Expression Of Presenilin Research Articles

Deficits in Enrichment-Dependent Neurogenesis and Enhanced Anxiety Behaviors Mediated by Expression of Alzheimer's Disease-Linked Ps1 Variants Are Rescued by Microglial Depletion.

Alzheimer's disease (AD) is a progressive neurodegenerative disorder that presently affects an estimated 5.7 million Americans. Understanding the basis for this disease is key for the development of a future successful treatment. In this effort, we previously reported that mouse prion protein-promoter-driven, ubiquitous expression of familial AD (FAD)-linked human PSEN1 variants in transgenic mice impairs environmental enrichment (EE)-induced proliferation and neurogenesis of adult hippocampal neural progenitor cells (AHNPCs) and in a non-cell autonomous manner. These findings were confirmed in PS1M146V/+ mice that harbor an FAD-linked mutation in the endogenous PSEN1 gene. We now demonstrate that CSF1R antagonist-mediated microglial depletion in transgenic male mice expressing mutant presenilin 1 (PS1) or PS1M146V/+ "knock-in" mice leads to a complete rescue of deficits in proliferation, differentiation and survival of AHNPCs. Moreover, microglia depletion suppressed the heightened baseline anxiety behavior observed in transgenic mice expressing mutant PS1 and PS1M146V/+ mice to levels observed in mice expressing wild-type human PS1 or nontransgenic mice, respectively. These findings demonstrate that in mice expressing FAD-linked PS1, microglia play a critical role in the regulation of EE-dependent AHNPC proliferation and neurogenesis and the modulation of affective behaviors.SIGNIFICANCE STATEMENT Inheritance of mutations in genes encoding presenilin 1 (PS1) causes familial Alzheimer's disease (FAD). Mutant PS1 expression enhances the levels and assembly of toxic Aβ42 peptides and impairs the self-renewal and neuronal differentiation of adult hippocampal neural progenitor cells (AHNPCs) following environmental enrichment (EE) that is associated with heightened baseline anxiety. We now show that microglial depletion fully restores the EE-mediated impairments in AHNPC phenotypes and suppresses the heightened baseline anxiety observed in mice expressing FAD-linked PS1. Thus, we conclude that the memory deficits and anxiety-related behaviors in patients with PS1 mutations is a reflection not just of an increase in the levels of Aβ42 peptides, but to impairments in the self-renewal and neuronal differentiation of AHNPCs that modulate affective behaviors.

Treadmill exercise decreases β-amyloid burden in APP/PS1 transgenic mice involving regulation of the unfolded protein response

The accumulation of β-amyloid protein (Aβ) in the brain is one of major pathological hallmarks of Alzheimer's disease (AD). Overactivation of the unfolded protein response (UPR) signaling has been reported to lead to β-amyloidogenesis. The current study aimed to investigate the effects of treadmill exercise on UPR signaling and the Aβ production and to demonstrate whether exercise-induced Aβ reduction was associated with changes in UPR signaling. Three-month old male APP/PS1 transgenic and wild-type mice were subjected to treadmill exercise for 3 months. At the end of exercise (6 months old), the levels of Aβ plaques and soluble forms of Aβ, and proteins involve in the unfolded protein response (UPR) were analyzed in the hippocampus. Three months of treadmill exercise resulted in a robust reduction in Aβ plaques and soluble forms of Aβ in the hippocampus of APP/PS1 mice. This was accompanied by a significant decrease in β-site amyloid precursor protein-cleaving enzyme 1 (BACE1) and presenilin-1 (PS1) expression. Meanwhile, we found that treadmill exercise down-regulated the expression of GRP78 and inhibited activation of PERK, eIF2α, and ATF4, reflecting the involvement of the UPR signaling. Overall, our findings suggest that treadmill exercise may suppresse the overactivation of the UPR signaling as well as inhibit the amyloidogenic pathway in APP/PS1 mice, thus may serve as an useful approach for the prevention and treatment of AD.

