A high-throughput protocol was developed for combined proteomics and glycomics purification and LC-MS/MS quantification in plasma. Deamidation analysis of N-linked glycosylation motifs was specific to deglycosylated sites. Accurate quantitation of N-glycans was achieved by coupling filter aided N-glycan separation to the individuality normalization when labeling with glycan hydrazide tags strategy.
There is a growing desire in the biological and clinical sciences to integrate and correlate multiple classes of biomolecules to unravel biology, define pathways, improve treatment, understand disease, and aid biomarker discovery. N-linked glycosylation is one of the most important and robust post-translational modifications on proteins and regulates critical cell functions such as signaling, adhesion, and enzymatic function. Analytical techniques to purify and analyze N-glycans have remained relatively static over the last decade. While accurate and effective, they commonly require significant expertise and resources. Though some high-throughput purification schemes have been developed, they have yet to find widespread adoption and often rely on the enrichment of glycopeptides. One promising method, developed by Thomas-Oates et al., filter aided N-glycan separation (FANGS), was qualitatively demonstrated on tissues. Herein, we adapted FANGS to plasma and coupled it to the individuality normalization when labeling with glycan hydrazide tags strategy in order to achieve accurate relative quantification by liquid chromatography mass spectrometry and enhanced electrospray ionization. Furthermore, we designed new functionality to the protocol by achieving tandem, shotgun proteomics and glycosylation site analysis on hen plasma. We showed that N-glycans purified on filter and derivatized by hydrophobic hydrazide tags were comparable in terms of abundance and class to those by solid phase extraction (SPE); the latter is considered a gold standard in the field. Importantly, the variability in the two protocols was not statistically different. Proteomic data that was collected in-line with glycomic data had the same depth compared to a standard trypsin digest. Peptide deamidation is minimized in the protocol, limiting non-specific deamidation detected at glycosylation motifs. This allowed for direct glycosylation site analysis, though the protocol can accommodate 18O site labeling as well. Overall, we demonstrated a new in-line high-throughput, unbiased, filter based protocol for quantitative glycomics and proteomics analysis.
プロテオミクスの分野では、フィルタ支援試料調製(FASP)が広く、出発材料の量を最小化する試料調製のアーティファクトを減少させる、およびサンプルスループット1を最大化する能力のために採用されています。しかしながら、このような方法は未だ出現し、グライコミクスの分野のための牽引力を獲得しています。高スループットの開発は、定量的なワークフローがあるため生体防御および癌または疾患2,3によってその変調におけるグリコシル化の重要な役割で必要とされています。哺乳類では、N個の -glycansは、コア構造を飾る糖単位(ヘキソース(16進数)、ヘキソサミン(のHexNAc)、シアル酸(NeuAcで)、およびフコース(Fucは))、(16進数3のHexNAc 2)4共有結合した繰り返しで構成されていますアスパラギンへ。異性体がカウントされるときglycospaceがかなり大きいですが(> 10 12)、それは、組成に基づいて非常に小さく、分子量は、典型的には1,000-8,000ダ5 <範囲/ SUP>。クラスの組成均一性およびグリカンの親水性は、精製、分離、および質量分析(MS)ワークフロー6に特有の課題を提起します。
伝統的には、Nの -glycansはF(PNGアーゼF)は、ペプチドのNによるタンパク質またはペプチドから-glycosidase消化され、次いで、ヒドラジドビーズ8によって、レクチンアフィニティークロマトグラフィー7によって濃縮捕捉、または固相抽出(SPE)9,10を介して精製しました。これらの方法は全て非常に有効であるが、これらは、脱塩のための余分な工程を導入し、同時に処理されたサンプルの数を制限します。過去10年間、グライコミクスのためのハイスループットプラットフォームの数が提案されています。 Kim らは、真空操作、SPE 96ウエルプレート11を用いて、半自動化された方法を発表しました。また、アフィニティーフィルター法は、(N -glyco-FASP)をFi接続の初期誘導体化を必要とマン・グループ、によって開発されましたレクチン12の合成とLTER。最後に、トーマス・オーツのグループは、半定量法、glycospace 13の狭い組成サイズを悪用フィルター支援N -Glycan分離(牙)を、提案しました。分子量カットオフフィルターに依存する、小さな汚染物質が第一無駄に洗浄し、次いで、N個の -glycansを消化し 、溶出しました。脱グリコシル化タンパク質は、このプロトコルでフィルター上に残存すると、インラインFASPに供することができます。
