Name: lerlic-ms/ms for in-depth characterization and quantification of glutamine and asparagine deamidation in shotgun proteomics
Uploaded: 2017-04-09T15:00:00
Description: Watch this Scientific Journal Video about LERLIC-MS/MS for In-depth Characterization and Quantification of Glutamine and Asparagine Deamidation in Shotgun Proteomics at JoVE.com

This work was in part supported by grants from the Singapore Ministry of Education (Tier 2: Grant ARC9/15), National Medical Research Council of Singapore (NMRC-OF-IRG-0003-2016), and NTU-NHG Ageing Research Grant (Grant ARG/14017). We would like to express our gratitude and most sincere thanks to Dr. Andrew Alpert and PolyLC team for kindly provided us with the packing materials that made possible this study.

1. Packing the Long-length Anion-exchange (LAX) Capillary Column
(Note: Although the LAX column can be in-home packed as we describe in this protocol, LAX columns are also commercially available, see Table of Materials and Reagents for further details).
<ol>
	<li>Suspend 50 mg of weak anion exchange packing material in 3.5 mL of packing buffer (Table 1) to prepare the slurry.</li>
	<li>Assemble the end of the capillary column (50 cm length - 200 &#1...

<ol>
	<li>Hao, P., Adav, S. S., Gallart-Palau, X., Sze, S. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recent+advances+in+mass+spectrometric+analysis+of+protein+deamidation.">Recent advances in mass spectrometric analysis of protein deamidation.</a> Mass Spectrom Rev. , (2016).</li><li>Geiger, T., Clarke, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Deamidation,+isomerization,+and+racemization+at+asparaginyl+and+aspartyl+residues+in+peptides.+Succinimide-linked+reactions+that+contribute+to+protein+degradation.">Deamidation, isomerization, and racemization at asparaginyl and aspartyl residues in peptides. Succinimide-linked reactions that contribute to protein degradation.</a> J Biol Chem. 262 (2), 785-794 (1987).</li><li>Serra, A., Gallart-Palau, X., Wei, J., Sze, S. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterization+of+Glutamine+Deamidation+by+Long-Length+Electrostatic+Repulsion-Hydrophilic+Interaction+Chromatography-Tandem+Mass+Spectrometry+(LERLIC-MS/MS)+in+Shotgun+Proteomics.">Characterization of Glutamine Deamidation by Long-Length Electrostatic Repulsion-Hydrophilic Interaction Chromatography-Tandem Mass Spectrometry (LERLIC-MS/MS) in Shotgun Proteomics.</a> Anal Chem. , (2016).</li><li>Reissner, K. J., Aswad, D. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Deamidation+and+isoaspartate+formation+in+proteins:+unwanted+alterations+or+surreptitious+signals.">Deamidation and isoaspartate formation in proteins: unwanted alterations or surreptitious signals.</a> Cell Mol Life Sci. 60 (7), 1281-1295 (2003).</li><li>Capasso, S., Mazzarella, L., Sica, F., Zagari, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=First+evidence+of+spontaneous+deamidation+of+glutamine+residue+via+cyclic+imide+to+[small+alpha]-+and+[gamma]-glutamic+residue+under+physiological+conditions.">First evidence of spontaneous deamidation of glutamine residue via cyclic imide to [small alpha]- and [gamma]-glutamic residue under physiological conditions.</a> JChem Soc, Chem Commun. (23), 1667-1668 (1991).</li><li>Gallart-Palau, X., Serra, A., Sze, S. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Enrichment+of+extracellular+vesicles+from+tissues+of+the+central+nervous+system+by+PROSPR.">Enrichment of extracellular vesicles from tissues of the central nervous system by PROSPR.</a> Mol Neurodegener. 11 (1), 41 (2016).</li><li>Gallart-Palau, X., 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=Gender+differences+in+white+matter+pathology+and+mitochondrial+dysfunction+in+Alzheimer's+disease+with+cerebrovascular+disease.">Gender differences in white matter pathology and mitochondrial dysfunction in Alzheimer's disease with cerebrovascular disease.</a> Mol Brain. 9, 27 (2016).</li><li>Gallart-Palau, X., 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=Temporal+lobe+proteins+implicated+in+synaptic+failure+exhibit+differential+expression+and+deamidation+in+vascular+dementia.">Temporal lobe proteins implicated in synaptic failure exhibit differential expression and deamidation in vascular dementia.</a> Neurochem Int. 80, 87-98 (2015).</li><li>Robinson, N. E., Robinson, A. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Molecular+clocks.">Molecular clocks.</a> Proc Natl Acad Sci U.S.A. 98 (3), 944-949 (2001).</li><li>Hao, 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=Enhanced+separation+and+characterization+of+deamidated+peptides+with+RP-ERLIC-based+multidimensional+chromatography+coupled+with+tandem+mass+spectrometry.">Enhanced separation and characterization of deamidated peptides with RP-ERLIC-based multidimensional chromatography coupled with tandem mass spectrometry.</a> J Proteome Res. 11 (3), 1804-1811 (2012).</li><li>Li, X., Lin, C., O'Connor, P. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Glutamine+deamidation:+differentiation+of+glutamic+acid+and+gamma-glutamic+acid+in+peptides+by+electron+capture+dissociation.">Glutamine deamidation: differentiation of glutamic acid and gamma-glutamic acid in peptides by electron capture dissociation.</a> Anal Chem. 82 (9), 3606-3615 (2010).</li><li>Smith, P. K., 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=Measurement+of+protein+using+bicinchoninic+acid.">Measurement of protein using bicinchoninic acid.</a> Anal Biochem. 150 (1), 76-85 (1985).</li><li>Serra, A., 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=Plasma+proteome+coverage+is+increased+by+unique+peptide+recovery+from+sodium+deoxycholate+precipitate.">Plasma proteome coverage is increased by unique peptide recovery from sodium deoxycholate precipitate.</a> Anal Bioanal Chem. , 1-11 (2016).</li><li>Gallart-Palau, X., Serra, A., Sze, S. