Many cases of early-onset inherited Alzheimer's disease (AD) are caused by mutations in the presenilin-1 (PS1) gene. PS1 mutations may perturb cellular Ca2+ homeostasis and thereby render neurons vulnerable to excitotoxicity and apoptosis. We now report that PC12 cells expressing PS1 mutations and primary hippocampal neurons from PSI mutant knockin mice exhibit greatly increased levels of ryanodine receptors (RyR) and enhanced Ca2+ release following stimulation with caffeine. Double-labeling immunostaining and co-immunoprecipitation analyses indicate that PS1 and RyR are colocalized and interact physically. Caffeine treatment sensitizes neurons expressing mutant PS1 to apoptosis induced by amyloid β-peptide, a neurotic peptide linked to the pathogenesis of AD. When taken together with recent evidence for alterations in RyR in brains of AD patients, our data suggest that PS1 mutations may promote neuronal degeneration in AD by increasing transcription and translation of RyR and altering functional properties of ryanodine-sensitive Ca2+ pools.
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