic Parameters menu set the Excitation wavelength to 485 nanometers, and the Emission to 520 nanometers.Select the Bottom optic to read fluorescence from the bottom. Then set the measurement start time to be zero seconds, the number of intervals to be 25, the number of flashes per well and interval to be 20, and the interval time to be 0.4 seconds. In the Layout menu draw a region of the plate to be read.In the Concentrations/Volumes/Shacking menu set the microplate reader to inject 100 microliters of I-solution to each well with an injection speed of 135 microliters per second. In the Injection Time menu set the injection start time to be one second. Then click the Start measurement button.When the incubation is complete, transfer the 96-well plates to the microplate reader and start the measurement by clicking the Start measurement button again. In this study, the iodine-yellow fluorescent protein-gap junction-intercellular communication assay is used with LN215-YFP and LN215-iodine cells to screen 2, 320 chemicals to identify novel gap junction intracellular communication modulators. Homosalate is seen to inhibit 50%of gap junction intracellular communication.While terbinafine completely inhibits it. This confirms terbinafine as a gap junction inhibitor. This assay measures GJIC between neighboring donor and acceptor cells, so the donor and acceptor cells must be completely dissociated before plating.And the confluence of the mixed culture should be 100%to maximize formation of gap junctions between cells. Time course data, dose response relationships, and assessing the reversibility of gap junction modulators can be obtained with Iodide-YFP-GJIC assay. Also, Iodide-YFP specific connexin GJIC assays can be established by inducing the expression of a connexin of interest into the cells devoid of functional gap junctions.This makes it possible to determine IC50 value of a chemical of a specific type of connexin. Iodide-YFP-GJIC assay can be used for high-throughput screening, because it is robust, repeatable, and inexpensive. This assays helps to find gap junction modulating chemicals for drug discovery and toxicological assessment.

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Research

JoVE Journal

Biology

Titration of Human Coronaviruses Using an Immunoperoxidase Assay

Determination of infectious viral titers is a basic and essential experimental approach for virologists. Classical plaque assays cannot be used for viruses that do not cause significant cytopathic effects, which is the case for prototype strains 229E and OC43 of human coronavirus (HCoV). Therefore, an alternative indirect immunoperoxidase assay (IPA) was developed for the detection and titration of these viruses and is described herein. Susceptible cells are inoculated with serial logarithmic dilutions of virus-containing samples in a 96-well plate format. After viral growth, viral detection by IPA yields the infectious virus titer, expressed as 'Tissue Culture Infectious Dose 50 percent' (TCID50). This represents the dilution of a virus-containing sample at which half of a series of laboratory wells contain infectious replicating virus. This technique provides a reliable method for the titration of HCoV-229E and HCoV-OC43 in biological samples such as cells, tissues and fluids. This article is based on work first reported in Methods in Molecular Biology (2008) volume 454, pages 93-102.

In this video, we demonstrate an alternative method for detection and titering of viruses using an enzymatic antigen detection technique known as an immunoperoxidase assay. Here, we will show you how to collect your viral samples, prepare the cells for testing, and finally the immunoperoxidase assay using serial dilutions to determine the viral titer.

Determination of infectious viral titers is a basic and essential experimental approach for virologists. Classical plaque assays cannot be used for ...

Homemade Site Directed Mutagenesis of Whole Plasmids

Site directed mutagenesis of whole plasmids is a simple way to create slightly different variations of an original plasmid. With this method the cloned target gene can be altered by substitution, deletion or insertion of a few bases directly into a plasmid. It works by simply amplifying the whole plasmid, in a non PCR-based thermocycling reaction. During the reaction mutagenic primers, carrying the desired mutation, are integrated into the newly synthesized plasmid. In this video tutorial we demonstrate an easy and cost effective way to introduce base substitutions into a plasmid. The protocol works with standard reagents and is independent from commercial kits, which often are very expensive. Applying this protocol can reduce the total cost of a reaction to an eighth of what it costs using some of the commercial kits. In this video we also comment on critical steps during the process and give detailed instructions on how to design the mutagenic primers.

Site directed mutagenesis of whole plasmids is a simple way to create slightly different variations of an original plasmid. Here we demonstrate an easy and cost effective way to introduce base substitutions into a plasmid using standard reagents.

