p75NTR regulates Abeta deposition by increasing Abeta production but inhibiting Abeta aggregation with its extracellular domain.

Accumulation of toxic amyloid-ß (Aß) in the cerebral cortex and hippocampus is a major pathological feature of Alzheimer's disease (AD). The neurotrophin receptor p75NTR has been proposed to mediate Aß-induced neurotoxicity; however, its role in the development of AD remains to be clarified. The p75NTR/ExonIII-/- mice and APPSwe/PS1dE9 mice were crossed to generate transgenic AD mice with deletion of p75NTR gene. In APPSwe/PS1dE9 transgenic mice, p75NTR expression was localized in the basal forebrain neurons and degenerative neurites in neocortex, increased with aging, and further activated by Aß accumulation. Deletion of the p75NTR gene in APPSwe/PS1dE9 mice reduced soluble Aß levels in the brain and serum, but increased the accumulation of insoluble Aß and Aß plaque formation. There was no change in the levels of amyloid precursor protein (APP) and its proteolytic derivatives, or α-, ß-, and γ-secretase activities, or in levels of BACE1, neprilysin (NEP), and insulin-degrading enzyme (IDE) proteins. Aß production by cortical neurons of APPSwe/PS1dE9 mice was reduced by deletion of p75NTR gene in vitro. Recombinant extracellular domain of p75NTR attenuated the oligomerization and fibrillation of synthetic Aß(42) peptide in vitro, and reduced local Aß plaques after hippocampus injection in vivo. In addition, deletion of p75NTR attenuated microgliosis but increased the microhemorrhage profiles in the brain. The deletion of p75NTR did not significantly change the cognitive function of the mice up to the age of 9 months. Our data suggest that p75NTR plays a critical role in regulating Aß levels by both increasing Aß production and attenuating its aggregation, and they caution that a therapeutic intervention simply reducing p75NTR may exacerbate AD pathology.

Presenilins promote the cellular uptake of copper and zinc and maintain copper chaperone of SOD1-dependent copper/zinc superoxide dismutase activity.

Dyshomeostasis of extracellular zinc and copper has been implicated in ß-amyloid aggregation, the major pathology associated with Alzheimer disease. Presenilin mediates the proteolytic cleavage of the ß-amyloid precursor protein to release ß-amyloid, and mutations in presenilin can cause familial Alzheimer disease. We tested whether presenilin expression affects copper and zinc transport. Studying murine embryonic fibroblasts (MEFs) from presenilin knock-out mice or RNA interference of presenilin expression in HEK293T cells, we observed a marked decrease in saturable uptake of radiolabeled copper and zinc. Measurement of basal metal levels in 6-month-old presenilin 1 heterozygous knock-out (PS1(+/-)) mice revealed significant deficiencies of copper and zinc in several tissues, including brain. Copper/zinc superoxide dismutase (SOD1) activity was significantly decreased in both presenilin knock-out MEFs and brain tissue of presenilin 1 heterozygous knock-out mice. In the MEFs and PS1(+/-) brains, copper chaperone of SOD1 (CCS) levels were decreased. Zinc-dependent alkaline phosphatase activity was not decreased in the PS null MEFs. These data indicate that presenilins are important for cellular copper and zinc turnover, influencing SOD1 activity, and having the potential to indirectly impact ß-amyloid aggregation through metal ion clearance.

Β-site APP-cleaving enzyme 1 trafficking and Alzheimer's disease pathogenesis.

ß-Site APP-cleaving enzyme (BACE1) cleaves the amyloid precursor protein (APP) at the ß-secretase site to initiate the production of Aß peptides. These accumulate to form toxic oligomers and the amyloid plaques associated with Alzheimer's disease (AD). An increase of BACE1 levels in the brain of AD patients has been mostly attributed to alterations of its intracellular trafficking. Golgi-associated adaptor proteins, GGA sort BACE1 for export to the endosomal compartment, which is the major cellular site of BACE1 activity. BACE1 undergoes recycling between endosome, trans-Golgi network (TGN), and the plasma membrane, from where it is endocytosed and either further recycled or retrieved to the endosome. Phosphorylation of Ser498 facilitates BACE1 recognition by GGA1 for retrieval to the endosome. Ubiquitination of BACE1 C-terminal Lys501 signals GGA3 for exporting BACE1 to the lysosome for degradation. In addition, the retromer mediates the retrograde transport of BACE1 from endosome to TGN. Decreased levels of GGA proteins and increased levels of retromer-associated sortilin have been associated with AD. Both would promote the co-localization of BACE1 and the amyloid precursor protein in the TGN and endosomes. Decreased levels of GGA3 also impair BACE1 degradation. Further understanding of BACE1 trafficking and its regulation may offer new therapeutic approaches for the treatment of Alzheimer's disease.

