Name: study of endoplasmic reticulum and mitochondria interactions by in situ proximity ligation assay in fixed cells
Uploaded: 2016-12-10T14:00:00
Description: Watch this Scientific Journal Video about Study of Endoplasmic Reticulum and Mitochondria Interactions by In Situ Proximity Ligation Assay in Fixed Cells at JoVE.com

We thank all the people in our laboratory who contributed to optimize and validate the protocol. This work was supported by INSERM and the national research agency (ANR-09-JCJC-0116 AND ANR-11-BSV1-033-02). E.T. was supported during her PhD by a research fellowship from the French ministry of higher education and research.

1. Preparation of Solutions
<ol>
	<li>Prepare 10% formaldehyde in PBS (low salt) by diluting 5.5 ml of 37% formaldehyde in 14.5 ml of PBS. Prepare 1 M glycine, pH 8.0, by dissolving 3.8 g of glycine in 50 ml of PBS; dilute this solution to obtain 100 mM glycine in 1x PBS.</li>
	<li>Prepare 0.1% Triton-X100 in 1x PBS. Prepare 20x Saline Sodium Citrate (SSC) by using 3.0 M sodium chloride and 0.30 M trisodium citrate prepared in a deionized water buffer with pH 7.0 at 25 &#176;C. Dilute this buffer to 1x and 0.01x using ...

<ol>
	<li>Bravo-Sagua, 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=Organelle+communication:+signaling+crossroads+between+homeostasis+and+disease.">Organelle communication: signaling crossroads between homeostasis and disease.</a> The international journal of biochemistry &amp; cell biology. 50, 55-59 (2014).</li><li>Giorgi, 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=Mitochondria-associated+membranes:+composition,+molecular+mechanisms,+and+physiopathological+implications.">Mitochondria-associated membranes: composition, molecular mechanisms, and physiopathological implications.</a> Antioxidants &amp; redox signaling. 22, 995-1019 (2015).</li><li>Phillips, M. J., Voeltz, G. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Structure+and+function+of+ER+membrane+contact+sites+with+other+organelles.">Structure and function of ER membrane contact sites with other organelles.</a> Nature reviews. Molecular cell biology. 17, 69-82 (2016).</li><li>Cosson, P., 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+RTM+resistance+to+potyviruses+in+Arabidopsis+thaliana:+natural+variation+of+the+RTM+genes+and+evidence+for+the+implication+of+additional+genes.">The RTM resistance to potyviruses in Arabidopsis thaliana: natural variation of the RTM genes and evidence for the implication of additional genes.</a> PLoS One. 7, 39169 (2012).</li><li>Mannella, C. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Structure+and+dynamics+of+the+mitochondrial+inner+membrane+cristae.">Structure and dynamics of the mitochondrial inner membrane cristae.</a> Biochim Biophys Acta. 1763, 542-548 (2006).</li><li>Csordas, 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=Structural+and+functional+features+and+significance+of+the+physical+linkage+between+ER+and+mitochondria.">Structural and functional features and significance of the physical linkage between ER and mitochondria.</a> The Journal of cell biology. 174, 915-921 (2006).</li><li>Mannella, C. A., Buttle, K., Rath, B. K., Marko, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electron+microscopic+tomography+of+rat-liver+mitochondria+and+their+interaction+with+the+endoplasmic+reticulum.">Electron microscopic tomography of rat-liver mitochondria and their interaction with the endoplasmic reticulum.</a> Biofactors. 8, 225-228 (1998).</li><li>Rizzuto, 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=Close+contacts+with+the+endoplasmic+reticulum+as+determinants+of+mitochondrial+Ca2++responses.">Close contacts with the endoplasmic reticulum as determinants of mitochondrial Ca2+ responses.</a> Science. 280, 1763-1766 (1998).</li><li>Wieckowski, M. R., Giorgi, C., Lebiedzinska, M., Duszynski, J., Pinton, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Isolation+of+mitochondria-associated+membranes+and+mitochondria+from+animal+tissues+and+cells.">Isolation of mitochondria-associated membranes and mitochondria from animal tissues and cells.</a> Nat Protoc. 4, 1582-1590 (2009).</li><li>Csordas, 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=Imaging+interorganelle+contacts+and+local+calcium+dynamics+at+the+ER-mitochondrial+interface.">Imaging interorganelle contacts and local calcium dynamics at the ER-mitochondrial interface.</a> Mol Cell. 39, 121-132 (2010).</li><li>Szabadkai, 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=Chaperone-mediated+coupling+of+endoplasmic+reticulum+and+mitochondrial+Ca2++channels.">Chaperone-mediated coupling of endoplasmic reticulum and mitochondrial Ca2+ channels.</a> J Cell Biol. 175, 901-911 (2006).</li><li>Tubbs, E., 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=Mitochondria-associated+endoplasmic+reticulum+membrane+(MAM)+integrity+is+required+for+insulin+signaling+and+is+implicated+in+hepatic+insulin+resistance.">Mitochondria-associated endoplasmic reticulum membrane (MAM) integrity is required for insulin signaling and is implicated in hepatic insulin resistance.</a> Diabetes. 63, 3279-3294 (2014).</li><li>Paillard, 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=Depressing+Mitochondria-Reticulum+Interactions+Protects+Cardiomyocytes+From+Lethal+Hypoxia-Reoxygenation+Injury.">Depressing Mitochondria-Reticulum Interactions Protects Cardiomyocytes From Lethal Hypoxia-Reoxygenation Injury.</a> Circulation. 128, 1555-1565 (2013).</li><li>Rieusset, 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=Disruption+of+calcium+transfer+from+ER+to+mitochondria+links+alterations+of+mitochondria-associated+ER+membrane+integrity+to+hepatic+insulin+resistance.">Disruption of calcium transfer from ER to mitochondria links alterations of mitochondria-associated ER membrane integrity to hepatic insulin resistance.</a> Diabetologia. 59, 614-623 (2016).</li><li>Allalou, A., Wahlby, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=BlobFinder,+a+tool+for+fluorescence+microscopy+image+cytometry.">BlobFinder, a tool for fluorescence microscopy image cytometry.</a> Computer methods and programs in biomedicine. 94, 58-65 (2009).</li><li>Theurey, P., 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=Mitochondria-associated+endoplasmic+reticulum+membranes+allow+adaptation+of+mitochondrial+metabolism+to+glucose+availability+in+the+liver.">Mitochondria-associated endoplasmic reticulum membranes allow adaptation of mitochondrial metabolism to glucose availability in the liver.</a> Journal of molecular cell biology. , (2016).</li><li>de Brito, O. M., Scorrano, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mitofusin+2+tethers+endoplasmic+reticulum+to+mitochondria.">Mitofusin 2 tethers endoplasmic reticulum to mitochondria.</a> Nature. 456, 605-610 (2008).</li><li>Soderberg, O., 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=Direct+observation+of+individual+endogenous+protein+complexes+in+situ+by+proximity+ligation.">Direct observation of individual endogenous protein complexes in situ by proximity ligation.</a> Nature methods. 3, 995-1000 (2006).</li><li>De Pinto, V., Messina, A., Lane, D. J., Lawen, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Voltage-dependent+anion-selective+channel+(VDAC)+in+the+plasma+membrane.">Voltage-dependent anion-selective channel (VDAC) in the plasma membrane.</a> FEBS letters. 584, 1793-1799 (2010).</li><li>Kaul, S. C., Taira, K., Pereira-Smith, O. M., Wadhwa, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mortalin:+present+and+prospective.">Mortalin: present and prospective.</a> Experimental gerontology. 37, 1157-1164 (2002).</li></ol>

