Fig. 3. The presence of multiple cytoplasmic tail signals is required for transcytotic routing of NgCAM chimeras. The site of initial surface delivery of LexNct1-114 (A), Lct27Nct45-114 (B) and LexNct45-114 (C) was determined using the Brefeldin A (BFA) block release assay. The percentage of neurons displaying the chimera on the surface uniformly (triangles), axonally enriched (squares) or somatodendritically enriched (circles) was determined for multiple time points after release from BFA. Additionally, the percentage of cells was scored in which no surface staining was detectable, but intracellular staining was present (broken line). The chimera LexNct45-114, which contains the cytoplasmic axonal signal of NgCAM but lacks the somatodendritic and endocytosis motifs, is delivered directly to the axonal plasma membrane (C). If the somatodendritic/endocytic signal surrounding Tyr33 is present [as in LexNct1-114 (A)], the first surface appearance was frequently somatodendritically enriched, suggestive of transcytosis. Inclusion of the LDLR-derived somatodendritic/endocytic signal in Lct27Nct45-114 (B) also led to initial somatodendritic surface appearance, suggesting transcytotic routing. One representative experiment (of a minimum of three) is shown for each construct.