Name: nitrogen cavitation and differential centrifugation allows for monitoring the distribution of peripheral membrane proteins in cultured cells
Uploaded: 2017-08-18T14:00:00
Description: Watch this Scientific Journal Video about Nitrogen Cavitation and Differential Centrifugation Allows for Monitoring the Distribution of Peripheral Membrane Proteins in Cultured Cells at JoVE.com

This work was funded by GM055279, CA116034 and CA163489.

1. Buffer and Equipment Preparations
<ol>
	<li>Chill 45 mL cell disruption bombs, 15 mL tubes, and ultracentrifugation tubes at 4 &#176;C.</li>
	<li>Prepare and chill 25 mL of homogenization buffer per 2 x 107 cells at 4 &#176;C. Add one protease inhibitor tablet just before use. 
	NOTE: Homogenization buffers typically contain KCl rather than NaCl to better reflect intracellular salt composition. Homogenization buffer used in this protocol consists of 10 mM HEPES at pH 7.4, 10 mM KCl and 1.5 mM MgCl<su...

<ol>
	<li>Miyawaki, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Proteins+on+the+move:+insights+gained+from+fluorescent+protein+technologies.">Proteins on the move: insights gained from fluorescent protein technologies.</a> Nat Rev Mol Cell Biol. 12 (10), 656-668 (2011).</li><li>Bunger, S., Roblick, U. J., Habermann, J. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparison+of+five+commercial+extraction+kits+for+subsequent+membrane+protein+profiling.">Comparison of five commercial extraction kits for subsequent membrane protein profiling.</a> Cytotechnology. 61 (3), 153-159 (2009).</li><li>Simpson, R. J. <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+cultured+cells+by+nitrogen+cavitation.">Disruption of cultured cells by nitrogen cavitation.</a> Cold Spring Harb Protoc. (11), (2010).</li><li>Klempner, M. S., Mikkelsen, R. B., Corfman, D. H., Andre-Schwartz, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neutrophil+plasma+membranes.+I.+High-yield+purification+of+human+neutrophil+plasma+membrane+vesicles+by+nitrogen+cavitation+and+differential+centrifugation.">Neutrophil plasma membranes. I. High-yield purification of human neutrophil plasma membrane vesicles by nitrogen cavitation and differential centrifugation.</a> J Cell Biol. 86 (1), 21-28 (1980).</li><li>Philips, M. 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=Low+molecular+weight+GTP-binding+proteins+in+human+neutrophil+granule+membranes.">Low molecular weight GTP-binding proteins in human neutrophil granule membranes.</a> Journal of Biological Chemistry. 266, 1289-1298 (1991).</li><li>Wallach, D. F., Soderberg, J., Bricker, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+phospholipides+of+Ehrlich+ascites+carcinoma+cells:+composition+and+intracellular+distribution.">The phospholipides of Ehrlich ascites carcinoma cells: composition and intracellular distribution.</a> Cancer Res. 20, 397-402 (1960).</li><li>Hunter, M. J., Commerford, S. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pressure+homogenization+of+mammalian+tissues.">Pressure homogenization of mammalian tissues.</a> Biochim Biophys Acta. 47, 580-586 (1961).</li><li>Wallach, D. F., Kamat, V. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Plasma+and+Cytoplasmic+Membrane+Fragments+from+Ehrlich+Ascites+Carcinoma.">Plasma and Cytoplasmic Membrane Fragments from Ehrlich Ascites Carcinoma.</a> Proc Natl Acad Sci U S A. 52, 721-728 (1964).</li><li>Birckbichler, P. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Preperation+of+plasma+membrane+vesicles+by+nitrogen+cavitation.">Preperation of plasma membrane vesicles by nitrogen cavitation.</a> TCA manual / Tissue Culture Association. 3 (3), 653-654 (1977).</li><li>Brock, T. G., Paine, R., Peters-Golden, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Localization+of+5-lipoxygenase+to+the+nucleus+of+unstimulated+rat+basophilic+leukemia+cells.">Localization of 5-lipoxygenase to the nucleus of unstimulated rat basophilic leukemia cells.</a> J Biol Chem. 269 (35), 22059-22066 (1994).</li><li>Dowben, R. M., Gaffey, A., Lynch, P. M. <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+liver+and+muscle+polyribosomes+in+high+yield+after+cell+disruption+by+nitrogen+cavitation.">Isolation of liver and muscle polyribosomes in high yield after cell disruption by nitrogen cavitation.</a> FEBS Letters. 2 (1), (1968).</li><li>Dai, Q., 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=Mammalian+prenylcysteine+carboxyl+methyltransferase+is+in+the+endoplasmic+reticulum.">Mammalian prenylcysteine carboxyl methyltransferase is in the endoplasmic reticulum.</a> J Biol Chem. 273 (24), 15030-15034 (1998).</li><li>Wynne, J. 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=Rap1-interacting+adapter+molecule+(RIAM)+associates+with+the+plasma+membrane+via+a+proximity+detector.">Rap1-interacting adapter molecule (RIAM) associates with the plasma membrane via a proximity detector.</a> J Cell Biol. , (2012).</li><li>Zhou, 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=VPS35+binds+farnesylated+N-Ras+in+the+cytosol+to+regulate+N-Ras+trafficking.">VPS35 binds farnesylated N-Ras in the cytosol to regulate N-Ras trafficking.</a> J Cell Biol. 214 (4), 445-458 (2016).</li><li>Sim, D. S., Dilks, J. R., Flaumenhaft, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Platelets+possess+and+require+an+active+protein+palmitoylation+pathway+for+agonist-mediated+activation+and+in+vivo+thrombus+formation.">Platelets possess and require an active protein palmitoylation pathway for agonist-mediated activation and in vivo thrombus formation.</a> Arterioscler Thromb Vasc Biol. 27 (6), 1478-1485 (2007).</li><li>Pace, P. E., Peskin, A. V., Han, M. H., Hampton, M. B., Winterbourn, C. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hyperoxidized+peroxiredoxin+2+interacts+with+the+protein+disulfide-+isomerase+ERp46.">Hyperoxidized peroxiredoxin 2 interacts with the protein disulfide- isomerase ERp46.</a> Biochem J. 453 (3), 475-485 (2013).</li><li>Annis, M. 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=Endoplasmic+reticulum+localized+Bcl-2+prevents+apoptosis+when+redistribution+of+cytochrome+c+is+a+late+event.">Endoplasmic reticulum localized Bcl-2 prevents apoptosis when redistribution of cytochrome c is a late event.</a> Oncogene. 20 (16), 1939-1952 (2001).</li><li>Berkowitz, S. A., Wolff, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Intrinsic+calcium+sensitivity+of+tubulin+polymerization.+The+contributions+of+temperature,+tubulin+concentration,+and+associated+proteins.">Intrinsic calcium sensitivity of tubulin polymerization. The contributions of temperature, tubulin concentration, and associated proteins.</a> J Biol Chem. 256 (21), 11216-11223 (1981).</li></ol>