TRIGONELLA FOENUM-GRAECUM L. EXHIBITS ESTROGENIC EFFECT THROUGH PRESENILIN 2 GENE EXPRESSION IN THE BREAST CANCER CELL LINE MCF-7

Objective: The objective of this study is to investigate the estrogenic and antiestrogenic activity of Fenugreek seeds, Trigonella foenum-graecum L. in the estrogen-dependent breast cancer cell line, MCF-7, including its effect on the expression of estrogen-dependent presenilin 2 (pS2) gene.Methods: An activity guided fractionation was carried out with extracts from fenugreek seeds in MCF-7 cells. Cytotoxic activity assays were conducted with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium (MTT) assay. Most fractions were also tested also tested in media with estradiol 10 nM We also analysed the expression of pS2 gene. For the analysis of pS2 gene expression we employed PCR primers for pS2 and for β-actin as a housekeeping gene using real-time polymerase chain reaction (RT-PCR).Results: Based on cytotoxic activity assay in MCF-7, the active fractions are ethyl acetic fraction and its phases ethyl acetic (EA) 2 and EA 2.2. The most active fraction was EA 2.2 (IC50=27.129 ppm), which exhibited a biphasic effect; at low concentrations, it stimulated the growth, and at high concentrations it showed strong cytotoxic effects. EA2.2 fraction in concentration 20 ppm, also could induce pS2 gene expression in media with and without estrogen.Conclusion: The most active fraction was the ethyl acetate phase and further subfractions. The most active fraction also induced the expression of pS2 gene which was studied by RT-PCR.

TRIGONELLA FOENUM-GRAECUM L. EXHIBITS ESTROGENIC EFFECT THROUGH PRESENILIN 2 GENE EXPRESSION IN THE BREAST CANCER CELL LINE MCF-7

Objective: The objective of this study is to investigate the estrogenic and antiestrogenic activity of Fenugreek seeds, Trigonella foenum-graecum L. in the estrogen-dependent breast cancer cell line, MCF-7, including its effect on the expression of estrogen-dependent presenilin 2 (pS2) gene.Methods: An activity guided fractionation was carried out with extracts from fenugreek seeds in MCF-7 cells. Cytotoxic activity assays were conducted with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium (MTT) assay. Most fractions were also tested also tested in media with estradiol 10 nM We also analysed the expression of pS2 gene. For the analysis of pS2 gene expression we employed PCR primers for pS2 and for β-actin as a housekeeping gene using real-time polymerase chain reaction (RT-PCR).Results: Based on cytotoxic activity assay in MCF-7, the active fractions are ethyl acetic fraction and its phases ethyl acetic (EA) 2 and EA 2.2. The most active fraction was EA 2.2 (IC50=27.129 ppm), which exhibited a biphasic effect; at low concentrations, it stimulated the growth, and at high concentrations it showed strong cytotoxic effects. EA2.2 fraction in concentration 20 ppm, also could induce pS2 gene expression in media with and without estrogen.Conclusion: The most active fraction was the ethyl acetate phase and further subfractions. The most active fraction also induced the expression of pS2 gene which was studied by RT-PCR.

MicroRNA-133a inhibits gastric cancer cells growth, migration, and epithelial-mesenchymal transition process by targeting presenilin 1.

Gastric cancer (GC) is one of the most common malignancies and a leading cause of cancer-related death worldwide. Accumulating evidence reported that microRNA (miR)-133a was involved in GC. This study aimed to investigate the function and mechanism of miR-133a in the development and progression of GC. The expression of miR-133a and presenilin 1 (PSEN1) in two GC cell lines, SGC-7901 and BGC-823, were inhibited and overexpressed by transient transfections. Thereafter, cell viability, migration, and apoptosis were measured by trypan blue exclusion assay, transwell migration assay, and flow cytometry assay, respectively. Dual-luciferase reporter assay was conducted to verify whether PSEN1 was a direct target of miR-133a. Furthermore, quantitative real-time polymerase chain reaction and Western blot analysis were mainly performed to assess the expression changes of epithelial-mesenchymal transition (EMT)-associated proteins, apoptosis-related proteins, and Notch pathway proteins. MiR-133a inhibitor significantly increased cell viability and migration, while miR-133a mimic decreased cell viability, migration, and induced apoptosis. miR-133a suppression accelerated transforming growth factor-β1 (TGF-β1)-induce EMT, as evidenced by upregulation of E-cadherin, and downregulation of N-cadherin, vimentin, and Slug. Of contrast, miR-133a overexpression blocked TGF-β1-induce EMT by altering these factors. PSEN1 was a direct target of miR-133a, and suppression of PSEN1 abolished the promoting functions of miR-133 suppression on cell growth and metastasis. Moreover, PSEN1 inhibition decreased Notch 1, Notch 2, and Notch 3 protein expressions. This study demonstrates an antigrowth and antimetastasis role of miR-133a in GC cells. Additionally, miR-133a acts as a tumor suppressor may be via targeting PSEN1.

