Name: dynamic proteomic and mirna analysis of polysomes from isolated mouse heart after langendorff perfusion
Uploaded: 2018-08-29T13:00:00
Description: Watch this Scientific Journal Video about Dynamic Proteomic and miRNA Analysis of Polysomes from Isolated Mouse Heart After Langendorff Perfusion at JoVE.com

NIH P01 HL112730 (RAG, JVE), NIH R01 HL132075 (RAG, JVE), Barbra Streisand Women&#39;s Heart Center (RAG, JVE), Dorothy and E. Phillip Lyon Chair in Molecular Cardiology (RAG), Erika Glazer Endowed Chair in Woman&#39;s Heart Health (JVE) and Czech Academy of Sciences Institutional Support RVO: 68081715 (MS).

All animal studies were performed in accordance with institutional guidelines and approved by the Institutional Animal Care and Use Committee of Cedars-Sinai Medical Center.
1. Langendorff Perfusion of Mouse Heart
<ol>
	<li>Langendorff perfusion of mouse heart with ischemia and reperfusion 
	<ol>
		<li>Administer intraperitoneal pentobarbital sodium 70 mg/kg to the adult mouse (8-week-old, male, C57BL6/j). Confirm deep anesthesia by lack of withdrawal to toe pinch.</li>
		<l...

<ol>
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Polysome profile analysis allows for the study of protein translation by analyzing the translational state of a specific mRNA or the whole transcriptome6,7. It is also of great help when local translation needs to be studied such as synaptosomes8. Traditionally, this method involves the separation of mono- and polyribosomes and the associated mRNAs on a sucrose gradient which could be coupled with genomic or proteomic techniques to obtain ...

The heart responds to the injury of ischemia (I) and reperfusion (R) in a dynamic fashion. However, there is little insight into acute changes in protein synthesis during the response. To address this, we took advantage of the well-established method of polysome profiling1 to identify changes in protein abundance that reflect redistribution of ribosomes and translational regulatory factors from cytosol to polysomes, and the increase in newly synthesized proteins (NSPs). In the setting of I/R, the increase in new protein synthesis occurs in a time frame that is inconsistent with transcription of new mRNAs2; moreover, discordance between mRNA expression levels and protein abundance has been reported3. For these reasons, we chose to analyze the changes in the dynamic proteome as reflected by protein translation. To do this, we quantify mRNA in the polysome fractions, and analyze the protein composition in the polysome fractions. Finally, because microRNAs (miRs) regulate availability of mRNAs for translation and can interfere with efficiency of protein translation4,5, we examined the distribution of miRs in the polysome fractions, focusing on the response to I/R.
We chose to use the isolated mouse Langendorff perfusion model and harvested tissue under basal conditions of continuous perfusion, after 30 min global no-flow ischemia, and after 30 min of ischemia followed by 30 min of reperfusion. We then solubilized the heart tissue and separated polysomes over a sucrose gradient, followed by proteomic analysis and selective detection of mRNAs and miRNAs by PCR and microarray, respectively. This combination of methods represents a powerful approach to understanding the dynamic proteome, enabling simultaneous detection of mRNA, miRNA, and NSPs, as well as the redistribution of regulatory proteins, miRNA, and mRNA between nontranslating fractions, low-efficiency polysomes, and high-efficiency polysomes (see Figure 1). Insights into the dynamic regulation of this process will be extended by further analysis of phosphorylation of key regulatory factors such as eIF2&#945; or mTOR. These individual steps are now described in detail.

