Fig. 4. Alterations of APP processing in LRP–/– cells are isoform independent. (A) LRP+/– and LRP–/– cells stably transfected with APP695 were analyzed for levels of APP-αCTFs. Single clones of similar APP expression were analyzed (top panel). Note the dramatic reduction in APP-CTF expression in LRP –/– cells (bottom panel). Quantitation of APP-αCTF (B) and APPs (C) levels in LRP-deficient CHO 13-5-1 and control CHO cells transfected with APP695. Note that APP-αCTF and APPs derived from APP695 were altered similarly in LRP-deficient cells as those from APP751. Introduction of LRP-CT in the LRP- deficient cells restored the abnormalities in APP-αCTF (B) and APPs (C) back to control levels. Results are the average ± SEM (n = 2).