エレクトロスプレーイオン化(ESI)MSによる同定およびグリカンの定量化は、異性体および低豊富な種の検出のための誘導体化の(部分的な)解決のためにオフライン分離を必要とします。個性で標識グリカンヒドラジドタグ戦略正規逆相液体クロマトグラフィー(RPLC)14,15との互換性を与えます。 4フェネチル – ベンゾヒドラジド(P2PGN)疎水性タグはENH、グリカンの親水性を仲介します、平均して、4倍の16でイオン化をancing。容易な条件で化学量論的に1:例えば過メチル化17またはアミン反応性タグ付け化学18のような他の技術が、同様の利点を提供するが、ヒドラジド反応において、グリカンは1を反応させます。相対的定量化は、天然の(NAT)または13 C 6安定同位体ラベル(SIL)で誘導体化された試料のタンデム分析によって達成されます。
以下の方法は、正確な相対的定量化のためのP2GPN疎水性タグにプラズマアプリケーションやカップル、それをするための牙を展開します。更に、分析の完全性を損なうことなく、サンプルの単一のアリコートにショットガンプロテオミクス、脱アミド化プロファイル、および定量的グライコミクスを実行するように設計されました。
High-throughput quantitative methods are needed to facilitate routine glycan analysis. For the last thirty years, glycomics analysis has been limited to a subset of research groups, despite its importance in disease, clinical applications, and pharmaceuticals. The FANGS-P2GPN purification and tagging method for glycomics and proteomics performs the same analysis on a single aliquot of sample, reducing the cost of supplies and the amount of material needed (particularly important in human and mouse studies). Furthermore, efforts to minimize variability in preparations are critically important, as every additional step contributes to error, potentially masking important but low-abundant changes in case-control studies. Coupling of FANGS to hydrophobic hydrazide tagging allows protein and glycan samples to be run on the same RPLC column, enhances glycan ionization, provides for relative quantification, and can be quantitatively applied to plasma.
For N-glycan analysis, it is critical to use the suggested level of PNGase F to achieve full de-glycosylation. Though glycans are solvent exposed, denaturation of proteins and excess enzyme help ensure efficient and complete cleavage. For accurate quantitation of the glycans, it is necessary to ensure that they are completely dried after derivatization to quench the reaction and prevent cross-reactions when mixing the NAT and SIL species. Finally, when extending the workflow to glycosite analysis, timing of the steps is critical to minimize non-specific deamidation. The modified protocols provided for combined glycomics and proteomics analysis work consistently when performed accordingly.
The workflow achieves accurate relative quantitation of N-glycans from plasma compared to the gold-standard, SPE method. There is no apparent bias in the types of glycans extracted in terms of molecular weight, hydrophilicity, and compositional structure. Though we have not explored the qualitative analysis of O-linked glycans, we expect that FANGS could accommodate the addition of a β-elimination step post-PNGase F digestion of N-linked glycans. However, procedures would require significant modification for reagent cleanup prior to mass spectrometry, and peptide analysis will be significantly impacted. For proteomics, the same depth of proteome coverage is achieved compared to traditional FASP methods. Importantly, methods achieve a minimal false discovery rate for N-glycan deamidation. While the method is compatible with 18O labeling of Asn during the PNGase digestion step22,23, the low glycosylation site false discovery rate suggests that it may not be necessary, further reducing costs and complexity.
The proteome is not enriched for glycoproteins in this method, which has both advantages and disadvantages. Certain low abundant glycoproteins may not be detected in the analysis. However, the occupancy of glycosylated sites per protein, can be compared between biological samples. Additionally, the error and bias introduced from lectin affinity purification or chemical enrichment is eliminated. In conclusion, coupling of FANGS to the individuality normalization when labeling with glycan hydrazide tags strategy results in a simplified, quantitative, high-throughput method for the tandem analysis of the glycome and proteome with great potential for application in clinical case-control studies.
