Koichi Ando

Amyloid β inhibits ectodomain shedding of N-cadherin via down-regulation of cell-surface NMDA receptor

Dysfunction in the synapse is recognized as an early and the primary pathological process in Alzheimers disease (AD). N-cadherin, an essential adhesion molecule for excitatory synaptic contact, forms a complex with presenilin 1 (PS1) and beta-catenin in the synaptic membrane. N-cadherin is sequentially cleaved by ADAM10 and PS1/gamma-secretase, producing a cytoplasmic fragment, N-cadherin C-terminal fragment (Ncad/CTF2) after NMDA receptor stimulation [Marambaud P, Wen PH, Dutt A, Shioi J, Takashima A, Siman R, Robakis NK (2003) A CBP binding transcriptional repressor produced by the PS1/epsilon-cleavage of N-cadherin is inhibited by PS1 FAD mutations. Cell 114:635-645; Reiss K, Maretzky T, Ludwig A, Tousseyn T, de Strooper B, Hartmann D, Saftig P (2005) ADAM10 cleavage of N-cadherin and regulation of cell-cell adhesion and beta-catenin nuclear signalling. EMBO J 24:1762]. Ncad/CTF2 translocates to the nucleus together with beta-catenin to enhance beta-catenin nuclear signaling [Uemura K, Kihara T, Kuzuya A, Okawa K, Nishimoto T, Bito H, Ninomiya H, Sugimoto H, Kinoshita A, Shimohama S (2006a) Activity-dependent regulation of beta-catenin via epsilon-cleavage of N-cadherin. Biochem Biophys Res Commun 345:951-958]. To examine whether an impairment of N-cadherin metabolism is involved in AD pathogenesis, we investigated the effect of amyloid beta peptide (Abeta) treatment on sequential N-cadherin cleavage. Here, we demonstrate that both synthetic and cell-derived Abeta species inhibit ectodomain shedding of mouse N-cadherin. Inhibition of N-cadherin cleavage by Abeta treatment was suggested to be mediated by the enhanced endocytosis of NMDA receptor, resulting in reduced turnover of N-cadherin. Since both N-cadherin and beta-catenin are essential for synaptic plasticity, impairment of N-cadherin cleavage caused by Abeta may underlie the synapse toxicity involved in AD pathogenesis.

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

J. Neurochem. (2011) 119, 354–363.

N-cadherin-based adhesion enhances Aβ release and decreases Aβ42/40 ratio

In neurons, Presenilin 1(PS1)/γ‐secretase is located at the synapses, bound to N‐cadherin. We have previously reported that N‐cadherin‐mediated cell–cell contact promotes cell‐surface expression of PS1/γ‐secretase. We postulated that N‐cadherin‐mediated trafficking of PS1 might impact synaptic PS1‐amyloid precursor protein interactions and Aβ generation. In the present report, we evaluate the effect of N‐cadherin‐based contacts on Aβ production. We demonstrate that stable expression of N‐cadherin in Chinese hamster ovary cells, expressing the Swedish mutant of human amyloid precursor protein leads to enhanced secretion of Aβ in the medium. Moreover, N‐cadherin expression decreased Aβ42/40 ratio. The effect of N‐cadherin expression on Aβ production was accompanied by the enhanced accessibility of PS1/γ‐secretase to amyloid precursor protein as well as a conformational change of PS1, as demonstrated by the fluorescence lifetime imaging technique. These results indicate that N‐cadherin‐mediated synaptic adhesion may modulate Aβ secretion as well as the Aβ42/40 ratio via PS1/N‐cadherin interactions.

Effect of glycogen synthase kinase 3 β-mediated presenilin 1 phosphorylation on amyloid β production is negatively regulated by insulin receptor cleavage.