Collectively, our studies indicate that the in situ proximity ligation assay is truly a relevant strategy to follow and quantify endogenous ER-mitochondria interactions in fixed cells, without the need for using organelle-specific fluorophores or fluorescent proteins. The specific use of VDAC1/IP3R1 antibodies has been adapted to study ER-mitochondria interactions in HuH7 cells. However, alternative isoforms of VDAC and IP3R may be used, depending on the cell type. In this case, antibodies need to be validated b...

Mitochondria and endoplasmic reticulum (ER) are not independent organelles in the cell, but they interact structurally and functionally at contact sites defined as mitochondria-associated endoplasmic reticulum membranes (MAM). In fact, MAMs correspond to regions where the membranes of the ER and mitochondria are closely apposed, allowing interactions between proteins from both sides. Nonetheless, the membranes of these organelles do not fuse within these regions, so they maintain their separate entities. The MAMs play a crucial role in calcium (Ca2+) and phospholipid transfer from ER to mitochondria, impacting energy metabolism and cell survival1-3.
The association between the ER and mitochondria was first visualized in the 1970s with electron microscopy. Since then, transmission electron microscopy4,5, electron tomography6,7 or immuno-localization of ER and mitochondria-specific fluorophores/fluorescent proteins8 were classically used to study ER-mitochondria interactions. Another useful tool for the analysis of MAM is based on the use of subcellular fractionation. It allows the isolation of MAM fractions by differential ultracentrifugation coupled to a Percoll gradient9. However, the final product contains enriched MAM fractions, rather than pure fractions. Altogether, these strategies are not particularly sensitive and/or quantitative, and they are not easily amenable to large screening. Alternatively, genetic approaches using drug-inducible fluorescent inter-organelle linkers have emerged, but they do not allow the analysis of organelle interactions at the endogenous expression levels of proteins10.
Based on Szabadkai&#39;s discovery of the IP3R/GRP75/VDAC complex at the MAM11, we developed a quantitative method to analyze ER-mitochondria interactions. We used the in situ proximity ligation assay to detect and quantify interactions between VDAC1 and IP3R1, two organelle-surface proteins involved in the Ca2+-channeling complex at the MAM interface in fixed cells12. Briefly, we probed VDAC1 at the outer mitochondrial membrane (mouse anti-VDAC1 primary antibody) and IP3R1 at the ER membrane (rabbit anti-IP3R1 primary antibody) (Figure 1, panel a). Then, according to the assay, we added both anti-mouse and anti-rabbit IgG (mouse and rabbit proximity ligation assay probes), which are conjugated to complementary oligonucleotide extensions. If the two targeted proteins are at a distance below 40 nm, the oligonucleotides can hybridize with the subsequently added connector oligos to allow the formation of a circular DNA template (Figure 1, panel b). This circular DNA molecule is ligated and amplified, creating a single-stranded DNA product covalently attached to one of the proximity probes (Figure 1, panel c). Since the distance between the ER and mitochondria at the MAM interface ranges from 10 nm to 25 nm6, proximity ligation and amplification can be done, leading to subsequent detection due to the hybridization of Texas red-labeled oligonucleotides probes (Figure 1, panel d). Each fluorescent dot represents interactions between VDAC1/IP3R1, thus allowing the quantification of in situ ER-mitochondria interactions in individual cells.
<img alt="Figure 1" src="/files/ftp_upload/54899/54899fig1.jpg" /> 
Figure 1: Schematic Illustration of the Detection of the Endoplasmic Reticulum-mitochondria Interactions by In Situ Proximity Ligation Assay. a) A mouse primary antibody directed against VDAC1 and a rabbit primary antibody directed against IP3R1 can bind to their epitopes in proximity at the MAM interface, b) The addition of a pair of proximity ligation probes directed against mouse and rabbit IgG. These probes have attached DNA strands that can form templates for the ligation of connector oligos. c) The circular DNA strand formed after ligation can be amplified and d) visualized by microscopy as a fluorescent dot by using Texas red-labeled oligonucleotides. <a href="http://cloudflare.jove.com/files/ftp_upload/54899/54899fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