Dissociation of ERK signalling inhibition from the anti-amyloidogenic action of synthetic ceramide analogues.

Inhibition of GSL (glycosphingolipid) synthesis reduces Aß (amyloid ß-peptide) production in vitro. Previous studies indicate that GCS (glucosylceramide synthase) inhibitors modulate phosphorylation of ERK1/2 (extracellular-signal-regulated kinase 1/2) and that the ERK pathway may regulate some aspects of Aß production. It is not clear whether there is a causative relationship linking GSL synthesis inhibition, ERK phosphorylation and Aß production. In the present study, we treated CHO cells (Chinese-hamster ovary cells) and SH-SY5Y neuroblastoma cells, that both constitutively express human wild-type APP (amyloid precursor protein) and process this to produce Aß, with GSL-modulating agents to explore this relationship. We found that three related ceramide analogue GSL inhibitors, based on the PDMP (D-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol) structure, reduced cellular Aß production and in all cases this was correlated with inhibition of pERK (phosphorylated ERK) formation. Importantly, the L-threo enantiomers of these compounds (that are inferior GSL synthesis inhibitors compared with the D-threo-enantiomers) also reduced ERK phosphorylation to a similar extent without altering Aß production. Inhibition of ERK activation using either PD98059 [2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one] or U0126 (1,4-diamino-2,3-dicyano-1,4-bis[2-aminophenylthio] butadiene) had no impact on Aß production, and knockdown of endogenous GCS using small interfering RNA reduced cellular GSL levels without suppressing Aß production or pERK formation. Our data suggest that the alteration in pERK levels following treatment with these ceramide analogues is not the principal mechanism involved in the inhibition of Aß generation and that the ERK signalling pathway does not play a crucial role in processing APP through the amyloidogenic pathway.

Modulation of amyloid precursor protein processing by synthetic ceramide analogues.

Previous studies suggest that membrane lipids may regulate proteolytic processing of the amyloid precursor protein (APP) to generate amyloid-beta peptide (Abeta). In the present study, we have assessed the capacity for a series of structurally related synthetic ceramide analogues to modulate APP processing in vitro. The compounds tested are established glucosylceramide synthase (GS) inhibitors based on the d-1-phenyl-2-decanoylamino-3-morpholino-1-propanol (PDMP) structure. PDMP and related compounds PPMP and EtDO-P4 inhibited Abeta secretion from Chinese hamster ovary cells expressing human APP (CHO-APP) with approximate IC(50) values of 15, 5, and 1 microM, respectively. A trend for reduced secretion of the APP alpha-secretase product, sAPPalpha, was also observed in PDMP-treated cells but not in PPMP- or ETDO-P4-treated cells, whereas levels of the cellular beta-secretase product APP C-terminal fragment, CTFbeta, were increased by both PDMP and PPMP but unaltered with EtDO-P4 treatment. Our data also revealed that EtDO-P4 inhibits endogenous Abeta production by human neurons. In conclusion, this study provides novel information regarding the regulation of APP processing by synthetic ceramide analogues and reveals that the most potent of these compounds is EtDO-P4.

Decreased expression of GGA3 protein in Alzheimer's disease frontal cortex and increased co-distribution of BACE with the amyloid precursor protein.

