Pharmacological modulation of septins restores calcium homeostasis and is neuroprotective in models of Alzheimer's disease.

Abnormal calcium signaling is a central pathological component of Alzheimer's disease (AD). Here, we describe the identification of a class of compounds called ReS19-T, which are able to restore calcium homeostasis in cell-based models of tau pathology. Aberrant tau accumulation leads to uncontrolled activation of store-operated calcium channels (SOCCs) by remodeling septin filaments at the cell cortex. Binding of ReS19-T to septins restores filament assembly in the disease state and restrains calcium entry through SOCCs. In amyloid-ß and tau-driven mouse models of disease, ReS19-T agents restored synaptic plasticity, normalized brain network activity, and attenuated the development of both amyloid-ß and tau pathology. Our findings identify the septin cytoskeleton as a potential therapeutic target for the development of disease-modifying AD treatments.

Modifying Rap1-signalling by targeting Pde6δ is neuroprotective in models of Alzheimer's disease.

BACKGROUND: Neuronal Ca2+ 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 Ca2+ influx and aberrant neuronal activity, which accelerates neurodegeneration in a feed-forward fashion. As such, identifying new targets and drugs to modulate excessive Ca2+ 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 Pde6δ normalises disease associated Ca2+ aberrations and neuronal activity, conferring neuroprotection in models of Alzheimer's disease. RESULTS: The newly identified inhibitors of the Rap1-Pde6δ interaction counteract AD phenotypes, by reconfiguring Rap1 signalling underlying synaptic efficacy, Ca2+ influx, and neuronal repolarisation, without adverse effects in-cellulo or in-vivo. Thus, modulation of Rap1 by Pde6δ 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 Pde6δ-Rap1 interaction has promising therapeutic potential for disorders characterised by neuronal hyperactivity, such as Alzheimer's disease.

Derailed intraneuronal signalling drives pathogenesis in sporadic and familial Alzheimer's disease.

Although a wide variety of genetic and nongenetic Alzheimer's disease (AD) risk factors have been identified, their role in onset and/or progression of neuronal degeneration remains elusive. Systematic analysis of AD risk factors revealed that perturbations of intraneuronal signalling pathways comprise a common mechanistic denominator in both familial and sporadic AD and that such alterations lead to increases in Aß oligomers (Aßo) formation and phosphorylation of TAU. Conversely, Aßo and TAU impact intracellular signalling directly. This feature entails binding of Aßo to membrane receptors, whereas TAU functionally interacts with downstream transducers. Accordingly, we postulate a positive feedback mechanism in which AD risk factors or genes trigger perturbations of intraneuronal signalling leading to enhanced Aßo formation and TAU phosphorylation which in turn further derange signalling. Ultimately intraneuronal signalling becomes deregulated to the extent that neuronal function and survival cannot be sustained, whereas the resulting elevated levels of amyloidogenic Aßo and phosphorylated TAU species self-polymerizes into the AD plaques and tangles, respectively.