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Journal of Proteomics & Bioinformatics
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Proteomics-based Development of Biomarkers for Prion Diseases

Bo-Yeong Choi, Yeong Seon Lee, Young Ran Ju, Chi-Kyeong Kim and Su Yeon Kim*

Division of Zoonoses, Center for Immunology and Pathology, Korea National Institute of Health, Centers for Disease Control and Prevention, Cheongju-si, Chungcheongbukdo, 28159, Republic of Korea

*Corresponding Author:
Su Yeon Kim
Division of Zoonoses, Center for Immunology and
Pathology, Korea National Institute of Health
Centers for Disease Control and Prevention, Cheongju-si
Chungcheongbuk-do, 28159, Republic of Korea
Tel: +82 43 719 8463
Fax: +82 43 719 8489
E-mail: [email protected]

Received Date: November 28, 2015; Accepted Date: March 15, 2016; Published Date: March 23, 2016

Citation: Bo-Yeong C, Lee YS, Ju YR, Chi-Kyeong K, Kim SY (2016) Proteomics-based Development of Biomarkers for Prion Diseases. J Proteomics Bioinform 9:087-100. doi:10.4172/jpb.1000394

Copyright: © 2016 Bo-Yeong C, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

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Abstract

We analyzed the proteomic profile of ME7 scrapie-infected mouse brains, and the interactions and functions of selected differentially expressed proteins to identify potential new biomarkers to be applicable for the diagnosis of Prion diseases. Mice were intracerebrally inoculated with 10% homogenate of ME7 scrapie-infected mouse brains, and monitored for neurological symptoms. We screened for proteins specifically expressed in infected brain samples using one-dimensional gel electrophoresis and liquid chromatography-mass spectrometry. 317 proteins based on their peptide scores and ratio values were selected. The major biological processes identified were cellular and metabolic processes, localization, and transport. Selected proteins had functions related to neurological processes, including cell-cell signaling, transmission of nerve impulse, and synaptic transmission. We analyzed infected host cells using experimental and computational methods, and found many significant protein expression changes. We identified 43 candidate proteins with high peptide scores and ratio values. Of these, 36 potential candidate proteins were related to up regulated biological processes, and 7 to down regulated biological processes. We confirmed the presence of two of these differentially expressed candidate proteins using immunoblotting.

Keywords

Proteomic; Biomarker; Diagnosis; Prion disease

Introduction

Transmissible spongiform encephalopathies (TSEs) are rare fatal neurodegenerative diseases that occur in animals and humans through conformational conversion of normal prion protein (PrPc) to an infectious PrPSc isoform. TSEs include scrapie, bovine spongiform encephalopathy, transmissible mink encephalopathy, Creutzfeldt- Jakob disease (CJD), Gerstmann–Sträussler–Scheinker syndrome, fatal familial insomnia, and kuru. The PrPSc isoform is more proteinase K-resistant than the PrPc. Detection of PrPSc in the central nervous tissue of CJD patients by immunohistochemistry and confirmation of protease-resistant PrPSc has diagnostic values of definite human TSE. However, definite diagnoses of prion diseases are limited because these analyses require neuropathological confirmation by brain biopsy or post-mortem examination. Several protein markers, including 14-3-3 protein [1,2], Tau [3], astrocytic protein S-100 [4], apolipoprotein E [5], neuron-specific enolase [6], and cystatin C [7] have been reported in the cerebrospinal fluid of patients showing clinical symptoms of CJD. The assay for 14-3-3 protein that has been used in the laboratory diagnosis of CJD has high false-positive rates. Diverse potential biomarkers have been identified through proteomic approaches, and many research groups have attempted to identify more sensitive and specific markers for use in the diagnosis of CJD and other neurodegenerative diseases [8,9]. However, the effectiveness of these markers, except the 14-3-3 protein has never been fully specified in prion diseases. We need to verify their availability in biological to apply them biochemically for pre-mortem diagnosis, understand their application and identify as surrogate markers. The development of molecular alternative biomarkers have been demanded to define the cause for occurrence, mechanism and pathological phenotypes of related diseases. Several significant genes have been identified through proteomic approach using microarray and quantitative real time PCR tools, and gene expression for up-regulated and down-regulated proteins especially in model of scrapie infected mouse brain [10-12]. Clq beta polypeptide, Cathepsin D, Cystatin C, Glial fibrillary acidic protein (GFAP), Clusterin, Peroxiredoxin-6 and EAAT-2, and S-Acetyltransferase, Syaptotagmin 1 or 5, Ubiquitinconjugating enzyme were reported as up-regulated proteins and downregulated proteins, respectively [13-16].

Mass spectrometry (MS)-based proteomics is a powerful tool for large-scale identification of peptides in protein complexes from cell lysates and tissue extracts. In addition, liquid chromatography-tandem MS (LC-MS/MS) is a high-throughput, highly sensitive method that requires only very low sample volumes [17], which enables its application to systems biology approaches such as in the investigation of signaling pathways and interrelationships among proteins [18]. Although 2D-polycrylammide gel electrophoresis (PAGE) has been widely used in the past to compare the relative abundances of proteins, this method has limitations, including low sensitivity and reduced resolution of proteins with extreme molecular weights and or pI-values. We profiled the proteome of ME7 scrapie-infected mouse brains and analyzed the interaction and function of selected proteins to develop their potential novel biomarkers for the differential diagnosis in prion diseases. In this study, we analyzed candidate protein biomarkers expressed in the brains of control and ME7 scrapie-infected mice using 1D-Gel-LC-MS / MS analysis (Figure 1).

proteomics-bioinformatics-overview-proteomic-analysis

Figure 1: Schematic overview of our proteomic analysis.

This approach may be useful for application of development biomarkers for diagnosis of human prion diseases through the specifying and confirmatory assay using body fluid as well as tissue. We also anticipate that these proteins could be used for ante-mortem diagnosis, prognosis, and therapeutic development.

Materials and Methods

Prion (PrPSc) inoculations

Four-week-old male C57BL / 6 mice (n = 3) were inoculated intracerebrally with 20 μL of 10% brain homogenate from an ME7 scrapie-infected mouse. Age- and gender-matched control male mice (n = 3) were inoculated intracerebrally with 20 μL of 10% brain homogenate from a normal mouse. Mice were monitored for clinical symptoms for up to 171 days post inoculation (dpi). All animal experiments were performed in the bio safety 2 level facility. Legal compulsory education is required for all researchers and users annually (more than 6 h/year). Animals were investigated twice per week after inoculation until the appearance of abdominal behavior and then examined daily.

Preparation of mouse brain samples

Brain homogenates from three infected mice and three control mice were prepared using a Precellys® 24 homogenizer (Bertin Technologies, Rockville, MD, USA) at 6,500 rpm for 35 sec (twice) in phosphate-buffered saline (PBS). Individual samples were diluted to 10% (w/v) with PBS and stored at -80°C until use. The 10% homogenates were lysed in 500 μL of radioimmunoprecipitation assay buffer (Thermo Scientific, Rockford, IL, USA) using a Precellys® 24 homogenizer at 6,500 rpm for 35 sec (twice). The homogenates were centrifuged at 14,000 rpm for 3 h at 4°C, the supernatant was discarded, and the pellet was resuspended in 2x lithium dodecyl sulfate sample loading buffer (Invitrogen, Carlsbad, CA, USA) for analysis.

Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) for LC-MS / MS

SDS-PAGE was performed using NuPAGE® Novex 4% – 12% Bis-Tris gels (Invitrogen, Carlsbad, CA, USA) with 2-(N-morpholino) ethanesulfonic acid running buffer at 100mA until the tracking dye reached the bottom of the gel. The proteins in the gel were visualized using the GelCode™ Blue Stain Reagent (Thermo Scientific).