BACE initiates the amyloidogenic processing of the amyloid precursor protein (APP) that results in the production of Aß peptides associated with Alzheimer's disease (AD). Previous studies have indicated that BACE is elevated in the frontal cortex of AD patients. Golgi-localized γ-ear containing ADP ribosylation factor-binding proteins (GGA) control the cellular trafficking of BACE and may alter its levels. To investigate a link between BACE and GGA expression in AD, frontal cortex samples from AD (N = 20) and healthy, age-matched controls (HC, N =17) were analyzed by immunoblotting. After normalization to the neuronal marker ß-tubulin III, the data indicate an average two-fold increase of BACE protein (p = 0.01) and a 64% decrease of GGA3 in the AD group compared to the HC (p = 0.006). GGA1 levels were also decreased in AD, but a statistical significance was not achieved. qRT-PCR analysis of GGA3 mRNA showed no difference between AD and HC. There was a strong correlation between GGA1 and GGA3 in both AD and HC, but no correlation between BACE and GGA levels. Subcellular fractionation of AD cortex with low levels of GGA proteins showed an alteration of BACE distribution and extensive co-localization with APP. These data suggest that altered compartmentalization of BACE in AD promotes the amyloidogenic processing of APP.

A domain level interaction network of amyloid precursor protein and Abeta of Alzheimer's disease.

The primary constituent of the amyloid plaque, beta-amyloid (Abeta), is thought to be the causal "toxic moiety" of Alzheimer's disease. However, despite much work focused on both Abeta and its parent protein, amyloid precursor protein (APP), the functional roles of APP and its cleavage products remain to be fully elucidated. Protein-protein interaction networks can provide insight into protein function, however, high-throughput data often report false positives and are in frequent disagreement with low-throughput experiments. Moreover, the complexity of the CNS is likely to be under represented in such databases. Therefore, we curated the published work characterizing both APP and Abeta to create a protein interaction network of APP and its proteolytic cleavage products, with annotation, where possible, to the level of APP binding domain and isoform. This is the first time that an interactome has been refined to domain level, essential for the interpretation of APP due to the presence of multiple isoforms and processed fragments. Gene ontology and network analysis were used to identify potentially novel functional relationships among interacting proteins.

Levels of [(3)H]pirenzepine binding in Brodmann's area 6 from subjects with schizophrenia is not associated with changes in the transcription factor SP1 or BACE1.

Decreased muscarinic M1 receptor (CHRM1) mRNA has been reported in Brodmann's area (BA) 6 from subjects with schizophrenia. We have extended this study by measuring levels of CHRM1 ([(3)H]pirenzepine binding), CHRM3 ([(3)H]4-DAMP binding), the transcription factor SP1 and the CHRM1 downstream target beta-site APP-cleaving enzyme 1 (BACE1) in BA 6 from 19 subjects with schizophrenia and 19 control subjects. Radioligand binding was quantified using either in situ radioligand binding with autoradiography or, in cohorts of 10 control subjects and 10 subjects with schizophrenia, membrane enriched fraction (MEF) CNS ([(3)H]pirenzepine binding only). Levels of SP1 and BACE1 were measured by Western blotting. [(3)H]pirenzepine binding to tissue sections was in two layers, binding to tissue sections (Binding layer 1: p<0.01; Binding layer 2: p<0.001) and MEF (p<0.05) were decreased in schizophrenia. Levels of [(3)H]4-DAMP binding, SP1 and BACE1 were not altered in subjects with the disorder. This study shows a decrease in levels of CHRM1 in BA 6 from subjects with schizophrenia; as CHRM1 and BA 6 are important in maintaining normal cognitive function, these data support the hypothesis that decreased levels of cortical CHRM1 may contribute to the cognitive deficits associated with schizophrenia. Our findings on BACE1 suggest that the schizophrenia phenotype reported in BACE(-/-) mice is not simply due to lack of that protein in the cortex.

Inhibition of gamma-secretase as a therapeutic intervention for Alzheimer's disease: prospects, limitations and strategies.

