Synapse-associated protein-97 mediates alpha-secretase ADAM10 trafficking and promotes its activity
ABSTRACT Alzheimer's disease (AD) is a chronic neurodegenerative disorder caused by a combination of events impairing normal neuronal function. Here we found a molecular bridge between key elements of primary and secondary pathogenic events in AD, namely the elements of the amyloid cascade and synaptic dysfunction associated with the glutamatergic system. In fact, we report that synapse-associated protein-97 (SAP97), a protein involved in dynamic trafficking of proteins to the excitatory synapse, is responsible for driving ADAM10 (a disintegrin and metalloproteinase 10, the most accredited candidate for alpha-secretase) to the postsynaptic membrane, by a direct interaction through its Src homology 3 domain. NMDA receptor activation mediates this event and positively modulates alpha-secretase activity. Furthermore, perturbing ADAM10/SAP97 association in vivo by cell-permeable peptides impairs ADAM10 localization in postsynaptic membranes and consequently decreases the physiological amyloid precursor protein (APP) metabolism. Our findings indicate that glutamatergic synapse activation through NMDA receptor promotes the non-amyloidogenic APP cleavage, strengthening the correlation between APP metabolism and synaptic plasticity.
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ABSTRACT: The amyloid hypothesis of Alzheimer's disease (AD) suggests that soluble amyloid β (Aβ) is an initiator of a cascade of events eventually leading to neurodegeneration. Recently, we reported that Aβ deranged Ca(2+) homeostasis specifically in hippocampal astrocytes by targeting key elements of Ca(2+) signaling, such as mGluR5 and IP3 R1. In the present study, we dissect a cascade of signaling events by which Aβ deregulates glial Ca(2+) : (i) 100 nM Aβ leads to an increase in cytosolic calcium after 4-6 h of treatment; (ii) mGluR5 is increased after 24 h of treatment; (iii) this increase is blocked by inhibitors of calcineurin (CaN) and NF-kB. Furthermore, we show that Aβ treatment of glial cells leads to de-phosphorylation of Bcl10 and an increased CaN-Bcl10 interaction. Last, mGluR5 staining is augmented in hippocampal astrocytes of AD patients in proximity of Aβ plaques and co-localizes with nuclear accumulation of the p65 NF-kB subunit and increased staining of CaNAα. Taken together our data suggest that nanomolar [Aβ] deregulates Ca(2+) homeostasis via CaN and its downstream target NF-kB, possibly via the cross-talk of Bcl10 in hippocampal astrocytes.Glia 07/2013; 61(7). DOI:10.1002/glia.22502 · 6.03 Impact Factor
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ABSTRACT: The pathogenesis of Alzheimer's disease includes accumulation of toxic amyloid beta (Aβ) peptides. A recently developed cell-permeable peptide, termed Tat-Pro, disrupts the complex between synapse-associated protein 97 (SAP97) and the α-secretase a disintegrin and metalloproteinase domain-containing protein 10 (ADAM10), thereby leading to an alteration of the trafficking of the enzyme, which is important for nonamyloidogenic processing of amyloid precursor protein (APP). We report that Tat-Pro treatment, as well as the treatment with exogenous Aβ, deregulates Ca(2+) homeostasis specifically in astrocytes through increased expression of key components of Ca(2+) signaling, metabotropic glutamate receptor-5 and inositol 1,4,5-trisphosphate receptor-1. This is accompanied by potentiation of (S)-3,5-dihydroxyphenylglycine-induced Ca(2+) transients. Calcineurin inhibition reverts all these effects. Furthermore, our data demonstrate that astrocytes express all the components for the amyloidogenic and nonamyloidogenic processing of APP including APP itself, beta-site APP-cleaving enzyme 1 (BACE1), ADAM10, γ-secretase, and SAP97. Indeed, treatment with Tat-Pro for 48 hours significantly increased the amount of Aβ(1-42) in the medium of cultured astrocytes. Taken together, our results suggest that astroglia might be active players in Aβ production and indicate that the calcium hypothesis of Alzheimer's disease may recognize glial cells as important intermediates.Neurobiology of aging 06/2012; 34(2). DOI:10.1016/j.neurobiolaging.2012.05.005 · 4.85 Impact Factor
- Neurobiology of Aging 06/2012; · 4.85 Impact Factor