This work is supported by a fellowship for S.H.-A. from NIH/NCATS (TL1TR001104), a Welch Foundation grant (I-1827), and a R01 grant from NIGMS (RGM120502A) to Z.W. Z.W. is the Virginia Murchison Linthicum Scholar in Medical Research and Cancer Prevention and Research Institute of Texas Scholar (R1222).

1. Prepare Samples
<ol>
	<li>Culture 2 x&#160;106 amyloid producing HT-29 colon cancer cells in a 10-cm tissue culture dish in 10 mL of Dulbecco&#39;s Modified Eagle Medium (DMEM) containing 10% fetal bovine serum and penicillin-streptomycin. Culture cells overnight in a 37 &#176;C incubator with 5% CO2.
	<ol>
		<li>After the cells grow to 80% confluency, wash the cells with 10 mL of phosphate-buffered saline (PBS). Add 3 mL of Trypsin solution and incubate at 37 &#176;C for 3 min.</li>
		<li>After the cells are totally dissociated from the dish, add 10 mL of culture medium and transfer the cells with a 10-mL pipette to a 15-mL conical tube. Centrifuge the cells at 1,000 x g for 3 min at room temperature. Aspirate the medium, resuspend the cells in 5 mL of culture medium, and count the cells using a cell counter. Plate 2 x&#160;106 cells in each of two 10-cm dishes.</li>
		<li>Allow the cells to adhere and recover overnight in a 37 &#176;C incubator with 5% CO2. Apply treatment to one dish to induce the formation of amyloids with 20 ng/mL Tumor Necrosis Factor-Alpha (TNF-&#945;), 100 nM Smac-mimetic, and 20 &#181;M pan-caspase inhibitor Z-VAD-FMK11. The combination is abbreviated as TSZ. Treat the other dish with vehicle as a control.</li>
	</ol>
	</li>
	<li>After the appropriate length of time, usually 6 h, harvest the cell lysate.
	<ol>
		<li>Scrape the cells off the plate with a plastic scraper and use a 10-mL pipette to transfer into a 15-mL conical tube. Centrifuge the cells at 1,000 x g for 3 min at 4 &#176;C.</li>
		<li>Wash the cells 2 times by resuspending in 10 mL of ice cold PBS and centrifuging at 1,000 x g for 3 min at 4 &#176;C. Aspirate the PBS solution. 
		Note: The process can be paused here by freezing the cell pellet in liquid nitrogen and storing at &#727;80 &#176;C for up to 1 month.</li>
		<li>Transfer the cell pellet to a 1.5-mL microcentrifuge tube and incubate in 0.3 mL of lysis buffer for 30 min on ice. Centrifuge at 20,000 x g for 15 min at 4 &#176;C. The supernatant is the whole cell lysate. 
		Note: The process can be paused here by storing the sample at -20 &#176;C for up to several months.</li>
		<li>Measure the protein concentration by a Bradford assay according to manufacturer&#39;s protocol. Add 4x&#160;SDD-AGE loading buffer to prepare 20 &#181;L of 3 &#181;g/&#181;L sample and incubate at room temperature for 10 min.</li>
	</ol>
	</li>
</ol>
2. Prepare and Run Gels
<ol>
	<li>Add 2 g of agarose to 200 mL of 1x&#160;Tris-acetate buffer (TAE) in a glass beaker and heat in a microwave to melt the agarose. Add 1 mL of 20% SDS for a final concentration of 0.1% SDS. Carefully swirl to mix. Take care not to generate bubbles after the SDS addition.</li>
	<li>Pour the agarose solution into a 15 cm x&#160;14 cm gel slab. Use a 1-mL pipette to eliminate any bubbles. Place one 20-well comb at the top.</li>
	<li>First dimension: Pipette 60 &#181;g of whole cell lysate in the far-right lane. Run the gel at 60 V for about 4 h (until the dye front is about &#190; through the gel) using the TAE containing 0.1% SDS as the running buffer.</li>
	<li>Second dimension: Carefully rotate the gel 90&#176; counter-clockwise (Figure 2A). Run the gel at 60 V for about 4 h. 
	Note: The general running condition is 4 V/cm gel length. It is important that the running conditions are exactly the same for the first and second dimensions.</li>
</ol>
3. Transfer
<ol>
	<li>Use the capillary transfer method to transfer the proteins to a polyvinylidene difluoride (PVDF) membrane (Figure 2B).
	<ol>
		<li>Add 500 mL of transfer buffer to an approximately 20 cm x&#160;20 cm container. Make a 5-cm high stack of paper towels next to the container. The surface area of the top of the stack must be greater than the gel dimensions.</li>
		<li>Soak a 14 cm x&#160;15 cm filter paper in transfer buffer and place on top of the paper towel stack. Take care to place on the paper with no wrinkles or bubbles. Repeat with another piece of filter paper.</li>
		<li>Activate a 14 cm x&#160;15 cm PVDF membrane in methanol for 30 s then layer it on the filter paper taking care to use a roller to remove all bubbles. Rinse the gel off with transfer buffer and layer it on top of the membrane, again rolling out any bubbles.</li>
		<li>Cover the edge of the paper towels closest to the container of transfer buffer with plastic wrap. It is important that the paper bridge constructed in the next step does not come into direct contact with the paper towel stack.</li>
		<li>Soak a piece of 15 cm x&#160;35 cm filter paper in transfer buffer and place it so one end covers the top of the gel and the other end is in the container of transfer buffer. Repeat with another bridge.</li>
		<li>Cover the container with plastic wrap and leave overnight at room temperature.</li>
	</ol>
	</li>
</ol>
4. Western Blotting Detection
<ol>
	<li>Rinse the membrane with 50 mL of PBS containing 0.05% Tween-20 (PBST) in a 20 cm &#215; 20 cm container. Add 20 mL of 5% milk in PBST. Rock at room temperature for 30 min to block.</li>
	<li>Pipette 10 &#181;L of rabbit anti-MLKL antibody into 20 mL of 5% milk in PBST and add to the container. Incubate on rocker overnight at 4 &#176;C.</li>
	<li>Wash the membrane in 20 mL of PBST for 5 min. Repeat 5 times.</li>
	<li>Pipette 4 &#181;L of anti-rabbit-HRP to 20 mL of 5% milk in PBST and add to the container. Incubate on rocker at room temperature for 2 h.</li>
	<li>Wash the membrane in 20 mL of PBST for 5 min. Repeat 5 times.</li>
	<li>Add enhanced chemiluminescence substrate (ECL) and expose to X-ray films according to the manufacturer&#39;s protocol.</li>
</ol>

