Figure 7.

Localization of β-actin protein and actin polymerization in response to NT-3. (A) Immunofluorescence localization of β-actin protein in starved cells. Weak staining was observed within growth cone (arrow) (example of nonlocalized cell). (B) Addition of NT-3 to the medium for 5 min resulted in the presence of focal staining within the peripheral margin of minor neurites and the axonal growth cone (arrow) (example of localized cell). (C) Addition of NT-3 to the medium for 10 min resulted in the localization of β-actin protein throughout the peripheral margin (arrow). (D) Starved cells were extracted with saponin (0.1 mg/ml) in buffer containing rhodamine-actin (0.45 mM) for 1 min, washed, and fixed in paraformaldehyde (4% in 1 PBS). There was no fluorescence staining in these untreated cells. Nucleus was stained with DAPI. (E) By contrast, stimulation of cells with NT-3 for 5 min resulted in visualization of fluorescence signal within the growth cone (arrow). (F) Stimulation with NT-3 for 10 min resulted in the incorporation of rhodamine-actin throughout the peripheral margin (arrow). Bar, 15 mm.