Figure 5.

Depolarization-induced phosphorylation of synapsin at site 1 requires PKA activation. A–G, After incubation in the absence (A, B, F) or presence of H89 (C), W7 (D), or KN93 (E, G), rat hippocampal neurons were exposed to 55 mm KCl for 1 min, except for the sample shown in B, in which the depolarizing stimulus was applied for 2 min. Neurons were fixed and processed for double immunofluorescence with an antibody that recognizes all synapsin isoforms (A–G, green) and either a phosphosite-1-specific anti-synapsin antibody (A–E, red) or an antibody against autophosphorylated CaMKII (F, G, red). Note that depolarization-induced phosphorylation of synapsin at site 1 is inhibited by both H89 and W7 but not by KN93, although KN93 prevents CaMKII autophosphorylation. Scale bar, 15 μm.