APP antibodies included the following: CT15, polyclonal rabbit antibody recognizing the C-terminal 15 amino acids of APP (Sisodia et al. 1993); a monoclonal antibody 26D6 recognizing the Ab peptide sequence of amino acids 1-12 (Lu et al. 2000); and a polyclonal antibody a664 directed against amino acids 657-664 of APP (Soriano et al. 2001). The latter antibody is end-specific and only recognizes APP when it has been cleaved after residue 664. Additional monoclonal antibodies include b-tubulin (Sigma-Aldrich), HA tag (Roche), and FLAG M2 (Sigma-Aldrich).