Aluminum toxicity related to SOD and expression of presenilin and CREB in Bombyx mori.

Aluminum (Al) is an important environmental metal factor that can be potentially associated with pathological changes leading to neurotoxicity. The silkworm, Bombyx mori, is an important economic insect and has also been used as a model organism in various research areas. However, the toxicity of Al on silkworm physiology has not been reported. Here, we comprehensively investigate the toxic effects of Al on the silkworm, focusing on its effects on viability and development, superoxide dismutase (SOD) activity, and the expression of presenilin and cAMP response element-binding protein (CREB) in BmE cells and silkworm larvae. BmE cell viability decreased after treatment with aluminum chloride (AlCl3 ) in both dose- and time-dependent manners. When AlCl3 solution was injected into newly hatched fifth instar larvae, both larval weight gain and survival rate were significantly decreased in a manner correlating with AlCl3 dose and developmental stage. Furthermore, when BmE cells and silkworm larvae were exposed to AlCl3 , SOD activity decreased significantly relative to the control group, whereas presenilin expression increased more than twofold. Additionally, CREB and phosphorylated CREB (p-CREB) expression in the heads of fifth instar larvae decreased by 28.0% and 50.0%, respectively. These results indicate that Al inhibits the growth and development of silkworms in vitro and in vivo, altering SOD activity and the expressions of presenilin, CREB, and p-CREB. Our data suggest that B. mori can serve as a model animal for studying Al-induced neurotoxicity or neurodegeneration.

Histological and Behavioral Phenotypes of a Novel Mutated APP Knock-In Mouse.

Gene mutations within amyloid precursor protein (APP or AβPP) and/or presenilin 1 (PS1) genes are determinants of familial Alzheimer's disease (fAD) and remain fundamental for experimental models. Here, we generated a neuronal knock-in mouse (PLB2APP) with mutated human APPSwe/Lon and investigated histopathology and behavioral phenotypes. Additionally, PLB2APP mice were cross-bred with a presenilin (PS1A246E) line to assess the impact of this gene combination. Immunohistochemistry determined amyloid-β (Aβ) pathology, astrogliosis (via GFAP labelling), and neuronal densities in hippocampal and cortical brain regions. One-year old PLB2APP mice showed higher levels of intracellular Aβ in CA1, dentate gyrus, and cortical regions compared to PLBWT controls. Co-expression of PS1 reduced hippocampal but elevated cortical Aβ build-up. Amyloid plaques were sparse in aged PLB2APP mice, and co-expression of PS1 promoted plaque formation. Heightened GFAP expression followed the region-specific pattern of Aβ in PLB2APP and PLB2APP/PS1 mice. Behaviorally, habituation to a novel environment was delayed in 6-month-old PLB2APP mice, and overall home-cage activity was reduced in both lines at 6 and 12 months, particularly during the dark phase. Spatial learning in the water maze was impaired in PLB2APP mice independent of PS1 expression and associated with reduced spatial navigation strategies. Memory retrieval was compromised in PLB2APP mice only. Our data demonstrate that low expression of APP is sufficient to drive histopathological and cognitive changes in mice without overexpression or excessive plaque deposition. AD-like phenotypes were altered by co-expression of PS1, including a shift from hippocampal to cortical Aβ pathology, alongside reduced deficits in spatial learning.