Presenilin 1 (PS1), a causative molecule of familial Alzheimers disease (AD), is known to be an unprimed substrate of glycogen synthase kinase 3 β (GSK3β) [Twomey and McCarthy (2006) FEBS Lett 580:4015-4020] and is phosphorylated at serine 353, 357 residues in its cytoplasmic loop region [Kirschenbaum et al. (2001) J Biol Chem 276:7366-7375]. In this report, we investigated the effect of PS1 phosphorylation on AD pathophysiology and obtained two important results--PS1 phosphorylation increased amyloid β (Aβ) 42/40 ratio, and PS1 phosphorylation was enhanced in the human AD brains. Interestingly, we demonstrated that PS1 phosphorylation promoted insulin receptor (IR) cleavage and the IR intracellular domain (IR ICD) generated by γ-secretase led to a marked transactivation of Akt (PKB), which down-regulated GSK3β activity. Thus, the cleavage of IR by γ-secretase can inhibit PS1 phosphorylation in the long run. Taken together, our findings indicate that PS1 phosphorylation at serine 353, 357 residues can play a pivotal role in the pathology of AD and that the dysregulation of this mechanism may be causally associated with its pathology.

Insulin regulates Presenilin 1 localization via PI3K/Akt signaling

Recently, insulin signaling has been highlighted in the pathology of Alzheimers disease (AD). Although the association between insulin signaling and Tau pathology has been investigated in several studies, the interaction between insulin signaling and Presenilin 1 (PS1), a key molecule of amyloid beta (Abeta) pathology, has not been elucidated so far. In this study, we demonstrated that insulin inhibited PS1 phosphorylation at serine residues (serine 353, 357) via phosphatidylinositol 3-kinase (PI3K)/Akt signal pathway and strengthened the trimeric complex of PS1/N-cadherin/beta-catenin, consequently relocalizing PS1 to the cell surface. Since our recent report suggests that PS1/N-cadherin/beta-catenin complex regulates Abeta production, it is likely that insulin signaling affects Abeta pathology by regulating PS1 localization.

Gain of function by phosphorylation in Presenilin 1‐mediated regulation of insulin signaling

J. Neurochem. (2012) 121, 964–973.

Environmental Enrichment ameliorates high fat diet induced memory deficit and β-amyloidosis

P3-q09 Molar extraction accelerates the ageing process of the hippocampus in SAMP8 mice Masatsuna Kawahata 1 , Yumie Ono 2, Akinori Ohno 1, Syouichi Kawamoto 1, Katsuhiko Kimoto 1, Minoru Onozuka 3 1 Dept.of Oral & Maxillofacial Rehabilitatin Kanagawa Dent. Col., Kanagawa, Japan 2 Dept. of Elec. and Bioinformatics, Sch. of Sci. and Eng., Meiji Univ., Kanagawa, Japan 3 Dept. Physiol. and Neurosci. Kanagawa Dent. Col., Kanagawa, Japan