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Uncovering+Neurodegenerative+Protein+Modifications+via+Proteomic+Profiling.">Uncovering Neurodegenerative Protein Modifications via Proteomic Profiling.</a> Int Rev Neurobiol. 121, 87-116 (2015).</li><li>Liu, Y. D., van Enk, J. Z., Flynn, G. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Human+antibody+Fc+deamidation+in+vivo.">Human antibody Fc deamidation in vivo.</a> Biologicals. 37 (5), 313-322 (2009).</li><li>Serra, A., 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=Commercial+processed+soy-based+food+product+contains+glycated+and+glycoxidated+lunasin+proteoforms.">Commercial processed soy-based food product contains glycated and glycoxidated lunasin proteoforms.</a> Sci Rep. 6, 26106 (2016).</li><li>Serra, A., 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=A+high-throughput+peptidomic+strategy+to+decipher+the+molecular+diversity+of+cyclic+cysteine-rich+peptides.">A high-throughput peptidomic strategy to decipher the molecular diversity of cyclic cysteine-rich peptides.</a> Sci Rep. 6, 23005 (2016).</li><li>Leo, 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=Deamidation+at+asparagine+and+glutamine+as+a+major+modification+upon+deterioration/aging+of+proteinaceous+binders+in+mural+paintings.">Deamidation at asparagine and glutamine as a major modification upon deterioration/aging of proteinaceous binders in mural paintings.</a> Anal Chem. 83 (6), 2056-2064 (2011).</li><li>Wilson, J., van Doorn, N. L., Collins, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Assessing+the+extent+of+bone+degradation+using+glutamine+deamidation+in+collagen.">Assessing the extent of bone degradation using glutamine deamidation in collagen.</a> Anal Chem. 84 (21), 9041-9048 (2012).</li><li>Buszewski, B., Noga, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hydrophilic+interaction+liquid+chromatography+(HILIC)--a+powerful+separation+technique.">Hydrophilic interaction liquid chromatography (HILIC)--a powerful separation technique.</a> Anal Bioanal Chem. 402 (1), 231-247 (2012).</li><li>Alpert, A. J., Hudecz, O., Mechtler, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Anion-exchange+chromatography+of+phosphopeptides:+weak+anion+exchange+versus+strong+anion+exchange+and+anion-exchange+chromatography+versus+electrostatic+repulsion-hydrophilic+interaction+chromatography.">Anion-exchange chromatography of phosphopeptides: weak anion exchange versus strong anion exchange and anion-exchange chromatography versus electrostatic repulsion-hydrophilic interaction chromatography.</a> Anal Chem. 87 (9), 4704-4711 (2015).</li><li>Adav, S. 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=Dementia-linked+amyloidosis+is+associated+with+brain+protein+deamidation+as+revealed+by+proteomic+profiling+of+human+brain+tissues.">Dementia-linked amyloidosis is associated with brain protein deamidation as revealed by proteomic profiling of human brain tissues.</a> Mol Brain. 9 (1), 20 (2016).</li><li>Golde, T. E., Borchelt, D. R., Giasson, B. I., Lewis, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Thinking+laterally+about+neurodegenerative+proteinopathies.">Thinking laterally about neurodegenerative proteinopathies.</a> J Clin Invest. 123 (5), 1847-1855 (2013).</li><li>Gallart-Palau, X., Ng, C. H., Ribera, J., Sze, S. K., Lim, K. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Drosophila+expressing+human+SOD1+successfully+recapitulates+mitochondrial+phenotypic+features+of+familial+amyotrophic+lateral+sclerosis.">Drosophila expressing human SOD1 successfully recapitulates mitochondrial phenotypic features of familial amyotrophic lateral sclerosis.</a> Neurosci Lett. 624, 47-52 (2016).</li><li>Ouellette, D., Chumsae, C., Clabbers, A., Radziejewski, C., Correia, I. <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+the+in+vitro+and+in+vivo+stability+of+a+succinimide+intermediate+observed+on+a+therapeutic+IgG1+molecule.">Comparison of the in vitro and in vivo stability of a succinimide intermediate observed on a therapeutic IgG1 molecule.</a> mAbs. 5 (3), 432-444 (2013).</li><li>Kumar, 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=Unexpected+functional+implication+of+a+stable+succinimide+in+the+structural+stability+of+Methanocaldococcus+jannaschii+glutaminase.">Unexpected functional implication of a stable succinimide in the structural stability of Methanocaldococcus jannaschii glutaminase.</a> Nat Commun. 7, 12798 (2016).</li><li>Alpert, A. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrostatic+Repulsion+Hydrophilic+Interaction+Chromatography+for+Isocratic+Separation+of+Charged+Solutes+and+Selective+Isolation+of+Phosphopeptides.">Electrostatic Repulsion Hydrophilic Interaction Chromatography for Isocratic Separation of Charged Solutes and Selective Isolation of Phosphopeptides.</a> Anal Chem. 80 (1), 62-76 (2008).</li><li>Hao, P., Ren, Y., Alpert, A. J., Sze, S. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Detection,+Evaluation+and+Minimization+of+Nonenzymatic+Deamidation+in+Proteomic+Sample+Preparation.">Detection, Evaluation and Minimization of Nonenzymatic Deamidation in Proteomic Sample Preparation.</a> Mol Cell Proteomics. 10 (10), 111 (2011).</li><li>Hao, P., Ren, Y., Datta, A., Tam, J. P., Sze, S. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evaluation+of+the+effect+of+trypsin+digestion+buffers+on+artificial+deamidation.">Evaluation of the effect of trypsin digestion buffers on artificial deamidation.</a> J Proteome Res. 14 (2), 1308-1314 (2015).</li><li>Liu, S., Moulton, K. R., Auclair, J. R., Zhou, Z. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mildly+acidic+conditions+eliminate+deamidation+artifact+during+proteolysis:+digestion+with+endoprotease+Glu-C+at+pH+4.5.">Mildly acidic conditions eliminate deamidation artifact during proteolysis: digestion with endoprotease Glu-C at pH 4.5.</a> Amino Acids. 48 (4), 1059-1067 (2016).</li></ol>