In-gel digestion

Individual gel lanes were excised into 10 gel slices, so digestion was performed to total 60 slices of each 10 gel slices from three individual of control and infected groups, respectively. The gel slices were destained with 50% acetonitrile (ACN) in 50 mM ammonium bicarbonate buffer (pH 7.8) and washed with 100% ACN. The proteins in the gel slices were reduced with 10 mM dithiothreitol for 45 min, and then alkylated with 55 mM iodoacetamide for 30 min. Trypsin digestion was performed with 500 ng of Sequencing Grade Modified Trypsin (Promega, Madison, WI, USA) in 50 mM ammonium bicarbonate buffer overnight at 37°C. The digested peptides were extracted using 5% formic acid in ACN, and the extract was dried in a Speed Vac. For mass analysis, the dried peptides were dissolved in 6 μL of solubilization buffer containing 5% ACN, 0.4% formic acid, and 0.1% trifluoroacetic acid (final concentrations). After desalting with a zip-tip (Millipore, Billerica, MA, USA), the digested peptides were loaded onto a fused silica microcapillary C18 column (75 μm × 150 mm).

Liquid chromatography-tandem mass spectrometry analysis and protein identification

LC (UltiMate, nano flow LC, Dionex) was conducted with a linear gradient as follows: 0 min, 3% B; 5 min, 3% B; 72 min, 40% B; 77 min, 90% B; 87min, 90% B; 92 min, 3% B; 120 min, 3% B. The initial solvent was 3% solvent B and the flow rate was 200 nL/min. Solvent A was 0.1% formic acid in H2O and solvent B was 0.1% formic acid in ACN. The separated peptides were subsequently analyzed on a linear trap quadrupole ion-trap mass spectrometer (Thermo Fisher, San Jose, CA, USA). The electrospray voltage was set at 2.0 kV, and the threshold for switching from MS to MS/MS was 250. The normalized collision energy for MS / MS was 35% of the main radiofrequency amplitude and the duration of activation was 30 ms. All spectra were acquired in data-dependent mode. Each full MS scan was followed by three MS / MS scans corresponding to from the most intense peak to the third intense peak of the full MS scan. The repeat count of the peaks for dynamic exclusion was 1, and its repeat duration was 30 sec. The dynamic exclusion duration was set at 180s, and the exclusion mass width was ± 1.5 Da. The list size for dynamic exclusion was 50.

Statistical tests

Data was analyzed for statistical significance using two-tailed unpaired Mann-Whitney t-test 95% confidence interval.

Database searching and validation

All MS / MS spectra recorded were searched on mice protein database downloaded from the National Center for Biotechnology Information (NCBI, on January 21st, 2008; 35129 entries). SEQUEST was used as the peptide-searching program, and dynamic modifications of oxidized methionine (+16 Da) and carboxyamidomethylated cysteine (+57 Da) were permitted. SEQUEST criteria for peptide selection were Xcorr, which must be greater than 1.8, 2.3, and 3.5 for +1, +2, and +3 charge state peptides, respectively, and Cn above 0.1. The criterion for protein selection was a consensus score above 10.1. Functional groupings, such as gene ontology (GO) mapping, and protein-protein interactions of the identified proteins were analyzed using the web-based programs DAVID (http://david.abcc.ncifcrf.gov/) and Cytoscape (http://cytoscape.org/).

The acquired LC-electron spry ionization-MS/MS fragment spectra were searched against the NCBI (http://www.ncbi.nlm.nih.gov/) non-redundant mouse database in the BioWorks Browser (version Rev. 3.3.1 SP1, Thermo Fisher Scientific, Inc., CA, USA) using the SEQUEST search engines. The search parameters included trypsin enzyme specificity, up to two permissible missed cleavages, peptide tolerance of ± 2 amu, mass error of ± 1 amu on fragment ions, and fixed modifications of carbamidomethylation of cysteine (+57 Da) and oxidation (+16 Da) of methionine residues. We performed the experiments in triplicate technically as three times running of MS / MS and three times repeatedly of analysis for the three sets of control and infected mice, and selected the proteins that were identified more than twice in the experiments. The two groups of proteins were then compared to identify control or ME7-infected specific proteins. To identify sample (control or ME7-infected mice)-specific proteins, we utilized a label-free protein quantification method [19], and a protein was considered specific to a certain sample if its quantity was more than twice that in the other sample (in our quantification method, Rsc value > 1.0).

Verification using western blot analysis

The 10% brain homogenates (20 μL) were lysed in 1mL of radio immunoprecipitation assay buffer using a Precellys® 24 homogenizer at 6,500 rpm for 35 sec (twice). The homogenates were centrifuged at 14,000 rpm for 3 h at 4°C. The supernatant was discarded, and the pellet was resuspended in 2x lithium dodecyl sulfate sample loading buffer for analysis. The samples were boiled for 10min and separated by SDS-PAGE on NuPAGE® Novex 4% – 12% Bis-Tris gels. Proteins were transferred to polyvinylidene fluoride membranes using iBlot® Gel Transfer stacks on an iBlot™ Gel Transfer system (Invitrogen, Carlsbad, CA, USA). The membranes were blocked with 5% nonfat milk in PBS containing 0.001% Tween-20 (PBST), and then incubated with specific antibodies against ACSBG1 (sc-130090, rabbit polyclonal; Santa Cruz Biotechnology, Santa Cruz, CA, USA);NARS (14882-1-AP, rabbit polyclonal; ProteinTechGroup, Inc., Chicago, IL); and β-actin (#4967, rabbit polyclonal; Cell Signaling Technology) in PBST containing 0.5% skim milk for 2 h at room temperature. After three washes in PBST, membranes were incubated with a horseradishperoxidase-conjugated secondary antibody (#7074; Cell Signaling Technology) in PBST. After three washes in PBST, membranes were developed with SuperSignal® West FemtoChemiluminescent Substrate (Pierce, Rockford, IL, USA) and visualized using ChemDoc XRS (Bio-Rad).

Results and Discussion

We used 1D-Gel-LC-MS / MS to identify differentially expressed proteins in brains obtained from mice with neurological symptoms. All infected mice showed neurodegenerative symptoms approximately 120 dpi – 150 dpi; moving impairment and loss their direction showing circulation behavior repeatedly in cage. Control mice did not show prion-associated clinical symptoms even beyond 171dpi.

Brain protein separation by 1D electrophoresis

In the initial step, the proteins in ME7scrapie-infected and control mouse brain homogenates were separated by SDS-PAGE. There were no visual differences in the protein band patterns between control and ME7scrapie-infected mouse brain samples (Figure 2).

proteomics-bioinformatics-infected-mouse-brain

Figure 2: SDS-PAGE analysis control and ME7 infected mouse brain (Ctrl, Control: three (#1~#3); ME7, infected: three (#1~#3). Marked ten gel lanes excised into gel slices from three control and infected groups used in gel digestion on right side, respectively.

LC-MS / MS and protein identification

In a subsequent step, we digested the proteins in the separated brain samples with trypsin, and analyzed the tryptic peptides using LC-MS / MS. The proteins from LC-MS / MS were identified by comparing them with those in a peptide mass database, and were bioinformatically annotated based on their molecular weight, peptide score, spectral count, and other parameters in the NCBI and GO databases. In the control and infected samples, 3,924 (1,837 and 2,953 for control #1 and control #2, respectively; #3 was not used protein identification for experiment error.) proteins and 4,262 (1,580, 1,325, and 3,000 for ME7 #1, ME7 #2, and ME7 #3, respectively) proteins were identified, respectively. Many changes in protein levels were observed in ME7 scrapie-infected samples (Figure 3).

proteomics-bioinformatics-venn-proteins-chromatography

Figure 3: Venn diagram showing the number of unique and shared proteins from each individual mouse. Venn diagram of the proteins identified by one-dimensional gel electrophoresis-liquid chromatography-tandem mass spectrometry (1D-Gel-LC-MS/MS) in ME7 scrapie-infected and control mice. (A) Two control mice (#1, #2). (B) Three ME7 scrapie-infected mice (#1, #2, #3).