The effect of N-cadherin/Nectin-1 expression on APP cis-dimerization

s / Neuroscience Research 68S (2010) e109–e222 e189 learning and memory function. The regulatory function of IR in neuron may provide new insights into the pathology of AD. doi:10.1016/j.neures.2010.07.2407 P1-n07 MicroRNA-29a decreased in Alzheimer disease brains targets neuron navigator-3 Junichi Satoh 1 , Mao Shioya 1, Hiroko Tabunoki 1, Shinya Obayashi 1, Kunimasa Arima 2, Yuko Saito 3, Tsuyoshi Ishida 4 1 Dept Bioinformatics, Meiji Pharm Univ, Tokyo 2 Dept Psychiatry, NCNP Hosp, Tokyo 3 Dept Lab Med, NCNP Hosp, Tokyo 4 Dept Lab Med, Kohnodai Hosp, IMC, Ichikawa Aims: MicroRNAs (miRNAs) are small noncoding RNAs that regulate translational repression of target mRNAs. Accumulating evidence indicate that various miRNAs, expressed in a spatially and temporally controlled manner in the brain, play a key role in neuronal development. However, at present, the pathological implication of aberrant miRNA expression in neurodegenerative events remains largely unknown. To identify miRNAs closely associated with neurodegeneration, we performed miRNA expression profiling of brain tissues of various neurodegenerative diseases. Methods: We initially studied the frontal cortex derived from three amyotrophic lateral sclerosis (ALS) patients by using a microarray of 723 human miRNAs. This was followed by enlargement of study population with quantitative RT-PCR (qRT-PCR) analysis (n = 21). Results: By microarray analysis, we identified upregulation of miR-29a, miR-29b, and miR-338-3p in ALS brains. However, due to a great interindividual variation, we could not validate these results by qRTPCR, but found significant downregulation of miR-29a in Alzheimer disease (AD) brains. The database search on TargetScan, PicTar, and miRBase Target identified neuron navigator 3 (NAV3), a regulator of axon guidance, as a principal target of miR-29a, and actually NAV3 mRNA levels were elevated in AD brains. MiR-29a-mediated downregulation of NAV3 was verified by the luciferase reporter assay. By immunohistochemistry, NAV3 expression was most evidently enhanced in degenerating pyramidal neurons in the cerebral cortex of AD. Conclusions: These observations suggest the hypothesis that underexpression of miR-29a affects neurodegenerative processes by enhancing neuronal NAV3 expression in AD brains. doi:10.1016/j.neures.2010.07.2408 P1-n08 Involvement of sphingomyelin in the generation of an endogenous seed for Alzheimer amyloid, GA Kohei Yuyama , Katsuhiko Yanagisawa Dept. Alzheimer’s Disease Research, National Center for Geriatrics and Gerontology The assembly of amyloid -protein (A ) into fibrils is an initial event of Alzheimer’s disease (AD). Previous studies suggest that ganglioside-bound A , GA , is an endogenous seed for amyloid fibril formation in AD brain and that GA is generated in the membrane microdomains, comprising cholesterol, sphingomyelin (SM) and GM1 ganglioside (GM1). We have recently demonstrated that endocytic pathway abnormality, which is one of the cell-pathological features of AD, enhances the GM1 accumulation in early endosomes, leading to the GA -dependent amyloidogenesis on the cell surface. In this study, we found that the level of SM also increased in association with endocytic perturbation, which was induced by Rab7 knockdown, in PC12 cells. Next, we treated the cells with GW4869, which is an specific inhibitor for sphingomyelinase, to increase intracellular SM. In the immunocytochemical analysis of GW4869-treated cells, enlarged early endosomes were observed. To obtain direct evidence that SM is involved in the induction of GA -dependent amyloid fibril formation, we incubated PC12 cells with A following pretreatment with GW4869. The marked increase in the level of amyloid fibril formation was observed only in the cell cultures, which had been treated with GW4869. Importantly, the amyloid fibril formation was significantly decreased in the presence of an antibody specific to GA . Conversely, we treated the cells with D609, an inhibitor of SM synthase activity, to reduce intracellular SM. D609 treatment significantly prevented the GAßdependent amyloid fibril formation, which was induced by Rab7 knockdown. Results of this study suggest that SM is one of the key molecules for GA generation and further imply that the interaction of A with membrane lipids is critical in amyloidogenesis in the brain. doi:10.1016/j.neures.2010.07.2409 P1-n10 The effect of N-cadherin/Nectin-1 expression on APP cis-dimerization Megumi Asada 1,2,3 , Kengo Uemura 2,3, Akira Kuzuya 2,3, Nao Yamada 1,3, Masato Maesako 1,3, Kiwamu Watanabe 2,3, Koichi