Figure 3.

Active zone protein CAST plays a role in synaptic vesicle loading. The presynaptic neurons were transfected with CAST^S45 DNA, 2 days before EPSP recording. (A) Phosphonegative-CAST^S45A relieved the second EPSP reduction, while phosphomimetic-CAST^S45D potentiated the reduction. Paired EPSP ratio was plotted against paired-AP interval. (Bar: SEM. * p < 0.05; unpaired student’s t-test. *green, CAST^S45A vs. CAST^WT; * navy, CAST^S45D vs. CAST^WT) (B) EPSP recovery from depletion of SVs. A 5-min train of APs at 5 Hz was applied, as indicated, for SV depletion. EPSP amplitude recovered with two different rates: fast (pink arrow) and slow phases (blue arrow) (left). The fast recovery rate is estimated by an exponential fit to the increase in EPSP amplitude from 0 to 8 s after the depletion (right). (* p < 0.05, ** p < 0.01, *** p < 0.001.; unpaired student’s t-test. *dark gray, CAST^S45D or CAST^WT vs. un-transfection; *green, CAST^S45D vs. CAST^S45A; *gray, CAST^S45D vs. CAST^WT) (C) Cascaded reactions of CAST phosphorylation. Adapted from Mochida et al., 2016 [56].