Functional categorization by gene ontology

We compared the protein expression profiles of infected and uninfected mouse brains using two controls and three ME7scrapie-infected mice. First, we investigated the biological processes using protein identification data. Proteins identified in the control samples (with peptide scores in control samples 2-fold higher than that in infected samples and being detected only in control samples) were generally associated with localization (GO: 0051179, p-value < 0.05), transport (GO: 0006810, p-value < 0.05), establishment of localization (GO: 0051234, p-value < 0.05), cellular component organization and biogenesis (GO:0016043, p-value < 0.05), and vesicle-mediated transport (GO:0016192, p-value < 0.05). The three major categories in biological process ontology were localization, transport, and establishment of localization. Proteins identified in the infected samples (with peptide scores in infected samples 2-fold higher than that in control samples and being detected only in infected samples) were generally associated with generation of precursor metabolites and energy (GO: 0006091, p-value < 0.05), transport (GO:0006810, p-value < 0.05), establishment of localization (GO:0051234, p-value < 0.05), localization (GO:0051179, p-value < 0.05), cellular metabolic process (GO:0044237, p-value < 0.05), carboxylic acid metabolic process (GO:0019752, p-value < 0.05), organic acid metabolic process (GO:0006082, p-value < 0.05), and metabolic process (GO:0008152, p-value < 0.05).The four major categories in biological process ontology were cellular process (GO: 0009987, p-value < 0.05), metabolic process, cellular metabolic process, and primary metabolic process (GO: 0044238, p-value < 0.05).In addition, several specific neuronal processes were enriched.

On the basis of the analysis with ClueGO [20], 2-fold up protein clusters involved three major biological processes such as glutamine family amino acid catabolic process, which included five proteins (i.e., argininosuccinate synthetase 1; glutamate oxaloacetate transaminase 2, mitochondrial; AU RNA binding protein/enoyl-coenzyme A hydratase; glutaminase; and aldehyde dehydrogenase family 6, subfamily A1); complement activation, a classical pathway which included three proteins (i.e., complement component 1, q subcomponent, alpha polypeptide; complement component 1, q subcomponent, beta polypeptide; and complement component 1, q subcomponent, C chain); and ATP biosynthetic process, which included six proteins (i.e., ATPase, Na+ / K+ transporting, alpha 2 polypeptide; ATPase, Ca++ transporting, plasma membrane 3; ATP synthase, H+ transporting, mitochondrial F1 complex, alpha subunit, isoform 1; ATP synthase, H+ transporting mitochondrial F1 complex, beta subunit; ATPase, H+ transporting, lysosomal V1 subunit A; and ATPase, H+ transporting, lysosomal V1 subunit B2). The same procedure revealed 17 2-folds down clusters such as regulation of neurotransmitter levels, exocytosis, and vesicle docking during exocytosis, and contained proteins such as syntaxin 1A (brain), reticulon 4, neurofibromatosis 1, and neurofilament, medium polypeptide. A total of 317 differentially expressed proteins with p-values less than 0.05 were selected. 165 proteins showed only to control group and defined increasing more than twice comparing infected group (down), 152 proteins showed only to infected group and defined increasing more than twice comparing control group (up). The identification of Gfap, Hspa5, Vim, chaperonin, Ywhaz, and Syn1 was highly significant because they are known to interact with PrP and are involved in disease progression (Tables 1 and 2).

