Detection of misfolded tau in human synaptoneurosomes. (A) SDS-PAGE and Western blots of total (T), cytosolic (C), and synaptoneurosomal (S) extracts show increases in hyperphosphorylated tau (detected by PHF1 antibody) and aggregated tau oligomers (smears above 75 kDa) in AD-affected synaptoneurosomes compared to non-demented controls. Actin and PSD95 are markers to confirm subcellular fractionation. (B) Using Alz-50 antibody to immunostain misfolded tau in synaptoneurosomes from control and AD subjects. VGluT1 and MAP2 are presynaptic and postsynaptic markers, respectively. (C) Quantification of Alz-50 immunostaining in synaptoneurosomes from control and AD subjects. Synaptic terminals of all morphologies were randomly counted based on stereology methods (3 controls, 300 presynapses, 195 postsynapses; 4 AD subjects, 400 presynapses, 320 postsynapses). Tau misfolding occurs more frequently in AD cases at both presynaptic and postsynaptic sites (two-tailed t-test, **p < 0.01).