The advantages of nitrogen cavitation over other methods of mechanical disruption are manifold. Perhaps the most significant benefit is its ability to gently yet efficiently homogenize specimens. The physical principles of decompression cools samples instead of generating local heating damage like ultrasonic and friction/shearing based techniques. Cavitation is also extremely efficient at disrupting the plasma membrane. Because nitrogen bubbles are generated within each individual cell upon decompression, the cavitation ...

Cellular proteins can be divided into two classes: those that are associated with membranes and those that are not. Non-membrane associated proteins are found in the cytosol, nucleoplasm and lumina of organelles such as the endoplasmic reticulum (ER). There are two classes of membrane-associated proteins, integral and peripheral. Integral membrane proteins are also known as transmembrane proteins because one or more segments of the polypeptide chain spans the membrane, typically as an &#945;-helix composed of hydrophobic amino acids. Transmembrane proteins are co-translationally inserted into membranes in the course of their biosynthesis and remain so configured until they are catabolized. Peripheral membrane proteins are secondarily driven to membranes, usually as a consequence of post-translational modification with hydrophobic molecules such as lipids. In contrast to integral membrane proteins, the association of peripheral membrane proteins with cellular membranes is reversible and can be regulated. Many peripheral membrane proteins function in signaling pathways, and regulated association with membranes is one mechanism for activating or inhibiting a pathway. One example of a signaling molecule that is a peripheral membrane protein is the small GTPase, RAS. After a series of post-translational modifications that include modification with a farnesyl lipid, the modified C-terminus of a mature RAS protein inserts into the cytoplasmic leaflet of the cellular membrane. Specifically, the plasma membrane is where the RAS engages its downstream effector RAF1. To prevent constitutive activation of mitogen-activated protein kinase (MAPK) pathway, multiple levels of control of RAS are in place. Besides rendering RAS inactive by hydrolyzing GTP into GDP, active RAS also can be released from the plasma membrane by modifications or interactions with solubilizing factors to inhibit signaling. Although fluorescent live imaging affords cell biologists the opportunity to observe the subcellular localization of fluorescent protein-tagged peripheral membrane proteins1, there remains a critical need to evaluate membrane association of endogenous proteins semi-quantitatively with simple biochemical approaches.
The proper biochemical evaluation of protein partitioning between membrane and soluble fractions is critically dependent on two factors: cellular homogenization and efficient separation of membrane and soluble fractions. Although some protocols, including the most widely used commercialized kits, depend on detergent-based cell homogenization, these methods can obfuscate analysis by extracting membrane proteins into the soluble phase2. Accordingly, non-detergent based, mechanical methods of cell disruption provide cleaner results. There are several methods of mechanical disruption of cells grown in culture or harvested from blood or organs. These include Dounce homogenization, fine needle disruption, ball-bearing homogenization, sonication and nitrogen cavitation. Here we evaluate nitrogen cavitation and compare it to other methods. Nitrogen cavitation relies on nitrogen that is dissolved in the cytoplasm of the cells under high pressure. After equilibration, the cell suspension is abruptly exposed to atmospheric pressure such that nitrogen bubbles are formed in the cytoplasm that tear open the cell as a consequence of their effervescence. If the pressure is sufficiently high, nitrogen effervescence can disrupt the nucleus3 and membrane bound organelles like lysosomes4. However, if the pressure is kept low enough, the decompression will disrupt the plasma membrane and ER but not other organelles, thereby spilling both cytosol and intact cytoplasmic organelles into the homogenate that is designated the cavitate5. For this reason, nitrogen cavitation is the method of choice for isolating organelles like lysosomes and mitochondria.
However, it is also an excellent way of preparing a homogenate that can be easily separated into membrane and soluble fractions. The pressure vessel (henceforth called &#34;the bomb&#34;) used during cavitation consists of a thick stainless steel casing that withstands high pressure, with an inlet for delivery of the nitrogen gas from a tank and an outlet port with an adjustable discharge valve.
Nitrogen cavitation has been used for cell homogenization since the 1960s6. In 1961, Hunter and Commerfold7 established nitrogen cavitation as a viable option for mammalian tissue disruption. Since then, researchers have adapted the technique to various cells and tissues with success, and nitrogen cavitation has become a staple in multiple applications, including membrane preparation8,9, nuclei and organelle preparation10,11, and labile biochemical extraction. Currently, cell biologists more often employ other methods of cell homogenization because the benefits of nitrogen homogenization have not been widely advertised, nitrogen bombs are expensive and there is a misconception that a relatively large number of cells is required. Protocols for nitrogen cavitation to achieve cell-free homogenates with intact nuclei have not been published, and in most published evaluations volumes of 20 mL of cell suspension were used. To adapt this classic technique to suit current requirements of working with small-scale samples, we present a modified protocol of nitrogen cavitation specifically designed for cultured cells. After nitrogen cavitation, the homogenate is separated into soluble (S) and membrane (P) fractions by differential centrifugation, first with a low-speed spin to remove nuclei and unbroken cells, and then with a high-speed spin (&#62;100,000 x g) to separate membranes from the soluble fraction. We analyze the efficiency of the separation with immunoblots and compare nitrogen cavitation with other mechanical disruption techniques. We also investigate the osmotic effect of homogenization buffer during nitrogen cavitation.