In this video-article we present a step-by-step protocol of LERLIC-MS/MS3, a method to perform in-depth characterization and to accurately determine the extent of protein deamidation and the enzymatic processes involved on this protein modification. LERLIC-MS/MS is based on the use of a long-length (50 cm) LAX under the principle of electrostatic repulsion-hydrophilic interaction chromatography (ERLIC)27. The use of a long-length column, as shown in our study<sup class="xre...

Deamidation is a protein posttranslational modification (PTM) that introduces a negative charge to the protein backbone through modification of asparagine (Asn) and/or glutamine (Gln) residues1. This modification while affecting Asn residues generates the isomeric products isoaspartic acid (isoAsp) and n-aspartic acid (Asp) at a common 3:1 ratio2. Notwithstanding, this ratio can be altered by the intervention of the repairing enzyme L-isoaspartyl methyltransferase (PIMT)3,4. Similarly, deamidation of Gln residues generates the isomeric gamma-glutamic acid (&#947;-Glu) and alpha-glutamic acid isoforms (&#945;-Glu) at an expected 1:7 ratio3,5, but this ratio can be shifted by the action of the ubiquitous enzyme transglutaminase 2 and other transglutaminases, including transglutaminase 1, an enzyme recently identified as associated with extracellular vesicles in the brain6.
The origin of deamidation can be either spontaneous or enzymatic, the former&#160;is especially common on Gln residues in which transglutaminases and other enzymes mediate&#160;inter/intra-molecular crosslinking via transamidation (see 3 for further details on Gln transamidation and its implications in several chronic and fatal human diseases). Therefore, deamidation is a PTM that has a crucial repercussion on the structure and function of affected molecules4,7,8 and requires an in-depth chemical characterization3 in the light of its diverse biochemical consequences including its service as molecular clock of aging9.
Although deamidation of Asn residues has been relatively well-characterized by bottom-up shotgun proteomics1,10, deamidation of Gln residues still does not have a suitable characterization method beyond the challenging analysis of model compounds by electron-based radical fragmentation11. We have recently developed a novel one-dimension shotgun proteomics strategy (LERLIC-MS/MS)3 that enables separation of Gln and Asn deamidation isoforms from complex biological samples and model compounds in a single analysis. LERLIC-MS/MS is based on the separation of tryptic digested peptides using a long-length (50 cm) ion exchange column (LAX) working on electrostatic repulsion-hydrophilic interaction chromatography (ERLIC) mode and coupled to tandem mass spectrometry (LC-MS/MS). This new analytical strategy has been used to characterize and relatively quantitate the extent of each deamidated residue in human brain tissues3. Nevertheless, the protocol outlined here will provide video imaging of LERLIC-MS/MS aimed to study the peculiarities of protein deamidation in the biochemical context of interest.
ETHICS STATEMENT
All procedures of this protocol have been approved by the institutional review board of the Nanyang Technological University in Singapore and have been performed in accordance to the institutional guidelines.