Similar in situ proximity ligation assay experiments can be performed with the GRP75/IP3R1 pair of antibodies, as well as cyclophilin D (CypD)/IP3R1 antibodies, considering that CypD was shown to interact with the IP3R/GRP75/VDAC complex at the MAM interface12-14.

<table border="0" cellpadding="0" cellspacing="0" width="919">
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		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Formaldehyde</td>
			<td style="width:169px;">Sigma</td>
			<td style="width:187px;">F-8775</td>
			<td style="width:320px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Glycine</td>
			<td style="width:169px;">Sigma</td>
			<td style="width:187px;">G-8898</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Triton</td>
			<td style="width:169px;">Sigma</td>
			<td style="width:187px;">T8532</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">35mm Glass bottom culture dishes</td>
			<td style="width:169px;">MatTeK corporation</td>
			<td style="width:187px;">P35G-0-14-C</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Blocking solution</td>
			<td style="width:169px;">Sigma</td>
			<td style="width:187px;">DUO-92004 or DUO-92002</td>
			<td>provided in the Duolink PLA probes, Sigma</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">VDAC1 antibody</td>
			<td style="width:169px;">Abcam</td>
			<td style="width:187px;">ab14734</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">IP3R1-H80 antibody</td>
			<td style="width:169px;">Santa Cruz</td>
			<td style="width:187px;">sc28614</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">CypD antibody</td>
			<td style="width:169px;">Abcam</td>
			<td style="width:187px;">ab110324</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Grp75 antibody</td>
			<td style="width:169px;">Santa Cruz</td>
			<td style="width:187px;">sc13967</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">TBS 10X</td>
			<td style="width:169px;">euromedex</td>
			<td style="width:187px;">ET220</td>
			<td>Dilute to obtain 1X</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Tween 100X</td>
			<td style="width:169px;">euromedex</td>
			<td style="width:187px;">2001-B</td>
			<td>dilute in TBS to obtain 0,01%</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">PLA Probes Mouse MINUS</td>
			<td style="width:169px;">Sigma</td>
			<td style="width:187px;">DUO-92004</td>
			<td>Duolink, Sigma</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">PLA Probes Rabbit PLUS</td>
			<td style="width:169px;">Sigma</td>
			<td style="width:187px;">DUO-92002</td>
			<td>Duolink, Sigma</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Duolink detection reagents red</td>
			<td style="width:169px;">Sigma</td>
			<td style="width:187px;">DUO-92008</td>
			<td>Duolink, Sigma</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Ligation solution</td>
			<td style="width:169px;">Sigma</td>
			<td style="width:187px;">DUO-92008</td>
			<td>Part of the Duolink detection reagents red, Sigma</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Ligase</td>
			<td style="width:169px;">Sigma</td>
			<td style="width:187px;">DUO-92008</td>
			<td>Part of the Duolink detection reagents red, Sigma</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Amplification solution</td>
			<td style="width:169px;">Sigma</td>
			<td style="width:187px;">DUO-92008</td>
			<td>Part of the Duolink detection reagents red, Sigma</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Polymerase</td>
			<td style="width:169px;">Sigma</td>
			<td style="width:187px;">DUO-92008</td>
			<td>Part of the Duolink detection reagents red, Sigma</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Duolink Mounting Medium</td>
			<td style="width:169px;">Sigma</td>
			<td style="width:187px;">DUO80102</td>
			<td>Duolink, Sigma</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Softwares:</td>
			<td style="width:169px;"></td>
			<td style="width:187px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Blob-finder software</td>
			<td style="width:169px;"></td>
			<td style="width:187px;"></td>
			<td>BlobFinder is a freely distributed software that can perform calculations on cells from fluorescence microscopy images. This software can be downloaded for free from The Centre for Image Analysis&#160;at Uppsala University who have developed the software and the work was supported by the EU FP6 Project&#160;ENLIGHT&#160;and&#160;&#160;Olink Bioscience. http://www.cb.uu.se/~amin/BlobFinder/index_files/Page430.htm</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">ImageJ software</td>
			<td style="width:169px;"></td>
			<td style="width:187px;"></td>
			<td>Can be downloaded for free from: http://rsb.info.nih.gov/ij/download.html</td>
		</tr>
	</tbody>
</table>