<table border="0" cellpadding="0" cellspacing="0" width="1015">
	<tbody>
		<tr height="33">
			<td height="33" style="height:33px;width:393px;">Cell Disruption Vessel (45 mL)</td>
			<td style="width:181px;">Parr Instrument</td>
			<td style="width:145px;">4639</td>
			<td style="width:296px;">Nitrogen cavitation Bomb</td>
		</tr>
		<tr height="33">
			<td height="33" style="height:33px;width:393px;">Dounce homogenizer (2 mL)</td>
			<td style="width:181px;">Kontes</td>
			<td style="width:145px;">885300-0002</td>
			<td style="width:296px;">Dounce pestle and tube</td>
		</tr>
		<tr height="33">
			<td height="33" style="height:33px;width:393px;">U-100 Insulin Syringe 28G&#189;</td>
			<td style="width:181px;">Becton Dickinson</td>
			<td style="width:145px;">329461</td>
			<td style="width:296px;">Needle</td>
		</tr>
		<tr height="33">
			<td height="33" style="height:33px;width:393px;">Atg12 antibody</td>
			<td style="width:181px;">Santa Cruz</td>
			<td style="width:145px;">271688</td>
			<td style="width:296px;">Mouse antibody, use at 1:1000 dilution</td>
		</tr>
		<tr height="33">
			<td height="33" style="height:33px;width:393px;">&#946;-actin antibody</td>
			<td style="width:181px;">Santa Cruz</td>
			<td style="width:145px;">47778</td>
			<td style="width:296px;">Mouse antibody, use at 1:1000 dilution</td>
		</tr>
		<tr height="33">
			<td height="33" style="height:33px;width:393px;">&#946;-tubulin antibody</td>
			<td style="width:181px;">DSHB</td>
			<td style="width:145px;">E7-s</td>
			<td style="width:296px;">Mouse antibody, use at 1:5000 dilution</td>
		</tr>
		<tr height="33">
			<td height="33" style="height:33px;width:393px;">Calnexin antibody</td>
			<td style="width:181px;">Santa Cruz</td>
			<td style="width:145px;">23954</td>
			<td style="width:296px;">Mouse antibody, use at 1:1000 dilution</td>
		</tr>
		<tr height="33">
			<td height="33" style="height:33px;width:393px;">Calregulin antibody</td>
			<td style="width:181px;">Santa Cruz</td>
			<td style="width:145px;">373863</td>
			<td style="width:296px;">Mouse antibody, use at 1:1000 dilution</td>
		</tr>
		<tr height="33">
			<td height="33" style="height:33px;width:393px;">Catalase antibody</td>
			<td style="width:181px;">Santa Cruz</td>
			<td style="width:145px;">271803</td>
			<td style="width:296px;">Mouse antibody, use at 1:1000 dilution</td>
		</tr>
		<tr height="33">
			<td height="33" style="height:33px;width:393px;">CIMPR antibody</td>
			<td style="width:181px;">Abcam</td>
			<td style="width:145px;">124767</td>
			<td style="width:296px;">Rabbit antibody, use at 1:1000 dilution</td>
		</tr>
		<tr height="33">
			<td height="33" style="height:33px;width:393px;">EEA1 antibody</td>
			<td style="width:181px;">Santa Cruz</td>
			<td style="width:145px;">137130</td>
			<td style="width:296px;">Mouse antibody, use at 1:1000 dilution</td>
		</tr>
		<tr height="33">
			<td height="33" style="height:33px;width:393px;">EGFR antibody</td>
			<td style="width:181px;">Santa Cruz</td>
			<td style="width:145px;">373746</td>
			<td style="width:296px;">Mouse antibody, use at 1:1000 dilution</td>
		</tr>
		<tr height="33">
			<td height="33" style="height:33px;width:393px;">F0-ATPase antibody</td>
			<td style="width:181px;">Santa Cruz</td>
			<td style="width:145px;">514419</td>
			<td style="width:296px;">Mouse antibody, use at 1:1000 dilution</td>
		</tr>
		<tr height="33">
			<td height="33" style="height:33px;width:393px;">F1-ATPase antibody</td>
			<td style="width:181px;">Santa Cruz</td>
			<td style="width:145px;">55597</td>
			<td style="width:296px;">Mouse antibody, use at 1:1000 dilution</td>
		</tr>
		<tr height="33">
			<td height="33" style="height:33px;width:393px;">Fibrillarin antibody</td>
			<td style="width:181px;">Santa Cruz</td>
			<td style="width:145px;">374022</td>
			<td style="width:296px;">Mouse antibody, use at 1:200 dilution</td>
		</tr>
		<tr height="33">
			<td height="33" style="height:33px;width:393px;">Golgin 97 antibody</td>
			<td style="width:181px;">Santa Cruz</td>
			<td style="width:145px;">59820</td>
			<td style="width:296px;">Mouse antibody, use at 1:1000 dilution</td>
		</tr>
		<tr height="33">
			<td height="33" style="height:33px;width:393px;">HDAC1 antibody</td>
			<td style="width:181px;">Santa Cruz</td>
