Alterations in both acetylcholinesterase activity and synaptic scaffolding protein localization in the nervous system of Drosophila presenilin mutants

Presenilins are one of two types of critical genetic factors in familial Alzheimer's disease, and they regulate various cellular functions such as intracellular Ca 2+ homeostasis, the endoplasmic reticulum (ER) stress response, apoptosis, and synaptic transmission. We utilized Drosophila presenilin ( psn) mutants as a model for studying the role of this gene in regulating acetylcholinesterase activity (AChE) and synaptic plasticity. Several lines of biochemical evidence indicated that AChE activity in a functionally null psn mutant ( psn B3) was significantly reduced. In addition, we also found that psn B3 mutant neuromuscular junctions (NMJs) had smaller synaptic boutons and altered localization of Discs large, a synaptic scaffolding protein at the synaptic terminals compared to wild-type controls. These phenotypic defects were completely rescued in transgenic lines expressing the long form of wild-type Psn under an endogenous psn promoter cassette (PEPC- Psn WT; psn B3 lines). Taken together, these results indicate that Psn is important for regulating AChE activity, the size of synaptic boutons, and the localization of DLG at synaptic terminals.