APP-BP1 expression increased APP processing in primary neurons. A. Expression of myc-tagged APP-BP1. Equal amount of total proteins from neurons infected with APP-BP1 virus or p1005+ virus was analyzed by western blotting using the mouse ant-myc antibody, 9E10. B. APP-BP1 overexpression downregulated rat endogenous APP. APP expression from 15 μg of proteins was analyzed by immunoblots using the anti-APP antibody 369. The amount of γ-tubulin from the same blot was reprobed with a mouse anti-γ-tubulin antibody. Representative blots from the same experiments are shown. C. Quantitative western blot analyses revealed that APP-BP1 significantly downregulated the endogenous APP but not APLPs in neurons overexpressing myc APP-BP1. mycAPP-BP1 expression significantly decreased APP levels compared to the sample infected with the vector (p1005+) (n = 4, p < 0.02, one-tail t-Test). APLP1 levels stayed the same, and APLP2 did not showed a significant change by t-Tests (n = 3, p = 0.1, one tail t-Test). D. RIPA buffer soluble protein extracts from primary neurons co-expressing APP-BP1 and APP695 or p1005+ and APP695 were precipitated with 6E10 followed by western blot analyses using 4G8. Mean levels of Aβ is presented in the graph (n = 4, p < 0.04). A representative of 4 independent blots was shown as an insert.