			<td style="width:145px;">81598</td>
			<td style="width:296px;">Mouse antibody, use at 1:1000 dilution</td>
		</tr>
		<tr height="33">
			<td height="33" style="height:33px;width:393px;">Hexokinase 1 antibody</td>
			<td style="width:181px;">Cell Signaling Technology</td>
			<td style="width:145px;">2024S</td>
			<td style="width:296px;">Rabbit antibody, use at 1:1000 dilution</td>
		</tr>
		<tr height="33">
			<td height="33" style="height:33px;width:393px;">Lamin A/C antibody</td>
			<td style="width:181px;">Santa Cruz</td>
			<td style="width:145px;">376248</td>
			<td style="width:296px;">Mouse antibody, use at 1:1000 dilution</td>
		</tr>
		<tr height="33">
			<td height="33" style="height:33px;width:393px;">LAMP1 antibody</td>
			<td style="width:181px;">DSHB</td>
			<td style="width:145px;">H4A3-c</td>
			<td style="width:296px;">Mouse antibody, use at 1:1000 dilution</td>
		</tr>
		<tr height="33">
			<td height="33" style="height:33px;width:393px;">Na+/K+ ATPase antibody</td>
			<td style="width:181px;">Santa Cruz</td>
			<td style="width:145px;">48345</td>
			<td style="width:296px;">Mouse antibody, use at 1:1000 dilution</td>
		</tr>
		<tr height="33">
			<td height="33" style="height:33px;width:393px;">Rab7 antibody</td>
			<td style="width:181px;">Abcam</td>
			<td style="width:145px;">137029</td>
			<td style="width:296px;">Rabbit antibody, use at 1:1000 dilution</td>
		</tr>
		<tr height="33">
			<td height="33" style="height:33px;width:393px;">Rab9 antibody</td>
			<td style="width:181px;">Thermo</td>
			<td style="width:145px;">MA3-067</td>
			<td style="width:296px;">Mouse antibody, use at 1:1000 dilution</td>
		</tr>
		<tr height="33">
			<td height="33" style="height:33px;width:393px;">RCAS1 antibody</td>
			<td style="width:181px;">Santa Cruz</td>
			<td style="width:145px;">398052</td>
			<td style="width:296px;">Mouse antibody, use at 1:1000 dilution</td>
		</tr>
		<tr height="33">
			<td height="33" style="height:33px;width:393px;">RhoGDI antibody</td>
			<td style="width:181px;">Santa Cruz</td>
			<td style="width:145px;">360</td>
			<td style="width:296px;">Rabbit antibody, use at 1:3000 dilution</td>
		</tr>
		<tr height="33">
			<td height="33" style="height:33px;width:393px;">Ribosomal protein S6 antibody</td>
			<td style="width:181px;">Santa Cruz</td>
			<td style="width:145px;">74459</td>
			<td style="width:296px;">Mouse antibody, use at 1:1000 dilution</td>
		</tr>
		<tr height="33">
			<td height="33" style="height:33px;width:393px;">Sec61a antibody</td>
			<td style="width:181px;">Santa Cruz</td>
			<td style="width:145px;">12322</td>
			<td style="width:296px;">Goat antibody, use at 1:1000 dilution</td>
		</tr>
		<tr height="33">
			<td height="33" style="height:33px;width:393px;">Thickwall Polycarbonate ultracentrifuge tube</td>
			<td style="width:181px;">Beckman Coulter</td>
			<td style="width:145px;">349622</td>
			<td style="width:296px;">Sample tube for ultracentrifugation</td>
		</tr>
		<tr height="33">
			<td height="33" style="height:33px;width:393px;">TLK-100.3 rotor</td>
			<td style="width:181px;">Beckman Coulter</td>
			<td style="width:145px;">349481</td>
			<td style="width:296px;">rotor for ultracentrifugation</td>
		</tr>
		<tr height="33">
			<td height="33" style="height:33px;width:393px;">Optima MAX High-Capacity Personal Ultracentrifuge</td>
			<td style="width:181px;">Beckman Coulter</td>
			<td style="width:145px;">364300</td>
			<td style="width:296px;">ultracentrifuge</td>
		</tr>
		<tr height="33">
			<td height="33" style="height:33px;width:393px;">cOmplete protease inhibitor cocktail tablets</td>
			<td>Roche</td>
			<td>11697498001</td>
			<td>protease inhibitors</td>
		</tr>
		<tr height="33">
			<td height="33" style="height:33px;">Cell Scrapers with 25cm Handle and 3.0cm Blade</td>
			<td>Corning</td>
			<td>353089</td>
			<td>large cell scraper</td>
		</tr>
		<tr height="33">
			<td height="33" style="height:33px;">Magnetic Stir Bar</td>
			<td>Fisher Scientific</td>
			<td>14-513-57SIX</td>
			<td>micro stir bar</td>
		</tr>
		<tr height="33">
			<td height="33" style="height:33px;">Ceramic-Top Magnetic Stirrer</td>
			<td>Fisher Scientific</td>
			<td>S504501AS</td>
			<td>magnetic stirrer</td>
		</tr>
	</tbody>
</table>

