Figure 2.

Presynaptic infusion of G85R-SOD1-YFP altered synaptic vesicle dynamics. A, Series of six continuous trains of HFS (each train is 50 Hz for 5 s with 5 s between trains) was applied to the synapses infused with SOD1 proteins for 15 min before HFS trains. WT-SOD1-GFP-injected synapses showed constant EPSP slope at the beginning of each train suggesting robust neurotransmission (>200, also see Extended Data Fig. 2-1 for the sixth train). However, G85R-SOD1-YFP-injected synapse started to show reductions in synaptic transmission, as evidenced by the dramatic decrease in EPSP slopes taken during the first train both at the beginning and at the steady state, suggesting severe depletion of synaptic vesicles from both the RRPs and the RPs. This inhibition was more obvious in the sixth train (Extended Data Fig. 2-1). B, EPSPs of the first train from WT-SOD1-YFP-injected synapses (black, n = 11) and from G85R-SOD1-YFP-injected synapses (red, n = 6) were integrated and averaged, followed by linear fit. The intersection with y-axis indicated the size of the RRP and the slope indicated the mobilization rate of vesicles from the RP to RRP. C, Normalized to baseline values before the injection of SOD1-YFP, RRP size and mobilization rate from the first train were plotted as individual biological replicates (n = 11 for WT-SOD1-infused synapses and n = 6 for G85R-SOD1-infused synapses) to show significant reductions in both RRP and mobilization of vesicles from the RP by G85R-SOD1-YFP, but not by WT-SOD1-YFP.