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. Author manuscript; available in PMC: 2010 Feb 12.
Published in final edited form as: Neuron. 2009 Feb 12;61(3):412–424. doi: 10.1016/j.neuron.2008.12.029

Figure 8. Dual roles of Snapin in synchronizing synaptic vesicle fusion and maintaining RRP size.

Figure 8

(A) Relative changes in total charge transfer at 50 Hz, 0.8 s stimulation when pIRES-EGFP-Snapin-C66A (SN-C66A) or pIRES-EGFP-Snapin (SN) was expressed at the presynaptic neuron compared to their EGFP controls. Total charge transfer displayed changes in opposite directions when SN-C66A or SN was expressed in the presynaptic (+/−) neurons (GFP: 0.42 ± 0.06, n=11; SN-C66A: 0.20 ± 0.05, n=8, p=0.017; SN: 0.79 ± 0.19, n=9, p=0.037. t test).

(B) Normalized EPSC peak amplitudes plotted against stimulus number at 50 Hz stimulus train for snapin (+/+), (+/−) and (−/−) neurons, and for (+/+) and (+/−) neurons with presynaptic expression of either SN or SN-C66A. Note that SN-C66A expression resulted in faster decay in both (+/+) and (+/−) neurons, while Snapin expression reversed the decay kinetics in (+/−) neurons to reach the (+/+) level.

(C) Bar graphs of normalized EPSC half-width, 10–90% rise time and decay time plotted for snapin (+/+) (upper panel), (+/−) (middle panel) and (−/−) neurons (lower panel) when expressed with SN, SN-C66A or GFP control. In (+/+) neurons, no overall significant change was observed. In contrast, transient expression of SN in the presynaptic (+/−) and (−/−) neurons significantly decreased half-width (for +/−, 0.67 ± 0.05, p=0.0004; for −/−, 0.69 ± 0.06, p=0.032, t test) and decay time (for +/−, 0.55 ± 0.06, p=0.00006; for −/−, 0.60 ± 0.06, p=0.0066, t test) of AMPA-EPSC relative to their GFP controls. SN-C66A expression rescued EPSC kinetics in both half-width (for +/−, 0.70 ± 0.09, p=0.014; for −/−, 0.60 ± 0.02, p=0.015, t test) and decay time (for +/−, 0.67 ± 0.10, p=0.017; for −/−, 0.51 ± 0.06, p=0.0019, t test) as effectively as expression of wild-type SN. In snapin (−/−) neurons, rise time was also remarkably decreased when expressing SN (0.72 ± 0.06, p=0.037) or SN-C66A (0.59 ± 0.08, p=0.0054) at the presynaptic neurons relative to snapin (−/−) neurons expressing GFP control.