<ol>
	<li>Ross, C. A., Poirier, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Protein+aggregation+and+neurodegenerative+disease.">Protein aggregation and neurodegenerative disease.</a> Nature medicine. 10, 10-17 (2004).</li><li>Hou, F., 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=MAVS+forms+functional+prion-like+aggregates+to+activate+and+propagate+antiviral+innate+immune+response.">MAVS forms functional prion-like aggregates to activate and propagate antiviral innate immune response.</a> Cell. 146, 448-461 (2011).</li><li>Li, 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=The+RIP1/RIP3+necrosome+forms+a+functional+amyloid+signaling+complex+required+for+programmed+necrosis.">The RIP1/RIP3 necrosome forms a functional amyloid signaling complex required for programmed necrosis.</a> Cell. 150, 339-350 (2012).</li><li>Liu, S., 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=MLKL+forms+disulfide+bond-dependent+amyloid-like+polymers+to+induce+necroptosis.">MLKL forms disulfide bond-dependent amyloid-like polymers to induce necroptosis.</a> Proceedings of the National Academy of Sciences of the United States of America. 114, 7450-7459 (2017).</li><li>Uptain, S. M., Lindquist, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Prions+as+protein-based+genetic+elements.">Prions as protein-based genetic elements.</a> Annual review of microbiology. 56, 703-741 (2002).</li><li>Halfmann, R., Lindquist, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Screening+for+amyloid+aggregation+by+Semi-Denaturing+Detergent-Agarose+Gel+Electrophoresis.">Screening for amyloid aggregation by Semi-Denaturing Detergent-Agarose Gel Electrophoresis.</a> J Vis Exp. , (2008).</li><li>Sipe, J. D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nomenclature+2014:+Amyloid+fibril+proteins+and+clinical+classification+of+the+amyloidosis.">Nomenclature 2014: Amyloid fibril proteins and clinical classification of the amyloidosis.</a> Amyloid : the international journal of experimental and clinical investigation : the official journal of the International Society of Amyloidosis. 21, 221-224 (2014).</li><li>Eisenberg, D. S., Sawaya, M. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Structural+Studies+of+Amyloid+Proteins+at+the+Molecular+Level.">Structural Studies of Amyloid Proteins at the Molecular Level.</a> Annual review of biochemistry. 86, 69-95 (2017).</li><li>Bagriantsev, S. N., Kushnirov, V. V., Liebman, S. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Methods in Enzymology. 412, 33-48 (2006).</li><li>Sun, 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=Mixed+lineage+kinase+domain-like+protein+mediates+necrosis+signaling+downstream+of+RIP3+kinase.">Mixed lineage kinase domain-like protein mediates necrosis signaling downstream of RIP3 kinase.</a> Cell. 148, 213-227 (2012).</li><li>He, S., 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=Receptor+interacting+protein+kinase-3+determines+cellular+necrotic+response+to+TNF-alpha.">Receptor interacting protein kinase-3 determines cellular necrotic response to TNF-alpha.</a> Cell. 137, 1100-1111 (2009).</li></ol>

The authors declare no conflict of interest.

The most critical aspect of the 2D SDD-AGE is that the electrophoresis conditions are the same for the first and second dimension. The ability to detect a sharp diagonal line at 45&#176; (indicating that no dissociation or degradation has occurred) depends on the fibers migrating in an identical manner during both electrophoreses. Using different conditions, for example changing the voltage or the length of run time, will obscure these results. Also, as is the case for traditional 1D SDD-AGE, boiling the sample should be...