study of endoplasmic reticulum and mitochondria interactions by in situ proximity ligation assay in fixed cells

Structural interactions between the endoplasmic reticular (ER) and mitochondrial membranes, in domains known as mitochondria-associated membranes (MAM), are crucial hubs for cellular signaling and cell fate. Particularly, these inter-organelle contact sites allow the transfer of calcium from the ER to mitochondria through the voltage-dependent anion channel (VDAC)/glucose-regulated protein 75 (GRP75)/inositol 1,4,5-triphosphate receptor (IP3R) calcium channeling complex. While this subcellular compartment is under intense investigation in both physiological and pathological conditions, no simple and sensitive method exists to quantify the endogenous amount of ER-mitochondria contact in cells. Similarly, MAMs are highly dynamic structures, and there is no suitable approach to follow modifications of ER-mitochondria interactions without protein overexpression. Here, we report an optimized protocol based on the use of an in situ proximity ligation assay to visualize and quantify endogenous ER-mitochondria interactions in fixed cells by using the close proximity between proteins of the outer mitochondrial membrane (VDAC1) and of the ER membrane (IP3R1) at the MAM interface. Similar in situ proximity ligation experiments can also be performed with the GRP75/IP3R1 and cyclophilin D/IP3R1 pairs of antibodies. This assay provides several advantages over other imaging procedures, as it is highly specific, sensitive, and suitable to multiple-condition testing. Therefore, the use of this in situ proximity ligation assay should be helpful to better understand the physiological regulations of ER-mitochondria interactions, as well as their role in pathological contexts.

Based on our experience using this protocol, we can safely recommend this method for the visualization and quantification of ER-mitochondria interactions in fixed cells. Representative images of in situ proximity ligation assay-visualized ER-mitochondria interactions in the HuH7 hepatocarcinoma cell line, using several pairs of antibodies, are shown. As shown in Figure 2 by fluorescent microscopy, each red dot represents an interaction between the two targeted pr...

Watch this Scientific Journal Video about Study of Endoplasmic Reticulum and Mitochondria Interactions by In Situ Proximity Ligation Assay in Fixed Cells at JoVE.com

Study of Endoplasmic Reticulum and Mitochondria Interactions by In Situ Proximity Ligation Assay in Fixed Cells

Here, we describe a procedure to visualize and quantify with high sensitivity the endogenous interactions between the endoplasmic reticulum and mitochondria in fixed cells. The protocol features an optimized in situ proximity ligation assay targeting the inositol 1,4,5-triphosphate receptor/glucose-regulated protein 75/voltage-dependent anion channel/cyclophilin D complex at the mitochondria-associated membrane interface.

Study of Endoplasmic Reticulum and Mitochondria Interactions by In Situ Proximity Ligation Assay in Fixed Cells

Structural interactions between the endoplasmic reticular (ER) and mitochondrial membranes, in domains known as mitochondria-associated membranes (MAM), ...