<table>
	<tbody>
		<tr>
			<td>Pentobarbital</td>
			<td>Vortech Phamaceuticals</td>
			<td>9373</td>
			<td>for euthansia</td>
		</tr>
		<tr>
			<td>Heparin</td>
			<td>Sagent</td>
			<td>103424</td>
			<td>used in langendorff preparation</td>
		</tr>
		<tr>
			<td>forceps</td>
			<td>Fine Science Tools</td>
			<td>91110-10</td>
			<td>used to hang the heart</td>
		</tr>
		<tr>
			<td>Langendorff system</td>
			<td>Radnoti + home made</td>
			<td>n/a</td>
			<td>A &#39;four heart&#39; system consisting of custom blown glass, tubing and water baths</td>
		</tr>
		<tr>
			<td>NaCl</td>
			<td>Sigma</td>
			<td>S7653-5KG</td>
			<td>Krebs buffer and Sucrose gradient</td>
		</tr>
		<tr>
			<td>KCl</td>
			<td>Sigma</td>
			<td>P5405</td>
			<td>Krebs buffer and Lysis buffer</td>
		</tr>
		<tr>
			<td>KH2PO4</td>
			<td>Sigma</td>
			<td>P-5504</td>
			<td>Krebs buffer</td>
		</tr>
		<tr>
			<td>MgSO4</td>
			<td>Sigma</td>
			<td>M7774-500G</td>
			<td>Krebs buffer</td>
		</tr>
		<tr>
			<td>Glucose</td>
			<td>Sigma</td>
			<td>G5767</td>
			<td>Krebs buffer</td>
		</tr>
		<tr>
			<td>CaCl2</td>
			<td>Sigma</td>
			<td>C1016-500G</td>
			<td>Krebs buffer</td>
		</tr>
		<tr>
			<td>Sucrose powder</td>
			<td>Sigma</td>
			<td>S0389-1KG</td>
			<td>Sucrose gradient</td>
		</tr>
		<tr>
			<td>MgCl2</td>
			<td>Sigma</td>
			<td>208337</td>
			<td>Sucrose gradient and Lysis buffer</td>
		</tr>
		<tr>
			<td>Tris-base</td>
			<td>Sigma</td>
			<td>T1503-1KG</td>
			<td>Sucrose gradient and Lysis buffer</td>
		</tr>
		<tr>
			<td>Xylene Cyanole</td>
			<td>Sigma</td>
			<td>X-4126</td>
			<td>Sucrose gradient</td>
		</tr>
		<tr>
			<td>Cycloheximide</td>
			<td>Sigma-aldrich</td>
			<td>239763</td>
			<td>Sucrose gradient and Lysis buffer</td>
		</tr>
		<tr>
			<td>RNaseOUT</td>
			<td>Life Technologies</td>
			<td>C00019</td>
			<td>RNAse inhibitor for Lysis buffer</td>
		</tr>
		<tr>
			<td>Igepal CA-360 (NP40)</td>
			<td>Sigma</td>
			<td>I3021</td>
			<td>Lysis buffer</td>
		</tr>
		<tr>
			<td>Protease Inhibitor Cocktail tablets, EDTA free</td>
			<td>Roche</td>
			<td>5056489001</td>
			<td></td>
		</tr>
		<tr>
			<td>Tube, Thinwall, Ultra-Clear, 13.2 mL, 14 x 89 mm</td>
			<td>Beckman Coulter</td>
			<td>344059</td>
			<td></td>
		</tr>
		<tr>
			<td>Ultracentrifuge</td>
			<td>Beckman</td>
			<td>LE-80K</td>
			<td>Ultracentrifugation of the gradients</td>
		</tr>
		<tr>
			<td>Rotor</td>
			<td>Beckman</td>
			<td>SW41</td>
			<td>Ultracentrifugation of the gradients</td>
		</tr>
		<tr>
			<td>Biologic LP (pump)</td>
			<td>Biorad</td>
			<td>731-8300</td>
			<td>Fractionation of the gradients</td>
		</tr>
		<tr>
			<td>BioFrac</td>
			<td>Biorad</td>
			<td>741-0002</td>
			<td>Fractionation of the gradients</td>
		</tr>
		<tr>
			<td>Eppendorf RNA/DNA LoBind microcentrifuge tubes, 2 mL tube</td>
			<td>Sigma</td>
			<td>Z666513-100EA</td>
			<td>Gradient fraction and RNA extraction</td>
		</tr>
		<tr>
			<td>TRIzol Reagent</td>
			<td>Life technologies</td>
			<td>AM9738</td>
			<td>RNA extraction</td>
		</tr>
		<tr>
			<td>Luciferase Control RNA</td>
			<td>Promega</td>
			<td>L4561</td>
			<td>RNA extraction</td>
		</tr>
		<tr>
			<td>Chloroform</td>
			<td>Fisher Scientific</td>
			<td>C606-4</td>
			<td>RNA extraction</td>
		</tr>
		<tr>
			<td>Glycogen, RNA grade</td>
			<td>Thermo Fisher Scientific</td>
			<td>R0551</td>
			<td>RNA extraction</td>
		</tr>
		<tr>
			<td>Isopropanol</td>
			<td>Sigma</td>
			<td>I9516</td>
			<td>RNA extraction</td>
		</tr>
		<tr>
			<td>Ethanol</td>
			<td>Sigma</td>
			<td>E7023-1L</td>
			<td>RNA extraction</td>
		</tr>
		<tr>
			<td>iScript cDNA Synthesis Kit</td>
			<td>BioRad</td>
			<td>170-8891</td>
			<td>Reverse transcription</td>
		</tr>
		<tr>
			<td>iTaq Universal SYBR Green Supermix</td>
			<td>BioRad</td>
			<td>175-5122</td>
			<td>Quantative PCR</td>
		</tr>
		<tr>
			<td>miRNeasy Micro Kit (50)</td>
			<td>Qiagen</td>
			<td>217084</td>
			<td>Kit for total RNA isolation</td>
		</tr>
		<tr>
			<td>miScript II RT Kit (50)</td>
			<td>Qiagen</td>
			<td>218161</td>
			<td>Kit for miRNA reverse transcription</td>
		</tr>
		<tr>
			<td>miScript Sybr Green PCR Kit (200)</td>
			<td>Qiagen</td>
			<td>218073</td>
			<td>Kit for real-time PCR expression analysis of miRNAs</td>
		</tr>
		<tr>
			<td>Centrifuge 5424R</td>
			<td>Eppendorf</td>
			<td></td>
			<td>For centrifugation of 1.5ml or 2.0ml tubes at different temperatures. Max speed - 21130g</td>
		</tr>
		<tr>
			<td>Centrifuge 5810R</td>
			<td>Eppendorf</td>
			<td></td>
			<td>For real-time PCR plate centrifugation at different temperatures. Max speed - 2039g</td>
		</tr>
		<tr>
			<td>My Cycler Thermal Cycler</td>
			<td>Bio-Rad</td>
			<td></td>
			<td>For reverse transcription</td>
		</tr>
		<tr>
			<td>CFX96 Real-Time System/C1000 Touch Thermal Cycler</td>
