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Macropinocytosis of Amyloid Precursor Protein Is Regulated by the Recruitment and Activity of Fe65, Arf6 and Rho

Jordan M Krupa1,2, Manoj Reddy Medapati2, Abdul M Naqvi1,2

  • 1Neuroscience Program, Schulich School of Medicine and Dentistry, University of Western Ontario, London, ON N6A 5B7, Canada.

Cells
|August 13, 2026
PubMed

Insights

Alzheimer's disease involves amyloid-beta (Aβ) buildup from amyloid precursor protein (APP) via macropinocytosis. This study reveals Fe65, Arf6, Rac1, Cdc42, and RhoA regulate APP macropinocytosis, offering potential therapeutic targets.

Area of Science:

  • Neuroscience
  • Cell Biology
  • Biochemistry

Background:

  • Alzheimer's disease (AD) is characterized by amyloid-beta (Aβ) peptide aggregation.
  • Aβ is produced from amyloid precursor protein (APP) after its lysosomal internalization via macropinocytosis.
  • Regulation of APP macropinocytosis in neurons is not well understood.

Purpose of the Study:

  • To investigate the regulatory mechanism of APP macropinocytosis in neuronal cells.
  • To determine the role of Fe65, Arf6, Rac1, Cdc42, and RhoA in APP trafficking.
  • To test the hypothesis that APP binding/crosslinking recruits Fe65, which then activates Arf6 and Rho GTPases to drive macropinocytosis.

Main Methods:

  • Antibody-mediated binding/crosslinking of APP on neuronal cells.
  • Immunofluorescence microscopy to track protein recruitment to APP.
  • Mutation of the APP 'YENPTY' sequence.
  • Pharmacological inhibition of Arf6 using NAV-2729.

Main Results:

  • Antibody-mediated APP binding/crosslinking transiently recruited Fe65 and Arf6 within 30 seconds.
  • Rac1, Cdc42, and RhoA were recruited to APP by 30 seconds and remained for 2 minutes.
  • Mutation of the APP 'YENPTY' sequence or Arf6 inhibition blocked Rac1, Cdc42, and RhoA recruitment.

Conclusions:

  • A network of regulatory proteins, including Fe65, Arf6, Rac1, Cdc42, and RhoA, is recruited to bound/crosslinked APP.
  • This protein network regulates APP macropinocytosis.
  • Targeting these proteins could offer a therapeutic strategy to reduce Aβ production in Alzheimer's disease by modulating APP lysosomal trafficking.
Keywords:
Alzheimer’s diseaseRho GTPaseamyloid betaamyloid precursor proteinendocytosislysosomemacropinocytosis

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