Figure 4: Aβ₄₂ oligomers diminish neurexin-mediated excitatory presynaptic differentiation.

(a) Representative images of triple immunolabeling for VGLUT1, VGAT and surface HA in HEK293 cells expressing the indicated extracellularly HA-tagged construct cocultured with cultured hippocampal neurons and treated with Aβ₄₂ oligomers (AβOs, 500 nM, monomer equivalent) or vehicle. HA-CD4 is used as a negative control protein as it lacks synaptogenic activity. AβOs seem not to affect VGLUT1 accumulation induced by an HA-TrkC non-catalytic isoform (HA-TrkC) or VGLUT1 or VGAT accumulation induced by HA-Slitrk2. In contrast, AβOs seem to decrease VGLUT1 accumulation induced by HA-NLG1, HA-NLG2, or HA-LRRTM2. AβOs seem not to affect VGAT accumulation induced by HA-NLG1 or HA-NLG2. Scale bar represents 20 μm. (b,c) Quantification of the total intensity of VGLUT1 (b) and VGAT (c) puncta on HEK293 cells expressing the indicated HA-tagged proteins divided by HEK293 cell area. n = 30 cells for each construct from three independent experiments, one-way ANOVA, P < 0.0001. ^#P < 0.05 and *P < 0.01 for the indicated comparisons between vehicle control and AβO treatment by Bonferroni multiple comparisons tests. n.s., not significant. Data are presented as mean ± SEM.