Fig. 5

PS1-Syt1 interaction modulates exocytosis/neurotransmitter release. a The graph presents the quantification of the total protein amount in the conditioned medium collected from neurons plated at 1.5x10⁶ cells/well, pre-treated for 2 h with scramble and PS1-LNT peptides, and stimulated for 15 min with 50 mM KCl. The protein secreted by the PS1-LNT pre-treated neurons is shown as a percent of the protein secreted by the scramble peptide pre-treated cells; mean ± SEM, n = 12. Statistical significance was determined using two-tailed unpaired Student’s t-test, ***p < 0.001. b The graph presents relative amounts of glutamate in the conditioned medium collected from neurons pre-treated for 2 h with PS1-LNT, scramble peptide or exocytosis inhibitor, tetanus toxin (TeTx), and depolarized using 50 mM KCl in the presence of the DL-TBOA, an inhibitor of the glutamate transporters EAAT1 and EAAT2. The data are presented as mean ± SEM, n = 31 for scramble and PS1-LNT, n = 6 for TeTx. Statistical significance was determined using two-way ANOVA followed by Bonferroni’s post-test, **p < 0.01, *** < 0.001. c The graph presents relative level of lactate dehydrogenase activity, indicative of the potential cytotoxicity of the applied treatment, in primary neurons pre-treated with PS1-LNT or scramble peptide for 2 h and depolarized using 50 mM KCl in the presence of the DL-TBOA for the duration of the assay. The data are presented as mean ± SEM, n = 7. Statistical significance was determined using two-way ANOVA followed by Bonferroni’s post-test. No significant toxicity of the applied treatments was observed. d, The pseudocolor-coded images present synaptophluorin (SypHy) fluorescence at the synaptic puncta in neurons pre-treated for 2 h with PS1-LNT or scramble peptide. The red spots indicate high fluorescence intensity corresponding to the high level of exocytosis observed immediately after the 50 mM KCl stimulation; scale bar 5 μm. The adjacent bar graph demonstrates the quantification of the increase in SypHy fluorescence at the synaptic ROIs in response to the depolarizing stimulus in the scramble and PS1-LNT pre-treated neurons. The data are presented as mean ± SEM, n = 263 for scramble and n = 255 for PS1-LNT, n = number of synaptic puncta analyzed in 4 independent experiments. Statistical significance was determined using Mann-Whitney’s U-test, ***p < 0.01