nitrogen cavitation and differential centrifugation allows for monitoring the distribution of peripheral membrane proteins in cultured cells

Cultured cells are useful for studying the subcellular distribution of proteins, including peripheral membrane proteins. Genetically encoded fluorescently tagged proteins have revolutionized the study of subcellular protein distribution. However, it is difficult to quantify the distribution with fluorescent microscopy, especially when proteins are partially cytosolic. Moreover, it is often important to study endogenous proteins. Biochemical assays such as immunoblots remain the gold standard for quantification of protein distribution after subcellular fractionation. Although there are commercial kits that aim to isolate cytosolic or certain membrane fractions, most of these kits are based on extraction with detergents, which may be unsuitable for studying peripheral membrane proteins that are easily extracted from membranes. Here we present a detergent-free protocol for cellular homogenization by nitrogen cavitation and subsequent separation of cytosolic and membrane-bound proteins by ultracentrifugation. We confirm the separation of subcellular organelles in soluble and pellet fractions across different cell types, and compare protein extraction among several common non-detergent-based mechanical homogenization methods. Among several advantages of nitrogen cavitation is the superior efficiency of cellular disruption with minimal physical and chemical damage to delicate organelles. Combined with ultracentrifugation, nitrogen cavitation is an excellent method to examine the shift of peripheral membrane proteins between cytosolic and membrane fractions.

Figure 2 shows the partitioning of cellular proteins from PNS into either the soluble cytosolic fraction (S) or membrane pellet fraction (P). We examined three representative cell lines from different cell types: HEK-293 (epithelial), NIH-3T3 (fibroblast), and Jurkat (lymphocyte). Rho Guanine Dissociation Inhibitor (RhoGDI) and cation-independent mannose-6-phosphate receptor (CIMPR) were used as positive controls for cytosolic and membrane fractions, respecti...

Watch this Scientific Journal Video about Nitrogen Cavitation and Differential Centrifugation Allows for Monitoring the Distribution of Peripheral Membrane Proteins in Cultured Cells at JoVE.com

Nitrogen Cavitation and Differential Centrifugation Allows for Monitoring the Distribution of Peripheral Membrane Proteins in Cultured Cells

Here we present protocols for detergent-free homogenization of cultured mammalian cells based on nitrogen cavitation and subsequent separation of cytosolic and membrane-bound proteins by ultracentrifugation. This method is ideal for monitoring the partitioning of peripheral membrane proteins between soluble and membrane fractions.

Cultured cells are useful for studying the subcellular distribution of proteins, including peripheral membrane proteins. Genetically encoded fluorescently ...

The overall goal of this experimental procedure, is to optimally homogenize cultured cells and to analyze partitioning of cellular proteins between membrane and soluble fractions. This method can help address one of the key challenges in cell biology, that is the subcellular compartmentalization of membrane peripheral proteins. The main advantage of this technique is, it can reproducibly detect partitioning of endogenous proteins, inside a solid and membrane fractions, with great accuracy and without use of detergents.To begin, culture HGK293 cells at 90%confluency, such that the yield per one 15 centimeter dish is about 2 x 10 to the 7th cells when cultured in DMEM at 37 degrees celsius, with 5%carbon dioxide. Then, aspirate the growth medium by vacuum. Next, place the culture dishes on ice and gently wash the cells twice on the culture dishes with 10 milliliters of chilled homogenization buffer per dish.After washing, use a large cell scrapper to harvest the cells, using an appropriate volume of homogenization buffer. Now, transfer the cell suspension to a clean, pre-chilled self destruction bomb, placed in an ice bath on a stir plate. To maintain suspension homogeneity, place a micro magnetic stir bar inside the bomb and turn on the stir plate.After that, add one protease inhibitor tablet to the suspension and close the bomb according to the manufacturer's instructions, including a crucial step of pushing the O ring upward to secure proper closing of the bomb. Once done, pressurize the bomb gradually with the nitrogen gas tank, as per the manufacturer's instructions, until the pressure gauge reads between 300 to 600 PSI. After the desired pressure is obtained, close all valves and disconnect the nitrogen tank.Allow 20 minutes for the nitrogen to dissolve and reach equilibrium within the cells. Next, use a disposable wipe to remove excess water around the discharge valve, and gently open the valve to achieve a drop wise release of homogenate, collect the homogenate in a pre-chilled 15 milliliter tube. Observe the milky appearance with foam on top of the cavitate.During the pressurization, it is critical to avoid simple loss by collecting the cavitate with slow, valvular discharge into a collection tube with an adequate access volume capacity that is optimally positioned to accommodate sudden discharge near the end of collection. After collecting the cavitate, centrifuge the tubes to remove unbroken cells in nuclei. And then collect the post-nuclear supernatant or PNS.Next, transfer the PNS to a polycarbonate ultracentrifuge tube. Perform ultracentrifugation to separate the cytosolic and membrane fractions. After ultra centrifugation and separation of pellet and supernatant.Use a one milliliter pipette to collect the supernatant or S fraction. After collecting the supernatant, rinse the pellet carefully with four milliliters of cold PBS, taking care not to disturb pellet and then remove the buffer by aspiration. Re-suspend the pellet, using the same volume of solubilization buffer, as the cytosolic fraction to achieve cell equivalence.Next, centrifuge the fully solubilized pellet suspension in a tabletop centrifuge. Use a one milliliter pipette to collect the supernatant or P fraction and discard the pellet. Finally, store the fractions at 80 degree celsius.Endogenous protein levels from both cytosolic and membrane fractions, isolated from three representative cell lines, are shown after western blot analysis. The presence of loosely associated peripheral membrane proteins such as, EEA1, Rab7, Rab9 and hexokinase 1 in both cytosolic and membrane fractions, demonstrate the utility of this technique and evaluating the strength of the membrane association of peripheral proteins. Via mounts of endogenous proteins in the PNS, were analyzed after subjecting jurkat cells to different mechanical disruption techniques.The yield of peripheral membrane proteins such as, hexokinase 1 and Ras, is higher in samples prepared with nitrogen cavitation. The homogenisation efficiency was compared between a hypotonic buffer and a buffer made isotonic with sucrose or sodium chloride. The protein levels in the PNS of cells disrupted using isotonic sucrose buffer, showed less recovery except for fibrollarin, which was enriched.These results indicate the partitioning of farnesylated NRAS into both P and S fractions. The absence of the preno modification of NRAS results in entirely cytosolic localisation, which therefore, confirms the reliability of this protocol for studying the dynamics of peripheral membrane protein partitioning. Once mastered, the separation of cytosolic and membrane fractions without re-suspension of the membrane fraction can be performed in an hour and 45 minutes or about 4 hours with re-suspension of the membrane fraction.Due to the inherent artifactual nature of bichemical fractionation, it is important to focus on the changes across experimental conditions in the partitioning of proteins, rather than the absolute distribution between cytosolic and membrane fractions. Additionally, we suggest testing different homogenization buffers for nitrogen cavitation to achieve optimal results. Post this procedure, immunoblotting and enzyme activity assays can be performed in order to answer additional questions like, membrane associated strength of peripheral proteins.Don't forget that working with high pressure nitrogen bombs can be extremely hazardous and precautions such as, wearing appropriate personal protection should always be taken while performing this procedure. Thanks for watching, good luck with your experiments.