The overall goal of this experiment is to visualize and quantify endoplasmic reticulum mitochondria interactions using an in situ proximity ligation assay in fixed cells.This method can help to answer key questions in the biomedical field to better analyze ER mitochondria interactions in fixed cells using a simple immunofluorescence technique.Hopefully suggesting new treatment strategies.The main advantage of this technique is that we can visualize and quantify ER mitochondria interactions in fixed cells and this technique can be applied to paraffin embedded tissue biopsies of patients.Using the in situ proximity ligation assay demonstrated in this video, a mouse primary antibody directed against VDAC1 at the outer mitochondrial membrane and a rabbit primary antibody directed against IP3R1 at the endoplasmic reticulum membrane combine to their epitopes in proximity at the mitochondrial associated membrane interface.Proximity ligation probes that have DNA end tails attached and that are directed against mouse and rabbit IgG are added and can form templates for the ligation of connector oligos and can be amplified and visualized using Texas Red Oligonucleotides.This can occur only if the two targeted proteins are at a distance below 40 nanometers.In agreement with the distance between both organelle membranes, at mitochondrial associated membrane interface.To fix and block cells for the in situ proximity ligation assay, plate human H7 cells at 150, 000 cells per uncoded 35 mm glass bottom dish.The next day, remove the culture medium and use 1 mL of PBS to wash the cells.Then, aspirate the buffer and add 1 mL of ten percent formaldehyde.Incubate the plates at room temperature with agitation for 10 minutes to fix the cells.To stop the reaction, add 1 mL of 1 M glycine and mix the plates by rotation.Remove the glycine solution and add 1 mL of 1XPBS.Then, briefly agitate the plates and aspirate the buffer.Next, add 1 mL of 100 mM glycine to the cells.Incubate the plates at room temperature with agitation for 15 minutes.After aspirating the solution, permeabilize the cells by adding 1 mL of 0.1%triton-X100 in PBS.And repeat the incubation.Aspirate the detergent and add 1 mL of PBS to wash the cells.After removing the buffer, add 40 microliters of blocking solution to each dish of cells and incubate the samples in a humid chamber at 37 degrees celsius for 30 minutes.Then tap the blocking solution off the dishes, trying to obtain equal residual volumes of buffer for each slide while not allowing the slides to dry.To carry out the proximity ligation assay, use PBS to dilute the primary antibodies.Vortex and add the solution to the dishes.Incubate the samples at 4

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Research

JoVE Journal

Biology

Clonogenic Assay: Adherent Cells

The clonogenic (or colony forming) assay has been established for more than 50 years; the original paper describing the technique was published in 19561. Apart from documenting the method, the initial landmark study generated the first radiation-dose response curve for X-ray irradiated mammalian (HeLa) cells in culture1. Basically, the clonogenic assay enables an assessment of the differences in reproductive viability (capacity of cells to produce progeny; i.e. a single cell to form a colony of 50 or more cells) between control untreated cells and cells that have undergone various treatments such as exposure to ionising radiation, various chemical compounds (e.g. cytotoxic agents) or in other cases genetic manipulation. The assay has become the most widely accepted technique in radiation biology and has been widely used for evaluating the radiation sensitivity of different cell lines. Further, the clonogenic assay is commonly used for monitoring the efficacy of radiation modifying compounds and for determining the effects of cytotoxic agents and other anti-cancer therapeutics on colony forming ability, in different cell lines. A typical clonogenic survival experiment using adherent cells lines involves three distinct components, 1) treatment of the cell monolayer in tissue culture flasks, 2) preparation of single cell suspensions and plating an appropriate number of cells in petri dishes and 3) fixing and staining colonies following a relevant incubation period, which could range from 1-3 weeks, depending on the cell line. Here we demonstrate the general procedure for performing the clonogenic assay with adherent cell lines with the use of an immortalized human keratinocyte cell line (FEP-1811)2. Also, our aims are to describe common features of clonogenic assays including calculation of the plating efficiency and survival fractions after exposure of cells to radiation, and to exemplify modification of radiation-response with the use of a natural antioxidant formulation.

The applicability of the clonogenic assay for evaluating reproductive viability has been established for more than 50 years. Here we demonstrate the general procedure for performing the clonogenic assay with adherent cells.

The clonogenic (or colony forming) assay has been established for more than 50 years; the original paper describing the technique was published in 19561. ...

