(a, b) APPwt N2a cells were transfected with the indicated constructs and biotinylation assays of (a) APP internalization or (b) APP recycling were performed (see Experimental Procedures). mAPP, mature APP; imAPP, immature APP. (c) Quantification of internalized APP normalized to mature APP, n=5. (d) Quantification of APP that remains intracellular after recycling, normalized to mature APP, n=4. (e) Hippocampal neurons were transfected with APP-RFP and the indicated constructs and live labeled with APP antibody. APP that has recycled to the cell surface was immunostained (green, see Experimental Procedures for details). (f) Quantification of the fluorescent intensity of APP that has recycled to the cell surface, normalized to the intensity of APP-RFP, n=8–12. Data were expressed as Mean ± SEM with Student's t test: *p<0.05; ** p<0.01. Scale bar: 10µm.