Figure 8.

(A) Western blot analysis of PC12-27TrkA clones. Total cell homogenates were processed as described in Figure 1. As a reference, equal amounts of lysates from wild-type PC12 (WT), trk-PC12, and PC12-27 cells were loaded. Although all markers analyzed are present in wild-type PC12 cells, their levels are below the threshold of detection in trk-PC12, PC12-27, and all PC12-27TrkA clones examined. p38, p38/synaptophysin; SgII, secretogranin II. (B) NGF-dependent neurite extension by PC12-27 and PC12-27/108 clones. Cells were photographed by phase-contrast microscopy under control (CONT) conditions or after treatment with NGF (50 ng/ml) for 72 h. Neurite outgrowth was quantitatively analyzed on digitized images. Bars represent means ± SE. A.U., arbitrary units. (C) Immunofluorescence analysis of neurofilament expression and localization in NGF-treated PC12-27/108 cells. Cells were fixed and analyzed for expression of the 200-kDa neurofilament subunit (α-NF 200 kDa) that appears to be enriched in the distal part of the neuritic shaft and in growth cones. Bar, 14 μm.