Detection of Signaling Effector-Complexes Downstream of BMP4 Using in situ PLA, a Proximity Ligation Assay

BMPs are responsible for a wide range of developmental and biological effects. BMP receptors activate (phosphorylate) the Smad1/5/8 effectors, which then, form a complex with Smad4 and translocate to the nucleus where they function as transcription factors to initiate BMP specific downstream effects 1. Traditional immuno-fluorescence techniques with antibodies against phospho-Smad peptides exhibit low sensitivity, high background and offer gross quantification as they rely on intensity of the antibody signal particularly if this is photosensitive fluorescent. In addition, phospho-Smads may not all be in complex with Smad4 and engaged in active transcription.
In situ PLA is a technology capable of detecting protein interactions with high specificity and sensitivity 2-4. This new technology couples antibody recognition with the amplification of DNA surrogate of the protein. It generates a localized, discrete signal in a form of spots revealing the exact position of the recognition event. The number of signals can be counted and compared providing a measurement. We applied in situ PLA, using the Duolink kit, with a combination of antibodies that allows the detection of the BMP signaling effectors phospho-Smad1/5/8 and Smad4 only when these are in proximity i.e. in a complex, which occurs only with signaling activation. This allowed for the first time, the visualization and measurement of endogenous BMP signaling with high specificity and sensitivity in a time course experiment under BMP4 stimulation.

Detection of Signaling Effector-Complexes Downstream of BMP4 Using in situ PLA, a Proximity Ligation Assay

Here we show how to use Proximity Ligation Assay (PLA), with a combination of antibodies to visualize Bone Morphogenetic Protein (BMP) signaling in fixed cells. This technique allowed us to follow the nuclear accumulation of endogenous BMP activated effector-complexes and quantify their levels over time under BMP4 stimulation.

BMPs are responsible for a wide range of developmental and biological effects. BMP receptors activate (phosphorylate) the Smad1/5/8 effectors, which then, ...

Do-It-Yourself Device for Recovery of Cryopreserved Samples Accidentally Dropped into Cryogenic Storage Tanks

Liquid nitrogen is colorless, odorless, extremely cold (-196 &deg;C) liquid kept under pressure. It is commonly used as a cryogenic fluid for long term storage of biological materials such as blood, cells and tissues 1,2. The cryogenic nature of liquid nitrogen, while ideal for sample preservation, can cause rapid freezing of live tissues on contact - known as 'cryogenic burn'2, which may lead to severe frostbite in persons closely involved in storage and retrieval of samples from Dewars. Additionally, as liquid nitrogen evaporates it reduces the oxygen concentration in the air and might cause asphyxia, especially in confined spaces2.
In laboratories, biological samples are often stored in cryovials or cryoboxes stacked in stainless steel racks within the Dewar tanks1. These storage racks are provided with a long shaft to prevent boxes from slipping out from the racks and into the bottom of Dewars during routine handling. All too often, however, boxes or vials with precious samples slip out and sink to the bottom of liquid nitrogen filled tank. In such cases, samples could be tediously retrieved after transferring the liquid nitrogen into a spare container or discarding it. The boxes and vials can then be relatively safely recovered from emptied Dewar. However, the cryogenic nature of liquid nitrogen and its expansion rate makes sunken sample retrieval hazardous. It is commonly recommended by Safety Offices that sample retrieval be never carried out by a single person. Another alternative is to use commercially available cool grabbers or tongs to pull out the vials3. However, limited visibility within the dark liquid filled Dewars poses a major limitation in their use.
In this article, we describe the construction of a Cryotolerant DIY retrieval device, which makes sample retrieval from Dewar containing cryogenic fluids both safe and easy.

Here we present a low cost, durable cryotolerant device for sample retrieval from Dewar tanks filled with liquid nitrogen. The ease of construction and modular design of the device makes the process of sample retrieval from cryogenic tanks safe and easy.

Liquid nitrogen is colorless, odorless, extremely cold (-196 &deg;C) liquid kept under pressure. It is commonly used as a cryogenic fluid for long term ...

Visualization of Endoplasmic Reticulum Localized mRNAs in Mammalian Cells

In eukaryotes, most of the messenger RNAs (mRNAs) that encode secreted and membrane proteins are localized to the surface of the endoplasmic reticulum (ER). However, the visualization of these mRNAs can be challenging. This is especially true when only a fraction of the mRNA is ER-associated and their distribution to this organelle is obstructed by non-targeted (i.e. "free") transcripts. In order to monitor ER-associated mRNAs, we have developed a method in which cells are treated with a short exposure to a digitonin extraction solution that selectively permeabilizes the plasma membrane, and thus removes the cytoplasmic contents, while simultaneously maintaining the integrity of the ER. When this method is coupled with fluorescent in situ hybridization (FISH), one can clearly visualize ER-bound mRNAs by fluorescent microscopy. Using this protocol the degree of ER-association for either bulk poly(A) transcripts or specific mRNAs can be assessed and even quantified. In the process, one can use this assay to investigate the nature of mRNA-ER interactions.

Here we describe a method to visualize endoplasmic reticulum-associated mRNAs in mammalian tissue culture cells. This technique involves the selective permeabilization of the plasma membrane with digitonin to remove cytoplasmic contents followed by fluorescent in situ hybridization to detect either bulk poly(A) mRNA or specific transcripts.

In eukaryotes, most of the messenger RNAs (mRNAs) that encode secreted and membrane proteins are localized to the surface of the endoplasmic reticulum ...

