Synaptic Vesicle Protein 2B Negatively Regulates the Amyloidogenic Processing of AßPP as a Novel Interaction Partner of BACE1.

BACKGROUND: Given that amyloid-ß (Aß) peptide is produced and released at synapses, synaptic Aß is one of the promising therapeutic targets to prevent synaptic dysfunction in Alzheimer's disease (AD). Although Aß production begins with the cleavage of the amyloid-ß protein precursor (AßPP) by ß-site AßPP cleaving enzyme 1 (BACE1), the mechanism on how BACE1 is involved in AßPP processing at synapses remains unclear. OBJECTIVE: This study aimed to identify novel BACE1 interacting proteins regulating Aß production at the synapse. METHODS: BACE1 interacting proteins were pulled down using a mass spectrometry-based proteomics of wild-type (WT) rat brain synaptoneurosome lysates utilizing anti-BACE1 antibody. Then, a novel BACE1 interactor was identified and characterized using experimental systems that utilized transfected cells and knockout (KO) mice. RESULTS: Synaptic vesicle protein 2B (SV2B) was identified as a novel presynaptic interaction partner of BACE1. In HEK293 cells, co-overexpression of SV2B with BACE1 significantly reduced the sAßPPß and Aß levels released in the media; thus, SV2B overexpression negatively affected the AßPP cleavage by BACE1. Compared with those of WT mice, the hippocampal lysates of SV2B knockout mice had significantly elevated Aß levels, whereas the ß-secretase activity and the AßPP and BACE1 protein levels remained unchanged. Finally, a fractionation assay revealed that BACE1 was mislocalized in SV2B KO mice; hence, SV2B may be involved in BACE1 trafficking downregulating the amyloidogenic pathway of AßPP. CONCLUSION: SV2B has a novel role of negatively regulating the amyloidogenic processing of AßPP at the presynapses.

Fibronectin type III domain-containing protein 5 interacts with APP and decreases amyloid ß production in Alzheimer's disease.

The deposition of Amyloid-beta peptides (Aß) is detected at an earlier stage in Alzheimer's disease (AD) pathology. Thus, the approach toward Aß metabolism is considered to play a critical role in the onset and progression of AD. Mounting evidence suggests that lifestyle-related diseases are closely associated with AD, and exercise is especially linked to the prevention and the delayed progression of AD. We previously showed that exercise is more effective than diet control against Aß pathology and cognitive deficit in AD mice fed a high-fat diet; however, the underlying molecular mechanisms remain poorly understood. On the other hand, a report suggested that exercise induced expression of fibronectin type III domain-containing protein 5 (FNDC5) in the hippocampus of mice through PGC1α pathway. Thus, in the current study, we investigated a possibility that FNDC5 interacts with amyloid precursor protein (APP) and affects Aß metabolism. As a result, for the first time ever, we found the interaction between FNDC5 and APP, and forced expression of FNDC5 significantly decreased levels of both Aß40 and Aß42 secreted in the media. Taken together, our results indicate that FNDC5 significantly affects ß-cleavage of APP via the interaction with APP, finally regulating Aß levels. A deeper understanding of the mechanisms by which the interaction between APP and FNDC5 may affect Aß production in an exercise-dependent manner would provide new preventive strategies against the development of AD.

High Fat Diet Enhances ß-Site Cleavage of Amyloid Precursor Protein (APP) via Promoting ß-Site APP Cleaving Enzyme 1/Adaptor Protein 2/Clathrin Complex Formation.

Obesity and type 2 diabetes are risk factors of Alzheimer's disease (AD). We reported that a high fat diet (HFD) promotes amyloid precursor protein (APP) cleavage by ß-site APP cleaving enzyme 1 (BACE1) without increasing BACE1 levels in APP transgenic mice. However, the detailed mechanism had remained unclear. Here we demonstrate that HFD promotes BACE1/Adaptor protein-2 (AP-2)/clathrin complex formation by increasing AP-2 levels in APP transgenic mice. In Swedish APP overexpressing Chinese hamster ovary (CHO) cells as well as in SH-SY5Y cells, overexpression of AP-2 promoted the formation of BACE1/AP-2/clathrin complex, increasing the level of the soluble form of APP ß (sAPPß). On the other hand, mutant D495R BACE1, which inhibits formation of this trimeric complex, was shown to decrease the level of sAPPß. Overexpression of AP-2 promoted the internalization of BACE1 from the cell surface, thus reducing the cell surface BACE1 level. As such, we concluded that HFD may induce the formation of the BACE1/AP-2/clathrin complex, which is followed by its transport of BACE1 from the cell surface to the intracellular compartments. These events might be associated with the enhancement of ß-site cleavage of APP in APP transgenic mice. Here we present evidence that HFD, by regulation of subcellular trafficking of BACE1, promotes APP cleavage.

[Supervised administration of Alzheimer's patients using information communication technology].