			<td>Bio-Rad</td>
			<td></td>
			<td>For real-time PCR analysis</td>
		</tr>
		<tr>
			<td>miRNeasy Serum/Plasma Spike-in Control</td>
			<td>Qiagen</td>
			<td>219610</td>
			<td>For quality control of RNA isolation</td>
		</tr>
		<tr>
			<td>Hard-Shell 96-Well PCR Plates, low profile, thin wall, skirted, green/clear</td>
			<td>Bio-Rad</td>
			<td>HSP9641</td>
			<td>For real-time PCR analysis</td>
		</tr>
		<tr>
			<td>Microseal &#39;B&#39; PCR Plate Sealing Film, adhesive, optical</td>
			<td>Bio-Rad</td>
			<td>MSB1001</td>
			<td>For real-time PCR plate sealing</td>
		</tr>
		<tr>
			<td>Research plus Single-Channel Pipette, Gray; 0.5-10 &#181;L</td>
			<td>Eppendorf</td>
			<td>UX-24505-02</td>
			<td>For pipetting</td>
		</tr>
		<tr>
			<td>PIPETMAN Classic Pipets, P20</td>
			<td>Gilson</td>
			<td>F123600G</td>
			<td>For pipetting</td>
		</tr>
		<tr>
			<td>PIPETMAN Classic Pipets, P200</td>
			<td>Gilson</td>
			<td>F144565</td>
			<td>For pipetting</td>
		</tr>
		<tr>
			<td>Rainin L-1000XLS Pipet-Lite XLS LTS Pipette 100-1000 &#181;L</td>
			<td>Gilson</td>
			<td>17011782</td>
			<td>For pipetting</td>
		</tr>
		<tr>
			<td>Glycogen, RNA grade</td>
			<td>Thermo Fisher Scientific</td>
			<td>R0551</td>
			<td>Improves total RNA isolation efficiency</td>
		</tr>
		<tr>
			<td>Posi-Click 1.7 mL Tubes, natural color</td>
			<td>Denville</td>
			<td>C2170</td>
			<td>RNA isolation and storage; reagent mix</td>
		</tr>
		<tr>
			<td>Thermal Cycling Tubes -0.2 mL Individual Caps, Standard 0.2 mL tubes with optically</td>
			<td>Denville</td>
			<td>C18098-4 (1000910)</td>
			<td>Reverse transcription reaction</td>
		</tr>
		<tr>
			<td>Sharp 10 Precision barrier Tips</td>
			<td>Denville</td>
			<td>P1096-FR</td>
			<td>For pipetting</td>
		</tr>
		<tr>
			<td>Sharp 20 Precision barrier Tips</td>
			<td>Denville</td>
			<td>P1121</td>
			<td>For pipetting</td>
		</tr>
		<tr>
			<td>Sharp 200 Precision barrier Tips</td>
			<td>Denville</td>
			<td>P1122</td>
			<td>For pipetting</td>
		</tr>
		<tr>
			<td>Tips LTS 1 mL Filter</td>
			<td>Rainin</td>
			<td>RT-L1000F</td>
			<td>For pipetting</td>
		</tr>
		<tr>
			<td>miScript Primer Assay (200)</td>
			<td>Qiagen</td>
			<td>(it changes according to the miRNA)</td>
			<td>For real-time PCR analysis</td>
		</tr>
		<tr>
			<td>Gradient Master ver 5.3 Model 108</td>
			<td>BioComp Instruments</td>
			<td></td>
			<td>For preparation of sucrose gradients</td>
		</tr>
		<tr>
			<td>trichloroacetic acid</td>
			<td>Sigma Aldrich</td>
			<td>T6399</td>
			<td></td>
		</tr>
		<tr>
			<td>acetone</td>
			<td>Sigma Aldrich</td>
			<td>650501</td>
			<td></td>
		</tr>
		<tr>
			<td>Tris hydrochloride</td>
			<td>Amresco</td>
			<td>M108</td>
			<td></td>
		</tr>
		<tr>
			<td>dithiothreitol</td>
			<td>Fisher Scientific</td>
			<td>BP172</td>
			<td></td>
		</tr>
		<tr>
			<td>iodoacetamide</td>
			<td>Gbiosciences</td>
			<td>RC-150</td>
			<td></td>
		</tr>
		<tr>
			<td>sequencing grade modified trypsine, porcine</td>
			<td>Promega</td>
			<td>V5111</td>
			<td></td>
		</tr>
		<tr>
			<td>ammonium bicarbonate</td>
			<td>BDH</td>
			<td>BDH9206</td>
			<td></td>
		</tr>
		<tr>
			<td>formic acid, Optima LC/MS</td>
			<td>Fisher Chemical</td>
			<td>A117</td>
			<td></td>
		</tr>
		<tr>
			<td>methanol, Optima LC/MS</td>
			<td>Fisher Chemical</td>
			<td>A454</td>
			<td></td>
		</tr>
		<tr>
			<td>acetonitrile, Optima LC/MS</td>
			<td>Fisher Chemical</td>
			<td>A996</td>
			<td></td>
		</tr>
		<tr>
			<td>Protein LoBind tubes 0.5 mL</td>
			<td>Eppendorf AG</td>
			<td>22431064</td>
			<td></td>
		</tr>
		<tr>
			<td>Protein LoBind tubes 1.5 mL</td>
			<td>Eppendorf AG</td>
			<td>22431081</td>
			<td></td>
		</tr>
		<tr>
			<td>HLB &#181;Elution plate 30 &#181;m</td>
			<td>Oasis</td>
			<td>186001828BA</td>
			<td></td>
		</tr>
		<tr>
			<td>SpeedVac concentrator</td>
			<td>Thermo Scientific</td>
			<td>Savant SPD2010</td>
			<td></td>
		</tr>
		<tr>
			<td>sonicator</td>
			<td>Qsonica</td>
			<td>Oasis180</td>
			<td></td>
		</tr>
		<tr>
			<td>centrifuge</td>
			<td>Thermo Scientific</td>
			<td colspan="2">Sorvall Legend micro 21R</td>
		</tr>
		<tr>
			<td>LC trap column PepMap 100 C18</td>
			<td>Thermo Scientific</td>
			<td>160454</td>
			<td></td>
		</tr>
		<tr>
			<td>LC separation column PepMap RSLC C18</td>
			<td>Thermo Scientific</td>
			<td>164536</td>
			<td></td>
		</tr>
		<tr>
			<td>mass spectrometer</td>
			<td>Thermo Scientific</td>
			<td colspan="2">Orbitrap Elite ion trap mass spectrometer</td>
		</tr>
		<tr>
			<td>MSConvert software</td>
			<td>ProteoWizard Toolkit</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Sorcerer-SEQUEST software</td>
			<td>Sage-N Research, Inc.</td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