PO-150 Tomatidine inhibits human osteosarcoma cells metastasis by down-regulation of presenilin-1 and the Raf/MEK/ERK pathway

IntroductionTomatidine, the major steroidal alkaloid glycoside presents in the tomato plant, has potent anti-inflammatory and anti-cancer activities. Numerous investigations demonstrated that tomatidine can suppress cancer cell growth and/or induce apoptosis in breast cancer, gastric cancer and lung cancer. However, the effect of tomatidine on human osteosarcoma progression remains uninvestigated. Therefore, we examined the effectiveness of tomatidine against cellular invasion and migration of human osteosarcoma and the underlying mechanisms.Material and methodsAfter treatment with various concentrations of tomatidine, we conducted MTT assay, wound healing assay, Boyden chamber assay, reverse transcription polymerase chain reaction (RT-PCR) and western blot to examine U2OS and HOS human osteosarcoma cell lines.Results and discussionsOur results found that tomatidine significantly reduced motility, migration and invasion without affecting cell proliferation in U2OS and HOS cells. In addition, tomatidine decreased the protein expression of presenilin-1 (PS1), phosphorylation expression in the extracellular signal-regulated kinase 1/2 (ERK1/2), mitogen-activated protein kinase-ERK kinase (MEK), and c-Raf signalling proteins in U2OS and HOS cells. Furthermore, transfection with PS1 siRNA inhibited the migration and invasion capacity of U2OS and HOS cells. Co-treatment with ERK siRNA and tomatidine further reduced U2OS cells migration and invasion.ConclusionThese results indicated that tomatidine inhibits human osteosarcoma U2OS and HOS cells motility, migration and invasion by down-regulating PS1 expressions via c-Raf/MEK/ERK pathways. Tomatidine has the potential to serve as an anti-metastatic agent for treating osteosarcoma.

Modulation of the gamma-secretase activity as a therapy against human hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) is the fifth most common tumor worldwide. The discovery of new therapies against HCC is highly dependable on finding molecules which play essential roles in cancer development. The objective of this study was to evaluate the activity of gamma secretase (γ-secretase), and the antitumor effects of a γ-secretase inhibitor (GSI) in HCC. The expression of presenilin 1 (PS1), a core component of γ-secretase, was examined by Western blot. Activity of γ-secretase was measured by a luciferase-based reporter system, and cancer cells were transfected either with PS1 dominant negative mutant (PS1D385A) or treated with GSI. Expression of PS1 was increased in HCC tissue and several HCC cell lines, which were accompanied by elevated γ-secretase activity. Cell colony formation and cell proliferation were decreased upon treatment with GSI but not with PS1D385A transfection. GSIs may be appealing candidates for the development of new therapies against HCC.

PO-154 Progesterone through progesterone receptor-B inhibits invasion of human breast cancer cells by targeting cytoplasmic cyclin D1

IntroductionTomatidine, the major steroidal alkaloid glycoside presents in the tomato plant, has potent anti-inflammatory and anti-cancer activities. Numerous investigations demonstrated that tomatidine can suppress cancer cell growth and/or induce apoptosis in breast cancer, gastric cancer and lung cancer. However, the effect of tomatidine on human osteosarcoma progression remains uninvestigated. Therefore, we examined the effectiveness of tomatidine against cellular invasion and migration of human osteosarcoma and the underlying mechanisms.Material and methodsAfter treatment with various concentrations of tomatidine, we conducted MTT assay, wound healing assay, Boyden chamber assay, reverse transcription polymerase chain reaction (RT-PCR) and western blot to examine U2OS and HOS human osteosarcoma cell lines.Results and discussionsOur results found that tomatidine significantly reduced motility, migration and invasion without affecting cell proliferation in U2OS and HOS cells. In addition, tomatidine decreased the protein expression of presenilin-1 (PS1), phosphorylation expression in the extracellular signal-regulated kinase 1/2 (ERK1/2), mitogen-activated protein kinase-ERK kinase (MEK), and c-Raf signalling proteins in U2OS and HOS cells. Furthermore, transfection with PS1 siRNA inhibited the migration and invasion capacity of U2OS and HOS cells. Co-treatment with ERK siRNA and tomatidine further reduced U2OS cells migration and invasion.ConclusionThese results indicated that tomatidine inhibits human osteosarcoma U2OS and HOS cells motility, migration and invasion by down-regulating PS1 expressions via c-Raf/MEK/ERK pathways. Tomatidine has the potential to serve as an anti-metastatic agent for treating osteosarcoma.

The presenilin loop region is essential for glycogen synthase kinase 3 β (GSK3β) mediated functions on motor proteins during axonal transport.

