Antibodies used in this study: goat polyclonal antibody to the N terminus of PAK3 (Santa Cruz Biotechnology, Santa Cruz, CA), and a rabbit polyclonal to mPAK3 (Up-State Biotechnology, Lake Placid, NY). The polyclonal antibody APP369 was raised against a region from amino acids 645-694 of human APP-695 (gift of Dr. Sam Gandy). Antibody C8 was raised against the C terminal 20 amino acids of APP (gift of Dr. Dennis Selkoe). Anti-rab5A(S-19) and anti-rab7(C19) were from Santa Cruz. Antibody 6E10 was from Signet (Dedham, MA). Anti-rab11 was from Transduction Laboratories (Lexington, KY). The anti-myc antibody 9E10 and the anti-APP antibody 22C11 were used.