Site directed mutagenesis of whole plasmids is a simple way to create slightly different variations of an original plasmid. With this method the cloned ...

An In vitro FluoroBlok Tumor Invasion Assay

The hallmark of metastatic cells is their ability to invade through the basement membrane and migrate to other parts of the body. Cells must be able to both secrete proteases that break down the basement membrane as well as migrate in order to be invasive. BD BioCoat Tumor Invasion System provides cells with conditions that allow assessment of their invasive property in vitro1,2. It consists of a BD Falcon FluoroBlok 24-Multiwell Insert Plate with an 8.0 micron pore size PET membrane that has been uniformly coated with BD Matrigel Matrix. This uniform layer of BD Matrigel Matrix serves as a reconstituted basement membrane in vitro providing a true barrier to non-invasive cells while presenting an appropriate protein structure to study invasion. The coating process occludes the pores of the membrane, blocking non-invasive cells from migrating through the membrane. In contrast, invasive cells are able to detach themselves from and migrate through the coated membrane. Quantitation of cell invasion can be achieved by either pre- or post-cell invasion labeling with a fluorescent dye such as DiIC12(3) or calcein AM, respectively, and measuring the fluorescence of invading cells. Since the BD FluoroBlok membrane effectively blocks the passage of light from 490-700 nm at &gt;99% efficiency, fluorescently-labeled cells that have not invaded are not detected by a bottom-reading fluorescence plate reader. However, cells that have invaded to the underside of the membrane are no longer shielded from the light source and are detected with the respective plate reader. This video demonstrates an endpoint cell invasion assay, using calcein AM to detect invaded cells.

An In vitro FluoroBlok Tumor Invasion Assay

This video demonstrates how to measure cell invasion through cell culture inserts using a fluorescence-based methodology.

The hallmark of metastatic cells is their ability to invade through the basement membrane and migrate to other parts of the body. Cells must be able to ...

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 ...

Single-cell Microinjection for Cell Communication Analysis

Gap junctions are intercellular channels that allow the communication of neighboring cells. This communication depends on the contribution of a hemichannel by each neighboring cell to form the gap junction. In mammalian cells, the hemichannel is formed by six connexins, monomers with four transmembrane domains and a C and N terminal within the cytoplasm. Gap junctions permit the exchange of ions, second messengers, and small metabolites. In addition, they have important roles in many forms of cellular communication within physiological processes such as synaptic transmission, heart contraction, cell growth and differentiation. We detail how to perform a single-cell microinjection of Lucifer Yellow to visualize cellular communication via gap-junctions in living cells. It is expected that in functional gap junctions, the dye will diffuse from the loaded cell to the connected cells. It is a very useful technique to study gap junctions since you can evaluate the diffusion of the fluorescence in real time. We discuss how to prepare the cells and the micropipette, how to use a micromanipulator and inject a low molecular weight fluorescent dye in an epithelial cell line.

We describe here how to perform a single-cell microinjection of Lucifer Yellow to visualize cellular communication via gap-junctions in living cells, and provide some useful tips. We expect that this paper will help everyone to evaluate the degree of cellular coupling due to functional gap junctions. Everything described here could be, in principle, adapted to other fluorescent dyes with molecular weight below 1,000 Daltons.

Gap junctions are intercellular channels that allow the communication of neighboring cells. This communication depends on the contribution of a ...

An Assay for Lateral Line Regeneration in Adult Zebrafish

Due to the clinical importance of hearing and balance disorders in man, model organisms such as the zebrafish have been used to study lateral line development and regeneration. The zebrafish is particularly attractive for such studies because of its rapid development time and its high regenerative capacity. To date, zebrafish studies of lateral line regeneration have mainly utilized fish of the embryonic and larval stages because of the lower number of neuromasts at these stages. This has made quantitative analysis of lateral line regeneration/and or development easier in the earlier developmental stages. Because many zebrafish models of neurological and non-neurological diseases are studied in the adult fish and not in the embryo/larvae, we focused on developing a quantitative lateral line regenerative assay in adult zebrafish so that an assay was available that could be applied to current adult zebrafish disease models. Building on previous studies by Van Trump et al.17&#160;that described procedures for ablation of hair cells in adult Mexican blind cave fish and zebrafish (Danio rerio), our assay was designed to allow quantitative comparison between control and experimental groups. This was accomplished by developing a regenerative neuromast standard curve based on the percent of neuromast reappearance over a 24 hr time period following gentamicin-induced necrosis of hair cells in a defined region of the lateral line. The assay was also designed to allow extension of the analysis to the individual hair cell level when a higher level of resolution is required.