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			<td style="width:424px;">PolyLC Inc.</td>
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			<td height="21" style="height:21px;width:359px;">Sodium deoxycholate</td>
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			<td height="21" style="height:21px;width:359px;">Dithiothreitol</td>
			<td style="width:424px;">Sigma-Aldrich</td>
			<td style="width:207px;">D0632</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:359px;">Iodoacetamide</td>
			<td style="width:424px;">Sigma-Aldrich</td>
			<td style="width:207px;">i6125</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:359px;">Formic acid</td>
			<td style="width:424px;">Sigma-Aldrich</td>
			<td style="width:207px;">F0507 (HONEYWELL)</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:359px;">Ammonium hydroxide</td>
			<td style="width:424px;">Sigma-Aldrich</td>
			<td style="width:207px;">338818 (HONEYWELL)</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:359px;">Acetonitrile HPLC grade</td>
			<td style="width:424px;">Sigma-Aldrich</td>
			<td style="width:207px;">675415</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:359px;">Isopropanol HPLC grade</td>
			<td style="width:424px;">Sigma-Aldrich</td>
			<td style="width:207px;">675431</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:359px;">Water HPLC grade</td>
			<td style="width:424px;">Sigma-Aldrich</td>
			<td style="width:207px;">14263</td>
			<td></td>
		</tr>
	</tbody>
</table>

lerlic-ms/ms for in-depth characterization and quantification of glutamine and asparagine deamidation in shotgun proteomics

Characterization of protein deamidation is imperative to decipher the role(s) and potentialities of this protein posttranslational modification (PTM) in human pathology and other biochemical contexts. In order to perform characterization of protein deamidation, we have recently developed a novel long-length electrostatic repulsion-hydrophilic interaction chromatography-tandem mass spectrometry (LERLIC-MS/MS) method which can separate the glutamine (Gln) and asparagine (Asn) isoform products of deamidation from model compounds to highly complex biological samples. LERLIC-MS/MS is, therefore, the first shotgun proteomics strategy for the separation and quantification of Gln deamidation isoforms. We also demonstrate, as a novelty, that the sample processing protocol outlined here stabilizes the succinimide intermediate allowing its characterization by LERLIC-MS/MS. Application of LERLIC-MS/MS as shown in this video article can help to elucidate the currently unknown molecular arrays of protein deamidation. Additionally, LERLIC-MS/MS provides further understanding of the enzymatic reactions that encompass deamidation in distinct biological backgrounds.

Deamidation of Gln and Asn residues is considered a degenerative protein modification (DPM) implicated in several chronic and fatal diseases14. It has been demonstrated that this PTM can predict the half-life and degradative states of antibodies and other molecules in the human body and similar biological backgrounds1,15. The significance of protein deamidation, in fact, goes beyond the biomedical context, ...

Watch this Scientific Journal Video about LERLIC-MS/MS for In-depth Characterization and Quantification of Glutamine and Asparagine Deamidation in Shotgun Proteomics at JoVE.com

LERLIC-MS/MS for In-depth Characterization and Quantification of Glutamine and Asparagine Deamidation in Shotgun Proteomics

Here we present a step-by-step protocol of the long-length electrostatic repulsion-hydrophilic interaction chromatography-tandem mass spectrometry (LERLIC-MS/MS) method. This is a novel methodology that enables for the first time quantification and characterization of the glutamine and asparagine deamidation isoforms by shotgun proteomics.

Characterization of protein deamidation is imperative to decipher the role(s) and potentialities of this protein posttranslational modification (PTM) in ...