Neurons require intracellular transport of essential components for function and viability and defects in transport has been implicated in many neurodegenerative diseases including Alzheimer's disease (AD). One possible mechanism by which transport defects could occur is by improper regulation of molecular motors. Previous work showed that reduction of presenilin (PS) or glycogen synthase kinase 3 beta (GSK3β) stimulated amyloid precursor protein vesicle motility. Excess GSK3β caused transport defects and increased motor binding to membranes, while reduction of PS decreased active GSK3β and motor binding to membranes. Here, we report that functional PS and the catalytic loop region of PS is essential for the rescue of GSK3β-mediated axonal transport defects. Disruption of PS loop (PSΔE9) or expression of the non-functional PS variant, PSD447A, failed to rescue axonal blockages in vivo. Further, active GSK3β associated with and phosphorylated kinesin-1 in vitro. Our observations together with previous work that showed that the loop region of PS interacts with GSK3β propose a scaffolding mechanism for PS in which the loop region sequesters GSK3β away from motors for the proper regulation of motor function. These findings are important to uncouple the complex regulatory mechanisms that likely exist for motor activity during axonal transport in vivo.

Pigment Epithelium-Derived Factor Plays a Role in Alzheimer\u2019s Disease by Negatively Regulating A\u03b242

Alzheimer’s disease (AD) is the most common cause of dementia. Pigment epithelium-derived factor (PEDF), a unique neurotrophic protein, decreases with aging. Previous reports have conflicted regarding whether the PEDF concentration is altered in AD patients. In addition, the effect of PEDF on AD has not been documented. Here, we tested serum samples of 31 AD patients and 271 normal controls. We found that compared to PEDF levels in young and middle-aged control subjects, PEDF levels were reduced in old-aged controls and even more so in AD patients. Furthermore, we verified that PEDF expression was much lower and amyloid β-protein (Aβ)42 expression was much higher in senescence-accelerated mouse prone 8 (SAMP8) strain mice than in senescence-accelerated mouse resistant 1 (SAMR1) control strain mice. Accordingly, high levels of Aβ42 were also observed in PEDF knockout (KO) mice. PEDF notably reduced cognitive impairment in the Morris water maze (MWM) and significantly downregulated Aβ42 in SAMP8 mice. Mechanistically, PEDF downregulated presenilin-1 (PS1) expression by inhibiting the c-Jun N-terminal kinase (JNK) pathway. Taken together, our findings demonstrate for the first time that PEDF negatively regulates Aβ42 and that PEDF deficiency with aging might play a crucial role in the development of AD.

Targeting Renin-Angiotensin System Against Alzheimer's Disease.

Renin Angiotensin System (RAS) is a hormonal system that regulates blood pressure and fluid balance through a coordinated action of renal, cardiovascular, and central nervous systems. In addition to its hemodynamic regulatory role, RAS involves in many brain activities, including memory acquisition and consolidation. This review has summarized the involvement of RAS in the pathology of Alzheimer’s disease (AD), and the outcomes of treatment with RAS inhibitors. We have discussed the effect of brain RAS in the amyloid plaque (Aβ) deposition, oxidative stress, neuroinflammation, and vascular pathology which are directly and indirectly associated with AD. Angiotensin II (AngII) via AT1 receptor is reported to increase brain Aβ level via different mechanisms including increasing amyloid precursor protein (APP) mRNA, β-secretase activity, and presenilin expression. Similarly, it was associated with tau phosphorylation, and reactive oxygen species generation. However, these effects are counterbalanced by Ang II mediated AT2 signaling. The protective effect observed with angiotensin receptor blockers (ARBs) and angiotensin converting enzyme inhibitors (ACEIs) could be as the result of inhibition of Ang II signaling. ARBs also offer additional benefit by shifting the effect of Ang II toward AT2 receptor. To conclude, targeting RAS in the brain may benefit patients with AD though it still requires further in depth understanding.