Because many zebrafish models of neurological and non-neurological diseases are studied in the adult fish rather than the embryo/larvae, we developed a quantitative lateral line regenerative assay that can be applied to adult zebrafish disease models. The assay involved resolution at the 1) neuromast and 2) individual hair cell levels.

Due to the clinical importance of hearing and balance disorders in man, model organisms such as the zebrafish have been used to study lateral line ...

Evaluation of Zebrafish Kidney Function Using a Fluorescent Clearance Assay

The zebrafish embryo offers a tractable model to study organogenesis and model human genetic disease. Despite its relative simplicity, the zebrafish kidney develops and functions in almost the same way as humans. A major difference in the construction of the human kidney is the presence of millions of nephrons compared to the zebrafish that has only two. However, simplifying such a complex system into basic functional units has aided our understanding of how the kidney develops and operates. In zebrafish, the midline located glomerulus is responsible for the initial blood filtration into two pronephric tubules that diverge to run bilaterally down the embryonic axis before fusing to each other at the cloaca. The pronephric tubules are heavily populated by motile cilia that facilitate the movement of filtrate along the segmented tubule, allowing the exchange of various solutes before finally exiting via the cloaca2-4. Many genes responsible for CKD, including those related to ciliogenesis, have been studied in zebrafish5. However, a major draw back has been the difficulty in evaluating zebrafish kidney function after genetic manipulation. Traditional assays to measure kidney dysfunction in humans have proved non translational to zebrafish, mainly due to their aquatic environment and small size. For example, it is not physically possible to extract blood from embryonic staged fish for analysis of urea and creatinine content, as they are too small. In addition, zebrafish do not produce enough urine for testing on a simple proteinuria &#8216;dipstick&#8217;, which is often performed during initial patient examinations. We describe a fluorescent assay that utilizes the optical transparency of the zebrafish to quantitatively monitor the clearance of a fluorescent dye, over time, from the vasculature and out through the kidney, to give a read out of renal function1,6-9.

The zebrafish is a popular tool to model chronic kidney disease (CKD). However, their small size makes it impossible to evaluate renal function using traditional methods. We describe a fluorescent dye kidney clearance assay1 that allows quantitative analysis of zebrafish kidney function in CKD.

The zebrafish embryo offers a tractable model to study organogenesis and model human genetic disease. Despite its relative simplicity, the zebrafish ...

Comet Assay as an Indirect Measure of Systemic Oxidative Stress

Higher eukaryotic organisms cannot live without oxygen; yet, paradoxically, oxygen can be harmful to them. The oxygen molecule is chemically relatively inert because it has two unpaired electrons located in different pi * anti-bonding orbitals. These two electrons have parallel spins, meaning they rotate in the same direction about their own axes. This is why the oxygen molecule is not very reactive. Activation of oxygen may occur by two different mechanisms; either through reduction via one electron at a time (monovalent reduction), or through the absorption of sufficient energy to reverse the spin of one of the unpaired electrons. This results in the production of reactive oxidative species (ROS). There are a number of ways in which the human body eliminates ROS in its physiological state. If ROS production exceeds the repair capacity, oxidative stress results and damages different molecules. There are many different methods by which oxidative stress can be measured. This manuscript focuses on one of the methods named cell gel electrophoresis, also known as &#8220;comet assay&#8221; which allows measurement of DNA breaks. If all factors known to cause DNA damage, other than oxidative stress are kept constant, the amount of DNA damage measured by comet assay is a good parameter of oxidative stress. The principle is simple and relies upon the fact that DNA molecules are negatively charged. An intact DNA molecule has such a large size that it does not migrate during electrophoresis. DNA breaks, however, if present result in smaller fragments which move in the electrical field towards the anode. Smaller fragments migrate faster. As the fragments have different sizes the final result of the electrophoresis is not a distinct line but rather a continuum with the shape of a comet. The system allows a quantification of the resulting &#8220;comet&#8221; and thus of the DNA breaks in the cell.

