Modeling presynaptic inhibition by the amyloid precursor protein demonstrates one potential mechanism for preventing runaway synaptic modification in Alzheimers disease

INTRODUCTIONPrevious simulations of Hebbian associative memory models inspired the malignant synaptic growth hypothesis of Alzheimers disease (AD), which suggests that cognitive impairments arise due to runaway synaptic modification resulting from poor separation between encoding and retrieval. METHODSWe computationally model presynaptic inhibition by the recently identified interaction of soluble amyloid precursor protein (sAPP) with the {gamma}-aminobutyric acid type B receptor (GABABR) as one potential biological mechanism which can enhance separation between encoding and retrieval. RESULTSSimulations predict that the dual effect of sAPP on long-term potentiation and presynaptic inhibition of glutamatergic synapses maintains effective associative memory function and prevents runaway synaptic modification. Moreover, computational modeling predicts that sAPP, which interacts with the 1a isoform of GABABR, is more effective at stabilizing associative memory than the GABABR agonist Baclofen. DISCUSSIONMolecular mechanisms that enhance presynaptic inhibition, such as sAPP-GABABR1a signaling, are potential therapeutic targets for preventing cognitive impairments in AD.