Fig. 9

Reduced Syt1 level and PS1-Syt1 interactions in human sporadic AD brains. a Representative images of the Syt1 immunoreactivity in the medial temporal cortex of control and Braak V-VI stage sporadic AD brains; scale bar 10 μm. The inserts present magnified areas from the images and demonstrate the individual synaptic puncta (arrows). The bar graph presents quantification of the number and intensity of the Syt1-positive puncta in control vs. sAD patients. The data are presented as mean ± SEM, n = 4, 4–5 fields analyzed for each case. Statistical significance was determined using two-tailed unpaired Student’s t-test. *p < 0.05, **p < 0.01. There is a significant reduction in the Syt1 immunofluorescence in sAD brains. b FLIM analysis of PS1-Syt1 interactions in medial temporal cortex of control vs. sAD presents reduced PS1-Syt1 binding in sAD. The tissue was immunostained with anti-PS1 NT (APS11) and anti-Syt1 antibodies, and relative proximity between the fluorescently labeled proteins was determined by FLIM. There is significant reduction in the FRET efficiency between PS1 and Syt1, indicative of a greater distance between the molecules, in sAD brains. The data are presented as mean ± SEM, n = 4; 20–25 neurons analyzed for each case. Statistical significance was determined using Mann-Whitney’s U-test. *p < 0.05. The fluorescence lifetimes and corresponding FRET efficiency values are shown in the Additional file 1