Genetic and experimental evidence points to amyloid-beta (Abeta) peptide as the culprit in Alzheimer's disease pathogenesis. This protein fragment abnormally accumulates in the brain cortex and hippocampus of patients with Alzheimer's disease, and self-aggregates to form toxic oligomers causing neurodegeneration.Abeta is heterogeneous and produced from a precursor protein (amyloid precursor protein [APP]) by two sequential proteolytic cleavages that involve beta- and gamma-secretases. This latter enzyme represents a potentially attractive drug target since it dictates the solubility of the generated Abeta fragment by creating peptides of various lengths, namely Abeta(40) and Abeta(42), the longest being the most aggregating. gamma-Secretase comprises a molecular complex of four integral membrane proteins - presenilin, nicastrin, APH-1 and PEN-2 - and its molecular mechanism remains under extensive scrutiny. The ratio of Abeta(42) over Abeta(40) is increased by familial Alzheimer's disease mutations occurring in the presenilin genes or in APP, near the gamma-secretase cleavage site. Potent gamma-secretase inhibitors have been identified by screening drug libraries or by designing aspartyl protease transition-state analogues based on the APP substrate cleavage site. Most of these compounds are not specific for gamma-secretase cleavage of APP, and equally inhibit the processing of other gamma-secretase substrates, such as Notch and a subset of cell-surface receptors and proteins involved in embryonic development, haematopoiesis, cell adhesion and cell/cell contacts. Therefore, current research aims at finding compounds that show selectivity for APP cleavage, and particularly that inhibit the formation of the aggregating form, Abeta(42). Compounds that target the substrate docking site rather than the enzyme active site are also being investigated as an alternative strategy. The finding that some NSAID analogues preferentially inhibit the formation of Abeta(42) over Abeta(40) and do not affect Notch processing has opened a new therapeutic window. The progress in design of selective inhibitors as well as recent results obtained in animal studies prove that gamma-secretase remains among the best targets for the therapeutic control of amyloid build-up in Alzheimer's disease. The full understanding of gamma-secretase regulation may yet uncover new therapeutic leads.

Future Therapeutics in Alzheimer's Disease: Development Status of BACE Inhibitors.

Alzheimer's disease (AD) is the primary cause of dementia in the elderly. It remains incurable and poses a huge socio-economic challenge for developed countries with an aging population. AD manifests by progressive decline in cognitive functions and alterations in behaviour, which are the result of the extensive degeneration of brain neurons. The AD pathogenic mechanism involves the accumulation of amyloid beta peptide (Aß), an aggregating protein fragment that self-associates to form neurotoxic fibrils that trigger a cascade of cellular events leading to neuronal injury and death. Researchers from academia and the pharmaceutical industry have pursued a rational approach to AD drug discovery and targeted the amyloid cascade. Schemes have been devised to prevent the overproduction and accumulation of Aß in the brain. The extensive efforts of the past 20 years have been translated into bringing new drugs to advanced clinical trials. The most progressed mechanism-based therapies to date consist of immunological interventions to clear Aß oligomers, and pharmacological drugs to inhibit the secretase enzymes that produce Aß, namely ß-site amyloid precursor-cleaving enzyme (BACE) and γ-secretase. After giving an update on the development and current status of new AD therapeutics, this review will focus on BACE inhibitors and, in particular, will discuss the prospects of verubecestat (MK-8931), which has reached phase III clinical trials.

Effects of Mild and Severe Oxidative Stress on BACE1 Expression and APP Amyloidogenic Processing.

This chapter describes methods for establishing oxidative stress conditions that do not induce cell death in a neuronal cell culture model. We termed these conditions "mild oxidative stress," as opposed to "severe oxidative stress," which results in significant cell loss. Mild oxidative stress resembles more closely what happens in the aging brain than severe oxidative stress. The protocols we have delineated include the preparation and maintenance of mouse primary cortical cultures, the induction of oxidative stress by treatment with hydrogen peroxide, the assessment of cell viability by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, the measurement of free radical production by the 2',7'-dichlorofluorescein (DCF) assay, and western blot analysis of the amyloid precursor protein (APP) and ß-site APP cleaving enzyme, BACE1, two key proteins associated with Alzheimer's disease pathology and oxidative stress.

In vitro gamma-secretase cleavage of the Alzheimer's amyloid precursor protein correlates to a subset of presenilin complexes and is inhibited by zinc.

