Small GTPases control macropinocytosis of amyloid precursor protein and cleavage to amyloid-β
Justin Chiu,
Jordan M. Krupa,
Claudia Seah,
Stephen H. Pasternak, MD/PhD
Affiliations
Justin Chiu
Department of Physiology and Pharmacology, The Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada; Robarts Research Institute, The Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada
Jordan M. Krupa
Neuroscience Program, The Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada; Robarts Research Institute, The Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada
Claudia Seah
Robarts Research Institute, The Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada
Stephen H. Pasternak, MD/PhD
Department of Physiology and Pharmacology, The Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada; Neuroscience Program, The Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada; Robarts Research Institute, The Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada; Department of Clinical Neurological Sciences, The Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada; Corresponding author. RRI 3243, Robarts Research Institute Schulich School of Medicine & Dentistry Western University 1151 Richmond St. N. London, ON N6A 5B7, Canada.
The overproduction of the toxic peptide amyloid-beta (Aβ) generated from the cleavage of amyloid precursor protein (APP) is proposed to be a critical event in the development of Alzheimer's disease. Evidence suggests that the cleavage of APP occurs after its internalization from the cell surface. Previously, we identified a novel pathway for APP internalization, which trafficks cell surface APP directly to lysosomes by macropinocytosis, leading to its processing into Aβ. We also demonstrated that ADP-ribosylation factor 6 (Arf6) is required for the macropinocytosis of APP. Here, we characterized the roles of Arf6's downstream effectors Rac1, Cdc42 and RhoA. Both pharmacological inhibition and siRNA knockdown of these proteins reduced the amount of APP colocalized with LAMP1-labeled lysosomes without affecting APP transport to early endosomes. Decreases in the production of both Aβ40 and Aβ42 were also observed by ELISA in response to inhibitor treatment. These findings together demonstrate that Rac1, Cdc42 and RhoA are components of the mechanism regulating the macropinocytosis of APP and targeting these components can reduce the production of Aβ.