dynamic proteomic and mirna analysis of polysomes from isolated mouse heart after langendorff perfusion

Studies in dynamic changes in protein translation require specialized methods. Here we examined changes in newly-synthesized proteins in response to ischemia and reperfusion using the isolated perfused mouse heart coupled with polysome profiling. To further understand the dynamic changes in protein translation, we characterized the mRNAs that were loaded with cytosolic ribosomes (polyribosomes or polysomes) and also recovered mitochondrial polysomes and compared mRNA and protein distribution in the high-efficiency fractions (numerous ribosomes attached to mRNA), low-efficiency (fewer ribosomes attached) which also included mitochondrial polysomes, and the non-translating fractions. miRNAs can also associate with mRNAs that are being translated, thereby reducing the efficiency of translation, we examined the distribution of miRNAs across the fractions. The distribution of mRNAs, miRNAs, and proteins was examined under basal perfused conditions, at the end of 30 min of global no-flow ischemia, and after 30 min of reperfusion. Here we present the methods used to accomplish this analysis&#8212;in particular, the approach to optimization of protein extraction from the sucrose gradient, as this has not been described before&#8212;and provide some representative results.

mRNA analysis 
mRNA results can be expressed as a distribution of a particular mRNA in each fraction (Figure 3A); for quantification, combine polyribosomal translating fractions and compare to the non-translating fraction (Figure 3B), presenting a ratio of mRNA abundance in translating to nontranslating fractions. Additional information is gained by examining the high efficiency polysome fractions separately from lo...

Watch this Scientific Journal Video about Dynamic Proteomic and miRNA Analysis of Polysomes from Isolated Mouse Heart After Langendorff Perfusion at JoVE.com

Dynamic Proteomic and miRNA Analysis of Polysomes from Isolated Mouse Heart After Langendorff Perfusion

Here we present a protocol to perform polysome profiling on the isolated perfused mouse heart. We describe methods for heart perfusion, polysome profiling, and analysis of the polysome fractions with respect to mRNAs, miRNAs, and the polysome proteome.

Studies in dynamic changes in protein translation require specialized methods. Here we examined changes in newly-synthesized proteins in response to ...