GI_number Protein name Average Control #1 (control 11-20) Control #2 (control 21-30)
Score 11-30 Spectral count11-30 Score 11-20 Spectral count 11-20 Score 21-30 Spectral count 21-30
6671565 adaptor-related protein complex 3, delta 1 subunit 20.20 2.5 20.21 2 20.19 3
6671600 solute carrier family 7 (cationic amino acid transporter, y+ system), member 3 10.16 1.5 10.15 1 10.16 2
6671684 catenin (cadherin associated protein), beta 1, 88 kDa 10.16 1 10.18 1 10.14 1
6678551 vesicle-associated membrane protein 2 15.21 1.5 10.22 1 20.20 2
6678553 vesicle-associated membrane protein 3 15.24 2.5 10.25 1 20.24 4
6679337 phosphatidylinositol transfer protein, alpha 40.22 5 40.18 4 40.27 6
6679379 phospholipase D2 10.12 1 10.12 1 10.12 1
6679597 kinesin family member 20A 10.13 1 10.15 1 10.12 1
6680095 glutamate receptor, ionotropic, NMDA1 (zeta 1) 10.13 1 10.13 1 10.12 1
6680560 kinesin family member 2A 10.12 1 10.12 1 10.12 1
6680722 ADP-ribosylation factor 5 30.14 5.5 30.15 7 30.14 4
6681233 solute carrier family 26 (sulfate transporter), member 2 10.14 1 10.13 1 10.14 1
6753144 ATPase, H+ transporting, lysosomal V0 subunit C 25.18 2.5 10.18 1 40.19 4
6753172 B-cell leukemia / lymphoma 6 10.13 1 10.12 1 10.14 1
6753912 ferritin heavy chain 1 15.18 1.5 20.19 2 10.17 1
6754426 potassium inwardly rectifying channel, subfamily J, member 11 10.11 2 10.10 2 10.13 2
6755040 profilin 1 10.15 1 10.18 1 10.12 1
6755448 SEC22 vesicle trafficking protein-like 1 30.19 3 40.23 4 20.15 2
7106303 EH-domain containing 1 15.14 2 10.12 1 20.17 3
7710086 RAB10, member RAS oncogene family 15.17 2 10.17 1 20.17 3
8394392 synaptotagmin V 15.14 2 20.14 2 10.14 2
8567336 chloride channel calcium activated 3 10.13 1.5 10.14 2 10.12 1
9506971 profilin 2 25.16 5 20.15 3 30.16 7
9790237 SMC1 structural maintenance of chromosomes 1-like 1 10.12 1 10.12 1 10.12 1
9910164 Double cortin-like kinase 1 isoform 1 10.20 1.5 10.16 2 10.25 1
9937988 secretory carrier membrane protein 5 10.17 1 10.17 1 10.17 1
12963633 NADH dehydrogenase (ubiquinone) 1 alpha sub-complex, 13 15.15 2 20.16 2 10.14 2
13385006 cytochrome c-1 10.18 1.5 10.18 1 10.18 2
13385054 NADH dehydrogenase (ubiquinone) 1 beta sub-complex 3 15.12 2 20.12 2 10.12 2
13385492 NADH dehydrogenase (ubiquinone) 1 alpha sub-complex, 6 (B14) 20.15 3.5 20.17 4 20.14 3
13386054 actin related protein 2 / 3 complex, subunit 4 20.16 2.5 30.18 3 10.14 2
13470090 RAB3C, member RAS oncogene family 15.23 2 10.24 1 20.22 3
15011853 syntaxin 1A (brain) 25.16 2.5 30.17 3 20.15 2
16716499 sideroflexin 3 30.22 3 30.20 3 30.24 3
19526968 tubulin, gamma complex associated protein 2 10.15 1.5 10.12 1 10.18 2
19527256 DEAD (Asp-Glu-Ala-Asp) box polypeptide 1 10.13 1 10.13 1 10.12 1
21312950 NADH dehydrogenase (ubiquinone) Fe-S protein 7 10.15 2 10.18 3 10.12 1
21313226 anti-silencing function 1B 10.15 1 10.17 1 10.12 1
21314824 ATPase, H+ transporting, lysosomal V1 subunit F 10.13 1 10.14 1 10.12 1
21361250 ATPase, H+ transporting, lysosomal accessory protein 2 10.17 1.5 10.17 2 10.18 1
22550098 AGP7 10.13 2 10.13 1 10.14 3
27228985 13kDa differentiation-associated protein 15.13 1.5 20.14 2 10.13 1
27229051 NECAP endocytosis associated 1 10.16 1.5 10.14 1 10.19 2
28202057 a disintegrin-like and metalloprotease (reprolysin type) with thrombospondin type 1 motif, 19 15.14 2 10.10 1 20.18 3
28316750 histone cluster 1, H2ba 15.18 6.5 20.17 10 10.18 3
28916667 cytochrome b5 reductase 4 10.15 1 10.15 1 10.14 1
29244298 transient receptor potential cation channel, subfamily A, member 1 10.13 1 10.13 1 10.13 1
29789343 eukaryotic translation initiation factor 3, subunit 9 10.11 1 10.12 1 10.11 1
30061401 histone cluster 2, H3c1 isoform 2 40.13 12 40.12 13 40.14 11
30410760 collagen, type XVI, alpha 1 10.15 1.5 10.15 2 10.16 1
30520173 BCSC-1 10.12 1 10.12 1 10.12 1
31324569 neurocalcin delta 10.16 1 10.17 1 10.14 1
31543971 YKT6 v-SNARE protein 25.19 2.5 20.21 2 30.17 3
31980729 RAS protein activator like 1 (GAP1 like) 10.15 1 10.12 1 10.18 1
31981304 ATPase, H+ transporting, V0 subunit D isoform 1 50.20 5.5 40.15 5 60.25 6
31981754 glycine receptor, beta subunit 10.16 1.5 10.15 2 10.16 1
31981826 electron transferring flavoprotein, alpha polypeptide 10.18 1.5 10.19 2 10.18 1
31982223 laminin, beta 2 25.18 2.5 30.20 3 20.16 2
31982236 integrin alpha 6 10.16 1 10.14 1 10.18 1
31982300 hemoglobin, beta adult major chain 55.22 16 70.23 23 40.20 9
31982452 collagen, type IX, alpha 1 10.18 1.5 10.17 1 10.18 2
32401469 kinesin family member 27 10.12 1 10.12 1 10.12 1
33859827 solute carrier family 17 (sodium-dependent inorganic phosphate cotransporter), member 7 10.15 2 10.16 1 10.14 3
34328045 procollagen, type IV, alpha 4 10.15 1.5 10.14 1 10.17 2
34328138 kinesin family member 3A 10.12 1 10.12 1 10.13 1
34328158 wingless-related MMTV integration site 6 10.14 1.5 10.13 1 10.16 2
34538601 cytochrome c oxidase subunit II 10.14 1 10.12 1 10.15 1
34878892 neurofibromin 35.17 6.5 30.15 4 40.20 9
38604071 exportin 1, CRM1 homolog 15.13 2 10.12 2 20.14 2
40254228 solute carrier family 39 (zinc transporter), member 10 10.15 1 10.15 1 10.14 1
40254514 GTPase activating protein and VPS9 domains 1 10.16 1.5 10.18 1 10.14 2
40254624 platelet-activating factor acetylhydrolase, isoform 1b, alpha2 subunit 10.14 1.5 10.15 2 10.14 1
40353214 suppressor of zeste 12 homolog 10.13 1.5 10.13 1 10.13 2
41054950 collagen, type VIII, alpha 2 10.14 1 10.11 1 10.16 1
41281837 chloride channel 3 isoform c 10.17 1 10.13 1 10.20 1
41281852 amphiphysin 30.21 3.5 20.21 2 40.21 5
41350312 nascent polypeptide-associated complex alpha subunit isoform b 15.23 2 10.24 2 20.23 2
45476581 sterol carrier protein 2, liver 10.14 1 10.15 1 10.13 1
45597447 superoxide dismutase 1, soluble 15.14 1.5 20.15 2 10.13 1
46195430 NADH dehydrogenase (ubiquinone) Fe-S protein 8 10.17 1 10.19 1 10.15 1
46559412 protein kinase C and casein kinase substrate in neurons 1 10.17 1 10.16 1 10.17 1
46849724 VPS9-ankyrin repeat-containing protein isoform 2 10.13 1 10.14 1 10.12 1
47604978 a disintegrin-like and metalloprotease (reprolysin type) with thrombospondin type 1 motif, 13 10.12 1 10.12 1 10.12 1
51491850 Rho guanine nucleotide exchange factor (GEF) 11 10.12 1 10.12 1 10.12 1
58037109 NADH dehydrogenase (ubiquinone) 1 beta subcomplex, 10 15.15 2 10.14 1 20.16 3
58037145 small nuclear ribonucleoprotein D2 10.21 2.5 10.24 3 10.18 2
60460915 regulating synaptic membrane exocytosis 1 isoform 2 10.12 1 10.12 1 10.12 1
61102728 inositol 1,4,5-triphosphate receptor 3 15.17 2 20.18 3 10.15 1
62990166 structural maintenance of chromosomes 2-like 1 10.13 1 10.12 1 10.13 1
68341935 microtubule-associated protein 2 isoform 2 15.16 2.5 10.20 3 20.12 2
70906474 Ca < 2+_dependent activator protein for secretion isoform 1 10.22 1 10.19 1 10.25 1
70906477 Calcium / calmodulin-dependent protein kinase II, delta isoform 2 35.20 5 40.17 6 30.24 4
73622271 absent, small, or homeotic discs 1 10.18 2 10.16 1 10.21 3
77812697 titin isoform N2-A 10.16 1.5 10.12 1 10.20 2
78000173 sorbin and SH3 domain containing 1 isoform 2 10.16 1 10.14 1 10.17 1
82533043 skeletal muscle receptor tyrosine kinase isoform 1 precursor 10.15 1 10.13 1 10.18 1
83523732 slit homolog 3 10.12 1.5 10.11 1 10.13 2
84781802 ATPase, aminophospholipid transporter (APLT), class I, type 8A, member 1 isoform a 10.13 1 10.14 1 10.12 1
85540453 pleckstrin and Sec7 domain containing 3 isoform 2 10.15 1.5 10.12 1 10.17 2
90903233 glutathione peroxidase 4 isoform 1 precursor 15.13 1.5 20.14 2 10.13 1
94398520 PREDICTED: similar to vacuolar protein sorting 13B isoform 5 10.14 1 10.12 1 10.17 1
106507168 RAB12, member RAS oncogene family 10.17 1 10.20 1 10.14 1
110225337 ATPase, H+ / K+ exchanging, gastric, alpha polypeptide 10.14 1 10.16 1 10.12 1
110625645 sortilin-related receptor, LDLR class A repeats-containing 10.14 1 10.16 1 10.13 1
110625819 hypothetical protein LOC268739 10.14 4 10.13 3 10.15 5
111955376 lysosomal trafficking regulator 10.12 1 10.12 1 10.12 1
112363107 neurofilament 3, medium 80.24 30 80.24 25 80.24 35
114155137 dynein, axonemal, heavy chain 5 10.13 1 10.13 1 10.13 1
114158695 ATP / GTP binding protein 1 isoform 1 10.14 1 10.14 1 10.13 1
115648153 cadherin EGF LAG seven-pass G-type receptor 1 precursor 10.12 1.5 10.12 1 10.12 2
116089327 a disintegrin and metalloprotease domain 2 (fertilin beta) 10.13 1 10.13 1 10.14 1
116089329 Snap-25-interacting protein 15.21 2.5 10.15 1 20.27 4
116174793 spectrin beta 4 10.16 2 10.15 1 10.16 3
116256491 ankyrin 3, epithelial isoform a 35.18 5 30.18 4 40.18 6
117414174 sodium channel, voltage-gated, type VIII, alpha 10.12 1 10.12 1 10.12 1
117956385 RUN and TBC1 domain containing 1 10.13 1 10.13 1 10.13 1
118403316 hypothetical protein LOC235461 10.13 1 10.12 1 10.14 1
119433657 histone cluster 2, H2ab 10.12 1 10.12 1 10.12 1
120587003 TBC1 domain family, member 1 10.13 1 10.13 1 10.13 1
121583653 a disintegrin-like and metalloprotease (reprolysin type) with thrombospondin type 1 motif, 18 10.17 3.5 10.20 3 10.14 4
122114537 vacuolar protein sorting 13C 20.13 2.5 30.15 3 10.12 2
124486650 SLIT-ROBO Rho GTPase activating protein 1 10.13 1.5 10.14 2 10.13 1
124486692 integrin, alpha 10 10.14 1 10.12 1 10.15 1
124487141 a disintegrin-like and metalloprotease (reprolysin type) with thrombospondin type 1 motif, 3 10.14 1.5 10.12 1 10.15 2
124487229 breakpoint cluster region homolog 15.15 1.5 10.12 1 20.18 2
124487372 low density lipoprotein receptor-related protein 2 15.17 2 20.14 2 10.19 2
124487493 signal-induced proliferation-associated 1 like 2 10.12 1 10.13 1 10.11 1
130502228 hypothetical protein LOC320484 10.14 1 10.12 1 10.15 1
131889984 sodium channel, voltage-gated, type X, alpha 10.13 2 10.13 3 10.13 1
133505571 M-phase phosphoprotein 1 10.14 1.5 10.14 1 10.14 2
134031976 leucine-rich PPR motif-containing protein 55.24 6.5 40.25 5 70.22 8
134053947 bridging integrator 1 isoform 2 10.13 1.5 10.12 1 10.15 2
144922716 common-site lymphoma / leukemia guanine nucleotide exchange factor isoform a 10.13 1 10.14 1 10.12 1
145275191 ATP-binding cassette, sub-family C, member 6 10.14 1 10.13 1 10.14 1
145587082 triple functional domain (PTPRF interacting) 10.12 1 10.13 1 10.12 1
146231960 chondroitin sulfate proteoglycan 4 10.12 1 10.13 1 10.12 1
146231996 HECT, UBA and WWE domain containing 1 10.13 2 10.14 3 10.12 1
147902443 kinesin family member 26A 10.14 1 10.13 1 10.14 1
148747179 lymphocyte antigen 75 10.12 1 10.12 1 10.12 1
149254026 PREDICTED: SEC31-like 1 10.14 1 10.15 1 10.13 1
149254379 PREDICTED: similar to hCG1811879 15.15 3 20.15 3 10.15 3
149255369 PREDICTED: IQ motif and Sec7 domain 1 10.12 1 10.12 1 10.12 1
149255409 PREDICTED: jumonji, AT rich interactive domain 1A (Rbp2 like) isoform 1 15.12 1.5 10.12 1 20.12 2
149260924 PREDICTED: jumonji domain containing 1C 10.14 1 10.14 1 10.13 1
153792247 low density lipoprotein-related protein 1B 10.18 2 10.18 1 10.17 3
154146254 insulin related protein 2 (islet 2) 10.13 2 10.14 1 10.13 3
157823695 kinesin family member 21A isoform 3 10.22 1 10.22 1 10.22 1
157909825 synaptic vesicle glycoprotein 2 b 15.13 2 20.13 3 10.13 1
158711686 solute carrier family 12, member 5 20.15 3.5 10.15 2 30.15 5
159110614 FYVE and coiled-coil domain containing 1 10.13 1 10.14 1 10.13 1
159110663 integrin alpha 2b 10.15 1 10.19 1 10.12 1
160333276 intersectin 1 isoform 2 10.17 1 10.14 1 10.19 1
160333789 sepiapterin reductase 45.20 4.5 40.15 4 50.24 5
160333877 kinesin family member 1A isoform b 20.18 2 20.19 2 20.17 2
160358856 integrin beta 3 precursor 20.15 2.5 20.14 2 20.16 3
160707901 synapsin I isoform a 95.25 34 100.25 24 90.24 44
160707911 ankyrin 1, erythroid isoform 2 35.19 4 50.18 5 20.21 3
160707971 adaptor-related protein complex 3, sigma 2 subunit 20.19 2 20.19 2 20.18 2
161016797 non-SMC condensin II complex, subunit D3 10.13 1 10.14 1 10.12 1
161016826 receptor accessory protein 5 15.14 3 20.16 4 10.13 2
161086984 adaptor-related protein complex 2, sigma 1 subunit 30.18 6.5 20.19 5 40.17 8
161353508 chromobox homolog 4 10.13 1.5 10.12 1 10.14 2
161702988 apolipoprotein B precursor 10.16 3.5 10.13 2 10.19 5
162139829 myelin protein zero 15.13 3 10.12 1 20.13 5
163965444 centrosomal protein 290 10.14 1.5 10.13 1 10.15 2

