Gamma secretase orthologs are required for lysosomal activity and autophagic degradation in Dictyostelium discoideum, independent of PSEN (presenilin) proteolytic function

Devdutt Sharma, Grant Otto, Eleanor Warren, Philip Beesley, Jason S. King, Robin Williams

Research output: Contribution to journalArticlepeer-review


Mutations in the gamma-secretase complex are strongly associated with familial Alzheimer disease. Both proteolytic and non-proteolytic functions for the gamma-secretase complex have been previously described in mammalian model organisms, but their relative contributions to disease pathology remain unclear. Here, we dissect the roles of orthologs of the gamma-secretase components in the model system Dictyostelium, focusing on endocytosis, lysosomal activity and autophagy. In this model, we show that the orthologs of PSEN (psenA and psenB), Ncstn (nicastrin) and Aph-1 (gamma-secretase subunit Aph-1), are necessary for optimal fluid-phase uptake by macropinocytosis and in multicellular development under basic condition. Disruption of either psenA/B or Aph-1 proteins also leads disrupted phagosomal proteolysis as well as decreased autophagosomal acidification and autophagic flux. This indicates a general defect in lysosomal trafficking and degradation, which we show leads to the accumulation of ubiquitinated protein aggregates in cells lacking psenA/B and Aph-1 proteins. Importantly, we find that all the endocytic defects observed in Dictyostelium PSEN ortholog mutants can be fully rescued by proteolytically inactive Dictyostelium psenB and human PSEN1 proteins. Our data therefore demonstrates an evolutionarily conserved non-proteolytic role for presenilin, and gamma-secretase component orthologs, in maintaining Dictyostelium lysosomal trafficking and autophagy.
Original languageEnglish
Pages (from-to)1407-1418
Number of pages12
Issue number8
Early online date26 Feb 2019
Publication statusE-pub ahead of print - 26 Feb 2019


  • Alzheimers disease
  • presenilin
  • nicastrin
  • lysosomal trafficking
  • gamma-secretase
  • Dictyostelium
  • development
  • autophagy

Cite this