FIGURE 7.

p75^ICD and c29 facilitate NGF binding to TrkA-expressing cells. a, flow cytometry histogram plots of TrkA^K538R-transfected HEK293 cells treated for 1 h with saturating concentrations (10 μm) of NGF-FITC (steady-state binding) following preincubation with or without c29. (All plots are representative of four experiments.) b, plot of on-rate (the cell population mean fluorescence due to bound NGF-FITC) of TrkA-transfected HEK293 cells with or without c29 preincubation and treated at time = 0 with 26 nm NGF-FITC. c, plot of on-rate (association) of NGF-FITC-treated p75^NTR-transfected HEK293 cells with or without c29 preincubation. Shown are flow cytometry histogram plots of HEK293 cells transfected with TrkA and either p75^ICD or non-cleavable p75^N-Gly (d) and TrkA and wild-type p75^NTR or p75^ΔJUX (e) treated for 1 h with NGF-FITC (steady-state binding). p75^ICD expression enhanced NGF-FITC binding, whereas expression of either of the p75^NTR variants inhibited NGF-FITC binding compared with TrkA alone (d) or TrkA and wild-type p75^NTR (e) (n = 4 for all experiments; mean ± S.E.).