Cardiac adenovirus-associated viral Presenilin 1 gene delivery protects the left ventricular function of the heart via regulating RyR2 function in post-ischaemic heart failure

Post-ischaemic heart failure is a major cause of death worldwide. Reperfusion of infarcted heart tissue after myocardial infarction has been an important medical intervention to improve outcomes. However, disturbances in Ca2+ and redox homeostasis at the cellular level caused by ischaemia/reperfusion remain major clinical challenges. In this study, we investigated the potential of adeno-associated virus (AAV)-9-mediated cardiac expression of a Type-2 ryanodine receptor (RyR2) degradation-associated gene, Presenilin 1 (PSEN1), to combat post-ischaemic heart failure. Adeno-associated viral PSEN1 gene delivery elevated PSEN1 protein expression in a post-infarction rat heart failure model, and this administration normalised the contractile dysfunction of the failing myocardium in vivo and in vitro by reversing myocardial Ca2+ handling and function. Moreover, PSEN1 gene transfer to failing cardiomyocytes reduced sarcoplasmic reticulum (SR) Ca2+ leak, thereby restoring the diminished intracellular Ca2+ transients and SR Ca2+ load. Moreover, PSEN1 gene transfer reversed the phosphorylation of RyR2 in failing cardiomyocytes. However, selective autophagy inhibition did not prevent the PSEN1-induced blockade of RyR2 degradation, making the participation of autophagy in PSEN1-associated RyR2 degradation unlikely. Our results established a role of the cardiac expression of PSEN1 with AAV9 vectors as a promising therapeutic approach for post-ischaemic heart failure.

Anti-amyloidgenic and neurotrophic effects of tetrahydroxystilbene glucoside on a chronic mitochondrial dysfunction rat model induced by sodium azide.

Alzheimer's disease (AD) is an irreversible neurodegenerative brain disorder with complex pathogenesis. Emerging evidence indicates that there is a tight relationship between mitochondrial dysfunction and β-amyloid (Aβ) formation. 2,3,5,4'-Tetrahydroxystilbene-2-O-β-D-glucoside (TSG) is one of the main active components extracted from Polygonum multiflorum. The purpose of the present study was to investigate the effects of TSG on Aβ production and neurotrophins in the brains of rats by using a mitochondrial dysfunction rat model induced by sodium azide (NaN3), an inhibitor of mitochondrial cytochrome c oxidase (COX). NaN3 was administered to rats by continuous subcutaneous infusion for 28days via implanted osmotic minipumps to establish the animal model. TSG was intragastrically administered starting 24h after the operation. The activity of mitochondrial COX was measured by a biochemical method. The content of Aβ 1-42 was detected by ELISA. The expression of neurotrophic factors was determined by Western blot and immunohistochemistry. The results showed that NaN3 infusion for 28days induced a decrease in mitochondrial COX activity, an increase in Aβ 1-42 content and the expression of amyloidogenic β-amyloid precursor protein (APP), beta-site APP cleaving enzyme 1 (BACE1) and presenilin 1 (PS1), and a decline in the expression of neurotrophins in the hippocampus of rats. Intragastrical administration of TSG elevated mitochondrial COX activity, decreased Aβ 1-42 content and the expression of APP, BACE1 and PS1, and enhanced the expression of nerve growth factor, brain-derived neurotrophic factor (BDNF) and its receptor tropomyosin-related kinase B (TrkB) in the hippocampus of NaN3-infused rats. These findings suggest that TSG may be beneficial in blocking or slowing the progression of AD by enhancing mitochondrial function, decreasing Aβ production and increasing neurotrophic factors at some extent.

Interactions of Neuronal Calcium Sensor Dream with Zinc

Maria J. Santiago Estevez and Jaroslava Miksovska Department of Chemistry and Biochemistry, Florida International University Neuronal calcium sensors regulate several physiological processes in the brain and are linked to numerous pathological conditions such as autism, Parkinson and Alzheimer disease. Downstream regulatory element antagonist modulator (DREAM) is among the neuronal calcium sensor family, it is an EF-hand protein highly expressed in the central nervous system in various areas such as the hippocampus and the neural cortex. It is responsible for regulating the kinetics of potassium channels, gene expression, calcium homeostasis and enzymatic activity of presenilin. The characterization of the metal-binding properties of DREAM and how it affects DREAM structure and DREAM interactions with effector proteins is fundamental to understand its biological function. Essential metals like Mg2+, Zn2+ and Ca2+ play extremely important roles in biological processes through direct interactions with proteins. DREAM carries out two Ca2+ binding EF hands and one Mg2+ binding EF hand, however, DREAM binding to other biologically significant metals is not very well known. Interactions of DREAM with Zn2+ have been monitored by using intrinsic and extrinsic fluorescent probes. Data shows that Zn2+ associates to DREAM with Kd ∼ 200 μM. Zn2+ and it does not compete for the same binding site as Ca2+ as the changes in the protein tertiary structure are distinct from those observed upon Ca2+association. Considering increased concentration of Zn2+ in neuronal tissue (150 - 200 μM), these results point towards the potential role of Zn2+ in modulating DREAM interactions with other intracellular proteins.