The overall goal of this procedure is to use shotgun proteomics to characterize and quantify endogenous glutamine and asparagine deamidation products in complex proteomes. This method can help answer key questions in biochemistry, such as the influence of a spontaneous and antimatic processors on the isometric product gluteo of glutamine and asparagime deamination. The main advantage of this technique is that glutamine deamination isomers are separated on a long length ionic change capillary column, maximizing the ability to separate peptides by the isomatic points.To begin column construction, suspend 50 milligrams of weak anion exchange packing material in 3.5 milliliters of 90%isopropanol, in water. Secure female to female fitting, a microferal, and a female nut at one end of a 50 centimeter length of peak tubing with an inner diameter of 200 micrometers. Fit a 1/16th inch screen with one micrometer pores at the end of the tubing inside the microferal.Using pressure pump set to 4, 500 psi, pack the anion exchange into the capillary until the material is visible at the top. Attach another female-to-female fitting, microferal, and female nut to the top of the packed capillary at the opposite end to finish assembling the column. Wash 50 to 100 milligrams of tissue with phosphate buffered saline for five minutes.Repeat this wash twice, and then place the washed tissue in tubes with safety caps. Add to each tube one weight equivalent of stainless steel beads, and 2.5 equivalents by volume of an aqueous 100 millimolar solution of ammonium acetate with 1%sodium deoxycholate. Homogenize the tissue at maximum intensity for five minutes at four degrees Celsius.Then, centrifuge the homogenate for ten minutes at 10, 000 x g and four degrees Celsius. Transfer the supernatant to a 1.5 milliliter tube. Continue homogenizing and centrifuging the tissue pellet, combining the supernatants each time until no pellet is observed.Quantify the protein concentration in the combined supernatants with a bicinchoninic acid assay. Next, add to the homogenate a one molar solution of dithiothreitol in 100 millimolar ammonium acetate to attain a ten millimolar dithiothreitol concentration in the sample. Incubate the homogenate in a water bath at 60 degrees Celsius for thirty minutes.Add to the homogenate a one molar solution of iodoacetamide in 100 millimolar ammonium acetate to attain a 20 millimolar iodoacetamide concentration in the sample. Incubate the homogenate at room temperature in the absence of light for 45 minutes. Then dilute the homogenate with two volume equivalents of a ten millimolar solution of dithiothreitol in 100 millimolar ammonium acetate.Incubate the homogenate at 37 degrees Celsius for 30 minutes. Add to the homogenate a sufficient volume of sequencing grade modified trypsin in 100 millimolar ammonium acetate to achieve a 1 to 50 protein enzyme ratio by weight in the sample. Incubate the sample at 30 degrees Celsius overnight to digest the homogenate.Quench the digestion with 0.5%of the sample weight of formic acid, precipitating the sodium deoxycholate salts. Gently vortex the samples containing SDC salts and then centrifuge the samples for ten minutes at 12, 000 x g and four degrees Celsius. Decant the supernatant into a new tube, being careful not to disturb the pellet of SDC salts.Redissolve the salts in a 0.5%by volume aqueous solution of ammonium hydroxide, vortexing vigorously. Condition a one gram C-18 sorbent cartridge with 5 milliliters of acetonitrile, followed by five milliliters of 0.1%trifluoroacetic acid in water. Then, load the digested sample onto the cartridge.Wash the samples three to five times with five milliliter portions of 0.1%TFA. Then dilute the peptides with five milliliters of an aqueous solution of 75%acetonitrile, and 0.1%formic acid. Dry the fluid in a vacuum concentrator.Add 200 microliters of 75%acetonitrile, with 0.1%formic acid to the residue. Vortex the mixture for at least ten minutes, and then sonicate the mixture for at least 30 minutes to reconstitute the dry peptides. Dilute the sample as needed, so that the injected sample contains one to three micrograms of protein.Connect the LAX capillary column to an ultra high pressure liquid chromatography instrument. Prepare 0.1%formic acid solutions in water and acetonitrile. Set the flow rate to 0.4 microliters per minute, and set up a 1, 200 minute gradient run.Configure the mass spectrometer scan events to alternate data acquisition, between full Fourier transform mass spectrometry and Fourier transform tandem mass spectrometry. Perform LERLIC MS/MS to separate and characterize the peptides. Use the resulting data and proteomic software to perform a protein database search.Export the database search results to spreadsheet software. Identify and extract the list of deamidated peptides and the corresponding non-deamidated peptides. Extract the ion chromatagrams of each of these peptides with five parts per million of mass tolerance.Inspect the extracted ion chromatagrams for separated double peak illusion of isomeric products. Using LERLIC MS/MS, deamidated isoforms of glutamine and asparagine were separated and identified from a protein sample at two different retention times. Enzymatically modified intermediate glutamine residues of transamidation showing an inverted gamma alpha glutamil ratio were identified.The succinimide intermediate in asparagine residues was also identified with this method. As the mildly acidic sample processing conditions stabilize the succinimide intermediate. This suggests that the LERLIC MS/MS technique can be applied to proteome wide study of succinimide intermediates.After its development, this technique paved the way for researchers in biochemistry to characterize protein deamidation in contexts ranging from archeology to biomedical research.

lerlic-msms-for-depth-characterization-quantification-glutamine

Research

JoVE Journal

Biochemistry

Deep Proteome Profiling by Isobaric Labeling, Extensive Liquid Chromatography, Mass Spectrometry, and Software-assisted Quantification