A Quantitative Assay to Study Protein:DNA Interactions, Discover Transcriptional Regulators of Gene Expression, and Identify Novel Anti-tumor Agents

Many DNA-binding assays such as electrophoretic mobility shift assays (EMSA), chemiluminescent assays, chromatin immunoprecipitation (ChIP)-based assays, and multiwell-based assays are used to measure transcription factor activity. However, these assays are nonquantitative, lack specificity, may involve the use of radiolabeled oligonucleotides, and may not be adaptable for the screening of inhibitors of DNA binding. On the other hand, using a quantitative DNA-binding enzyme-linked immunosorbent assay (D-ELISA) assay, we demonstrate nuclear protein interactions with DNA using the RUNX2 transcription factor that depend on specific association with consensus DNA-binding sequences present on biotin-labeled oligonucleotides. Preparation of cells, extraction of nuclear protein, and design of double stranded oligonucleotides are described. Avidin-coated 96-well plates are fixed with alkaline buffer and incubated with nuclear proteins in nucleotide blocking buffer. Following extensive washing of the plates, specific primary antibody and secondary antibody incubations are followed by the addition of horseradish peroxidase substrate and development of the colorimetric reaction. Stop reaction mode or continuous kinetic monitoring were used to quantitatively measure protein interaction with DNA. We discuss appropriate specificity controls, including treatment with non-specific IgG or without protein or primary antibody. Applications of the assay are described including its utility in drug screening and representative positive and negative results are discussed.

We developed a quantitative DNA-binding, ELISA-based assay to measure transcription factor interactions with DNA. High specificity for the RUNX2 protein was achieved with a consensus DNA-recognition oligonucleotide and specific monoclonal antibody. Colorimetric detection with an enzyme-coupled antibody substrate reaction was monitored in real time.

Many DNA-binding assays such as electrophoretic mobility shift assays (EMSA), chemiluminescent assays, chromatin immunoprecipitation (ChIP)-based assays, ...

MicroRNA In situ Hybridization for Formalin Fixed Kidney Tissues

In this article we describe a method for colorimetric detection of miRNA in the kidney through in situ hybridization with digoxigenin tagged microRNA probes. This protocol, originally developed by Kloosterman and colleagues for broad use with Exiqon miRNA probes1, has been modified to overcome challenges inherent in miRNA analysis in kidney tissues. These include issues such as structure identification and hard to remove residual probe and antibody. Use of relatively thin, 5 mm thick, tissue sections allowed for clear visualization of kidney structures, while a strong probe signal was retained in cells. Additionally, probe concentration and incubation conditions were optimized to facilitate visualization of microRNA expression with low background and nonspecific signal. Here, the optimized protocol is described, covering the initial tissue collection and preparation through the mounting of slides at the end of the procedure. The basic components of this protocol can be altered for application to other tissues and cell culture models.

MicroRNA In situ Hybridization for Formalin Fixed Kidney Tissues

This article describes an in situ hybridization protocol optimized for colormetric detection of microRNA expression in formalin fixed kidney sections.

In this article we describe a method for colorimetric detection of miRNA in the kidney through in situ hybridization with digoxigenin tagged microRNA ...

Confocal Imaging of Single Mitochondrial Superoxide Flashes in Intact Heart or In Vivo

Mitochondrion is a critical intracellular organelle responsible for energy production and intracellular signaling in eukaryotic systems. Mitochondrial dysfunction often accompanies and contributes to human disease. Majority of the approaches that have been developed to evaluate mitochondrial function and dysfunction are based on in vitro or ex vivo measurements. Results from these experiments have limited ability in determining mitochondrial function in vivo. Here, we describe a novel approach that utilizes confocal scanning microscopy for the imaging of intact tissues in live aminals, which allows the evaluation of single mitochondrial function in a real-time manner in vivo. First, we generate transgenic mice expressing the mitochondrial targeted superoxide indicator, circularly permuted yellow fluorescent protein (mt-cpYFP). Anesthetized mt-cpYFP mouse is fixed on a custom-made stage adaptor and time-lapse images are taken from the exposed skeletal muscles of the hindlimb. The mouse is subsequently sacrificed and the heart is set up for Langendorff perfusion with physiological solutions at 37 &deg;C. The perfused heart is positioned in a special chamber on the confocal microscope stage and gentle pressure is applied to immobilize the heart and suppress heart beat induced motion artifact. Superoxide flashes are detected by real-time 2D confocal imaging at a frequency of one frame per second. The perfusion solution can be modified to contain different respiration substrates or other fluorescent indicators. The perfusion can also be adjusted to produce disease models such as ischemia and reperfusion. This technique is a unique approach for determining the function of single mitochondrion in intact tissues and in vivo.