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Research

JoVE Journal

Biochemistry

Using Scaffold Liposomes to Reconstitute Lipid-proximal Protein-protein Interactions In Vitro

Studies of integral membrane proteins in vitro are frequently complicated by the presence of a hydrophobic transmembrane domain. Further complicating these studies, reincorporation of detergent-solubilized membrane proteins into liposomes is a stochastic process where protein topology is impossible to enforce. This paper offers an alternative method to these challenging techniques that utilizes a liposome-based scaffold. Protein solubility is enhanced by deletion of the transmembrane domain, and these amino acids are replaced with a tethering moiety, such as a His-tag. This tether interacts with an anchoring group (Ni2+ coordinated by nitrilotriacetic acid (NTA(Ni2+)) for His-tagged proteins), which enforces a uniform protein topology at the surface of the liposome. An example is presented wherein the interaction between Dynamin-related protein 1 (Drp1) with an integral membrane protein, Mitochondrial Fission Factor (Mff), was investigated using this scaffold liposome method. In this work, we have demonstrated the ability of Mff to efficiently recruit soluble Drp1 to the surface of liposomes, which stimulated its GTPase activity. Moreover, Drp1 was able to tubulate the Mff-decorated lipid template in the presence of specific lipids. This example demonstrates the effectiveness of scaffold liposomes using structural and functional assays and highlights the role of Mff in regulating Drp1 activity.

Using Scaffold Liposomes to Reconstitute Lipid-proximal Protein-protein Interactions In Vitro

This paper describes a method for assessing the interactions and assemblies of integral membrane proteins in vitro with various partner factors in a lipid-proximal environment.

Studies of integral membrane proteins in vitro are frequently complicated by the presence of a hydrophobic transmembrane domain. Further complicating ...

Preparation of Giant Vesicles Encapsulating Microspheres by Centrifugation of a Water-in-oil Emulsion

The constructive biology and the synthetic biology approach to creating artificial life involve the bottom-up assembly of biological or nonbiological materials. Such approaches have received considerable attention in research on the boundary between living and nonliving matter and have been used to construct artificial cells over the past two decades. In particular, Giant Vesicles (GVs) have often been used as artificial cell membranes. In this paper, we describe the preparation of GVs encapsulating highly packed microspheres as a model of cells containing highly condensed biomolecules. The GVs were prepared by means of a simple water-in-oil emulsion centrifugation method. Specifically, a homogenizer was used to emulsify an aqueous solution containing the materials to be encapsulated and an oil containing dissolved phospholipids, and the resulting emulsion was layered carefully on the surface of another aqueous solution. The layered system was then centrifuged to generate the GVs. This powerful method was used to encapsulate materials ranging from small molecules to microspheres.

Giant vesicles containing highly packed micrometer-sized components are useful cell models. The water-in-oil emulsion centrifugation method is a simple, powerful tool for the preparation of giant vesicles with encapsulated materials.

The constructive biology and the synthetic biology approach to creating artificial life involve the bottom-up assembly of biological or nonbiological ...

