Modifying Rap1-signalling by targeting Pde6[delta] is neuroprotective in models of Alzheimer's disease

Background Neuronal Ca.sup.2+ dyshomeostasis and hyperactivity play a central role in Alzheimer's disease pathology and progression. Amyloid-beta together with non-genetic risk-factors of Alzheimer's disease contributes to increased Ca.sup.2+ influx and aberrant neuronal activity, which accelerates neurodegeneration in a feed-forward fashion. As such, identifying new targets and drugs to modulate excessive Ca.sup.2+ signalling and neuronal hyperactivity, without overly suppressing them, has promising therapeutic potential. Methods Here we show, using biochemical, electrophysiological, imaging, and behavioural tools, that pharmacological modulation of Rap1 signalling by inhibiting its interaction with Pde6[delta] normalises disease associated Ca.sup.2+ aberrations and neuronal activity, conferring neuroprotection in models of Alzheimer's disease. Results The newly identified inhibitors of the Rap1-Pde6[delta] interaction counteract AD phenotypes, by reconfiguring Rap1 signalling underlying synaptic efficacy, Ca.sup.2+ influx, and neuronal repolarisation, without adverse effects in-cellulo or in-vivo. Thus, modulation of Rap1 by Pde6[delta] accommodates key mechanisms underlying neuronal activity, and therefore represents a promising new drug target for early or late intervention in neurodegenerative disorders. Conclusion Targeting the Pde6[delta]-Rap1 interaction has promising therapeutic potential for disorders characterised by neuronal hyperactivity, such as Alzheimer's disease. Keywords: Alzheimer's disease, Hyperexcitability, Neuroprotection, Pde6[delta], Rap1