This method can help answer key questions about dynamic protein synthesis and the proteome involved in the process. This technique allows identification of the mRNAs that are being selected for translation, the microRNAs that can participate in the process and interfere with translation, and the proteins that contribute to protein translation or are themselves being translated. This method can provide insight into cardiac responses to stress, but can also be applied to the study of acute responses to stress in other organs.Demonstrating the procedure will be Miroslava Stastna, a project scientist from Jennifer Van Eyk's laboratory. On the day of the experiment, fill the left compartment of a gradient mixer with five milliliters of 15%sucrose gradient solution, and fill the right compartment with five milliliters of 50%sucrose gradient solution. Open the tap and switch on the pump to stir the two small compartments with a magnetic stirrer, and use a tube linked to the second tap to allow the mixed sucrose solutions to flow into a single ultracentrifuge tube with thin walls on ice.Next, homogenize the fresh or frozen heart tissue with a POLYTRON in filtered lysis buffer for 15 seconds on ice. At the end of the incubation, centrifuge the lysate to remove the insoluble material, and harvest the supernatant. Set aside 50 microliters of the supernatant for protein determination, RNA isolation, and RNA integrity analysis, and layer 100 to 500 microliters of the remaining supernatant over the gradient solution.Use fresh lysis buffer to balance the volumes between the two gradient tubes, and ultracentrifuge the samples in an ultracentrifuge with a swinging bucket rotor. Be very careful not to disturb the sucrose gradient before or after centrifugation. To collect the gradients, program the fraction collector to discard the first three minutes of collection and to collect the heavy, light, and non-translating fractions at the speed of one milliliter per minute in 17 fractions from four to 19 minutes with continuous monitoring of the absorbance at 254 nanometers.Place each fraction on ice as soon as it is collected. Then store the samples at minus 80 degrees Celsius, if they are not being processed immediately. To extract proteins from the polysome fractions, combine the collected sucrose fractions into three final fractions, and mark the fractions as heavy, light, and non-translating.Mix 0.5 milliliters of each sample with 60 microliters of 100%trichloroacetic acid, or TCA. Incubate the fractions overnight at minus 20 degrees Celsius in the dark. The next morning, thaw the samples on ice before pelleting the proteins by centrifugation.Discard the supernatants, and wash the pellets two times with 0.5 milliliters of minus 20 degrees Celsius chilled acetone per centrifugation. Make sure pellet, after TCA precipitation, is completely dissolved, using pulse sonication to ensure complete solubilization, as necessary. Air dry the pellets after the last wash before resuspension in 360 microliters of Tris-HCl buffer.Then add 40 microliters of dithiothreitol for a 45-minute incubation at 55 degrees Celsius with shaking. At the end of the incubation, add 50 microliters of iodoacetamide to the samples for a 30-minute incubation on the shaker at room temperature, protected from light, followed by digestion of the samples with a one-to-50 weight-to-weight trypsin-to-protein ratio for an overnight shaking incubation at 37 degrees Celsius. The next morning, after cooling, briefly centrifuge the samples, and adjust the pH to two to three with 10%formic acid to quench the trypsin activity.To desalt the samples, first condition the sorbent in the wells of a 96-well plate with 200 microliters of methanol three times, followed by conditioning with 200 microliters of 0.1%formic acid per well three times. Next, load the samples onto each well, and wash the samples three times with 200 microliters of 0.1%formic acid per wash. Using gravitation, followed by low vacuum, elute the samples with 100 microliters of 0.1%formic acid in 50%acetonitrile two times into one low protein retention 0.5-milliliter tube per sample.Then use a concentrator to evaporate the sample eluates to dryness, and reconstitute each tryptic peptide pellet in 50 to 100 microliters of 0.1%formic acid for mass spectrometry analysis. mRNA analysis can be performed to assess the distribution of a particular mRNA of interest in each fraction or for quantification and comparison of the combined polyribosomal translating fractions to the non-translating fraction as a ratio of mRNA abundance each fraction. For example, here, the changes in mRNA distribution across the translating and non-translating fractions after mouse heart subjection to ischemia or ischemia reperfusion, compared to sham heart treatment are shown.In this representative experiment, the analysis of a subset of microRNAs in the pooled heavy fractions revealed that 22 microRNAs were associated with polysomes during ischemia, nine were associated during ischemia and reperfusion, and seven were common to both conditions, demonstrating that the association of microRNAs is dynamic in response to the stresses of ischemia and reperfusion. Further, the majority of mitochondrial ribosomal proteins were identified in the light fraction, and the majority of the cytosolic ribosomal proteins were identified commonly in both the heavy and light fractions. While attempting this procedure, it's important to remember to be very careful with the sucrose gradient.TCA precipitation for extraction of proteins from polysome fractions was selected in our workflow based on both the ability to process the fraction with high concentration of sucrose and the number of proteins identified by mass spectrometry. Generally, individuals new to this method may struggle because of the challenges associated with the reproducibility of the sucrose gradient. TCA precipitation is advantageous since only small volumes is needed to precipitate the proteins, the pellet is visibile at the tube bottom, and there is no accumulation of sucrose during precipitation.

dynamic-proteomic-mirna-analysis-polysomes-from-isolated-mouse-heart

Research

JoVE Journal

Biochemistry

Resolving Affinity Purified Protein Complexes by Blue Native PAGE and Protein Correlation Profiling

Most proteins act in association with others; hence, it is crucial to characterize these functional units in order to fully understand biological processes. Affinity purification coupled to mass spectrometry (AP-MS) has become the method of choice for identifying protein-protein interactions. However, conventional AP-MS studies provide information on protein interactions, but the organizational information is lost. To address this issue, we developed a strategy to unravel the distinct functional assemblies a protein might be involved in, by resolving affinity-purified protein complexes prior to their characterization by mass spectrometry. Protein complexes isolated through affinity purification of a bait protein using an epitope tag and competitive elution are separated through blue native electrophoresis. Comparison of protein migration profiles through correlation profiling using quantitative mass spectrometry allows assignment of interacting proteins to distinct molecular entities. This method is able to resolve protein complexes of close molecular weights that might not be resolved by traditional chromatographic techniques such as gel filtration. With little more work than conventional AP-geLC-MS/MS, we demonstrate this strategy may in many cases be adequate for obtaining protein complex topological information concomitantly to identifying protein interactions.

