TABLE 1.
Results of brain tumor exosome proteomic analyses
| Spot | Protein name | Accession no. | Mass/pI | Peptide count (match score) | Ion score | Function | Subcellular localization | Exosome reference |
|---|---|---|---|---|---|---|---|---|
| 1 | Serum albumin (precursor, bovine) | P02769 | 69.3/5.82 | 13 (255) | 189 | Ion, lipid transport; osmotic pressure | Extracellular space | 35 |
| 2 | Serum albumin (precursor, murine) | P07724 | 68.7/5.75 | 8 (91) | 67 | Ion, lipid transport; osmotic pressure | Extracellular space | 88, 89 |
| 3 | α-1-Antitrypsin (precursor, bovine) | P34955 | 46.1/6.05 | 12 (260) | 174 | Secreted extracellular protease inhibitor | Extracellular space | 66 |
| 4 | Vitamin D-binding protein (precursor, bovine) | Q3MHN5 | 53.3/5.36 | 4 (67) | 55 | Sterol transport; actin and Ig binding | Extracellular space | |
| 5 | β-Actin | P60710 | 41.7/5.29 | 10 (161) | 104 | Cytoarchitecture, motility | Cytosola | 90b |
| 6 | GAPDH | P16858 | 35.8/8.44 | 7 (95) | 63 | Step 1 of glycolytic enzyme complex | Plasma membrane | 91b |
| 7 | Gag-pro-pol polyprotien (precursor, murine) | Q1KYM2 | 194/9.05 | 12 (94) | 79 | Endogenous murine retroviral polyprotein (processed) | Plasma membrane | 35 |
| 8 | Gag polyprotein pr65 | Q1KYL8 | 60.1/8.52 | 5 (158) | 145 | Isoelectric variant of #7 | Plasma membrane | |
| 9 | Gag polyprotein pr65 | Q1KYL8 | 60.1/8.52 | 7 (133) | 114 | Isoelectric variant of #7, 8 | Plasma membrane | |
| 10 | Apolipoprotein A-1 (precursor) | JC137 (MSDB) | 30.4/5.52 | 5 (65) | 50 | Lipid binding, cholesterol metabolism | Extracellular space | 35, 67 (bovine) |
| 11 | Major vault protein | Q922X6 | 95.9/5.43 | 20 (128) | 18 | Ribonucleoprotein; “vault” subunit | Nucleusc | 90, 92 |
| 12 | Transitional ER ATPase (p97/VCP) | Q01853 | 89.3/5.14 | 23 (355) | 210 | ER vesicular trafficking | ER/Golgi | 7 |
| 13 | Arrestin domain-containing protein 2 | Q9D668 | 44.3/9.32 | 2 (33) | 27 | Scaffold/adaptor G-protein regulator | Cytosolc | |
| 14 | Transitional ER ATPase (p97/VCP) | Q01853 | 89.3/5.14 | 14 (87) | 42 | Modified variant of #12 | ER/Golgi | |
| 15 | Heat shock cognate 71 (HSC70, HSP70) | P63017 | 70.9/5.37 | 26 (495) | 289 | Chaperone, protein folding | Cytosola | 67b |
| 16 | Pyruvate kinase isozyme M1/M2 | P52480 | 57.8/7.15 | 23 (218) | 54 | Step 5 of glycolytic enzyme complex | Cytosold | 7, 90, 93 |
| 17 | Pyruvate kinase isozyme M1/M2 | P52480 | 57.8/7.15 | 20 (210) | 71 | Isoelectric variant of #16 | Cytosold | |
| 18 | Pyruvate kinase isozyme M1/M2 | P52480 | 57.8/7.15 | 10 (57) | 23 | Isoelectric variant of #16, 17 | Cytosold | |
| 19 | TCP-1ζ (HSP60) | P80317 | 58.0/6.63 | 11 (78) | 31 | Chaperonin complex | Cytosola | 92 |
| 20 | α-2-HS-glycoprotein (Fetuin-A, bovine precursor) | P12763 | 38.4/5.26 | 5 (102) | 74 | Lipid binding, promotes endocytosis; protease inhibitor | Extracellular space | 67, 94 (human) |
| 21 | α-2-HS-glycoprotein (Fetuin-A, bovine precursor) | P12763 | 38.4/5.26 | 6 (187) | 144 | Isoelectric variant of #21 | Extracellular space | |
| 22 | No significant hits | |||||||
| 23 | d-3 phosphoglycerate dehydrogenase (3PDGH, rat) | O08651 | 56.5/6.28 | 10 (90) | 27 | Enzyme of serine biosynthesis | Cytosol | |
| 24 | Collapsing response mediator protein 2 | P47942 | 62.3/5.95 | 17 (235) | 125 | Growth cone collapse; axon formation | Cytosolc | |
| 25 | TCP-1β (HSP60) | P80314 | 57.5/5.97 | 24 (317) | 122 | Chaperonin complex | Cytosola | 92, 95 |
| 26 | Centromere protein P | Q9CZ92 | 33.3/5.18 | 5 (39) | 24 | Component of centromere complex | Nucleus | |
| 27 | α-Enolase | P17182 | 47.1/6.37 | 19 (322) | 167 | Step 4 of glycolytic enzyme complex | Cytosold | 90b |
