Table 2.
List of autoantigens and biomarkers assessed, and the method used for their detection, within the human islet conditioned media.
| Marker | Category | Description | Detection |
|---|---|---|---|
| GAD65 (GAD2) | Diabetes autoantigen | Diabetes autoantigen; enzyme that converts glutamate to GABA for storage in secretory vesicles in pancreatic β-cells and GABA-secreting neurons41. | Flow Cytometry, TEM |
| IA-2 (PTPRN) | Diabetes autoantigen | Islet antigen-2; protein tyrosine phosphatase family (PTPRN); enriched in pancreatic β-cells. Membrane bound associated with insulin granule5, 64. | Not detected |
| ZnT8 (SLC30A8) | Diabetes autoantigen | Zinc transporter present on the cell surface and localized to the insulin storage granules. Highest levels are within the pancreatic β-cell45. | Flow Cytometry, TEM |
| Glut2 (SLC2A2) | β-cell marker; New-onset diabetes autoantigen | Glucose transporter-2; resident on cell surface for passive diffusion of glucose into cell. High levels on pancreatic β-cells, hepatocytes, kidney proximal tubule cells and cells within the small intestine49. | Flow Cytometry, TEM |
| Hsc70 | β-cell marker | Heat shock cognate protein 70, membrane associated, maintains GAD65 in close proximity to GABA-containing vesicles65, common EV marker. | LC-MS/MS |
| Hsp70 | Injury marker | Highly stress-inducible injury marker, stabilizes proteins against aggregation, known to be pro-inflammatory66, common marker of EV. | Flow Cytometry, LC-MS/MS |
| CD9 | EV marker | Tetraspanin, four transmembrane spanning regions involved in protein scaffold maintenance, modulation of cell adhesion, motility and migration, membrane fusion, and exocytic vesicle formation67. | Flow Cytometry |
| CD14 | EV Marker | Monocyte differentiation antigen. Acts as a GPI-anchored coreceptor for TLR2:TLR6; internalized into the endosomal compartment in a lipid raft-dependent mechanism68. | Flow Cytometry, LC-MS/MS |
| Annexin V (ANXA5) | EV marker | Intracellular protein with anchoring domains that binds to calcium and to phospatidylserine69. | Flow Cytometry, LC-MS/MS, TEM |