Fig. 7. Receptor phosphorylation at increasing NT concentration. Western blot analysis of Trk phosphorylation status in NT-3-treated SH-SY5/trkC (clone 3:1) and NGF-treated SH-SY5/trkA cells. Serum-starved cells were incubated at 37°C for 10 min with increasing concentrations of NT-3 or NGF. After immunoprecipitation with anti-Pan-Trk antiserum and SDS-PAGE, the filter was incubated first with an anti-phosphotyrosine (-PY) antibody and then reprobed with anti-Pan-Trk antiserum. The positions of p145trkC and p140trkA are indicated by an arrow and *, respectively. IP, immunoprecipitation; IB, immunoblot.