Many exceptional advances have been made in mass spectrometry (MS)-based proteomics, with particular technical progress in liquid chromatography (LC) coupled to tandem mass spectrometry (LC-MS/MS) and isobaric labeling multiplexing capacity. Here, we introduce a deep-proteomics profiling protocol that combines 10-plex tandem mass tag (TMT) labeling with an extensive LC/LC-MS/MS platform, and post-MS computational interference correction to accurately quantitate whole proteomes. This protocol includes the following main steps: protein extraction and digestion, TMT labeling, 2-dimensional (2D) LC, high-resolution mass spectrometry, and computational data processing. Quality control steps are included for troubleshooting and evaluating experimental variation. More than 10,000 proteins in mammalian samples can be confidently quantitated with this protocol. This protocol can also be applied to the quantitation of post translational modifications with minor changes. This multiplexed, robust method provides a powerful tool for proteomic analysis in a variety of complex samples, including cell culture, animal tissues, and human clinical specimens.

We present a protocol to accurately quantitate proteins with isobaric labelling, extensive fractionation, bioinformatics tools, and quality control steps in combination with liquid chromatography interfaced to a high-resolution mass spectrometer.

Many exceptional advances have been made in mass spectrometry (MS)-based proteomics, with particular technical progress in liquid chromatography (LC) ...

Characterization of Glycoproteins with the Immunoglobulin Fold by X-Ray Crystallography and Biophysical Techniques

Glycoproteins on the surface of cells play critical roles in cellular function, including signalling, adhesion and transport. On leukocytes, several of these glycoproteins possess immunoglobulin (Ig) folds and are central to immune recognition and regulation. Here, we present a platform for the design, expression and biophysical characterization of the extracellular domain of human B cell receptor CD22. We propose that these approaches are broadly applicable to the characterization of mammalian glycoprotein ectodomains containing Ig domains. Two suspension human embryonic kidney (HEK) cell lines, HEK293F and HEK293S, are used to express glycoproteins harbouring complex and high-mannose glycans, respectively. These recombinant glycoproteins with different glycoforms allow investigating the effect of glycan size and composition on ligand binding. We discuss protocols for studying the kinetics and thermodynamics of glycoprotein binding to biologically relevant ligands and therapeutic antibody candidates. Recombinant glycoproteins produced in HEK293S cells are amenable to crystallization due to glycan homogeneity, reduced flexibility and susceptibility to endoglycosidase H treatment. We present methods for soaking glycoprotein crystals with heavy atoms and small molecules for phase determination and analysis of ligand binding, respectively. The experimental protocols discussed here hold promise for the characterization of mammalian glycoproteins to give insight into their function and investigate the mechanism of action of therapeutics.

We present approaches for the biophysical and structural characterization of glycoproteins with the immunoglobulin fold by biolayer interferometry, isothermal titration calorimetry, and X-ray crystallography.

Glycoproteins on the surface of cells play critical roles in cellular function, including signalling, adhesion and transport. On leukocytes, several of ...

Extracellular Protein Microarray Technology for High Throughput Detection of Low Affinity Receptor-Ligand Interactions

Secreted factors, membrane-tethered receptors, and their interacting partners are main regulators of cellular communication and initiation of signaling cascades during homeostasis and disease, and as such represent prime therapeutic targets. Despite their relevance, these interaction networks remain significantly underrepresented in current databases; therefore, most extracellular proteins have no documented binding partner. This discrepancy is primarily due to the challenges associated with the study of the extracellular proteins, including expression of functional proteins, and the weak, low affinity, protein interactions often established between cell surface receptors. The purpose of this method is to describe the printing of a library of extracellular proteins in a microarray format for screening of protein-protein interactions. To enable detection of weak interactions, a method based on multimerization of the query protein under study is described. Coupled to this microbead-based multimerization approach for increased multivalency, the protein microarray allows robust detection of transient protein-protein interactions in high throughput. This method offers a rapid and low sample consuming-approach for identification of new interactions applicable to any extracellular protein. Protein microarray printing and screening protocol are described. This technology will be useful for investigators seeking a robust method for discovery of protein interactions in the extracellular space.

Here, we present a protocol to screen extracellular protein microarrays for identification of novel receptor-ligand interactions in high throughput. We also describe a method to enhance detection of transient protein-protein interactions by using protein-microbead complexes.

Secreted factors, membrane-tethered receptors, and their interacting partners are main regulators of cellular communication and initiation of signaling ...

