Table 1.
Some neurological symptoms caused by COVID-19.
Fig 1.
Effect of SARS-CoV-2 3CLpro on 2N4R tau aggregation and effect of 3CLpro inactivation on tau aggregation.
A: ThT assay of 2N4R tau, α-Synuclein and TDP-43, 3CLpro used as aggregation inducer. The experiment was performed for 24 h, 37°C and 600 rpm. B: Control ThT assay of single 3CLpro, α-Synuclein, TDP-43 and tau. C: ThT assay of inactivated 3CLpro, tau aggregation was not observed. D: ThT assay of 2N4R tau, aggregation was induced by 3CLpro. After 24h DSF inactivated the protease and after 30 minutes of incubation, 10 μM fresh tau was added. Data shown are the mean ± SD from three independent measurements (n = 3).
Fig 2.
Negative stain TEM of 3CLpro induced tau fibrils.
A: Representative micrograph at medium (6700x) magnification. B: Representative micrographs at high (73kx) magnification. Asterisks label vesicle structures.
Fig 3.
Effect of SARS-CoV-2 3CLpro on 2N4R tau degradation.
A: Analytical HPLC analysis of 2N4R tau incubated with SARS-CoV-2 3CLpro for 0, 24, 48 and 72h. The corresponding chromatogram regions of the tau monomer and related metabolites are labelled (I-III). B: Stability of 2N4R tau monomer after treatment with 3CLpro over 72h. Single tau and 3CLpro are shown as control. After 3CLpro treatment, the tau monomer amount decreases by about 60%. C: Chromatogram of peak I (Tau) shown enlarged, a silver stained SDS PAGE demonstrated that the 2N4R tau amount decreased over 72h treatment with 3CLpro and a protein band increases at 25 kDa. D: Chromatogram of peak region II shows enlarged three protein bands appearing over 72h experimental time. E: Chromatogram of peak region III shown enlarged, two protein bands appear over the 72h experimental time.
Fig 4.
Mass spectrometry analysis of tau metabolites.
A: Example of an MS spectrum corresponding to a tryptic peptide derived from 2N4R tau (AEPRQEFEVMEDHAGTYGGLGDR), b- and y-ions are labelled. B: 2N4R tau sequences and tryptic peptides, which could be identified in the corresponding samples, are highlighted. Asterisks label tryptic 2N4R tau peptides, which could not be identified in the three peak samples.
Table 2.
The number of tryptic tau peptides in control and the tested HPLC samples.
Table 3.
Examples of proteases with proteolytic activity against tau.
Fig 5.
Samples, buffer control (BC) and capture control (CC) were tested. Pixel counts per concentration are shown for A: Tau monomer control, B: Tau aggregate control, C: Tau SiNaPs and D: Influence of active 3CLpro on tau aggregation.