The formation of amyloid fibers due to protein misfolding has long been known to play a role in pathologic conditions such as Alzheimer&#39;s disease, Parkinson&#39;s disease, and Huntington&#39;s disease1. More recently, the formation of amyloid or amyloid-like fibers has been shown to be a part of signaling pathways in humans, including during anti-viral innate immune response2 and necroptosis3,4, and in lower organisms such as yeast5,6. Therefore, the ability to detect these fibers in the lab is important. Currently, there are three main ways to detect amyloid and amyloid-like fibers: the use of dyes, EM, and SDD-AGE.
The use of dyes, such as Congo Red or Thioflavin T, offers the advantage of being rapid and easily detectable using either microscopy or spectroscopy7. However, detection by microscopy, in the case of Congo Red, provides no specificity about which proteins comprise the fibers, or the size of the fibers. Similarly, the use of spectroscopy to detect Congo Red or Thioflavin T binding to protein complexes provides only a positive or negative result.
EM provides conclusive evidence of the presence of fibers and also quantitative information about the fiber length and diameter8. However, this method requires very stringent purification. Additionally, EM is a specialized technique which uses expensive equipment.
SDD-AGE has been used to detect SDS-resistant mega Dalton protein complexes including amyloid or amyloid-like fibers. It offers many advantages. First, it does not require the purification of the fibers and is easy to peform9. Second, it provides qualitative information about the size of the fibers, including relative size and amount of fiber heterogenicity. Lastly, because Western blotting can be performed after electrophoresis, it is easy to detect the presence of any protein for which there is an antibody, although it should be noted that because SDD-AGE is semi-denaturing, some epitopes may remain concealed which complicates detection by antibody.
Recently, receptor interacting protein kinase 1 (RIPK1) and 3 (RIPK3) have been reported to form amyloid fibers to serve as signaling platforms during necroptosis, a programmed form of necrosis3. While studying these fibers, our lab showed that another necroptosis-associated protein, mixed lineage kinase domain-like (MLKL), also formed amyloid-like fibers4. However, upon examination with SDD-AGE, the size of the MLKL fibers appeared distinct from the RIPK1 and RIPK3 fibers, which appeared identical to each other (Figure 1). This was unexpected because it is well-known that MLKL binds to RIPK1/RIPK3 to form the necroptosis signaling complex called the necrosome10.
There are at least two explanations. First, two totally distinct amyloid-like fibers may form during necroptosis, one containing RIPK1/RIPK3 and the other containing MLKL. Second, only one type of amyloid-like fibers containing RIPK1/RIPK3/MLKL may be formed during necroptosis, but the association of MLKL with the other proteins is weak enough that it dissociates during SDD-AGE.
To address this, we propose performing a two-dimensional (2D) SDD-AGE. SDD-AGE-stable amyloid or amyloid-like fibers will have the same migration pattern during the first and second dimension electrophoresis. This will be detectable after transferring the proteins to a membrane and carrying out a Western blot. Stable fibers will exhibit a sharp diagonal pattern. Any deviation from this would suggest that the fibers undergo changes due to the SDS-electrophoresis.