Confocal Imaging of Single Mitochondrial Superoxide Flashes in Intact Heart or In Vivo

Confocal scanning microscopy is applied for imaging single mitochondrial events in perfused heart or skeletal muscles in live animal. Real-time monitoring of single mitochondrial processes such as superoxide flashes and membrane potential fluctuations enables the evaluation of mitochondrial function in a physiologically relevant context and during pathological perturbations.

Mitochondrion is a critical intracellular organelle responsible for energy production and intracellular signaling in eukaryotic systems. Mitochondrial ...

Visualization of Endoplasmic Reticulum Subdomains in Cultured Cells

The lipids and proteins in eukaryotic cells are continuously exchanged between cell compartments, although these retain their distinctive composition and functions despite the intense interorganelle molecular traffic. The techniques described in this paper are powerful means of studying protein and lipid mobility and trafficking in vivo and in their physiological environment. Fluorescence recovery after photobleaching (FRAP) and fluorescence loss in photobleaching (FLIP) are widely used live-cell imaging techniques for studying intracellular trafficking through the exo-endocytic pathway, the continuity between organelles or subcompartments, the formation of protein complexes, and protein localization in lipid microdomains, all of which can be observed under physiological and pathological conditions. The limitations of these approaches are mainly due to the use of fluorescent fusion proteins, and their potential drawbacks include artifactual over-expression in cells and the possibility of differences in the folding and localization of tagged and native proteins. Finally, as the limit of resolution of optical microscopy (about 200 nm) does not allow investigation of the fine structure of the ER or the specific subcompartments that can originate in cells under stress (i.e. hypoxia, drug administration, the over-expression of transmembrane ER resident proteins) or under pathological conditions, we combine live-cell imaging of cultured transfected cells with ultrastructural analyses based on transmission electron microscopy.

We describe the imaging approaches we use to investigate the distribution and mobility of the transfected fluorescent proteins resident in the endoplasmic reticulum (ER) by means of the confocal imaging of living cells. We also ultrastructurally analyze the effect of their expression on the architecture of this subcellular compartment.

The lipids and proteins in eukaryotic cells are continuously exchanged between cell compartments, although these retain their distinctive composition and ...

Profiling Individual Human Embryonic Stem Cells by Quantitative RT-PCR

Heterogeneity of stem cell population hampers detailed understanding of stem cell biology, such as their differentiation propensity toward different lineages. A single cell transcriptome assay can be a new approach for dissecting individual variation. We have developed the single cell qRT-PCR method, and confirmed that this method works well in several gene expression profiles. In single cell level, each human embryonic stem cell, sorted by OCT4::EGFP positive cells, has high expression in OCT4, but a different level of NANOG expression. Our single cell gene expression assay should be useful to interrogate population heterogeneities.

Single cell gene expression assay is needed for understanding stem cell heterogeneities.

Heterogeneity of stem cell population hampers detailed understanding of stem cell biology, such as their differentiation propensity toward different ...

In Vivo 4-Dimensional Tracking of Hematopoietic Stem and Progenitor Cells in Adult Mouse Calvarial Bone Marrow

Through a delicate balance between quiescence and proliferation, self renewal and production of differentiated progeny, hematopoietic stem cells (HSCs) maintain the turnover of all mature blood cell lineages. The coordination of the complex signals leading to specific HSC fates relies upon the interaction between HSCs and the intricate bone marrow microenvironment, which is still poorly understood[1-2].
We describe how by combining a newly developed specimen holder for stable animal positioning with multi-step confocal and two-photon in vivo imaging techniques, it is possible to obtain high-resolution 3D stacks containing HSPCs and their surrounding niches and to monitor them over time through multi-point time-lapse imaging. High definition imaging allows detecting ex vivo labeled hematopoietic stem and progenitor cells (HSPCs) residing within the bone marrow. Moreover, multi-point time-lapse 3D imaging, obtained with faster acquisition settings, provides accurate information about HSPC movement and the reciprocal interactions between HSPCs and stroma cells.
Tracking of HSPCs in relation to GFP positive osteoblastic cells is shown as an exemplary application of this method. This technique can be utilized to track any appropriately labeled hematopoietic or stromal cell of interest within the mouse calvarium bone marrow space.

In Vivo 4-Dimensional Tracking of Hematopoietic Stem and Progenitor Cells in Adult Mouse Calvarial Bone Marrow

The nature of the interactions between hematopoietic stem and progenitor cells (HSPCs) and bone marrow niches is poorly understood. Custom hardware modifications and a multi-step acquisition protocol allow the use of two-photon and confocal microscopy to image ex vivo labeled HSPCs homed within bone marrow areas, tracking interactions and movement.

Through a delicate balance between quiescence and proliferation, self renewal and production of differentiated progeny, hematopoietic stem cells (HSCs) ...