Fig 2: Characteristics and biological validation of the Tau-A assay.A) Standard curves with either the selection peptide or the elongated peptide at concentrations of 0, 0.59, 1.17, 2.34, 4.69, 9.38, 18.75, 37.5, 75, 150, and 300 ng/ml. B) Measurement of Tau-A fragments in in vitro digests of tau. C) Western blots of extracted tissues, D) ELISA measurement of brain extracts in the presence or absence of ADAM10. E) Tau-A levels in extracted brains from either control or Tg4510 mice (a model of Alzheimer's disease) measured using the ELISA. F) Western blots comparing brain extracts from wild type and Tg4510 mice. Left: a western blot conducted with an antibody recognizing intact tau (MAB3420 Chemicon). Right: Western blot conducted with our in-house antibody (NB191).

Fig 3: Suppression of Rab1A increases Golgi fragmentation and Tau secretion in primary cortical neurons.(A) GFP-Rab1A co-localizes with GM130 in primary cortical neurons (arrow). Scale bar = 30μm. (B) The knockdown of Rab1A was confirmed by immunoblotting in neurons. (C) Immunostaining of the GM130 antibody (red) and the A0024 antibody (green). The Golgi was fragmented when Rab1A was suppressed in neurons. Scale bar = 30μm. (D) Quantification of the surface area of the Golgi complex (μm2) when Rab1A was suppressed in neurons. (n = 7, mean ± SEM, unpaired t-test two tailed, ****P < 0.0001) (E) Immunoblot analysis of Tau secretion in neurons treated either with Rab1A siRNA or control siRNA (NegCTL). (F) Tau secretion was increased upon Rab1A suppression in neurons. Quantification by densitometry (arbitrary unit) of the ratio of total Tau in the medium to total Tau in the cell lysate. (n = 5, mean ± SEM, unpaired t-test two-tailed, **P < 0.01). (G) Cell damage was evaluated by measuring the amount of LDH released in the culture medium. The amount of LDH in the medium was not affected by the suppression of Rab1A (ns). (n = 5, mean ± SEM, unpaired t-test two-tailed).

Fig 4: CA-tau structures are present in human CSF. A Representative brightfield image of CA in the hippocampal sulcus of AD patient tissue section. Inset (dashed box) centered on a CA in the glia limitans ensheathed in AT8+ processes on the edge of the parenchyma. Scale bar = 50 µm. B Representative immunofluorescent confocal image of CA in the hippocampal sulcus of AD patient tissue section stained with GFAP (grey), Tau-1 (red), and IgM (green). Nuclei stained with DAPI (blue). Inset (dashed box) centered on Tau-1-immunoreactive CA in the glia limitans ensheathed in GFAP+ processes on the edge of the parenchyma. Scale bar = 50 µm. C Representative immunofluorescent confocal images of CSF containing CA were stained with Tau5 IgG1 (red) and IgM (green) and subsequently imaged at 120× magnification. Scale bar = 50 µm (i) 20 µm (ii–v). Maximum intensity z-projection frames are shown in panels i and v, higher magnification inset frames are shown in panels ii-iv, and single plane inset frames are shown in panels vi–viii. D Representative immunofluorescent confocal images of CA present in CSF that were pre-digested with amylo-glucosidase were imaged at 20× magnification to detect Tau5 IgG1 (red) and IgM (green, brightness increased for visualization). Scale bar = 500 µm (top row), 10 µm (bottom row)

Fig 5: Axon-dendrite control of single neurons by the shape of the microplates. (a) Immunofluorescent image of a neuron on a microplate (Tau-1: axon marker, MAP2: dendrite marker); Maximum intensity of (b) Tau-1; and (c) MAP2 on the Axon and Dendrite parts of the microplate.