<table><tbody><tr><td>gel electrophoresis unit</td><td>Fisher</td><td>HE99XPRO</td><td>appratus for gel running.</td></tr><tr><td>agrose</td><td>VWR</td><td>97062-250</td><td>For agarose gel.</td></tr><tr><td>paper tower</td><td>Fisher</td><td>19-120-2484</td><td>for transfering</td></tr><tr><td>filter paper</td><td>VWR</td><td>21427-386</td><td>for transfering</td></tr><tr><td>PVDF membrane</td><td>Bio-Rad</td><td>162-0177</td><td>for transfering</td></tr><tr><td>blocking milk powder</td><td>Bio-Rad</td><td>1706404XTU</td><td>for blocking in Western blot</td></tr><tr><td>MLKL antibody</td><td>Genetex</td><td>GTX107538</td><td>rabbit anti-MLKL antibody</td></tr><tr><td>RIPK1 antibody</td><td>BD Biosciences</td><td>610459</td><td>mouse anti-RIPK1 antibody</td></tr><tr><td>RIPK3 antibody</td><td>gift from Dr. Xiaodong Wang</td><td></td><td>rabbit anti-RIPK3. See refenence 11.</td></tr><tr><td>anti-Rabbit-HRP</td><td>Sigma</td><td>A6154</td><td>secondary antibody</td></tr><tr><td>ECL</td><td>Fisher</td><td>WBKLS0500</td><td>Western chemiluminescent HRP substrate</td></tr><tr><td>X-ray film</td><td>Fisher</td><td>F-BX810</td><td>for Western blot result</td></tr><tr><td>DMEM</td><td>Sigma</td><td>D6429</td><td>for cell culture</td></tr><tr><td>fetal bovine serum</td><td>Sigma</td><td>F4135</td><td>for cell culture</td></tr><tr><td>penicilin-streptomycin</td><td>Sigma</td><td>P4333</td><td>for cell culture</td></tr><tr><td>Trypsin solution</td><td>Sigma</td><td>T4049</td><td>for cell culture</td></tr><tr><td>PBS for tissue culture</td><td>Sigma</td><td>D8662</td><td>for cell culture</td></tr><tr><td>recombinant TNF</td><td>made in our lab</td><td></td><td>for inducing necroptosis. See reference 11.</td></tr><tr><td>smac-mimetic</td><td>gift from Dr. Xiaodong Wang</td><td></td><td>for inducing necroptosis. See reference 11.</td></tr><tr><td>ZVAD-FMK</td><td>ApexBio</td><td>A1902</td><td>for inducing necroptosis. See reference 11.</td></tr><tr><td>Cell Counter</td><td>Bio-Rad</td><td>1450102</td><td>Model TC20; for counting cells</td></tr><tr><td>Pierce&amp;trade; BCA Protein Assay Kit</td><td>Thermo Scientific</td><td>23225</td><td>for measuring protein concentration in cell lysates</td></tr><tr><td>Cell lifter</td><td>Fisher</td><td>07-200-364</td><td>to remove cells from dish</td></tr><tr><td>Lysis Buffer (1 L)</td><td></td><td></td><td>20 mL 1 M Tris pH 7.4&lt;br/&gt; 10 mL glycerol&lt;br/&gt; 30 mL 5 M NaCl&lt;br/&gt; 840 mL ddH&lt;sub&gt;2&lt;/sub&gt;O&lt;br/&gt; 10 mL Triton-X100&lt;br/&gt; (protease and phosphates inhibitors as desired)</td></tr><tr><td>10X TAE (1 L)</td><td></td><td></td><td>48.4 g Tris base&lt;br/&gt; 11.42 mL glacial acetic acid&lt;br/&gt; 20 mL 0.5M EDTA pH 8&lt;br/&gt; ddH&lt;sub&gt;2&lt;/sub&gt;0 to 1 L</td></tr><tr><td>4X SDD-AGE loading buffer (50 mL)</td><td></td><td></td><td>5 mL 10X TAE&lt;br/&gt; 10 mL glycerol&lt;br/&gt; 4 mL 20% SDS&lt;br/&gt; 0.5 mL 10% bromophenol blue&lt;br/&gt; 31 mL ddH&lt;sub&gt;2&lt;/sub&gt;O</td></tr><tr><td>TBS Transfer Buffer (1 L)</td><td></td><td></td><td>20 mL 1 M Tris pH 7.4&lt;br/&gt; 30 mL 5 M NaCl&lt;br/&gt; 950 mL ddH&lt;sub&gt;2&lt;/sub&gt;O</td></tr><tr><td>PBST Wash Buffer (1 L)</td><td></td><td></td><td>100 mL 10xPBS&lt;br/&gt; 800 mL ddH&lt;sub&gt;2&lt;/sub&gt;O&lt;br/&gt; 1 mL Tween20</td></tr><tr><td>10X PBS (10 L)</td><td></td><td></td><td>800 g NaCl&lt;br/&gt; 20 g KCl&lt;br/&gt; 144 g Na&lt;sub&gt;2&lt;/sub&gt;HPO&lt;sub&gt;4&lt;/sub&gt;&amp;middot;2H&lt;sub&gt;2&lt;/sub&gt;O&lt;br/&gt; 24 g KH&lt;sub&gt;2&lt;/sub&gt;PO&lt;sub&gt;4&lt;/sub&gt;&lt;br/&gt; add ddH&lt;sub&gt;2&lt;/sub&gt;O to 10 L</td></tr></tbody></table>

use of two dimensional semi-denaturing detergent agarose gel electrophoresis to confirm size heterogeneity of amyloid or amyloid-like fibers

Amyloid or amyloid-like fibers have been associated with many human diseases, and are now being discovered to be important for many signaling pathways. The ability to readily detect the formation of these fibers under various experimental conditions is essential for understanding their potential function. Many methods have been used to detect the fibers, but not without some drawbacks. For example, electron microscopy (EM), or staining with Congo Red or Thioflavin T often requires purification of the fibers. On the other hand, semi-denaturing detergent agarose gel electrophoresis (SDD-AGE) allows detection of the SDS-resistant amyloid-like fibers in the cell extracts without purification. In addition, it allows the comparison of the size difference of the fibers. More importantly, it can be used to identify specific proteins within the fibers by Western blotting. It is less time consuming and more easily accessible to a wider number of labs. SDD-AGE results often show variable degree of heterogeneity. It raises the question whether part of the heterogeneity results from the dissociation of the protein complex during the electrophoresis in the presence of SDS. For this reason, we have employed a second dimension of SDD-AGE to determine if the size heterogeneity seen in SDD-AGE is truly a result of fiber heterogeneity in vivo and not a result of either degradation or dissociation of some of the proteins during electrophoresis. This method allows fast, qualitative confirmation that the amyloid or amyloid-like fibers are not partially dissociating during the SDD-AGE process.

After necroptosis induction, RIPK1 and RIPK3 showed almost identical amyloid-like patterns (lanes 2 and 4, Figure 1). However, MLKL fibers were more heterogeneous and seemed to be smaller than RIPK1/RIPK3 fibers (lane 6, Figure 1). That prompted us to develop the 2D SDD-AGE method to address the possibility whether MLKL forms RIPK1/RIPK3-independent fibers or MLKL simply dissociates from the large RIPK1/RIPK3/MLKL fibers during S...