Comet assay measures DNA breaks, induced by different factors. If all factors (except oxidative stress) causing DNA damage are kept constant, the amount of DNA damage is a good indirect parameter of oxidative stress. The goal of this protocol is to use comet assay for indirect measurement of oxidative stress.

Higher eukaryotic organisms cannot live without oxygen; yet, paradoxically, oxygen can be harmful to them. The oxygen molecule is chemically relatively ...

Imaging Molecular Adhesion in Cell Rolling by Adhesion Footprint Assay

Rolling adhesion, facilitated by selectin-mediated interactions, is a highly dynamic, passive motility in recruiting leukocytes to the site of inflammation. This phenomenon occurs in postcapillary venules, where blood flow pushes leukocytes in a rolling motion on the endothelial cells. Stable rolling requires a delicate balance between adhesion bond formation and their mechanically-driven dissociation, allowing the cell to remain attached to the surface while rolling in the direction of flow. Unlike other adhesion processes occurring in relatively static environments, rolling adhesion is highly dynamic as the rolling cells travel over thousands of microns at tens of microns per second. Consequently, conventional mechanobiology methods such as traction force microscopy are unsuitable for measuring the individual adhesion events and the associated molecular forces due to the short timescale and high sensitivity required. Here, we describe our latest implementation of the adhesion footprint assay to image the P-selectin: PSGL-1 interactions in rolling adhesion at the molecular level. This method utilizes irreversible DNA-based tension gauge tethers to produce a permanent history of molecular adhesion events in the form of fluorescence tracks. These tracks can be imaged in two ways: (1) stitching together thousands of diffraction-limited images to produce a large field of view, enabling the extraction of adhesion footprint of each rolling cell over thousands of microns in length, (2) performing DNA-PAINT to reconstruct super-resolution images of the fluorescence tracks within a small field of view. In this study, the adhesion footprint assay was used to study HL-60 cells rolling at different shear stresses. In doing so, we were able to image the spatial distribution of the P-selectin: PSGL-1 interaction and gain insight into their molecular forces through fluorescence intensity. Thus, this method provides the groundwork for the quantitative investigation of the various cell-surface interactions involved in rolling adhesion at the molecular level.

This protocol presents the experimental procedures to perform the adhesion footprint assay to image the adhesion events during fast cell rolling adhesion.

Rolling adhesion, facilitated by selectin-mediated interactions, is a highly dynamic, passive motility in recruiting leukocytes to the site of ...

Isolation and Characterization of the Immune Cells from Micro-dissected Mouse Choroid Plexuses

The brain is no longer considered as an organ functioning in isolation; accumulating evidence suggests that changes in the peripheral immune system can indirectly shape brain function. At the interface between the brain and the systemic circulation, the choroid plexuses (CP), which constitute the blood-cerebrospinal fluid barrier, have been highlighted as a key site of periphery-to-brain communication. CP produce the cerebrospinal fluid, neurotrophic factors, and signaling molecules that can shape brain homeostasis. CP are also an active immunological niche. In contrast to the brain parenchyma, which is populated mainly by microglia under physiological conditions, the heterogeneity of CP immune cells recapitulates the diversity found in other peripheral organs. The CP immune cell diversity and activity change with aging, stress, and disease and modulate the activity of the CP epithelium, thereby indirectly shaping brain function. The goal of this protocol is to isolate murine CP and identify about 90% of the main immune subsets that populate them. This method is a tool to characterize CP immune cells and understand their function in orchestrating periphery-to-brain communication. The proposed protocol may help decipher how CP immune cells indirectly modulate brain function in health and across various disease conditions.

This study uses flow cytometry and two different gating strategies on isolated perfused mice brain choroid plexuses; this protocol identifies the main immune cell subsets that populate this brain structure.

The brain is no longer considered as an organ functioning in isolation; accumulating evidence suggests that changes in the peripheral immune system can ...