Figure 4.

Phosphorylation of synapsin at site 1 and synapsin dispersion occur independently of CaM-dependent enzymatic activities. A, Rat hippocampal neurons were fixed either at rest (control) or after a 30 min treatment with W7 in the presence or absence of dibutyryl-cAMP. Neurons were processed for double immunofluorescence with an antibody that recognizes all synapsin isoforms (left column) and a phosphosite-1-specific anti-synapsin antibody (right column). B, Histograms of the mean ± SE fluorescence intensities of site1-phosphorylated synapsin of the samples shown in A. A.U., Arbitrary units. C, High-magnification image of a sample treated with W7 and cAMP and processed as described in A. Note the diffusion of synapsin along the axons. Scale bar: A, 20 μm; C, 10 μm.