Watch this Scientific Journal Video about Use of Two Dimensional Semi-denaturing Detergent Agarose Gel Electrophoresis to Confirm Size Heterogeneity of Amyloid or Amyloid-like Fibers at JoVE.com

Use of Two Dimensional Semi-denaturing Detergent Agarose Gel Electrophoresis to Confirm Size Heterogeneity of Amyloid or Amyloid-like Fibers

Here we use two-dimensional semi-denaturing agarose gel electrophoresis to confirm the presence of amyloid-like fibers of heterogeneous size and exclude the possibility that the size heterogeneity is due to dissociation of the amyloid fibers during the gel running process.

Amyloid or amyloid-like fibers have been associated with many human diseases, and are now being discovered to be important for many signaling pathways. ...

use-two-dimensional-semi-denaturing-detergent-agarose-gel

Research

JoVE Journal

Biochemistry

9.7K Views.  UT Southwestern Medical Center. Hier gebruiken we de Elektroforese van het gel van de tweedimensionale semi-denatureren agarose bevestigen de aanwezigheid van amyloid-achtige vezels van heterogene grootte en uitsluiten van de mogelijkheid dat de heterogeniteit van grootte te wijten aan de dissociatie van de amyloïde vezels tijdens de gel is lopend proces.

Video: Use of Two Dimensional Semi-denaturing Detergent Agarose Gel Electrophoresis to Confirm Size Heterogeneity of Amyloid or Amyloid-like Fibers

SDS-PAGE/Immunoblot Detection of A&beta; Multimers in Human Cortical Tissue Homogenates using Antigen-Epitope Retrieval

The anomalous folding and polymerization of the &beta;-amyloid (A&beta;) peptide is thought to initiate the neurodegenerative cascade in Alzheimer's disease pathogenesis1. A&beta; is predominantly a 40- or 42-amino acid peptide that is prone to self-aggregation into &beta;-sheet-rich amyloid fibrils that are found in the cores of cerebral senile plaques in Alzheimer's disease. Increasing evidence suggests that low molecular weight, soluble A&beta; multimers are more toxic than fibrillar A&beta; amyloid2. The identification and quantification of low- and high-molecular weight multimeric A&beta; species in brain tissue is an essential objective in Alzheimer's disease research, and the methods employed also can be applied to the identification and characterization of toxic multimers in other proteopathies3. Naturally occurring A&beta; multimers can be detected by SDS-polyacrylamide gel electrophoresis followed by immunoblotting with A&beta;-specific antibodies. However, the separation and detection of multimeric A&beta; requires the use of highly concentrated cortical homogenates and antigen retrieval in small pore-size nitrocellulose membranes. Here we describe a technique for the preparation of clarified human cortical homogenates, separation of proteins by SDS-PAGE, and antigen-epitope retrieval/Western blotting with antibody 6E10 to the N-terminal region of the A&beta; peptide. Using this protocol, we consistently detect A&beta; monomers, dimers, trimers, tetramers, and higher molecular weight multimers in cortical tissue from humans with Alzheimer's pathology.

SDS-PAGE/Immunoblot Detection of A&#946; Multimers in Human Cortical Tissue Homogenates using Antigen-Epitope Retrieval

We describe a technique for the preparation of clarified human cortical homogenates, protein separation by SDS-PAGE, antigen retrieval and immunoblotting with an antibody to the A&beta; peptide. Using this protocol, we consistently detect monomeric and multimeric A&beta; in cortical tissue from humans with Alzheimer's pathology.

The anomalous folding and polymerization of the &beta;-amyloid (A&beta;) peptide is thought to initiate the neurodegenerative cascade in Alzheimer's ...

Neuroscience

Screening for Amyloid Aggregation by Semi-Denaturing Detergent-Agarose Gel Electrophoresis

Amyloid aggregation is associated with numerous protein misfolding pathologies and underlies the infectious properties of prions, which are conformationally self-templating proteins that are thought to have beneficial roles in lower organisms.  Amyloids have been notoriously difficult to study due to their insolubility and structural heterogeneity.  However, resolution of amyloid polymers based on size and detergent insolubility has been made possible by Semi-Denaturing Detergent-Agarose Gel Electrophoresis (SDD-AGE).  This technique is finding widespread use for the detection and characterization of amyloid conformational variants.  Here, we demonstrate an adaptation of this technique that facilitates its use in large-scale applications, such as screens for novel prions and other amyloidogenic proteins.  The new SDD-AGE method uses capillary transfer for greater reliability and ease of use, and allows any sized gel to be accomodated.  Thus, a large number of samples, prepared from cells or purified proteins, can be processed simultaneously for the presence of SDS-insoluble conformers of tagged proteins.

SDD-AGE is a useful technique for the detection and characterization of amyloid-like polymers in cells. Here we demonstrate an adaptation that makes this technique amenable to large-scale applications.

Amyloid aggregation is associated with numerous protein misfolding pathologies and underlies the infectious properties of prions, which are ...