Table 1: The 165 differentially expressed proteins selected preferentially over score 10.1 and increased by more than 2-fold compared with infected mice based on the Gene Ontology and Cytoscape with p-values less than 0.05.

GI_number Protein name Average Infected #1 (1-10) Infected #2 (11-20) Infected #3 (21-30)
Score 1-30 Spectral count 1-30 Score 1-10 Spectral count 1-10 Score 11-20 Spectral count 11-20 Score 21-30 Spectral count 21-30
6671539 aldolase 1, A isoform 16.85 2 30.18 3 10.13 1 10.24 1
6671549 peroxiredoxin 6 16.83 2 20.16 2 10.13 1 20.20 2
6671664 calnexin 23.52 2 30.20 3 20.15 2 20.21 2
6671702 chaperonin subunit 5 (epsilon) 30.24 3 40.26 4 40.25 4 10.20 1
6677809 ribosomal protein S6 20.17 2 30.23 3 20.14 3 10.13 1
6678047 synuclein, alpha 10.15 1 10.11 1 10.16 1 10.17 1
6678483 ubiquitin-activating enzyme E1 110.24 16 130.23 19 120.22 14 80.26 14
6679243 phosphodiesterase 1B, Ca2+ - calmodulin dependent 10.17 1 10.16 1 10.20 1 10.16 1
6679345 protein kinase C, beta 1 23.48 2 40.17 4 10.12 1 20.15 2
6679935 growth associated protein 43 10.17 1 10.16 1 10.15 1 10.19 2
6680345 isocitrate dehydrogenase 3 (NAD+), gamma 20.19 2 30.22 3 20.15 2 10.20 1
6680720 ADP-ribosylation factor 4 13.47 2 20.14 2 10.13 1 10.15 2
6681069 cysteine and glycine-rich protein 36.88 6 50.23 7 20.17 3 40.23 7
6753220 complement component 1, q subcomponent, B chain 26.86 3 40.21 5 10.17 1 30.21 4
6753280 caspase 14 10.17 1 10.18 1 10.14 1 10.20 1
6753320 chaperonin subunit 3 (gamma) 40.16 4 70.20 8 30.17 3 20.12 2
6753322 chaperonin subunit 4 (delta) 36.87 5 40.17 6 50.21 6 20.22 2
6753324 chaperonin subunit 6a (zeta) 13.50 2 10.22 1 10.12 1 20.14 3
6753992 gap junction protein, alpha 1 26.86 7 30.19 10 20.18 5 30.23 5
6754004 guanine nucleotide binding protein, alpha 11 10.15 3 10.18 6 10.13 2 10.14 1
6754036 glutamate oxaloacetate transaminase 2, mitochondrial 43.52 5 60.23 6 40.18 4 30.14 4
6754086 glutathione S-transferase, mu 5 13.49 2 10.16 2 20.14 2 10.17 1
6754206 hexokinase 1 50.17 5 80.20 8 50.19 5 20.13 2
6754624 mitogen activated protein kinase kinase 5 10.17 7 10.16 7 10.18 9 10.18 4
6755002 programmed cell death 6 interacting protein 13.51 1 10.18 1 20.15 2 10.20 1
6755080 protein kinase C, gamma 73.59 10 120.26 16 40.21 6 60.29 9
6755256 muscle glycogen phosphorylase 20.15 2 20.15 2 30.12 3 10.17 1
6755372 ribosomal protein S3 46.82 6 60.18 9 40.15 6 40.13 4
6755588 synaptosomal-associated protein 25 13.48 1 10.16 1 10.12 1 20.16 2
6755809 talin 1 16.85 2 10.13 2 20.21 2 20.22 2
6755863 tumor rejection antigen gp96 60.20 10 80.20 13 60.19 10 40.22 7
6755911 thioredoxin 1 13.54 2 10.21 1 10.20 1 20.22 3
6755967 voltage-dependent anion channel 3 23.51 3 40.21 5 20.19 3 10.12 1
6996911 argininosuccinate synthetase 20.16 2 20.14 2 30.20 3 10.15 1
7305029 erythrocyte protein band 4.1-like 1 isoform a 16.88 3 20.22 3 10.20 2 20.22 3
8392847 ARP1 actin-related protein 1 homolog A 16.90 2 30.24 3 10.23 1 10.23 1
8393544 heterogeneous nuclear ribonucleoprotein C 16.83 2 30.19 3 10.13 1 10.16 1
8567410 synapsin II isoform IIb 36.90 7 70.28 14 20.18 3 20.24 5
9507023 Rab geranylgeranyl transferase, a subunit 10.15 2 10.14 2 10.13 3 10.19 1
9789991 hydroxysteroid (17-beta) dehydrogenase 12 protein 16.84 2 30.22 3 10.16 1 10.13 1
9790051 phosphofructokinase, platelet 50.24 6 60.25 9 50.25 6 40.22 4
9790055 mitochondrial carrier homolog 2 23.50 2 50.23 5 10.16 1 10.12 1
10946940 RAB2, member RAS oncogene family 16.82 2 30.19 3 10.12 1 10.14 1
11230802 actinin alpha 4 63.55 8 80.22 10 70.21 9 40.23 6
12963511 ribosomal protein S19 10.14 2 10.11 1 10.15 3 10.15 2
12963737 chromosome segregation 1-like 23.51 3 40.24 4 20.15 2 10.14 2
13173473 prion protein 66.86 14 70.26 19 60.16 9 70.17 15
13385998 TNF receptor-associated protein 1 20.21 2 30.24 3 10.16 1 20.22 2
13928670 vacuolar protein sorting 35 23.53 2 30.20 3 30.19 3 10.20 1
14149645 methyl CpG binding protein 2 isoform 2 13.47 2 10.15 2 20.12 3 10.13 1
16716465 acyl-CoA synthetase bubblegum family member 1 70.20 7 90.23 9 60.18 7 60.19 6
18079339 aconitase 2, mitochondrial 63.55 7 100.24 11 40.21 5 50.21 5
18266680 3-oxoacid CoA transferase 1 13.50 1 20.21 2 10.17 1 10.13 1
19705578 vacuolar H+ ATPase B2 36.84 6 40.17 6 60.19 10 10.16 2
21311845 solute carrier family 25 (mitochondrial carrier, glutamate), member 22 23.53 3 30.20 3 10.16 1 30.22 4
21313308 heterogeneous nuclear ribonucleoprotein M isoform a 10.14 1 10.14 2 10.13 1 10.16 1
21426889 ribosomal protein S11 13.45 1 20.12 2 10.10 1 10.14 1
21704020 NADH dehydrogenase (ubiquinone) Fe-S protein 1 30.22 3 50.25 5 20.21 2 20.20 3
21704162 ubiquitin-conjugating enzyme E2M 23.47 2 40.15 4 20.13 2 10.12 1
21704242 CaM kinase-like vesicle-associated 50.22 7 100.25 13 30.22 3 20.19 4
21746161 tubulin, beta 10.18 2 10.19 2 10.17 2 10.18 3
22267442 ubiquinol cytochrome c reductase core protein 2 20.19 2 30.22 3 20.22 2 10.13 1
23943838 solute carrier family 25, member 1 13.48 1 20.18 2 10.14 1 10.13 1
24233554 solute carrier family 1 (glial high affinity glutamate transporter), member 3 10.21 2 10.26 2 10.21 2 10.15 2
24418919 brain glycogen phosphorylase 60.22 6 70.23 8 80.23 8 30.20 3
24429570 exportin 5 10.13 1 10.12 1 10.14 2 10.13 1
25742730 ribosomal protein L32 10.22 1 10.23 1 10.22 1 10.21 1
27369581 solute carrier family 25 (mitochondrial carrier, Aralar), member 12 120.24 14 160.26 19 110.22 13 90.22 10
27369896 transcriptional regulating factor 1 isoform 2 10.16 1 10.14 1 10.13 1 10.21 1
29336026 myosin, heavy polypeptide 14 20.20 3 20.16 4 20.18 2 20.24 4
29789191 asparaginyl-tRNA synthetase 30.18 3 60.24 6 20.16 2 10.13 1
29789199 RAN binding protein 5 20.17 3 20.16 3 10.15 1 30.20 5
30409956 ATPase, Na+ / K+ transporting, alpha 2 polypeptide 106.88 41 140.23 54 100.19 40 80.21 28
30425158 zinc finger protein 526 10.13 1 10.14 1 10.13 1 10.13 1
31542608 elongation protein 4 homolog 10.13 1 10.14 1 10.13 1 10.12 1
