Fig. 6

Proximity ligation assay (PLA) to visualize the PS1/MAO-B and γ-secretase/MAO-B interactions in postmortem human brain cortex. PLA using the traditional setup, with antibodies for MAO-B and PSI, in neurons in Cntr (a, c) and AD (b, d). PLA signals are shown in red. The samples were costained with DAPI to visualize nuclei (blue) and FluoroPan marker to visualize the neuronal structure (green). An image of a Cntr sample showing both neuronal stain (green) and astrocytic stain (yellow) shows that a few PLA signals were also present in astrocytes (e). PLA signals/image from the standard PLA setup were quantified using at least three images from four different experiments using the Duolink image tool (f).The human cortex was also subjected to PLA using the GTB-PLA method and directly labeled MAO-B antibody to visualize the association between active γ-secretase and MAO-B in control brain (g, i) and AD brain (h, j) where neurons are visualized with FluoroPan neuronal marker (green) and astrocytes with GFAP (yellow). White scale bar, 50 μm (a, b, g, h) and 10 μm (c, d, e, i, j). AD Alzheimer disease (Color figure online)