Table 2.
Selected proteins of moderate–lower abundance from 1-D LC-MS/MS analysis of peak 1 immunodepleted material
| Number of proteins depleted | Length of LC-MS/MS run (h) | Protein name | Expected location(s) | Significance/functional comments | Concentration in normal serum where known |
|---|---|---|---|---|---|
| 20 | 4 | IL-6 receptor subunit β | Membrane/secreted | Signal transduction, immune response | 453 pg/mL [34] |
| Hypoxia up-regulated protein 1 | Endoplasmic reticulum | Cytoprotective | – | ||
| Macrophage CSF 1 receptor | Membrane/secreted | Transmembrane receptor for CSF-1 and IL-34 | – | ||
| IL-1 receptor | Membrane | Links to NF-κB pathway and immune response | – | ||
| Fatty acid binding protein 4 | Cytoplasm/nucleus | Biomarker of acute kidney injury | 13.3–18.3 μg/L [35] | ||
| Vinculin | Cytoplasm/cytoskeleton | Cell adhesion | – | ||
| Transforming growth factor β receptor | Membrane | TGF-β receptor, immune response | 0.1–21.0 ng/mL [36] | ||
| 14 | 4 | Pyruvate kinase M1/M2 | Cytoplasm/ nucleus | Known tumour biomarker. Involved in apoptosis | M2 7.2 U/mL [37] |
| Protein S A100 A8 | Cytoplasm/cytoskeleton/membrane/secreted | Calcium binding, antimicrobial, pro-inflammatory, up-regulates IL-8 and cell surface ICAM1 | A8/A9 complex 0.77 μg/mL [38] | ||
| CD59 glycoprotein | Membrane | Inhibition of membrane attack complex, signal transduction for T-cell activation | – | ||
| Transferrin receptor protein 1 | Membrane/secreted | Cellular uptake of iron | – | ||
| Profilin-1 | Cytoplasm/cytoskeleton | Binds actin and affects cytoskeletal structure | – | ||
| 5 | Osteopontin | Secreted | Type I immunity | 309–413 pg/mL [39] | |
| Inducible T-cell co-stimulator ligand (B7-related protein 1) | Membrane | Co-stimulator for T-cell proliferation/cytokine secretion | – | ||
| IL-1 receptor accessory protein | Membrane/secreted | Cytokine signalling | >300 ng/mL | ||
| 14 and 20 | 4 | Neutrophil gelatinase-associated lipocalin | Secreted | Known biomarker of renal injury | 76.3 ng/mL [40] |
| Secreted protein acidic and rich in cysteine (SPARC) | Basement membrane/secreted | Possible regulator of cell growth | 66.8 ng/mL [41] | ||
| Intercellular adhesion molecule 2 | Membrane | Adhesive interactions important for antigen-specific immune response | 400 ng/mL [42] | ||
| Macrophage mannose receptor 1 | Membrane | Involved in phagocytosis by macrophages | – | ||
| Insulin-like growth factor (IGF) binding protein 7 | Secreted | Growth factor | – | ||
| Hepatocyte growth factor-like protein | Secreted | Cell proliferation and differentiation, macrophage activation | – | ||
| 6, 14 and 20 | 4 | Neutrophil defensins 1–3 | Secreted | Defensins 1 and 2 have antimicrobial activities | 42 ng/mL – for defensins 1–3 combined [43] |
| CD166 antigen | Membrane | Expressed by activated T and B cells | – | ||
| Matrix metalloproteinase 9 | Secreted | Local proteolysis of ECM, leucocyte migration | 16.15 ng/mL [44] | ||
| E-cadherin | Cell junction/membrane | Regulating cell adhesion, mobility/proliferation of epithelial cells | Soluble plasma form – median 3.53 ng/mL [45] |
Previously reported concentrations in normal serum are shown where known to illustrate likely abundance range while recognising that concentrations may be increased in the samples analysed here. All were present at ≥2 unique peptides with the exception of TGF-β receptor which was a single peptide.