Biology

Consensus Brain-derived Protein, Extraction Protocol for the Study of Human and Murine Brain Proteome Using Both 2D-DIGE and Mini 2DE Immunoblotting

Two-dimensional gel electrophoresis (2DE) is a powerful tool to uncover proteome modifications potentially related to different physiological or pathological conditions. Basically, this technique is based on the separation of proteins according to their isoelectric point in a first step, and secondly according to their molecular weights by SDS polyacrylamide gel electrophoresis (SDS-PAGE). In this report an optimized sample preparation protocol for little amount of human post-mortem and mouse brain tissue is described. This method enables to perform both two-dimensional fluorescence difference gel electrophoresis (2D-DIGE) and mini 2DE immunoblotting. The combination of these approaches allows one to not only find new proteins and/or protein modifications in their expression thanks to its compatibility with mass spectrometry detection, but also a new insight into markers validation. Thus, mini-2DE coupled to western blotting permits to identify and validate post-translational modifications, proteins catabolism and provides a qualitative comparison among different conditions and/or treatments. Herein, we provide a method to study components of protein aggregates found in AD and Lewy body dementia such as the amyloid-beta peptide and the alpha-synuclein. Our method can thus be adapted for the analysis of the proteome and insoluble proteins extract from human brain tissue and mice models too. In parallel, it may provide useful information for the study of molecular and cellular pathways involved in neurodegenerative diseases as well as potential novel biomarkers and therapeutic targets.

A common protein extraction protocol using urea/thiourea/SDS buffer for human and mice brain tissue allows indentification of proteins by 2D-DIGE and their subsequent characterization by mini 2DE immunoblotting. This method enables one to obtain more reproducible and reliable results from human biopsies and experimental models.

Two-dimensional gel electrophoresis (2DE) is a powerful tool to uncover proteome modifications potentially related to different physiological or ...

Biochemical Purification and Proteomic Characterization of Amyloid Fibril Cores from the Brain

Proteinaceous fibrillar inclusions are key pathological hallmarks of multiple neurodegenerative diseases. In the early stages of Alzheimer&#39;s disease (AD), amyloid-beta peptides form protofibrils in the extracellular space, which act as seeds that gradually grow and mature into large amyloid plaques. Despite this basic understanding, current knowledge of the amyloid fibril structure, composition, and deposition patterns in the brain is limited. One major barrier has been the inability to isolate highly purified amyloid fibrils from brain extracts. Affinity purification and laser capture microdissection-based approaches have been previously used to isolate amyloids but are limited by the small quantity of material that can be recovered. This novel, robust protocol describes the biochemical purification of amyloid plaque cores using sodium dodecyl sulfate (SDS) solubilization with sucrose density gradient ultracentrifugation and ultrasonication and yields highly pure fibrils from AD patients and AD model brain tissues. Mass spectrometry (MS)-based bottom-up proteomic analysis of the purified material represents a robust strategy to identify nearly all the primary protein components of amyloid fibrils. Previous proteomic studies of proteins in the amyloid coronae have revealed an unexpectedly large and functionally diverse collection of proteins. Notably, after refining the purification strategy, the number of co-purifying proteins was reduced by more than 10-fold, indicating the high purity of the isolated SDS insoluble material. Negative staining and immuno-gold electron microscopy allowed confirmation of the purity of these preparations. Further studies are required to understand the spatial and biological attributes that contribute to the deposition of these proteins into amyloid inclusions. Taken together, this analytical strategy is well-positioned to increase the understanding of amyloid biology.

This biochemical purification method with mass spectrometry-based proteomic analysis facilitates the robust characterization of amyloid fibril cores, which may accelerate the identification of targets for preventing Alzheimer's disease.

Proteinaceous fibrillar inclusions are key pathological hallmarks of multiple neurodegenerative diseases. In the early stages of Alzheimer&#39;s disease ...

Separating Protein with SDS-PAGE

Sodium Dodecyl Sulfate Poly-Acrylamide Gel Electrophoresis, or SDS-PAGE, is a widely-used technique for separating mixtures of proteins based on their size and nothing else. SDS, an anionic detergent, is used to produce an even charge across the length of proteins that have been linearized. By first loading them into a gel made of polyacrylamide and then applying an electric field to the gel, SDS-coated proteins are then separated. The electric field acts as the driving force, drawing the SDS coated proteins towards the anode with larger proteins moving more slowly than small proteins. In order to identify proteins by size, protein standards of a known size are loaded along with samples and run under the same conditions.
This video presents an introduction to SDS-PAGE by first explaining the theory behind it and later demonstrating its step-by-step procedure. Various experimental parameters, such as the polyacrylamide concentration and voltage applied to the gel are discussed. Downstream staining methods like Coomassie and silver stains are introduced, and variations of the method, like 2D gel electrophoresis are presented.

Separating Protein with SDS-PAGE: Procedure and Applications

Sodium Dodecyl Sulfate Poly-Acrylamide Gel Electrophoresis, or SDS-PAGE, is a widely-used technique for separating mixtures of proteins based on their ...