31543797 synaptotagmin II 26.86 3 50.19 5 20.16 3 10.21 1
31560433 sorting nexin 3 10.15 1 10.16 1 10.14 1 10.15 1
31560731 ATPase, H+ transporting, lysosomal V1 subunit A 83.56 11 160.27 20 80.20 9 10.20 3
31980648 ATP synthase, H+ transporting mitochondrial F1 complex, beta subunit 106.86 22 120.21 24 120.21 26 80.17 16
31980844 Dehydrogenase / reductase (SDR family) member 1 36.88 4 60.26 7 10.14 1 40.25 4
31981185 phosphofructokinase, muscle 86.93 11 110.29 12 80.23 13 70.26 7
31981237 thimet oligopeptidase 1 10.16 1 10.17 1 10.12 2 10.17 1
31981722 heat shock protein 5 36.85 4 70.21 7 20.14 2 20.21 2
31981769 glycerol phosphate dehydrogenase 2, mitochondrial 10.15 1 10.19 1 10.12 1 10.12 2
31982178 malate dehydrogenase 1, NAD (soluble) 33.50 3 60.17 6 20.12 2 20.19 2
31982186 malate dehydrogenase 2, NAD (mitochondrial) 90.22 14 90.20 12 110.17 18 70.28 11
31982332 glutamine synthetase 20.17 2 30.20 3 10.14 1 20.16 2
31982497 ATP synthase, H+ transporting, mitochondrial F0 complex, subunit c, isoform 1 10.11 3 10.11 3 10.11 3 10.10 2
31982664 inosine triphosphatase 20.15 2 30.17 3 20.14 2 10.13 1
31982755 vimentin 106.88 24 110.24 26 140.22 23 70.17 24
31982856 dihydrolipoamide dehydrogenase 13.50 1 10.17 1 20.17 2 10.15 1
32567788 phosphatidylinositol-binding clathrin assembly protein 20.18 3 30.17 5 20.17 3 10.20 2
33859474 complement receptor 2 10.12 2 10.11 1 10.12 4 10.12 1
33859811 mitochondrial trifunctional protein, alpha subunit 73.55 8 100.24 11 70.19 8 50.22 6
34740335 tubulin, alpha 1B 13.56 7 10.15 8 20.18 5 10.35 8
36031132 ATPase, Ca++ transporting, fast twitch 1 16.83 3 20.17 3 20.19 3 10.14 3
37202121 4-aminobutyrate aminotransferase 30.20 4 30.19 4 50.20 6 10.20 1
38372907 DEAD (Asp-Glu-Ala-Asp) box polypeptide 39 20.14 3 30.15 3 10.14 1 20.12 4
39930477 septin 8 20.19 2 30.23 3 20.20 2 10.16 1
40254635 kinesin family member 5A 23.56 3 20.25 2 30.20 3 20.23 3
52353955 3-phosphoglycerate dehydrogenase 46.87 5 40.17 4 50.22 6 50.22 6
56699478 plasma membrane calcium ATPase 3 20.17 2 10.12 1 10.16 1 40.23 4
58037481 sec1 family domain containing 1 10.17 1 10.16 1 10.16 2 10.19 1
61097906 actinin, alpha 1 56.87 6 60.24 6 70.19 8 40.20 4
61888842 partitioning-defective protein 3 homolog isoform 2 10.16 2 10.15 1 10.16 2 10.17 3
67763830 zinc finger protein 62 isoform 1 10.12 1 10.13 1 10.12 1 10.12 1
71725385 DIRAS family, GTP-binding RAS-like 2 13.52 1 10.21 1 20.16 2 10.19 1
71774133 peptidylprolyl isomerase B 20.20 2 30.20 3 10.21 1 20.18 2
75992915 acyl-CoA synthetase long-chain family member 6 isoform 3 70.23 7 90.24 9 50.23 5 70.23 8
75992920 acyl-CoA synthetase long-chain family member 3 23.50 2 50.21 5 10.13 1 10.16 1
82891441 PREDICTED: similar to DnaJ (Hsp40) homolog, subfamily B, member 14 isoform 8 10.13 1 10.12 1 10.17 1 10.11 1
83776571 protein kinase C-binding protein NELL1 10.17 1 10.16 1 10.15 1 10.19 1
83816893 DEAD (Asp-Glu-Ala-Asp) box polypeptide 5 20.24 3 40.24 4 10.17 2 10.30 2
83921618 villin 2 16.84 2 20.18 3 20.19 2 10.14 1
84000448 glial fibrillary acidic protein 236.90 116 280.25 141 250.22 99 180.23 108
85861218 guanine monphosphate synthetase 16.85 2 10.17 1 10.18 1 30.20 4
87298845 calmodulin binding protein 1 10.13 2 10.12 2 10.13 2 10.14 1
88196800 myosin VI 30.21 4 20.20 3 20.21 3 50.22 5
88853578 adaptor protein complex AP-1, beta 1 subunit 90.24 20 100.26 23 110.21 26 60.24 10
91992157 AP2 associated kinase 1 isoform 1 10.15 1 10.12 1 10.19 2 10.14 1
93102409 fatty acid synthase 150.22 18 140.21 14 150.21 17 160.24 22
93102417 glycyl-tRNA synthetase 13.53 1 20.17 2 10.17 1 10.25 1
110625886 alpha isoform of regulatory subunit B55, protein phosphatase 2 10.18 3 10.18 3 10.19 3 10.16 2
110625979 eukaryotic translation elongation factor 1 gamma 23.51 3 40.22 5 20.17 3 10.12 1
111185930 transmembrane protease, serine 13 10.13 1 10.13 1 10.11 1 10.15 1
112734861 importin 9 10.15 1 10.19 1 10.13 2 10.14 1
113680120 complement component 1, q subcomponent, gamma polypeptide 30.17 3 30.20 3 20.12 2 40.18 4
113865903 hypothetical protein LOC216976 10.16 2 10.19 3 10.17 1 10.13 1
114155155 mediator of RNA polymerase II transcription, subunit 8 homolog isoform 1 10.13 2 10.13 2 10.13 1 10.13 2
116256510 adaptor protein complex AP-2, alpha 1 subunit isoform b 136.89 23 170.21 30 140.22 23 100.24 15
116268115 AU RNA-binding enoyl-coenzyme A hydratase 23.53 3 30.30 4 30.15 4 10.13 1
117606277 excitatory amino acid transporter 2 isoform 1 13.47 1 20.18 2 10.12 1 10.12 1
118136297 chapsyn-110 10.13 1 10.14 1 10.12 1 10.13 1
118918400 nuclear receptor-binding SET-domain protein 1 10.15 1 10.18 1 10.12 1 10.16 2
120586994 homeobox D13 10.12 1 10.12 1 10.13 1 10.13 1
124486670 solute carrier family 25 (mitochondrial carrier), member 18 20.13 3 20.13 4 20.12 2 20.14 3
124487037 myosin IA 10.14 1 10.15 1 10.16 2 10.12 1
124487313 glutaminase isoform 1 40.20 5 70.23 9 30.21 3 20.15 3
124494256 low density lipoprotein receptor-related protein 1 40.20 6 30.17 3 20.20 2 70.22 12
125347376 filamin, alpha 20.14 2 40.17 4 10.12 1 10.13 1
126090749 inositol polyphosphate-4-phosphatase, type I isoform 2 13.50 2 20.19 2 10.14 1 10.18 2
130505929 potassium inwardly-rectifying channel J16 10.11 2 10.10 2 10.11 2 10.12 1
147899467 plakophilin 4 isoform 2 10.12 3 10.11 3 10.11 2 10.13 4
149268231 PREDICTED: similar to synaptojanin 20.17 3 30.18 3 20.20 3 10.14 2
153792586 SPEG complex locus isoform 10.13 1 10.12 2 10.12 1 10.15 1
157951604 CAP, adenylate cyclase-associated protein 1 40.21 5 70.22 8 40.24 5 10.17 1
157951686 ATPase, class V, type 10A 10.13 1 10.16 1 10.12 1 10.12 1
157951727 catenin (cadherin associated protein), alpha 2 isoform 1 23.51 3 50.16 5 10.13 2 10.24 1
158508501 septin 5 36.83 4 50.20 5 20.14 2 40.16 4
160333829 sorting nexin 12 isoform 3 10.16 1 10.22 1 10.12 1 10.12 1
162461907 heat shock protein 9 36.89 4 70.26 7 20.19 2 20.23 2
164698474 cytoplasmic FMR1 interacting protein 1 13.50 1 10.21 1 10.12 1 20.17 2

