Fig. 2
SIPA1L2/TrkB interaction at presynapses is crucial for the function of the DG. a Confocal images of rat hippocampal neurons immunostained against SIPA1L2, Synaptophysin 1 and Tau. Scale bar is 5 μm. b Pearson’s correlation coefficient calculated for SIPA1L2 and Synaptophysin 1 from a. Circles represent averaged values per region of interest (ROI) analyzed from three independent images. c Endogenous TrkB coimmunoprecipitates SIPA1L2 from rat hippocampal lysates. The two bands in TrkB correspond to the full length (TrkB-FL) and the truncated form (TrkBt). Goat anti-TrkB antibody (R&D) is used for precipitation and detection. d DIC coimmunoprecipitates SIPA1L2 and TrkB but not GM130 from mouse whole brain crude light membrane fraction. Note that the band revealing TrkB corresponds to the full-length form. e Confocal images from rat hippocampal neurons immunostained against SIPA1L2, TrkB and Synaptophysin 1 (Sphy1). Scale bar is 10 μm. f STED images from hippocampal neurons immunostained against SIPA1L2, TrkB and Synaptophysin 1 (confocal). Line profiles (g) indicate relative intensities for STED channels along 1 µm. Scale bar is 1 µm. h Pull-down assay between the juxtamembrane region of TrkB and the 14aa of the binding interface in ActI-SIPA1L2. i Pull-down assay between TrkB and ActI-SIPA1L2 in the presence of 10× TAT binding peptide (TAT) or 10× scrambled peptide (TAT-scr). j Cartoon representing the timeline used for the pattern separation test performed in wt animals infused with TAT peptides and the location of the infusion (red dot). k Exploring time from mice injected with TAT-SIPA1L2 or TAT-scr during the sample phase (two-way ANOVA). l Discrimination indexes obtained during the choice phase in SLR and dSLR groups injected with either TAT-SIPA1L2 or TAT-scr. The number of subjects is depicted in k (unpaired Student’s t test). m fEPSP amplitudes recorded during the last 45–70 min after MF-LTP upon bath perfusion of TAT-SIPA1L2 or TAT-scr peptides. Right, averaged values of fEPSP amplitudes during last 10 min of LTP recording before DCG IV application (Mann-Whitney U test). Bars and error bars represent data as mean ± SEM in all graphs. Circles represent mean values of individual subjects (k–l) or slices (m). "*" indicates P ≤ 0.05; "***" indicates P ≤ 0.001.