Drug adherence is central to the treatment of dementia, which might reduce compliance due to memory loss, particularly among home-based patients with dementia. In order to improve drug adherence, we suggest the efficient and effective supervised administration by use of information communication technology(ICT). ICT makes face-to-face real-time communication possible, and it also enables picture sharing. Therefore, it might be useful to apply ICT to controlling and supervising medication for patients with dementia to improve drug adherence. Accordingly, we enrolled patients who were supposed to take a newly prescribed anti-dementia patch containing the choline esterase inhibitor rivastigmine(Rivastach®)and investigated the effect of ICT-based intervention for drug adherence, emotional change, and cognitive change, utilizing Skype, a free communication software program. Scheduled Skype interventions increased drug adherence ratio, levels of subjective satisfaction, and instrumental activities of daily living(IADL). Furthermore, we can provide patients and their caregivers with a feeling of safety through regular bidirectional communication, as patients can easily consult medical staff regarding the adverse effects of newly prescribed drugs. Instead of frequent visits to their primary physicians, ICT-based communications can be used as a substitute for supervision of medication, given the availability of the telecommunication system. By directly connecting the medical institution to the home, we expect that this ICT-based system will expand into the geriatric care field, including the care of elderly individuals living alone.

Continuation of exercise is necessary to inhibit high fat diet-induced ß-amyloid deposition and memory deficit in amyloid precursor protein transgenic mice.

High fat diet (HFD) is prevalent in many modern societies and HFD-induced metabolic condition is a growing concern worldwide. It has been previously reported that HFD clearly worsens cognitive function in amyloid precursor protein (APP) transgenic mice. On the other hand, we have demonstrated that voluntary exercise in an enriched environment is an effective intervention to rescue HFD-induced ß-amyloid (Aß) deposition and memory deficit. However, it had been unclear whether consumption of HFD after exercising abolished the beneficial effect of exercise on the inhibition of Alzheimer's disease (AD) pathology. To examine this question, we exposed wild type (WT) and APP mice fed with HFD to exercise conditions at different time periods. In our previous experiment, we gave HFD to mice for 20 weeks and subjected them to exercise during weeks 10-20. In the present study, mice were subjected to exercise conditions during weeks 0-10 or weeks 5-15 while being on HFD. Interestingly, we found that the effect of exercise during weeks 0-10 or weeks 5-15 on memory function was not abolished in WT mice even if they kept having HFD after finishing exercise. However, in APP transgenic mice, HFD clearly disrupted the effect of exercise during weeks 0-10 or weeks 5-15 on memory function. Importantly, we observed that the level of Aß oligomer was significantly elevated in the APP mice that exercised during weeks 0-10: this might have been caused by the up-regulation of Aß production. These results provide solid evidence that continuation of exercise is necessary to rescue HFD-induced aggravation of cognitive decline in the pathological setting of AD.

Copper enhances APP dimerization and promotes Aß production.

Alzheimer's disease (AD) is characterized by the deposition of amyloid-ß (Aß) plaques, senile plaque. The Aß peptide is cleaved from amyloid precursor protein (APP) by ß-secretase and γ-secretase. Until now, many literatures have documented that the high concentration of copper is present in Aß plaques and enhances aggregation of. The APP copper binding domain (CuBD) is located in the N-terminal next to the growth factor-like domain that gets involved in APP homodimerization. Importantly, dimerization of APP has profound effect on Aß production. We investigated whether copper alters the state of APP dimerization and how it affects APP metabolism. Here, we demonstrate that copper enhanced APP dimerization and increased extracellular release of Aß. Moreover, copper chelator, D-penicillamine, suppressed APP dimerization and decreased extracellular release of Aß. These results suggest that the action of copper may be profoundly associated with the pathway of Aß production in AD pathogenesis.

N-cadherin enhances APP dimerization at the extracellular domain and modulates Aß production.

Sequential processing of amyloid precursor protein (APP) by ß- and γ-secretase leads to the generation of amyloid-ß (Aß) peptides, which plays a central role in Alzheimer's disease pathogenesis. APP is capable of forming a homodimer through its extracellular domain as well as transmembrane GXXXG motifs. A number of reports have shown that dimerization of APP modulates Aß production. On the other hand, we have previously reported that N-cadherin-based synaptic contact is tightly linked to Aß production. In the present report, we investigated the effect of N-cadherin expression on APP dimerization and metabolism. Here, we demonstrate that N-cadherin expression facilitates cis-dimerization of APP. Moreover, N-cadherin expression led to increased production of Aß as well as soluble APPß, indicating that ß-secretase-mediated cleavage of APP is enhanced. Interestingly, N-cadherin expression affected neither dimerization of C99 nor Aß production from C99, suggesting that the effect of N-cadherin on APP metabolism is mediated through APP extracellular domain. We confirmed that N-cadherin enhances APP dimerization by a novel luciferase-complementation assay, which could be a platform for drug screening on a high-throughput basis. Taken together, our results suggest that modulation of APP dimerization state could be one of mechanisms, which links synaptic contact and Aß production.