Presenilin1/γ-secretase protects neurons from glucose deprivation-induced death by regulating miR-212 and PEA15.

Reduced cerebral glucose utilization is found in aged individuals and often is an early sign of neurodegeneration. Here, we show that under glucose deprivation (GD) conditions, decreased expression of presenilin 1 (PS1) results in decreased neuronal survival, whereas increased PS1 increases neuronal survival. Inhibition of γ-secretase also decreases neuronal survival under GD conditions, which suggests the PS1/γ-secretase system protects neurons from GD-induced death. We also show that neuronal levels of the survival protein, phosphoprotein enriched in astrocytes at ∼15 kDa (PEA15), and its mRNA are regulated by PS1/γ-secretase. Furthermore, down-regulation of PEA15 decreases neuronal survival under reduced glucose conditions, whereas exogenous PEA15 increases neuronal survival even in the absence of PS1, which indicates that PEA15 promotes neuronal survival under GD conditions. The absence or reduction of PS1, as well as γ-secretase inhibitors, increases neuronal miR-212, which targets PEA15 mRNA. PS1/γ-secretase activates the transcription factor, cAMP response element-binding protein, regulating miR-212, which targets PEA15 mRNA. Taken together, our data show that under conditions of reduced glucose, the PS1/γ-secretase system decreases neuronal losses by suppressing miR-212 and increasing its target survival factor, PEA15. These observations have implications for mechanisms of neuronal death under conditions of reduced glucose and may provide targets for intervention in neurodegenerative disorders.-Huang, Q., Voloudakis, G., Ren, Y., Yoon, Y., Zhang, E., Kajiwara, Y., Shao, Z., Xuan, Z., Lebedev, D., Georgakopoulos, A., Robakis, N. K. Presenilin1/γ-secretase protects neurons from glucose deprivation-induced death by regulating miR-212 and PEA15.

Chronic Cerebral Hypoperfusion Promotes Amyloid-Beta Pathogenesis via Activating β/γ-Secretases.

Chronic cerebral hypoperfusion (CCH) contributes to the Alzheimer's-like pathogenesis, but the relationship between CCH and the occurrence of Alzheimer's disease (AD) remains obscure. The aim is to elucidate the potential pathophysiological mechanism in the field of amyloid-beta (Aβ) pathology induced by CCH. A rat model of CCH has been developed with permanent bilateral occlusion of common carotid arteries (BCCAO). The cognitive function of rats was tested by the Morris water maze. The levels of Aβ (Aβ40 and Aβ42) and soluble amyloid precursor protein (sAPP: sAPPα and sAPPβ) were determined by enzyme linked immunosorbent assay. The expression of beta-site amyloid precursor protein cleaving enzyme 1 (BACE1), presenilin1 (PS1), nicastrin (NCT), anterior pharynx-defective 1alpha (Aph-1α) and presenilin enhancer 2 (Pen-2), sAPPα and sAPPβ were detected by Western blotting. Morris water maze test showed that CCH induced decline in learning and memory related to Aβ levels in the hippocampus. The levels of sAPPα, ADAM10 and ADAM17 in the hippocampus of CCH rats were higher than the control ones (P < 0.05); the levels of sAPPβ, BACE and BACE1 increased more than the control ones (P < 0.05). CCH intervention (1-week or 4-week) markedly increased the expression of PS1, Aph-1α and Pen-2 in the hippocampus of rats, but had no effect on NCT. CCH contributed to cognitive impairment and altered the amyloidogenic and non-amyloidogenic pathway of APP processing by boosting the activity of β-secretase/γ-secretase and α-secretase respectively. The non-amyloidogenic pathway can't overcome the damage role of the amyloidogenic pathway in the process of chronic cerebral hypoperfusion which promotes amyloid-beta pathogenesis.

