Figure 9.

NCAM-mediated neurite outgrowth depends on PrP. (A and B) Wild-type hippocampal neurons were incubated with PrP-Fc (A) or polyclonal PrP antibodies (B). Note enhanced neurite outgrowth after PrP-Fc application and reduced neurite outgrowth after incubation with polyclonal PrP antibodies. (C and D) NCAM^−/− (C) or PrP^−/− (D) neurons were incubated with PrP-Fc. PrP-Fc increased neurite lengths in PrP^−/− but not NCAM^−/− neurons. (E) Neurons from PrP^−/− mice transfected with GFP alone or cotransfected with GFP and PrP were incubated with NCAM-Fc after transfection. NCAM-Fc increased neurite lengths of GFP-transfected neurons. NCAM-Fc–stimulated neurite outgrowth was further increased in neurons cotransfected with PrP. (F) PrP^+/+ neurons were incubated with NCAM-Fc and NCAM-Fc together with polyclonal PrP antibodies. Note inhibition of NCAM-Fc–induced neurite outgrowth after incubation with PrP antibodies. Lengths of longest neurites were measured and mean values ± SEM are shown (n > 150 neurons, *, P < 0.05, t test, for A–F).