The gamma-secretase complex mediates the final proteolytic event in Alzheimer's disease amyloid-beta biogenesis. This membrane complex of presenilin, anterior pharynx defective, nicastrin, and presenilin enhancer-2 cleaves the C-terminal 99-amino acid fragment of the amyloid precursor protein intramembranously at gamma-sites to form C-terminally heterogeneous amyloid-beta and cleaves at an epsilon-site to release the intracellular domain or epsilon-C-terminal fragment. In this work, two novel in vitro gamma-secretase assays are developed to further explore the biochemical characteristics of gamma-secretase activity. During development of a bacterial expression system for a substrate based on the amyloid precursor protein C-terminal 99-amino acid sequence, fragments similar to amyloid-beta and an epsilon-C-terminal fragment were observed. Upon purification this substrate was used in parallel with a transfected source of substrate to measure gamma-secretase activity from detergent extracted membranes. With these systems, it was determined that recovery of size-fractionated cellular and tissue-derived gamma-secretase activity is dependent upon detergent concentration and that activity correlates to a subset of high molecular mass presenilin complexes. We also show that by changing the solvent environment with dimethyl sulfoxide, detection of epsilon-C-terminal fragments can be elevated. Lastly, we show that zinc causes an increase in the apparent molecular mass of an amyloid precursor protein gamma-secretase substrate and inhibits its cleavage. These studies further refine our knowledge of the complexes and biochemical factors needed for gamma-secretase activity and suggest a mechanism by which zinc dysregulation may contribute to Alzheimer's disease pathogenesis.

Expression of truncated presenilin 2 splice variant in Alzheimer's disease, bipolar disorder, and schizophrenia brain cortex.

We have analysed the expression of a truncated variant presenilin 2 protein (PS2V) in frontal cortex from subjects with Alzheimer's disease (AD) and age-matched controls, and compared these results with cortex from bipolar disorder (BP), schizophrenia (SZ) and controls in a second brain bank collection. PS2V protein was detected as a 14 kDa species with antibodies directed to the PS2 N-terminal region and to the new C-terminus created by alternative transcription. PS2V protein levels were significantly increased by two-fold in AD cortex, as compared to age-matched controls. In tissue from the second collection, levels of PS2V were markedly elevated in some BP and SZ cases, but there was no overall difference between diagnostic groups. Our findings support previous evidence for increased expression of this variant PS2 isoform in sporadic AD and suggest this isoform may contribute to neurodegeneration.

Alternative transcripts of presenilin-1 associated with frontotemporal dementia.

We have analyzed the expression of Alzheimer's disease-associated presenilin 1 (PS1) in various neurodegenerative disorders. Western blotting identified PS1 N- and C-terminal fragments similarly in the cortex of controls, Parkinson, Huntington and schizophrenia subjects. Additional PS1 immunoreactive species of 42 and 46 kDa were present in six out of seven cases of sporadic frontotemporal dementia (FTD) and these were particularly prominent in two cases. RT-PCR analysis using nested primers showed the presence of PS1 gene products with deletions within the exon 4-8 region. Our results suggest that alternative transcription of PS1 may be associated with FTD.

Alternative transcripts of presenilin-1 associated with frontotemporal dementia.

We have analyzed the expression of Alzheimer's disease-associated presenilin 1 (PS1) in various neurodegenerative disorders. Western blotting identified PS1 N- and C-terminal fragments similarly in the cortex of controls, Parkinson, Huntington and schizophrenia subjects. Additional PS1 immunoreactive species of 42 and 46 kDa were present in six out of seven cases of sporadic frontotemporal dementia (FTD) and these were particularly prominent in two cases. RT-PCR analysis using nested primers showed the presence of PS1 gene products with deletions within the exon 4-8 region. Our results suggest that alternative transcription of PS1 may be associated with FTD.

Biogenesis and metabolism of Alzheimer's disease Abeta amyloid peptides.

Biochemical and genetic evidence indicates the balance of biogenesis/clearance of Abeta amyloid peptides is altered in Alzheimer's disease. Abeta is derived, by two sequential cleavages, from the receptor-like amyloid precursor protein (APP). The proteases involved are beta-secretase, identified as the novel aspartyl protease BACE, and gamma-secretase, a multimeric complex containing the presenilins (PS). Gamma-secretase can release either Abeta40 or the more aggregating and cytotoxic Abeta42. Secreted Abeta peptides become either degraded by the metalloproteases insulin-degrading enzyme (IDE) and neprilysin or metabolized through receptor uptake mediated by apolipoprotein E. Therapeutic approaches based on secretase inhibition or amyloid clearance are currently under development.

Critical analysis of the use of ß-site amyloid precursor protein-cleaving enzyme 1 inhibitors in the treatment of Alzheimer's disease.