Purification of Biotinylated Cell Surface Proteins from Rhipicephalus microplus Epithelial Gut Cells

Rhipicephalus microplus &#8211; the cattle tick &#8211; is the most significant ectoparasite in terms of economic impact on livestock as a vector of several pathogens. Efforts have been dedicated to the cattle tick control to diminish its deleterious effects, with focus on the discovery of vaccine candidates, such as BM86, located on the surface of the tick gut epithelial cells. Current research focuses upon the utilization of cDNA and genomic libraries, to screen for other vaccine candidates. The isolation of tick gut cells constitutes an important advantage in investigating the composition of surface proteins upon the tick gut cells membrane. This paper constitutes a novel and feasible method for the isolation of epithelial cells, from the tick gut contents of semi-engorged R. microplus. This protocol utilizes TCEP and EDTA to release the epithelial cells from the subepithelial support tissues and a discontinuous density centrifugation gradient to separate epithelial cells from other cell types. Cell surface proteins were biotinylated and isolated from the tick gut epithelial cells, using streptavidin-linked magnetic beads allowing for downstream applications in FACS or LC-MS/MS-analysis.

Purification of Biotinylated Cell Surface Proteins from Rhipicephalus microplus Epithelial Gut Cells

A modified density centrifugation gradient-based methodology was utilized to isolate epithelial cells from Rhipicephalus microplus gut tissue. Surface-bound proteins were biotinylated and purified through streptavidin magnetic beads for utilization in downstream applications.

Rhipicephalus microplus &#8211; the cattle tick &#8211; is the most significant ectoparasite in terms of economic impact on livestock as a vector of ...

Dissipative Microgravimetry to Study the Binding Dynamics of the Phospholipid Binding Protein Annexin A2 to Solid-supported Lipid Bilayers Using a Quartz Resonator

The dissipative quartz crystal microbalance technique is a simple and label-free approach to measure simultaneously the mass uptake and viscoelastic properties of the absorbed/immobilized mass on sensor surfaces, allowing the measurements of the interaction of proteins with solid-supported surfaces, such as lipid bilayers, in real-time and with a high sensitivity. Annexins are a highly conserved group of phospholipid-binding proteins that interact reversibly with the negatively charged headgroups via the coordination of calcium ions. Here, we describe a protocol that was employed to quantitatively analyze the binding of annexin A2 (AnxA2) to planar lipid bilayers prepared on the surface of a quartz sensor. This protocol is optimized to obtain robust and reproducible data and includes a detailed step-by-step description. The method can be applied to other membrane-binding proteins and bilayer compositions.

Here, we present an experimental protocol that can be employed to determine the binding affinities and mode of interaction of label-free phospholipid-binding protein annexin A2 with immobilized solid-supported bilayers (SLB) by simultaneously measuring the mass uptake and the viscoelastic properties of the protein annexin A2.

The dissipative quartz crystal microbalance technique is a simple and label-free approach to measure simultaneously the mass uptake and viscoelastic ...

A Fluorescence Fluctuation Spectroscopy Assay of Protein-Protein Interactions at Cell-Cell Contacts

A variety of biological processes involves cell-cell interactions, typically mediated by proteins that interact at the interface between neighboring cells. Of interest, only few assays are capable of specifically probing such interactions directly in living cells. Here, we present an assay to measure the binding of proteins expressed at the surfaces of neighboring cells, at cell-cell contacts. This assay consists of two steps: mixing of cells expressing the proteins of interest fused to different fluorescent proteins, followed by fluorescence fluctuation spectroscopy measurements at cell-cell contacts using a confocal laser scanning microscope. We demonstrate the feasibility of this assay in a biologically relevant context by measuring the interactions of the amyloid precursor-like protein 1 (APLP1) across cell-cell junctions. We provide detailed protocols on the data acquisition using fluorescence-based techniques (scanning fluorescence cross-correlation spectroscopy, cross-correlation number and brightness analysis) and the required instrument calibrations. Further, we discuss critical steps in the data analysis and how to identify and correct external, spurious signal variations, such as those due to photobleaching or cell movement.
In general, the presented assay is applicable to any homo- or heterotypic protein-protein interaction at cell-cell contacts, between cells of the same or different types and can be implemented on a commercial confocal laser scanning microscope. An important requirement is the stability of the system, which needs to be sufficient to probe diffusive dynamics of the proteins of interest over several minutes.

This protocol describes a fluorescence fluctuation spectroscopy-based approach to investigate interactions among proteins mediating cell-cell interactions, i.e. proteins localized in cell junctions, directly in living cells. We provide detailed guidelines on instrument calibration, data acquisition and analysis, including corrections to possible artefact sources.

A variety of biological processes involves cell-cell interactions, typically mediated by proteins that interact at the interface between neighboring ...

Cell Fractionation of U937 Cells in the Absence of High-speed Centrifugation

In this protocol we detail a method to obtain subcellular fractions of U937 cells without the use of ultracentrifugation or indiscriminate detergents. This method utilizes hypotonic buffers, digitonin, mechanical lysis and differential centrifugation to isolate the cytoplasm, mitochondria and plasma membrane. The process can be scaled to accommodate the needs of researchers, is inexpensive and straightforward. This method will allow researchers to determine protein localization in cells without specialized centrifuges and without the use of commercial kits, both of which can be prohibitively expensive. We have successfully used this method to separate cytosolic, plasma membrane and mitochondrial proteins in the human monocyte cell line U937.

Here, we present a protocol to isolate the plasma membrane, cytoplasm and mitochondria of U937 cells without the use of high-speed centrifugation. This technique can be used to purify subcellular fractions for subsequent examination of protein localization via immunoblotting.

In this protocol we detail a method to obtain subcellular fractions of U937 cells without the use of ultracentrifugation or indiscriminate detergents. ...

