Figure 5

We transfected neurons in hippocampal organotypic cultures with a FRET sensor of TrkB, the primary receptor for mBDNF. The sensor is composed of two fusion proteins: TrkB linked with GFP (donor) and SH2-domain of PLC-δ linked with a pair of mCherry proteins (acceptor). Upon BDNF binding, TrkB autophosphorylates its cytoplasmic domain, allowing for SH2-mCherry domain interaction and effective FRET to occur. Glutamate uncaging decreased the fluorescence lifetime of GFP, which reflected an increase in the binding fraction between TrkB and SH2-domain of the sensor. The data contain chanes in binding fraction (TrkB activation) upon uncaging protocol in the following conditions: blocking MMP-9 activity with chemical Inhibitor I or using slices from MMP-9 KO mice.