NEPRILYSIN IS THE MAJOR ENZYME TO DEGRADE EXTRACELLULAR Aβ IN NOVEL AD ANIMAL MODELS

Alzheimer's disease (AD) is the most common cause of dementia, which is pathologically characterized by the presence of senile plaques composed of amyloid β peptide (Aβ). In sporadic AD, it is hypothesized that an age-related decrease in extracellular Aβ catabolism causes Aβ accumulation. Neprilysin (NEP) and insulin degrading enzyme (IDE) are two major candidates considered to degrade extracellular Aβ in brain. They have, however, never been compared to each other in a side-by-side manner in vivo. In order to achieve objective comparison, we crossbred our single App knock-in mice, AppNL-F mice (NL-F mice) with NEP-knockout (KO) and IDE-KO mice. We observed an increase in the insoluble Aβ42 in NL-F x NEP-KO mice and, by contrast, a decrease in NL-F x IDE-KO mice by ELISA. NEP deficiency significantly increased pathological Aβ deposition in NL-F mice, whereas IDE deficiency decreased Aβ deposition. Expression of NEP was increased in NL-F x IDE-KO mice compared to NL-F mice, suggesting that the decrease of Aβ in NL-F x IDE-KO mice was likely a consequence of compensatory NEP upregulation. Expression of presenilin 1, BACE-1 and C-terminal fragment-β (CTF-β) remained unchanged in NL-F x IDE-KO mice, indicating that the decrease of Aβ in the double mutant mice was not due to alteration of intracellular APP processing. These observations establish NEP as the major Aβ-degrading enzyme in vivo. We conclude that NEP can become an ideal therapeutic target for reducing Aβ burdens in the preclinical stage of AD patients and that our new generation AD mice are relevant models for AD prevention study. Using a similar strategy, we are now trying to generate a novel non-human primate model of AD.

Intermittent hypoxia training blunts cerebrocortical presenilin 1 overexpression and amyloid-β accumulation in ethanol-withdrawn rats.

Abrupt cessation of chronic alcohol consumption triggers signaling cascades that harm vulnerable brain regions and produce neurobehavioral deficits. We have demonstrated that a program of intermittent, normobaric hypoxia training (IHT) in rats prevents brain damage and neurobehavioral impairment resulting from abrupt ethanol withdrawal (EW). Moreover, EW induced expression of stress-activated protein kinase p38 and presenilin 1 (PS1), the catalytic subunit of γ-secretase that produces the neurotoxic amyloid-β (Aβ) peptides Aβ40 and Aβ42. We tested the hypotheses that 1) IHT limits EW-induced activation of the p38-PS1 axis, thereby attenuating γ-secretase activation and Aβ accumulation, and 2) EW disables heat shock protein 25 (HSP25), a p38 substrate, molecular chaperone, and antioxidant, and provokes protein carbonylation in a manner suppressed by IHT. Adult male rats completed two cycles of a 4-wk ethanol diet (6.5% wt/vol) and a 3-wk EW or an isocaloric, dextrin-based control diet. A 20-day IHT program (5-8 daily cycles of 5-10 min of 9.5-10% fractional inspired O2 + 4 min of 21% fractional inspired O2) was administered during the first EW phase. After the second EW phase, the brain was excised and the prefrontal cortex extracted. PS1, phosphorylated p38 (p-p38), and HSP25 were analyzed by immunoblot, PS1 messenger RNA by quantitative polymerase chain reaction, protein carbonyl content by spectrometry, and Aβ40 and Aβ42 contents by enzyme-linked immunosorbent assay. IHT attenuated the EW-associated increases in PS1, p-p38, Aβ40, Aβ42, and protein carbonyl contents, but not that of PS1 messenger RNA, while preserving functionally competent HSP25 dimers in EW rats. Collectively, these findings suggest that IHT may attenuate EW-induced γ-secretase overactivation by suppressing activation of the p38-PS1 axis and by preventing oxidative protein damage.