Here we present protocols for affinity purification of protein complexes and their separation by blue native PAGE, followed by protein correlation profiling using label free quantitative mass spectrometry. This method is useful to resolve interactomes into distinct protein complexes.

Most proteins act in association with others; hence, it is crucial to characterize these functional units in order to fully understand biological ...

Dissection of Human Retina and RPE-Choroid for Proteomic Analysis

The human retina is composed of the sensory neuroretina and the underlying retinal pigmented epithelium (RPE), which is firmly complexed to the vascular choroid layer. Different regions of the retina are anatomically and molecularly distinct, facilitating unique functions and demonstrating differential susceptibility to disease. Proteomic analysis of each of these regions and layers can provide vital insights into the molecular process of many diseases, including Age-Related Macular Degeneration (AMD), diabetes mellitus, and glaucoma. However, separation of retinal regions and layers is essential before quantitative proteomic analysis can be accomplished. Here, we describe a method for dissection and collection of the foveal, macular, and peripheral retinal regions and underlying RPE-choroid complex, involving regional punch biopsies and manual removal of tissue layers from a human eye.One-dimensional SDS-PAGE as well as downstream proteomic analysis, such as liquid chromatography-tandem mass spectrometry (LC-MS/MS), can be used to identify proteins in each dissected retinal layer, revealing molecular biomarkers for retinal disease.

The human retina is composed of functionally and molecularly distinct regions, including the fovea, macula, and peripheral retina. Here, we describe a method using punch biopsies and manual removal of tissue layers from a human eye to dissect and collect these distinct retinal regions for downstream proteomic analysis.

The human retina is composed of the sensory neuroretina and the underlying retinal pigmented epithelium (RPE), which is firmly complexed to the vascular ...

Purification of Hepatocytes and Sinusoidal Endothelial Cells from Mouse Liver Perfusion

This protocol demonstrates a method for obtaining high yield and viability for mouse hepatocytes and sinusoidal endothelial cells (SECs) suitable for culturing or for obtaining cell lysates. In this protocol, the portal vein is used as the site for catheterization, rather than the vena cava, as this limits contamination of other possible cell types in the final liver preparation. No special instrumentation is required throughout the procedure. A water bath is used as a source of heat to maintain the temperature of all the buffers and solutions. A standard peristaltic pump is used to drive the fluid, and a refrigerated table-top centrifuge is required for the centrifugation procedures. The only limitation of this technique is the placement of the catheter within the portal vein, which is challenging on some of the mice in the 18 - 25 g size range. An advantage of this technique is that only one vein is utilized for the perfusion and the access to the vein is quick, which minimizes ischemia and reperfusion of the liver that reduces hepatic cell viability. Another advantage to this protocol is that it is easy to distinguish live from dead hepatocytes by eyesight due to the difference in cellular density during the centrifugation steps. Cells from this protocol may be used in cell culture for any downstream application as well as processed for any biochemical assessment.

The goal of this protocol is to obtain high viability and high yield of hepatocytes and sinusoidal endothelial cells from liver. This is accomplished by perfusing the liver with a type IV collagenase solution via the portal vein, followed by differential centrifugation to obtain hepatocytes and sinusoidal endothelial cells.

This protocol demonstrates a method for obtaining high yield and viability for mouse hepatocytes and sinusoidal endothelial cells (SECs) suitable for ...

Split-BioID &#8212; Proteomic Analysis of Context-specific Protein Complexes in Their Native Cellular Environment

To complement existing affinity purification (AP) approaches for the identification of protein-protein interactions (PPI), enzymes have been introduced that allow the proximity-dependent labeling of proteins in living cells. One such enzyme, BirA* (used in the BioID approach), mediates the biotinylation of proteins within a range of approximately 10 nm. Hence, when fused to a protein of interest and expressed in cells, it allows the labeling of proximal proteins in their native environment. As opposed to AP that relies on the purification of assembled protein complexes, BioID detects proteins that have been marked within cells no matter whether they are still interacting with the protein of interest when they are isolated. Since it biotinylates proximal proteins, one can moreover capitalize on the exceptional affinity of streptavidin for biotin to very efficiently isolate them. While BioID performs better than AP for identifying transient or weak interactions, both AP- and BioID-mass spectrometry approaches provide an overview of all possible interactions a given protein may have. However, they do not provide information on the context of each identified PPI. Indeed, most proteins are typically part of several complexes, corresponding to distinct maturation steps or different functional units. To address this common limitation of both methods, we have engineered a protein-fragments complementation assay based on the BirA* enzyme. In this assay, two inactive fragments of BirA* can reassemble into an active enzyme when brought in close proximity by two interacting proteins to which they are fused. The resulting split-BioID assay thus allows the labeling of proteins that assemble around a pair of interacting proteins. Provided these two only interact in a given context, split-BioID then allows the analysis of specific context-dependent functional units in their native cellular environment. Here, we provide a step-by-step protocol to test and apply split-BioID to a pair of interacting proteins.