Detection of Protein Ubiquitination Sites by Peptide Enrichment and Mass Spectrometry

The posttranslational modification of proteins by the small protein ubiquitin is involved in many cellular events. After tryptic digestion of ubiquitinated proteins, peptides with a diglycine remnant conjugated to the epsilon amino group of lysine (&#39;K-&#949;-diglycine&#39; or simply &#39;diGly&#39;) can be used to track back the original modification site. Efficient immunopurification of diGly peptides combined with sensitive detection by mass spectrometry has resulted in a huge increase in the number of ubiquitination sites identified up to date. We have made several improvements to this workflow, including offline high pH reverse-phase fractionation of peptides prior to the enrichment procedure, and the inclusion of more advanced peptide fragmentation settings in the ion routing multipole. Also, more efficient cleanup of the sample using a filter-based plug in order to retain the antibody beads results in a greater specificity for diGly peptides. These improvements result in the routine detection of more than 23,000 diGly peptides from human cervical cancer cells (HeLa) cell lysates upon proteasome inhibition in the cell. We show the efficacy of this strategy for in-depth analysis of the ubiquitinome profiles of several different cell types and of in vivo samples, such as brain tissue. This study presents an original addition to the toolbox for protein ubiquitination analysis to uncover the deep cellular ubiquitinome.

We present a method for the purification, detection, and identification of diGly peptides that originate from ubiquitinated proteins from complex biological samples. The presented method is reproducible, robust, and outperforms published methods with respect to the level of depth of the ubiquitinome analysis.

The posttranslational modification of proteins by the small protein ubiquitin is involved in many cellular events. After tryptic digestion of ...

SUMO-Binding Entities (SUBEs) as Tools for the Enrichment, Isolation, Identification, and Characterization of the SUMO Proteome in Liver Cancer

Post-translational modification is a key mechanism regulating protein homeostasis and function in eukaryotic cells. Among all ubiquitin-like proteins in liver cancer, the modification by SUMO (Small Ubiquitin MOdifier) has been given the most attention. Isolation of endogenous SUMOylated proteins in vivo is challenging due to the presence of active SUMO-specific proteases. Initial studies of SUMOylation in vivo were based on the molecular detection of specific SUMOylated proteins (e.g., by western blot). However, in many cases, antibodies, generally made with non-modified recombinant protein, did not immunoprecipitate SUMOylated forms of the protein of interest.&#160;Nickel chromatography has been the other approach to study SUMOylation by capturing histidine-tagged versions of SUMO molecules. This approach is mainly used in cells stably expressing or transiently transfected with His-SUMO molecules. To overcome these limitations, SUMO-binding entities (SUBEs) were developed to isolate endogenous SUMOylated proteins. Herein, we describe all the steps required for the enrichment, isolation, and identification of SUMOylated substrates from human hepatoma cells and hepatic tissues from a liver cancer mouse model by using SUBEs. Firstly, we describe methods involved in the preparation and lysis of the human hepatoma cells and liver tumor tissue samples. Then, a thorough explanation of the preparation of SUBEs and controls is detailed along with the protocol for the protein pull-down assays. Finally, some examples are provided regarding the options available for the identification and characterization of the SUMOylated proteome, namely the use of western-blot analysis for the detection of a specific SUMOylated substrate from liver tumors or the use of proteomics by mass spectrometry for high-throughput characterization of the SUMOylated proteome and interactome in hepatoma cells.

SUMO-Binding Entities SUBEs as Tools for the Enrichment, Isolation, Identification, and Characterization of the SUMO Proteome in Liver Cancer

Here, we present a protocol to enrich, isolate, identify, and characterize proteins modified by SUMO in vivo both from human hepatoma cells and liver tumors obtained from mouse models of hepatocellular carcinoma by using SUMO-binding entities (SUBEs).

Post-translational modification is a key mechanism regulating protein homeostasis and function in eukaryotic cells. Among all ubiquitin-like proteins in ...

Quantification of Coenzyme A in Cells and Tissues

Emerging research has revealed that the cellular coenzyme A (CoA) supply can become limiting with a detrimental impact on growth, metabolism and survival. Measurement of cellular CoA is a challenge due to its relatively low abundance and the dynamic conversion of free CoA to CoA thioesters that, in turn, participate in numerous metabolic reactions. A method is described that navigates through potential pitfalls during sample preparation to yield an assay with a broad linear range of detection that is suitable for use in many biomedical laboratories.

This method describes sample preparation from cultured cells and animal tissues, extraction and derivatization of coenzyme A in the samples, followed by high pressure liquid chromatography for purification and quantification of the derivatized coenzyme A by absorbance or fluorescence detection.

Emerging research has revealed that the cellular coenzyme A (CoA) supply can become limiting with a detrimental impact on growth, metabolism and survival. ...

TMT Sample Preparation for Proteomics Facility Submission and Subsequent Data Analysis

Proteomic technologies are powerful methodologies that can aid our understanding of mechanisms of action in biological systems by providing a global view of the impact of a disease, treatment, or other condition on the proteome as a whole. This report provides a detailed protocol for the extraction, quantification, precipitation, digestion, labeling, and subsequent data analysis of protein samples. Our optimized TMT labeling protocol requires a lower tag-label concentration and achieves consistently reliable data. We have used this protocol to evaluate protein expression profiles in a variety of mouse tissues (i.e., heart, skeletal muscle, and brain) as well as cells cultured in vitro. In addition, we demonstrate how to evaluate thousands of proteins from the resulting dataset.