The authors have nothing to disclose.
This research was generously funded by the NIH NCI IMAT Program Grant R33 (CA147988-02), the NIH NIGMS Graduate Training in Molecular Biotechnology at NC State Grant (T32GM008776), the US Dept. of Education GAANN Fellowship Program in Molecular Biotechnology at NC State Grant (P200A140020), the W.M. Keck Foundation, and North Carolina State University. Hen plasma was obtained with the assistance of Dr. James N. Petitte and Rebecca Wysocky in the NC State University Dept. of Poultry Science.
Acetic Acid (50%): | Sigma Aldrich | 45754 | |
Acetonitrile, HPLC grade | Burdick & Jackson | AH015-4 | |
Ammonium Bicarbonate | Sigma Aldrich | A6141 | |
Bradford Reagent | Sigma Aldrich | B6916 | Alternative: Bicinchoninic acid kit (Sigma Aldrich BCA1) |
Calcium chloride | Sigma Aldrich | C1016 | |
Centrifuge | Eppendorf | 5804 R | Alternate centrifuges that reach 14,000 x g are suitable |
DL-Dithiothreitol, 1M in solution | Sigma Aldrich | 646563 | |
Easy-nLC 1000 | Thermo Scientific | LC120 | Alternate nano or ultra high pressure LCs will produce similar data, such as: 1. Dionex UltiMateÒ 3000 LC (Thermo Scientific) 2. Acquity UPLC (Waters) |
Floating Tube Rack | TedPella | 20831-20 | |
Fetuin | New England Biolabs | P6042S | |
Fisher Scientific Isotemp Standard Lab Ovens | Fisher Scientific | 11-690-625F | Alternate incubators that reach 56 °C are suitable |
Formic Acid | Sigma Aldrich | 56302 | |
GE Microwave Oven | General Electric | 57B5 E82904 | Any microwave with adjustable power settings is suitable |
INLIGHT Glycan Tagging Kit | Cambridge Isotope Laboratories | GTK-1000 | The INLIGHT kit provides NAT and SIL versions of the P2GPN reagent. |
Iodoacetamide | Sigma Aldrich | A3221 | |
Kinetix 2.6 mM, 100 Å, C18 bulk stationary phase | Phenomenex | Bulk Media | Alternative: Any C18 stationary phase £ 5 mM |
Mascot Daemon Software and Server | Matrix Science | Alternative: Proteome Discoverer Software (Thermo Scientific) | |
Methanol, HPLC grade | Burdick & Jackson | AH230-4 | |
PicoFrit Self-Pack Column: 360 um, OD 75um ID, 15 um tip, non-coated, 5 per box, 50 cm | New Objective | 1 5 PF360-75-15-N-5 | |
PNGase F (glycerol-free), 75,000 units/ml | New England BioLabs | P0705L | |
Q Exactive HF Hybrid Quadrupole-Orbitrap Mass Spectrometer | Thermo Scientific | Alternate high mass accuracy (£ 5 ppm) mass spectrometers will provide similar data | |
RNase B | New England Biolabs | P7817S | |
Trypsin from Porcine Pancreas | Sigma Aldrich | T6567-5X | |
Urea | Sigma Aldrich | 51456 | |
Vacuum ConcentratorSavant SPD131DDA SpeedVac Concentrator | Thermo Scientific | SPD131DDA | Alternate vacuum concentrators are suitable |
Vivacon 500 30 kDa Filters | Sartorius Stedim Biotech | VN01H22 | Alternative: Amicon Ultra 0.5 Centrifugal Filter Units with Ultracel-10 kDa Membrane (Millipore UFC501096) |
Water, HPLC grade | Burdick & Jackson | AH365-4 | |
Water, 18O | Cambridge Isotope Laboratories | OLM-240-97-1 | The addition of 18O in the PNGase F digest step is optional and may not be necessary for deamidation studies completed with 95% confidence |
Xcalibur 2.0 | Thermo Scientific | XCALIBUR20 | |
Zwittergent Test Kit | Merck Millipore | 693030 |