Split-BioID &amp;#8212; Proteomic Analysis of Context-specific Protein Complexes in Their Native Cellular Environment

We provide a step-by-step protocol for split-BioID, a protein fragments-complementation assay based on the proximity-labeling technique BioID. Activated on the interaction of two given proteins, it allows the proteomics analysis of context-dependent protein complexes in their native cellular environment. The method is simple, cost-effective and only requires standard laboratory equipment.

To complement existing affinity purification (AP) approaches for the identification of protein-protein interactions (PPI), enzymes have been introduced ...

Analyzing Dynamic Protein Complexes Assembled On and Released From Biolayer Interferometry Biosensor Using Mass Spectrometry and Electron Microscopy

In vivo, proteins are often part of large macromolecular complexes where binding specificity and dynamics ultimately dictate functional outputs. In this work, the pre-endosomal anthrax toxin is assembled and transitioned into the endosomal complex. First, the N-terminal domain of a cysteine mutant lethal factor (LFN) is attached to a biolayer interferometry (BLI) biosensor through disulfide coupling in an optimal orientation, allowing protective antigen (PA) prepore to bind (Kd 1 nM). The optimally oriented LFN-PAprepore complex then binds to soluble capillary morphogenic gene-2 (CMG2) cell surface receptor (Kd 170 pM), resulting in a representative anthrax pre-endosomal complex, stable at pH 7.5. This assembled complex is then subjected to acidification (pH 5.0) representative of the late endosome environment to transition the PAprepore into the membrane inserted pore state. This PApore state results in a weakened binding between the CMG2 receptor and the LFN-PApore and a substantial dissociation of CMG2 from the transition pore. The thio-attachment of LFN to the biosensor surface is easily reversed by dithiothreitol. Reduction on the BLI biosensor surface releases the LFN-PAprepore-CMG2 ternary complex or the acid transitioned LFN-PApore complexes into microliter volumes. Released complexes are then visualized and identified using electron microscopy and mass spectrometry. These experiments demonstrate how to monitor the kinetic assembly/disassembly of specific protein complexes using label-free BLI methodologies and evaluate the structure and identity of these BLI assembled complexes by electron microscopy and mass spectrometry, respectively, using easy-to-replicate sequential procedures.

Here we present a protocol to monitor the assembly and disassembly of the anthrax toxin using biolayer interferometry (BLI). Following assembly/disassembly on the biosensor surface, the large protein complexes are released from the surface for visualization and identification of components of the complexes using electron microscopy and mass spectrometry, respectively.

In vivo, proteins are often part of large macromolecular complexes where binding specificity and dynamics ultimately dictate functional outputs. In this ...

Calibration-free In Vitro Quantification of Protein Homo-oligomerization Using Commercial Instrumentation and Free, Open Source Brightness Analysis Software

Number and brightness is a calibration-free fluorescence fluctuation spectroscopy (FFS) technique for detecting protein homo-oligomerization. It can be employed using a conventional confocal microscope equipped with digital detectors. A protocol for the use of the technique in vitro is shown by means of a use case where number and brightness can be seen to accurately quantify the oligomeric state of mVenus-labelled FKBP12F36V before and after the addition of the dimerizing drug AP20187. The importance of using the correct microscope acquisition parameters and the correct data preprocessing and analysis methods are discussed. In particular, the importance of the choice of photobleaching correction is stressed. This inexpensive method can be employed to study protein-protein interactions in many biological contexts.

Calibration-free In Vitro Quantification of Protein Homo-oligomerization Using Commercial Instrumentation and Free, Open Source Brightness Analysis Software

This protocol describes a calibration-free approach for quantifying protein homo-oligomerization in vitro based on fluorescence fluctuation spectroscopy using commercial light scanning microscopy. The correct acquisition settings and analysis methods are shown.

Number and brightness is a calibration-free fluorescence fluctuation spectroscopy (FFS) technique for detecting protein homo-oligomerization. It can be ...

Proteomic Analysis of Human Macrophage Polarization Under a Low Oxygen Environment

Macrophages are innate immune cells involved in a number of physiological functions ranging from responses to infectious pathogens to tissue homeostasis. The various functions of these cells are related to their activation states, which is also called polarization. The precise molecular description of these various polarizations is a priority in the field of macrophage biology. It is currently acknowledged that a multidimensional approach is necessary to describe how polarization is controlled by environmental signals. In this report, we describe a protocol designed to obtain the proteomic signature of various polarizations in human macrophages. This protocol is based on a label-free quantification of macrophage protein expression obtained from in-gel fractionated and Lys C/trypsin-digested cellular lysis content. We also provide a protocol based on in-solution digestion and isoelectric focusing fractionation to use as an alternative. Because oxygen concentration is a relevant environmental parameter in tissues, we use this protocol to explore how atmospheric composition or a low oxygen environment affects the classification of macrophage polarization.