Education

JoVE Science Education

Basic Biology

Basic Methods in Cellular and Molecular Biology

Two-Dimensional Gel Electrophoresis

Two-dimensional gel electrophoresis (2DGE) is a technique that can resolve thousands of biomolecules from a mixture. This technique involves two distinct separation methods that have been coupled together: isoelectric focusing (IEF) and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). This physically separates compounds across two axes of a gel by their isoelectric points (an electrochemical property) and their molecular weights.
The procedure in this video covers the main concepts of 2DGE and a general procedure for characterizing the composition of a complex protein solution. Three examples of this technique are shown in the applications section, including biomarker detection for disease initiation and progress, monitoring treatment in patients, and the study of proteins following posttranslational modification (PTM).
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Two-dimensional, or 2D, gel electrophoresis is a technique utilizing two distinct separation methods which can separate thousands of proteins from a single mixture. One of the techniques, SDS-PAGE or sodium dodecyl sulfate polyacrylamide gel electrophoresis, cannot fully separate complex mixtures alone. 2D gel electrophoresis couples the SDS-PAGE to a second method, isoelectric focusing or IEF, which separates based on isoelectric points, allowing for the resolution of potentially all proteins in a cell lysate. This video will show the principles of 2D gel electrophoresis, a general procedure, and some of its biomedical applications.
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2D gel electrophoresis begins with IEF as the first dimension. Every protein has a pH value, called the isoelectric point or pI, where the net charge is zero. When a protein is subjected to an electric field, it will move toward the electrode with opposite charge. Samples of interest are loaded onto immobilized pH gradient, or IPG, strips which have embedded ampholytes, molecules containing both acidic and basic groups. An electric field is then applied to the pH gradient strip, causing the proteins to migrate until they reach the pH value matching their pI, where they lose their net charge.
Prior to running the second-dimension, the embedded proteins are treated with SDS, denaturing them and providing a uniform negative charge. Once completed, the IPG strips are placed onto a polyacrylamide gel. An applied electric field draws the proteins toward the anode, with larger proteins moving more slowly through the gel.
Once the protein mixture has been separated according to pI and molecular weight, the proteome map is visualized using stains, and proteins of interest are identified.
Now that we have discussed the principles of 2D gel electrophoresis, let&#39;s go over a typical laboratory procedure.
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Before the experiment can be performed, the proteins must be solubilized into media. Solubilization of the sample is achieved by de-aggregating proteins with a combination of chaotropic agents for disrupting hydrogen-bonding interactions, nonionic detergents to prevent altering of the proteins&#39; charge, reducing agents to break disulfide bonds, and buffers. To remove interfering abundant proteins and other molecules, the material is sequentially extracted by centrifugation, and collection of the resulting pellet; followed by treatment with endonuclease, an enzyme used to consume any DNA that would interfere with the experiment.
Once the proteins have been solubilized, IPG strips are prepared by rinsing with a strip-cleaning solution and left upside-down to dry. Each strip is then assigned a strip holder number. Once ready, the cellular extract is loaded onto the strips in a slow, sliding motion from the negative to the positive end. For the purpose of rehydration, damp blotting paper is placed on top of the electrode and under the gel strips; the IPG strips are then lined onto the IEF instrument. A high electric current is applied, and the proteins begin to migrate.
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Following completion of the first dimension, the gel for SDS-PAGE is prepared in a casting apparatus. The IPG strips are treated by placing them face down in SDS-containing equilibration buffer. The electrophoresis unit is readied with the addition of electrophoresis buffer. The treated IPG strips are collected using tweezers, placed on top of the gel plates, and sealed with agarose-sealing solution. A voltage source then applies an electric field, which is held until the fastest-moving proteins are 1 cm from the bottom of the gel.
After completion of the electrophoresis, the proteins must be visualized. Traditionally this is performed by staining with Coomassie blue or silver nitrate. Proteins of interest may be transferred from the gel, and analyzed by Western blot analysis.
A second identification approach involves excision of the proteins from the gel, digesting them, than analyzing them by mass spectrometry.
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Now that we&#39;ve reviewed a procedure, let&#39;s look at some of the uses for 2D gel electrophoresis.
One of the most common uses for this technique is the identification of molecules involved in disease initiation and progression. 2D gel electrophoresis, coupled with mass spectrometry, can detect the up- or down-regulation of specific proteins in diseased areas in comparison to healthy ones.
Additionally, 2D gel electrophoresis is useful in following the progress of patients&#39; response to a potential therapeutic drug. Specimens may be taken from patients at various timepoints following administration of the treatment. In this way, 2D gel electrophoresis coupled with Western blot or mass spectrometry analysis, can detect proteins associated with negative responses such as inflammation; or the absence of proteins in an alleviated state.
Another use for 2D gel electrophoresis is in the study of protein structure and function following posttranslational modification, or PTM, which are additions to proteins following their translation from mRNA. PTM&#39;s can regulate a variety of functions, including protein signaling, gene expression, or cause oxidative damage. 2D gel electrophoresis is sensitive to modifications such as methylation or acetylation, which can cause a shift in pI as well as the molecular weight.
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You&#39;ve just watched JoVE&#39;s video on 2D gel electrophoresis. This video described the principles of the technique, a typical experimental procedure, and several of its applications in the field of biomedicine.
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Two-dimensional gel electrophoresis (2DGE) is a technique that can resolve thousands of biomolecules from a mixture. This technique involves two distinct ...

