Suppression of A? toxicity by puromycin-sensitive aminopeptidase is independent of its proteolytic activity.

ABSTRACT: The accumulation of ?-amyloid (A?) peptide in the brain is one of the pathological hallmarks of Alzheimer's disease and is thought to be of primary aetiological significance. In an unbiased genetic screen, we identified puromycin-sensitive aminopeptidase (PSA) as a potent suppressor of A? toxicity in a Drosophila model system. We established that coexpression of Drosophila PSA (dPSA) in the flies' brains improved their lifespan, protected against locomotor deficits, and reduced brain A? levels by clearing the A? plaque-like deposits. However, confocal microscopy and subcellular fractionation of amyloid-expressing 7PA2 cells demonstrated that PSA localizes to the cytoplasm. Therefore, PSA and A? are unlikely to be in the same cellular compartment; moreover, when we artificially placed them in the same compartment in flies, we could not detect a direct epistatic interaction. The consequent hypothesis that PSA's suppression of A? toxicity is indirect was supported by the finding that A? is not a proteolytic substrate for PSA in vitro. Furthermore, we showed that the enzymatic activity of PSA is not required for rescuing A? toxicity in neuronal SH-SY5Y cells. We investigated whether the stimulation of autophagy by PSA was responsible for these protective effects. However PSA's promotion of autophagosome fusion with lysosomes required proteolytic activity and so its effect on autophagy is not identical to its protection against A? toxicity.

SUBMITTER: Kruppa AJ 

PROVIDER: S-EPMC3898073 | biostudies-literature | 2013 Dec

REPOSITORIES: biostudies-literature