We present a protocol to obtain proteomic signatures of human macrophages and apply this to determination of the impact of a low oxygen environment on macrophage polarization.

Macrophages are innate immune cells involved in a number of physiological functions ranging from responses to infectious pathogens to tissue homeostasis. ...

Profiling Ubiquitin and Ubiquitin-like Dependent Post-translational Modifications and Identification of Significant Alterations

Ubiquitin (ub) and ubiquitin-like (ubl) dependent post-translational modifications of proteins play fundamental biological regulatory roles within the cell by controlling protein stability, activity, interactions, and intracellular localization. They enable the cell to respond to signals and to adapt to changes in its environment. Alterations within these mechanisms can lead to severe pathological situations such as neurodegenerative diseases and cancers. The aim of the technique described here is to establish ub/ubls dependent PTMs profiles, rapidly and accurately, from cultured cell lines. The comparison of different profiles obtained from different conditions allows the identification of specific alterations, such as those induced by a treatment for example. Lentiviral mediated cell transduction is performed to create stable cell lines expressing a two-tags (6His and Flag) version of the modifier (ubiquitin or a ubl such as SUMO1 or Nedd8). These tags permit the purification of ubiquitin and therefore of ubiquitinated proteins from the cells. This is done through a two-step purification process: The first one is performed in denaturing conditions using the 6His tag, and the second one in native conditions using the Flag tag. This leads to a highly specific and pure isolation of modified proteins which are subsequently identified and semi-quantified by liquid chromatography followed by tandem mass spectrometry (LC-MS/MS) technology. Easy informatics analysis of MS data using Excel software enables the establishment of PTM profiles by eliminating background signals. These profiles are compared between each condition in order to identify specific alterations which will then be studied more specifically, starting with their validation by standard biochemistry techniques.

This protocol aims at establishing ubiquitin (Ub) and ubiquitin-likes (Ubls) specific proteomes in order to identify alterations of these kind of post-translational modifications (PTMs), associated with a specific condition such as a treatment or a phenotype.

Ubiquitin (ub) and ubiquitin-like (ubl) dependent post-translational modifications of proteins play fundamental biological regulatory roles within the ...

Proteomic Profile of EPS-Urine through FASP Digestion and Data-Independent Analysis

Filter-aided sample protocol (FASP) is widely used for proteomics sample preparation because it allows to concentrate diluted samples and it is compatible with a wide variety of detergents. Bottom-up proteomics workflows like FASP increasingly rely on LC-MS/MS methods performed in data-independent analysis (DIA) mode, a scanning method that allows deep proteome coverage and low incidence of missing values. 
In this report, we will provide the details of a workflow that combines a FASP protocol, a double StageTip purification step and LC-MS/MS in DIA mode for urinary proteome mapping. As a model sample, we analyzed expressed prostatic secretions (EPS)-urine, a sample collected after a digital rectal exam (DRE), which is of interest in prostate cancer biomarker discovery studies.

Here, we present an optimized on-filter digestion protocol with detailed information about the following: protein digestion, peptide purification and data independent acquisition analysis. This strategy is applied to the analysis of expressed prostatic secretions-urine samples and allows high proteome coverage and low missing value label-free profiling of the urinary proteome.

Filter-aided sample protocol (FASP) is widely used for proteomics sample preparation because it allows to concentrate diluted samples and it is compatible ...

F&#246;rster Resonance Energy Transfer Measurements in Living Plant Cells

Sensitized emission-based F&#246;rster resonance energy transfer (FRET) experiments are easily done but depend on the microscopic setup. Confocal laser scanning microscopes have become a workhorse for biologists. Commercial systems offer high flexibility in laser power adjustment and detector sensitivity and often combine different detectors to obtain the perfect image. However, the comparison of intensity-based data from different experiments and setups is often impossible due to this flexibility. Biologist-friendly procedures are of advantage and allow for simple and reliable adjustment of laser and detector settings. 
Furthermore, as FRET experiments in living cells are affected by the variability in protein expression and donor-acceptor ratios, protein expression levels must be considered for data evaluation. Described here is a simple protocol for reliable and reproducible FRET measurements, including routines for the estimation of protein expression and adjustment of laser intensity and detector settings. Data evaluation will be performed by calibration with a fluorophore fusion of known FRET efficiency. To improve simplicity, correction factors have been compared that have been obtained in cells and by measuring recombinant fluorescent proteins.

F&amp;#246;rster Resonance Energy Transfer Measurements in Living Plant Cells

A protocol is provided for setting up a standard confocal laser-scanning microscope for in vivo F&#246;rster resonance energy transfer measurements, followed by data evaluation.

Sensitized emission-based F&#246;rster resonance energy transfer (FRET) experiments are easily done but depend on the microscopic setup. Confocal laser ...