Alzheimer's disease (AD) is the major cause of dementia in the elderly and an unmet clinical challenge. A variety of therapies that are currently under development are directed to the amyloid cascade. Indeed, the accumulation and toxicity of amyloid-ß (Aß) is believed to play a central role in the etiology of the disease, and thus rational interventions are aimed at reducing the levels of Aß in the brain. Targeting ß-site amyloid precursor protein-cleaving enzyme (BACE)-1 represents an attractive strategy, as this enzyme catalyzes the initial and rate-limiting step in Aß production. Observation of increased levels of BACE1 and enzymatic activity in the brain, cerebrospinal fluid, and platelets of patients with AD and mild cognitive impairment supports the potential benefits of BACE1 inhibition. Numerous potent inhibitors have been generated, and many of these have been proved to lower Aß levels in the brain of animal models. Over 10 years of intensive research on BACE1 inhibitors has now culminated in advancing half a dozen of these drugs into human trials, yet translating the in vitro and cellular efficacy of BACE1 inhibitors into preclinical and clinical trials represents a challenge. This review addresses the promises and also the potential problems associated with BACE1 inhibitors for AD therapy, as the complex biological function of BACE1 in the brain is becoming unraveled.

BACE1 as a therapeutic target in Alzheimer's disease: rationale and current status.

Alzheimer's disease (AD) is a neurodegenerative disease of the central nervous system that causes dementia in a large percentage of the aged population and for which there are only symptomatic treatments. Disease-modifying therapies that are currently being pursued are based on the amyloid cascade theory. This states that accumulation of amyloid ß (Aß) in the brain triggers a cascade of cellular events leading to neurodegeneration. Aß, which is the major constituent of amyloid plaques, is a peptidic fragment derived from proteolytic processing of the amyloid precursor protein (APP) by sequential cleavages that involve ß-site APP-cleaving enzyme 1 (BACE1) and γ-secretase. Targeting BACE1 is a rational approach as its cleavage of APP is the rate-limiting step in Aß production and this enzyme is elevated in the brain of patients with AD. Furthermore, knocking out the BACE1 gene in mice showed little apparent consequences. Ten years of intensive research has led to the design of efficacious BACE1 inhibitors with favorable pharmacological properties. Several drug candidates have shown promising results in animal models, as they reduce amyloid plaque pathology in the brain and rescue cognitive deficits. Phase I clinical trials indicate that these drugs are well tolerated, and the results from further trials in AD patients are now awaited eagerly. Yet, recent novel information on BACE1 biology, and the discovery that BACE1 cleaves a selection of substrates involved in myelination, retinal homeostasis, brain circuitry, and synaptic function, alert us to potential side effects of BACE1 inhibitors that will require further evaluation to provide a safe therapy for AD.

Mild oxidative stress induces redistribution of BACE1 in non-apoptotic conditions and promotes the amyloidogenic processing of Alzheimer's disease amyloid precursor protein.

BACE1 is responsible for ß-secretase cleavage of the amyloid precursor protein (APP), which represents the first step in the production of amyloid ß (Aß) peptides. Previous reports, by us and others, have indicated that the levels of BACE1 protein and activity are increased in the brain cortex of patients with Alzheimer's disease (AD). The association between oxidative stress (OS) and AD has prompted investigations that support the potentiation of BACE1 expression and enzymatic activity by OS. Here, we have established conditions to analyse the effects of mild, non-lethal OS on BACE1 in primary neuronal cultures, independently from apoptotic mechanisms that were shown to impair BACE1 turnover. Six-hour treatment of mouse primary cortical cells with 10-40 µM hydrogen peroxide did not significantly compromise cell viability but it did produce mild oxidative stress (mOS), as shown by the increased levels of reactive radical species and activation of p38 stress kinase. The endogenous levels of BACE1 mRNA and protein were not significantly altered in these conditions, whereas a toxic H2O2 concentration (100 µM) caused an increase in BACE1 protein levels. Notably, mOS conditions resulted in increased levels of the BACE1 C-terminal cleavage product of APP, ß-CTF. Subcellular fractionation techniques showed that mOS caused a major rearrangement of BACE1 localization from light to denser fractions, resulting in an increased distribution of BACE1 in fractions containing APP and markers for trans-Golgi network and early endosomes. Collectively, these data demonstrate that mOS does not modify BACE1 expression but alters BACE1 subcellular compartmentalization to favour the amyloidogenic processing of APP, and thus offer new insight in the early molecular events of AD pathogenesis.