Immunochemical Detection of α‑Synuclein Autoantibodies in Parkinson’s Disease: Correlation between Plasma and Cerebrospinal Fluid Levels

Autoantibodies to Parkinson’s disease (PD) amyloidogenic protein, α-synuclein, were recognized as a prospective biomarker for early disease diagnostics, yet there is inconsistency in previous reports, potentially related to PD status. Therefore, plasma and cerebrospinal fluid (CSF) of the cross-sectional cohort of 60 individuals, including recently diagnosed PD patients with mild and moderate PD and age-matched controls, were examined by enzyme-linked immunosorbent assay (ELISA). Nonparametric statistics was used for data analysis. We found significantly elevated levels of α-synuclein autoantibodies in both plasma and CSF in mild PD compared to controls, followed by some decrease in moderate PD. Receiver operating characteristic and effect size analyses confirmed the diagnostic power of α-synuclein antibodies in both plasma and CSF. For the first time, we showed the correlation between plasma and CSF α-synuclein antibody levels for mild, moderate, and combined PD groups. This indicates the potentiality of α-synuclein antibodies as PD biomarker and the increased diagnostic power of their simultaneous analysis in plasma and CSF

Additional file 1: of Co-aggregation of pro-inflammatory S100A9 with α-synuclein in Parkinson’s disease: ex vivo and in vitro studies

Cross-seeding of α-syn amyloid formation by S100A9 amyloid fibrils. (A) Normalized kinetic curves of amyloid formation monitored by ThT fluorescence and fitted by sigmoidal function for 70 μM α-syn (shown in black), in the presence of 5% (magenta) and 10% (cyan) of S100A9 fibrillar samples. Experimental data points are shown in gray. (B) Lag phase (filled bars) and midpoint of growth phase (striped bars) of the amyloid formation kinetics derived from fitting. Protein samples are indicated under x-axis and in the same color coding as in (A). (C) Growth rate constant derived from fitting. Protein samples are indicated under x-axis and in the same color coding as in (A). Error bars represent SD. p ≤ 0.05 is indicated by *. (PDF 104 kb

Additional file 2: of Co-aggregation of pro-inflammatory S100A9 with α-synuclein in Parkinson’s disease: ex vivo and in vitro studies

Statistical analysis of the effects of S100A9, α-syn and mixed specimens on SH-SY5Y cellular viability presented in Fig. 5l. Cell viability values were compared pair-wise by using two-sample t-test, n ≥ 9. NS denotes non-significant difference, * − p ≤ 0.05 and ** − p ≤ 0.01. (PDF 100 kb

Mechanisms of Protein Oligomerization: Inhibitor of Functional Amyloids Templates α-Synuclein Fibrillation

Small organic molecules that inhibit functional bacterial amyloid fibers, curli, are promising new antibiotics. Here we investigated the mechanism by which the ring-fused 2-pyridone FN075 inhibits fibrillation of the curli protein CsgA. Using a variety of biophysical techniques, we found that FN075 promotes CsgA to form off-pathway, non-amyloidogenic oligomeric species. In light of the generic properties of amyloids, we tested whether FN075 would also affect the fibrillation reaction of human α-synuclein, an amyloid-forming protein involved in Parkinson’s disease. Surprisingly, FN075 stimulates α-synuclein amyloid fiber formation as measured by thioflavin T emission, electron microscopy (EM), and atomic force microscopy (AFM). NMR data on ¹⁵N-labeled α-synuclein show that upon FN075 addition, α-synuclein oligomers with 7 nm radius form in which the C-terminal 40 residues remain disordered and solvent exposed. The polypeptides in these oligomers contain β-like secondary structure, and the oligomers are detectable by AFM, EM, and size-exclusion chromatography (SEC). Taken together, FN075 triggers oligomer formation of both proteins: in the case of CsgA, the oligomers do not proceed to fibers, whereas for α-synuclein, the oligomers are poised to rapidly form fibers. We conclude that there is a fine balance between small-molecule inhibition and templation that depends on protein chemistry