Table 2: The 152 differentially expressed proteins selected preferentially over score 10.2 and increased by more than 2-fold compared with control based on the Gene Ontology and Cytoscape with p- values less than 0.05

Differentially regulated brain proteins

Seven proteins with average scores greater than 20.0 and spectral counts of 3.0 among the proteins expressed in control mice and with spectral count ratios greater than 2.0 among the infected mice were selected and classified as downregulated. We selected 36 proteins that were remarkably upregulated in the ME7-infected samples (Table 3). Among these, we found six proteins associated with neuronal processes such as transmission of nerve impulse, synaptic transmission, regulation of neurotransmitter levels, cell-cell signaling, neurotransmitter transport, neurotransmitter uptake, and neurological control of breathing. Proteins involved in neurological processes, including 4-aminobutyrate aminotransferase, ATPase, Na+ / K+ transporting, alpha 2 polypeptide, glutaminase isoform 1, myosin VI, and synapsin II isoform IIb, were upregulated, while sepiapterinreductase was downregulated.

Gi_number Protein name Gene symbols Protein MW Control (C) ME7 (M) ratio
Score Spectral count Score Spectral count (c/m)
up-regulated proteins
31981185 phosphofructokinase, muscle Pfkm 85248.63     86.93 11  
75992915 acyl-CoAsynthetaselong-chainfamilymember6isoform3 Acsl6 77967.26     70.23 7  
16716465 acyl-CoAsynthetasebubblegumfamilymember1 Acsbg1 80374.56     70.2 7  
11230802 actininalpha4 Actn4 104911.4     63.55 8  
61097906 actinin,alpha1 Actn1 103003.6     56.87 6  
21704242 CaMkinase-likevesicle-associated Camkv 54785.59     50.22 7  
6754206 hexokinase1 Hk1 105506.5     50.17 5  
6754036 glutamateoxaloacetatetransaminase2,mitochondrial Got2 47381.25     43.52 5  
124487313 glutaminaseisoform1 Gls 73916.26     40.2 5  
6753320 chaperoninsubunit3(gamma) Cct3 60591.46     40.16 4  
8567410 synapsinIIisoformIIb Syn2 52418.46     36.9 7  
162461907 heatshockprotein9 Hspa9 73415.7     36.89 4  
31980844 Dehydrogenase / reductase (SDRfamily) member1 Dhrs1 33983.37     36.88 4  
31981722 heatshockprotein5 Hspa5 72378.49     36.85 4  
6671702 chaperoninsubunit5 (epsilon) Cct5 59586.04     30.24 3  
88196800 myosinVI Myo6 145641.3     30.21 4  
37202121 4-aminobutyrateaminotransferase Abat 56415.68     30.2 4  
29789191 asparaginyl-tRNAsynthetase Nars 63025.58     30.18 3  
113680120 complementcomponent1, qsubcomponent,gammapolypeptide C1qc 25974.87     30.17 3  
84000448 glialfibrillaryacidicprotein Gfap 49869.61 45.18 10 236.9 116 12.2
13173473 prionprotein PrnP 27959.5 20.18 2 66.86 14 7.2
31982755 vimentin Vim 53655.16 20.16 4 106.88 24 7
24418919 brainglycogenphosphorylase Pygb 96668.61 10.13 1 60.22 6 6.3
18079339 aconitase2,mitochondrial Aco2 85410.13 15.18 2 63.55 7 4.7
9790051 phosphofructokinase,platelet Pfkp 85400.41 15.19 2 50.24 6 4.2
31980648 ATPsynthase, H+ transportingmitochondrialF1complex, betasubunit Atp5b 56265.58 35.16 7 106.86 22 3.4
6755863 tumorrejectionantigengp96 Hsp90b1 92418.14 20.15 3 60.2 10 3.3
27369581 solutecarrierfamily25 (mitochondrialcarrier, Aralar), member12 Slc25a12 74522.94 40.22 5 120.24 14 2.8
31560731 ATPase, H+ transporting, lysosomalV1subunitA Atp6v1a 68282.63 40.17 4 83.56 11 2.7
6678483 ubiquitin-activatingenzymeE1 Uba1 117734.1 45.2 6 110.24 16 2.6
6755080 ProteinkinaseC, gamma Prkcg 78307.24 25.2 4 73.59 10 2.6
116256510 adaptorproteincomplexAP-2,alpha1subunitisoformb Ap2a1 105413.1 60.18 10 136.89 23 2.4
93102409 fattyacidsynthase Fasn 272254.3 60.25 8 150.22 18 2.4
31982186 malatedehydrogenase2,NAD(mitochondrial) Mdh2 35588.76 50.19 6 90.22 14 2.3
30409956 ATPase, Na+ / K+ transporting,alpha2polypeptide Atp1a2 112145.6 100.24 20 106.88 41 2.1
88853578 adaptorproteincomplexAP-1,beta1subunit Ap1b1 103869.1 50.17 10 90.24 20 2.1
down-regulated proteins
31982300 hemoglobin, betaadultmajorchain Hbb_bt 15738.15 55.22 16 40.18 5 3.2
112363107 neurofilament3,medium Nefm 95883.48 80.24 30 43.52 10.3 2.9
161086984 adaptor-relatedproteincomplex2,sigma1subunit Ap2s1 17006.7 30.18 6.5 16.81 2.3 2.8
6680722 ADP-ribosylationfactor5 Arf5 20516.58 30.14 5.5 20.17 2 2.8
160333789 sepiapterinreductase Spr 27910.39 45.2 4.5 16.84 1.7 2.7
116256491 ankyrin3,epithelialisoforma Ank3 188126 35.18 5 10.17 2 2.5
28316750 histonecluster1,H2ba Th2b 14105 15.1 6.5 20.15 3 2.2

Table 3: Summary of the biological processes associated with the differentially regulated proteins in ME7 scrapie-infected mouse brains. On the basis of the host response to the scrapie agent, we selected 36 up-regulated and 7 down-regulated proteins as potential biomarkers.

