Figure 1.
Phospho-JNK is enriched in axons. a, After 1 week in culture, phospho-JNK immunoreactivity (red) was concentrated in the axons of hippocampal neurons, but essentially absent from dendrites (labeled with antibodies against MAP2; green). b, A representative stage 3 neuron (24 h in culture) showing that phospho-JNK (red) was already enriched in the axon. c, Quantitative analysis revealed a pronounced proximodistal gradient of phospho-JNK in the neuron shown in b. Changes in cell volume were corrected using expressed YFP as a cytoplasmic marker (green). d, e, Immunoreactivity for total JNK protein (regardless of phosphorylation state) was present throughout neurons at developmental stages 3 and 4. f, g, Representative stage 2 neurons transfected to express soluble YFP. Although most stage 2 neurons showed an absence of phospho-JNK in all processes (f), some had phospho-JNK enriched in the shaft and growth cone of a single neurite (g, arrow). Scale bars: a, 50 μm; b, d, e, 25 μm; f, g, 20 μm.