Measuring Nucleotide Binding to Intact, Functional Membrane Proteins in Real Time

We have developed a method to measure binding of adenine nucleotides to intact, functional transmembrane receptors in a cellular or membrane environment. This method combines expression of proteins tagged with the fluorescent non-canonical amino acid ANAP, and FRET between ANAP and fluorescent (trinitrophenyl) nucleotide derivatives. We present examples of nucleotide binding to ANAP-tagged KATP ion channels measured in unroofed plasma membranes and excised, inside-out membrane patches under voltage clamp. The latter allows for simultaneous measurements of ligand binding and channel current, a direct readout of protein function. Data treatment and analysis are discussed extensively, along with potential pitfalls and artefacts. This method provides rich mechanistic insights into the ligand-dependent gating of KATP channels and can readily be adapted to the study of other nucleotide-regulated proteins or any receptor for which a suitable fluorescent ligand can be identified.

This protocol presents a method for measuring adenine nucleotide binding to receptors in real time in a cellular environment. Binding is measured as F&#246;rster resonance energy transfer (FRET) between trinitrophenyl nucleotide derivatives and protein labeled with a non-canonical, fluorescent amino acid.

We have developed a method to measure binding of adenine nucleotides to intact, functional transmembrane receptors in a cellular or membrane environment. ...

Transverse Sectioning of Mature Rice (Oryza sativa L.) Kernels for Scanning Electron Microscopy Imaging Using Pipette Tips as Immobilization Support

Starch granules (SGs) exhibit different morphologies depending on the plant species, especially in the endosperm of the Poaceae family. Endosperm phenotyping can be used to classify genotypes based on SG morphotype using scanning electron microscopic (SEM) analysis. SGs can be visualized using SEM by slicing through the kernel (pericarp, aleurone layers, and endosperm) and exposing the organellar contents. Current methods require the rice kernel to be embedded in plastic resin and sectioned using a microtome or embedded in a truncated pipette tip and sectioned by hand using a razor blade. The former method requires specialized equipment and is time-consuming, while the latter introduces a new host of problems depending on rice genotype. Chalky rice varieties, particularly, pose a problem for this type of sectioning due to the friable nature of their endosperm tissue. Presented here is a technique for preparing translucent and chalky rice kernel sections for microscopy, requiring only pipette tips and a scalpel blade. Preparing the sections within the confines of a pipette tip prevents rice kernel endosperm from shattering (for translucent or &#8216;vitreous&#8217; phenotypes) and crumbling (for chalky phenotypes). Using this technique, endosperm cell patterning and the structure of intact SGs can be observed.

Transverse Sectioning of Mature Rice Oryza sativa L. Kernels for Scanning Electron Microscopy Imaging Using Pipette Tips as Immobilization Support

This protocol allows for the preparation of transverse sections of cereal seeds (e.g., rice) for the analysis of endosperm and starch granule morphology using scanning electron microscopy.

Starch granules (SGs) exhibit different morphologies depending on the plant species, especially in the endosperm of the Poaceae family. Endosperm ...

Cell-Free Production of Proteoliposomes for Functional Analysis and Antibody Development Targeting Membrane Proteins

Membrane proteins play essential roles in a variety of cellular processes and perform vital functions. Membrane proteins are medically important in drug discovery because they are the targets of more than half of all drugs. An obstacle to conducting biochemical, biophysical, and structural studies of membrane proteins as well as antibody development has been the difficulty in producing large amounts of high-quality membrane protein with correct conformation and activity. Here we describe a &#8220;bilayer-dialysis method&#8221; using a wheat germ cell-free system, liposomes, and dialysis cups to efficiently synthesize membrane proteins and prepare purified proteoliposomes in a short time with a high success rate. Membrane proteins can be produced as much as in several milligrams, such as GPCRs, ion channels, transporters, and tetraspanins. This cell-free method contributes to reducing the time, cost and effort for preparing high-quality proteoliposomes, and provides suitable means for functional analysis of membrane proteins, drug targets screening, and antibody development.

This protocol describes an efficient cell-free method for production of high-quality proteoliposome by bilayer-dialysis method using wheat cell-free system and liposomes. This method provides suitable means for functional analysis of membrane proteins, drug targets screening, and antibody development.

Membrane proteins play essential roles in a variety of cellular processes and perform vital functions. Membrane proteins are medically important in drug ...

Identifying the Binding Proteins of Small Ligands with the Differential Radial Capillary Action of Ligand Assay (DRaCALA)

The past decade has seen tremendous progress in the understanding of small signaling molecules in bacterial physiology. In particular, the target proteins of several nucleotide-derived secondary messengers (NSMs) have been systematically identified and studied in model organisms. These achievements are mainly due to the development of several new techniques including the capture compound technique and the differential radial capillary action of ligand assay (DRaCALA), which were used to systematically identify target proteins of these small molecules. This paper describes the use of the NSMs, guanosine penta- and tetraphosphates (p)ppGpp, as an example and video demonstration of the DRaCALA technique. Using DRaCALA, 9 out of 20 known and 12 new target proteins of (p)ppGpp were identified in the model organism, Escherichia coli K-12, demonstrating the power of this assay. In principle, DRaCALA could be used for studying small ligands that can be labeled by radioactive isotopes or fluorescent dyes. The critical steps, pros, and cons of DRaCALA are discussed here for further application of this technique.

Identifying the Binding Proteins of Small Ligands with the Differential Radial Capillary Action of Ligand Assay DRaCALA

The Differential Radial Capillary Action of Ligand Assay (DRaCALA) can be used to identify small ligand binding proteins of an organism by using an ORFeome library.

The past decade has seen tremendous progress in the understanding of small signaling molecules in bacterial physiology. In particular, the target proteins ...