These results showed that significantly more proteins were identified in the infected mouse brains than in the controls.

Neurodegenerative diseases associated with proteins

The 43 differentially regulated proteins was uploaded into Michigan Molecular interactions Cytoscape plug-in and a network was generated using the “Query genes + nearest neighbors” option. These networks diseases associated with proteins of the Kyoto Encyclopedia of Genes and Genomes (http://www.genome.jp/kegg/) pathway: Alzheimer’s disease [mmu05010], Parkinson’s disease [mmu05012], amyotrophic lateral sclerosis [mmu05014], Huntington’s disease [mmu05016], and prion disease [mmu05020]. The proteins related to neurodegenerative diseases were17, such as Gfap, Apoe, Ncor1, Prnp, Bcl2, Calm3, Grb2, Apbb1, Calm1, Calm2, Uba1, Hspa5, Aplp1, Crebbp, Ppp3ca, Cat, and Trp53. Among these, the seeds proteins were Gfap, Prnp, Uba1, and Hspa5. PRNP, which consisted of 241 nodes, was one of the interaction networks and included 20 proteins such as Syn2 acting direct interaction (network distance=1).

Western blotting of acyl-CoA synthetase bubblegum family member 1 (ACSBG1) and asparaginyl-tRNAsynthetase (NARS)

Our proteomics results indicated that ACSBG1 and NARS are significantly increased in ME7scrapie-infected mice. We conducted biological validation of ACSBG1 and NARS, which were not reported to interact with prion protein among 43 candidates. To validate our proteomic results, we analyzed their protein levels in mouse brain homogenates by western blotting. The predicted molecular size of ACSBG1 was approximately 80kDa. Western blotting showed that the levels of ACSBG1 were significantly increased in ME7scrapie-infected mice. NARS, a member of the class II aminoacyl-tRNAsynthetases, was observed as a distinct band at the appropriate molecular weight of 63kDa in ME7scrapie-infected mouse brain (Figure 4).

proteomics-bioinformatics-synthetase-bubblegum-asparaginyl

Figure 4: Confirmation of acyl-CoA synthetase bubblegum family member 1 (ACSBG1) (A) and asparaginyl-tRNAsynthetase (NARS) (B) expressed by western blotting including corresponding bar graphs of them below. Brain homogenates were analyzed with antibodies against ACSBG1 (1:200) and NARS (1:2,000) based on the total loading amount. Expression levels were normalized to β-actin levels.

Conclusion

Proteomics is a powerful method for the study of protein expression pattern and protein interactions in the blood, in particular the discovery and development of novel biomarkers for diagnosis of disease. We used proteomics to study the correlation between differentially expressed genes and their GO in scrapie-infected mice brains. Each gene was involved in one or more biological processes, and most candidate biomarkers were associated with cellular process, metabolic process, or cellular metabolic process. Many of these proteins are associated with neural processes, including cell-cell signaling, transmission of nerve impulse, and synaptic transmission. The control group included19 proteins such as Sptbn4, Cadps, Slc17a7, Grin1, Musk, Ctnnb1, Glrb, Agtpbp1, Vamp2, Nf1, Stx1a, Slc12a5, Sod1, Spr, Sv2b, Syn1, Celsr1, Cyb5r4, and Wnt6. The ME7 scrapie-infected group contained 12 proteins such as Snca, Gls, Myo6, Snap25, Abat, Dlg2, Syn2, Gna11, dac3, Atp1a2, Gja1, and Synj.

The differentially expressed proteins identified in this study that have not been previously reported as related to human prion diseases were those involved in metabolic processes (i.e., phosphofructokinase, muscle; acyl-CoA synthetase long-chain family member 6 isoform 3; ACGSBG1; glutamate oxaloacetate transaminase 2, mitochondrial; aconitase 2, mitochondrial; and ATP synthase, H+ transporting, mitochondrial F1 complex, beta subunit), glycolysis (i.e., hexokinase 1 and phosphofructokinase, platelet), glutamine catabolic process (i.e., glutaminase isoform 1), oxidation reduction processes (i.e., dehydrogenase / reductase [SDR family] member 1and fatty acid synthase) and asparaginyl-tRNAaminoacylation and generic transcription (i.e., NARS), which is related to asparagine tRNA ligase activity and nucleic acid binding, and is affected in diseases such as inclusion conjunctivitis and filariasis.

Proteins with several major functions were identified in this study. Acyl-CoA synthetase is related to metabolic pathways and participates in gene expression. It may also play a role in aerobic respiration as an energy producer, and in the mitochondrial matrix as an electron carrier. ACSBG1 interacts with 14-3-3 beta (Ywhab) and is an important paralog ofacyl-CoA synthetase long-chain family member 6 isoform 3. The lipidosin mouse homologue ACSBG1,which has long chain acyl-CoA synthetase activity, is exclusively expressed in the brain, adrenal gland, and testis, and is a key enzyme in the initial step of very-long-chain fatty acid β-oxidation.ACSBG1 is affected in neurodegenerative disorders such as human X-linked adrenoleukodystrophy [21], and in tuberculosis. X-linked adrenoleukodystrophyis associated with accumulation of very-long-chain fatty acid, and is related to metabolism and myelinogenesis attributed to reduced peroxisomal β-oxidation. Asparaginyl-tRNAsynthetase is classified as class-II aminoacyl-tRNAsynthetases, and is responsible for catalyzing the ligation of amino acids to their cognate tRNAs [22,23]. The etiology of various human diseases, including neuronal diseases, cancer, autoimmune diseases, and diabetes is connected to specific class-II aminoacyl-tRNAsynthetases, particularly affects neuronal diseases such as Charcot–Marie–Tooth disease, ataxia, amyotrophic lateral sclerosis, leukoencephalopathy and Parkinson’s disease [24].

Therefore, we suggest that ACSBG1 and NARS, which are related to metabolic and neurodegenerative disorders, can be applied as candidate biomarkers in the pre-mortem diagnosis for neuronal disorders.

In conclusion, we expect that our data may provide comprehensive information for significant proteins that are consistently differentially expressed in Prion diseases caused by amplification and aggregation of PrPSc though our study has the limitation in that numerous differentially expressed proteins were identified in the scrapie-infected mouse brain. The candidate biomarkers identified in this study might be useful for correlating responsiveness to experimental therapeutic or diagnostic regimens. Thus, clinical validation as well as further investigations using quantitative assay and immunohistochemistry with high diagnostic specificity and sensitivity is necessary to confirm the expression of these candidate biomarkers to apply human prion diseases’ diagnosis. Moreover, the current approach will provide us new insight and help defining the change of physiological mechanism through understand of the protein interaction or function and to develop therapeutic strategies in the field of neurodegenerative diseases.

Acknowledgement

We thank to Dr. Hyeong Soon Park and Dr. Soo Jae Lee (DIATECH Korea Co., Ltd. South Korea) for contribution of valuable comments for analysis mass data and interpretation. This study was supported by grants from the Korea Centers for Disease Control and Prevention (Funding no. 4800-4847-311-210-13 and 2014-NG52001-00).

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