We present an optimized tandem mass tag (TMT) labeling protocol that includes detailed information for each of the following steps: protein extraction, quantification, precipitation, digestion, labeling, submission to a proteomics facility, and data analyses.

Proteomic technologies are powerful methodologies that can aid our understanding of mechanisms of action in biological systems by providing a global view ...

A Mass Spectrometry-Based Proteomics Approach for Global and High-Confidence Protein R-Methylation Analysis

Protein Arginine (R)-methylation is a widespread protein post-translational modification (PTM) involved in the regulation of several cellular pathways, including RNA processing, signal transduction, DNA damage response, miRNA biogenesis, and translation.
In recent years, thanks to biochemical and analytical developments, mass spectrometry (MS)-based proteomics has emerged as the most effective strategy to characterize the cellular methyl-proteome with single-site resolution. However, identifying and profiling in vivo protein R-methylation by MS remains challenging and error-prone, mainly due to the substoichiometric nature of this modification and the presence of various amino acid substitutions and chemical methyl-esterification of acidic residues that are isobaric to methylation. Thus, enrichment methods to enhance the identification of R-methyl-peptides and orthogonal validation strategies to reduce False Discovery Rates (FDR) in methyl-proteomics studies are required.
Here, a protocol specifically designed for high-confidence R-methyl-peptides identification and quantitation from cellular samples is described, which couples metabolic labeling of cells with heavy isotope-encoded Methionine (hmSILAC) and dual protease in-solution digestion of whole cell extract, followed by off-line High-pH Reversed Phase (HpH-RP) chromatography fractionation and affinity enrichment of R-methyl-peptides using anti-pan-R-methyl antibodies. Upon high-resolution MS analysis, raw data are first processed with the MaxQuant software package and the results are then analyzed by hmSEEKER, a software designed for the in-depth search of MS peak pairs corresponding to light and heavy methyl-peptide within the MaxQuant output files.

Protein Arginine (R)-methylation is a wide-spread post-translational modification regulating multiple biological pathways. Mass spectrometry is the best technology to globally profile the R-methyl-proteome, when coupled to biochemical approaches for modified peptide enrichment. The workflow designed for the high confidence identification of global R-methylation in human cells is described here.

Protein Arginine (R)-methylation is a widespread protein post-translational modification (PTM) involved in the regulation of several cellular pathways, ...

JUMPn: A Streamlined Application for Protein Co-Expression Clustering and Network Analysis in Proteomics

With recent advances in mass spectrometry-based proteomics technologies, deep profiling of hundreds of proteomes has become increasingly feasible. However, deriving biological insights from such valuable datasets is challenging. Here we introduce a systems biology-based software JUMPn, and its associated protocol to organize the proteome into protein co-expression clusters across samples and protein-protein interaction (PPI) networks connected by modules (e.g., protein complexes). Using the R/Shiny platform, the JUMPn software streamlines the analysis of co-expression clustering, pathway enrichment, and PPI module detection, with integrated data visualization and a user-friendly interface. The main steps of the protocol include installation of the JUMPn software, the definition of differentially expressed proteins or the (dys)regulated proteome, determination of meaningful co-expression clusters and PPI modules, and result visualization. While the protocol is demonstrated using an isobaric labeling-based proteome profile, JUMPn is generally applicable to a wide range of quantitative datasets (e.g., label-free proteomics). The JUMPn software and protocol thus provide a powerful tool to facilitate biological interpretation in quantitative proteomics.

We present a systems biology tool JUMPn to perform and visualize network analysis for quantitative proteomics data, with a detailed protocol including data pre-processing, co-expression clustering, pathway enrichment, and protein-protein interaction network analysis.

With recent advances in mass spectrometry-based proteomics technologies, deep profiling of hundreds of proteomes has become increasingly feasible. ...

Shotgun Proteomics Sample Processing Automated by an Open-Source Lab Robot

Mass spectrometry-based shotgun proteomics experiments require multiple sample preparation steps, including enzymatic protein digestion and clean-up, which can take up significant person-hours of bench labor and present a source of batch-to-batch variability. Lab automation with pipetting robots can reduce manual work, maximize throughput, and increase research reproducibility. Still, the steep starting prices of standard automation stations make them unaffordable for many academic laboratories. This article describes a proteomics sample preparation workflow using an affordable, open-source automation system (The Opentrons OT-2), including instructions for setting up semi-automated protein reduction, alkylation, digestion, and clean-up steps; as well as accompanying open-source Python scripts to program the OT-2 system through its application programming interface.

Detailed protocol and three Python scripts are provided for operating an open-source robotic liquid handling system to perform semi-automated protein sample preparation for mass spectrometry experiments, covering detergent removal, protein digestion, and peptide desalting steps.

Mass spectrometry-based shotgun proteomics experiments require multiple sample preparation steps, including enzymatic protein digestion and clean-up, ...