Figure 3.

Over‐expressing Casein kinase 2α (CK2α) reduces the number synaptic vesicles released from the reserved pool in neurons. (a) Representative images of neurons transfected with synaptophysin‐pHluorin (SypHy) and either mCherry alone or mCherry‐CK2α. Illustrative images of SypHy fluorescence prior to stimulation [rest, 0 s in (a)], after a stimulation at 900 action potentials (APs) at 20Hz (900 AP; 40 s) and after the NH₄Cl wash to reveal maximal fluorescence. Scale bar = 10µm. (b) Exocytosis profile measured by SypHy signal in control (N = 8 cells from at least three independent cell culture preparations) versus neurons over‐expressing mCherry‐CK2α (N = 6). The stimulation protocols were as in Figure 2. SypHy fluorescence was normalized to baseline and expressed as a percentage of total SypHy signal obtained by an NH₄Cl wash. Graph shows mean ± SEM. (c) Quantification areas under the curves from 25 to 35 s. Areas under the curve data are presented as mean ± SD. *p < .05, Student's t test, N = 8 cells from at least three independent cell culture preparations for mCherry control and N = 6 for mCherry‐CK2α. (d) SypHy fluorescence decay profiles between 40 and 90 s were normalized to the peak evoked signal. Decay profiles are all best described by exponential functions, and are presented as mean only without error bars for clarity. (e) Quantification of data presented in (d). There was no difference in the decay profiles of control and CK2α‐over‐expressing neurons. Graph shows mean ± SD. *p < .05, Student's t test, N = 7 cells from at least three independent cell culture preparations for mCherry control and N = 6 for mCherry‐CK2α