Chemistry

Isolation of Amyloid Fibrils from Brain Tissue Extract

Source: Upadhyay, A. et al., <a href="https://app.jove.com/v/63816">Biochemical Purification and Proteomic Characterization of Amyloid Fibril Cores from the Brain.</a> J. Vis. Exp. (2022)
This video demonstrates the protocol for isolating&#160; amyloid fibrils from mouse brain tissue extract using density gradient centrifugation and digestion of non-amyloid proteins.

All procedures involving animal samples have been reviewed and approved by the appropriate animal ethical review committee.
1. Tissue harvesting and ...

JoVE Encyclopedia of Experiments

Neuropathology

Neurodegenerative Diseases

Two-Dimensional Semi-Denaturing Agarose Gel Electrophoresis: A Technique to Separate Polymorphic Amyloids Fibers Based on Size Heterogeneity

Source: Hanna-Addams, S., et al. <a href="https://www.jove.com/v/57498">Use of Two Dimensional Semi-denaturing Detergent Agarose Gel Electrophoresis to Confirm Size Heterogeneity of Amyloid or Amyloid-like Fibers</a>. J. Vis. Exp. (2018).
This video demonstrates the two-dimensional semi-denaturing detergent agarose gel electrophoresis-based separation of amyloid fibers. The technique separates the polymorphic amyloid aggregates based on their heterogeneous size.

Source: Hanna-Addams, S., et al. Use of Two Dimensional Semi-denaturing Detergent Agarose Gel Electrophoresis to Confirm Size Heterogeneity of Amyloid or ...

Biological Techniques

Electrophoresis Techniques

Two-Dimensional Polyacrylamide Gel Electrophoresis: A Separation Technique for Analysis of Proteins in Complex Protein Mixture Based on Charge and Molecular Weight

Source: Zhan, X., et al. <a href="https://www.jove.com/v/56739">Two-dimensional Gel Electrophoresis Coupled with Mass Spectrometry Methods for an Analysis of Human Pituitary Adenoma Tissue Proteome</a> J. Vis. Exp. (2018)
In this video, we demonstrate a two-dimensional gel electrophoresis method that separates individual proteins from a complex protein mixture obtained from tumor tissues of human nonfunctional pituitary adenoma (NFPA). The proteins are separated based on their electric charge in the first dimension and further separated based on molecular weights in the second dimension.

Source: Zhan, X., et al. Two-dimensional Gel Electrophoresis Coupled with Mass Spectrometry Methods for an Analysis of Human Pituitary Adenoma Tissue ...

Two-dimensional Gel Electrophoresis

Two-dimensional gel electrophoresis is a high-resolution protein separation method first introduced by O&#39;&#160;Farrell and Klose in 1975. This method involves protein separation by two dimensions, mass and charge, making it more accurate than one-dimensional gel electrophoresis.
The first dimension separation uses the isoelectric focusing or IEF technique performed on immobilized pH gradient (IPG) strips that separate proteins according to their isoelectric points.
Biological samples, such as&#160; cells and tissues, are first prepared for IEF by treatment with a buffer containing urea, dithiothreitol, detergents, and ampholytes. Here, urea and detergent solubilize and denature the proteins. Dithiothreitol is a reducing agent that cleaves disulfide bonds. Ampholytes used in a suitable concentration solubilize the protein and maintain pH. The buffer also rehydrates the IPG strip that helps it absorb the proteins before their charge-based separation.
Proteins are amphoteric molecules with positive and negative charges. The amphoteric protein molecules migrate on the pH gradient of the IPG strip under the electric current. Once the proteins reach their isoelectric point, they immobilize because, at this point, they have no net charge. IPG strips have a fixed pH gradient; for instance, strips with a smaller pH range (for example, pH 4-7) can detect proteins with higher accuracy than those with a broader range (pH 3-10). Once the proteins separate, the IPG strips are treated with sodium dodecyl sulfate (SDS) buffer to proceed to the next phase, i.e., mass-based separation using SDS-PAGE (polyacrylamide gel electrophoresis). SDS covers the uncharged protein on the IPG strips with a negative charge, and glycerol reduces electroendosmosis which helps the transfer of proteins from the first to the second dimension.
Generally, bands on the gel can be visualized upon staining. Sometimes radiolabelled samples are used to obtain an autoradiographic image. Samples capable of producing fluorescent images can also be used.
Two-dimensional gel electrophoresis has gained importance owing to the precision of the outcome results. However, the method is unsuitable for distinguishing highly hydrophobic proteins,&#160; proteins with high molecular mass, or those present in very low quantities per cell.

Two-dimensional gel electrophoresis is a high-resolution protein separation method first introduced by O&#39;&#160;Farrell and Klose in 1975. This method ...

Use of Two Dimensional Semi-denaturing Detergent Agarose Gel Electrophoresis to Confirm Size Heterogeneity of Amyloid or Amyloid-like Fibers

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