| 28 | α-Enolase | P17182 | 47.1/6.37 | 14 (124) | 34 | Isoform of #28 | Cytosold | |
| 29 | Phosphoglycerate kinase 1 | P09411 | 44.4/8.02 | 4 (36) | 26 | Step 2 of glycolytic enzyme complex | Cytosold | 7, 66, 95 |
| 30 | Sialic acid synthase | Q3TFB5 | 31.2/7.14 | 9 (183) | 130 | Sialic acid synthesis | Cytosol | |
| 31 | 40S ribosomal protein SA (34/67 kDa laminin receptor) | P14206 | 32.8/4.80 | 8 (101) | 54 | Ribosome component; on tumor surfaces, binds laminin | Plasma membrane | 7 |
| 32 | GAPDH | P16858 | 35.8/8.44 | 8 (128) | 87 | Isoelectric variant of #6 | Plasma membrane | |
| 33 | GAPDH | P16858 | 35.8/8.44 | 9 (85) | 37 | Isoelectric variant of #6 | Plasma membrane | |
| 34 | Eukaryotic translation initiation factor 3 subunit 2 (eIF3β) | Q9QZD9 | 36.5/5.38 | 13 (213) | 120 | Protein translation; binds 40S ribosome, initiator methionine tRNA | Cytosol | |
| 35 | Syntenin | O88601 | 32.3/6.66 | 2 (65) | 51 | Scaffold/adaptor Proteolypid complexes | Plasma membrane | 35b |
| 36 | Tubulin β-5 | P99024 | 49.7/4.78 | 13 (166) | 82 | Cytoskeleton, cell division, transport | Cytosol | 35 |
| 37 | Proliferating cell nuclear Ag (PCNA) | P17918 | 28.8/4.66 | 9 (123) | 150 | DNA replication | Nucleus | |
| 38 | S-methyl-5-thio-adenosine phosphorylase (MTApase) | Q9CQ65 | 31.1/6.71 | 18 (303) | 150 | Polyamine metabolism salvage pathway | Nucleus | |
| 39 | Elongation factor 1-β (EF-1β) | O70251 | 24.7/4.53 | 3 (58) | 45 | Protein synthesis, GDP/GTP exchange | Cytosol | |
| 40 | RAN (Ras family member; TC4) | Q3ULW0 | 24.7/7.71 | 10 (163) | 92 | Nucleocytoplasmic transport, GTP binding | Nucleusc | 95 |
| 41 | Proteasome subunit α type-2 component C3 | P49722 | 25.9/8.39 | 10 (165) | 91 | Protease, regulatory subunit of proteasome | Cytosol | |
| 42 | Glutathione S-transferase P1 (GST-pi) | P19157 | 23.6/7.69 | 3 (73) | 59 | Conjugates GSH in detoxification reactions | Cytosol, nucleus | 95 |
| 43 | Adenine phosphoribosyl transferase (APRT) | Q564P4 | 19.7/6.31 | 10 (338) | 258 | Purine salvage pathway, formation of AMP | Cytosol | 66 |
| 44 | Ferritin heavy chain | P09528 | 20.9/5.53 | 5 (108) | 82 | Iron binding complex | Cytosola | 7 |
| 45 | Ig γ-3 C region (IgG3 constant region) | P22436 | 36.2/8.53 | 10 (353) | 282 | Constant region of IgG heavy chain | Extracellular space | 88 |
Accession numbers are from the UniProt Knowledge base (Swiss-Prot/TrEMBL), http://us.expasy.org/sprot/(spot 10 is from MSDB; http://csc-fserve.hh.med.ic.ac.uk/msdb.html). Mass/pI refers to predicted molecular mass (kDa) and isoelectric point of the protein using the program Compute pI/Mw (http://ca.expasy.org/cgi-bin/pi_tool). Peptide count refers to number of peptides that match the theoretical digest of the primary protein identified. Match score refers to quality of the peptide-mass fingerprint match and quality of the MS/MS peptide fragment ion matches (if MS/MS data were generated). Scores ≥ 95 are considered significant. Ion score is quality of MS/MS peptide fragment ion matches only (if MS/MS data were generated). Scores ≥ 20 are significant. Functions and subcellular localizations were inferred from literature searches, from the TargetP algorithm, and from Ingenuity software; exosome reference denotes literature citations of previous proteomic analyses for the given protein.
Cytosolic protein that has been identified on tumor cell surfaces or extracellularly.
Protein has been identified in numerous exosome types; only limited reference citations are shown.
Cytosolic or nuclear protein that has known associations with intracellular membranes.
Cytosolic protein that has known alternate extracellular or membrane localizations in normal cell types.