Alzheimer's disease neurons fail the acid test.

Mutations in the presenilin genes are the most common cause of familial forms of Alzheimer's disease. Although it is well known for its role in the generation of amyloid peptide, Lee et al. (2010) now report that presenilin 1 deficiency also impacts maturation of the lysosomal proton pump, affecting autophagocytosis and protein turnover.