Ando 2,3, Oksana Berezovska 4,3, Bradley T. Hyman 4,3, Ryosuke Takahashi 2,3, Ayae Kinoshita 1,3 1 Human Health Science, Graduate School of Medicine,Kyoto University 2 Dept. Neuro. Kyoto Univ 3 Dept. Neurol. Sappro Med. Univ 4 Alzheimer Research Unit, MassGeneral Institute for Neurodegenerative Diseases, Massachusetts General Hospital In Alzheimer disease, synaptic loss correlates with the severity of cognitive impairment. We have previously demonstrated that N-cadherin,an essential adhesion molecule for excitatory synaptic contact, can interact with amyloid precursor protein (APP) to enhance its dimerization. Dimerization of APP led to various changes in APP metabolism, such as increased sAPP / ratio, enhancement of extracellular A release and, interestingly, reduced A 42/40 ratio. In order to elucidate further the contribution of synaptic adhesion molecules in APP metabolism, we transfected Nectin-1 into HEK293 cells and analyzed APP dimerization. Nectin-1 is an adhesion molecule, which works in concert with N-cadherin to form synaptic contact. We take advantage of a luciferase-based technique to quantify the APP dimerization in a highthroughput manner and demonstrate that Nectin-1 expression enhances APP dimerization similarly to N-cadherin expression to modify APP metabolism. Our result indicates that cell-cell contact have profound effects on A production. doi:10.1016/j.neures.2010.07.2410 P1-n11 Effects of Dihydrohonokiol-B on amyloid 1-42induced neurotoxicity in rat cultured hippocampal cells Yasuhisa Nakayama , Tomoyuki Nakamura Department of Pharmacology, Kansai Medical University Dihydrohonokiol-B (DHH-B), a partially reduced derivative of honokiol isolated from magnolia bark, has been used in traditional Chinese medicine. We previously showed that DHH-B protected pathophysiological concentration of amyloid 25-35 A 25-35)/glutamate-induced cell death. However, protective effects against A 1-42, regarding as the main pathogenic species causing Alzheimer’s disease, and intracellular mechanisms of DHH-B are little known. In this study, we attempted to elucidate the neuroprotective effects of DHHB, especially focusing on the Akt/protein kinase B (PKB) and extracellular signal-regulated kinases (ERK1/2) signaling pathways. Rat hippocampal neuronal cells exposed to A 1-42 increased the number of apoptotic cells and cleaved caspase-3. A 1-42 suppressed phosphorylation of phosphatidylinositol 3-kinase (PI3K) substrate Akt and activated ERK1/2 phosphorylation. Pretreatment of hippocampal cells with DHH-B suppressed increases of cleaved caspase-3 induced by A 1-42 in a dose-dependent manner. DHH-B also recovered suppression of Akt phosphorylation and activation of ERK1/2 phosphorylation by A 1-42. Pretreatment with PI3K inhibitor, LY293002, inhibited the recovering effects by DHH-B such as activation of Akt phosphorylation, but had no effect on suppression of ERK1/2 phosphorylation. In addition, MAPK kinase inhibitor, U0126, inhibited A 1-42-induced ERK1/2 phosphorylation, however, U0126 had no effect on Akt phosphorylation. DHH-B also induced the Ser9 phosphorylation of glycogen synthase kinase-3 under A 1-42 treated conditions. These results suggest that DHHB exerts a protective effect against apoptosis induced by A 1-42 through recovery of Akt and ERK signaling pathway. doi:10.1016/j.neures.2010.07.2411 P1-n12 Alzheimer-like pathology induced by potent ACE inhibition in APP transgenic mouse brain Kun Zou 1 , Junjun Liu 1, Shuyu Liu 1, Chiaki Tanabe 1, Tomoji Maeda 1, Makoto Michikawa 2, Hiroto Komano 1 1 Dept Neurosci, Iwate Med Univ, Yahaba, Japan 2 Dept Alzheimer’s Dis Res, Natl Center Geriatrics and Gerontology, Obu, Japan Amyloid -protein 1-42 (A 42), as well as the elevation of the ratio of A 42 to the shorter major form of A 40, has been identified as important in early events in the pathogenesis of Alzheimer’s disease. We have reported that A 40 has neuroprotective effects against metal-induced oxidative damage and A 42-induced neuronal death. We then identified angiotensinconverting enzyme (ACE) as an A 42-to-A 40-converting enzyme and found

Effects of presenilin 1 phosphorylation on insulin receptor

people with memory dysfunction. However, molecular and cellular effects of TMS on neural tissue have not been well explored. We thus set out to study electrophysiological properties, such as long-term potentiation and neuronal excitability, in cortical and hippocampal slices obtained from 3xTg AD model mice (Oddo et al, 2003), in which genes for amyloid precursor protein, tau, and presenilin-1 have been modified to produce excessive extracellular amyloid deposits as well as in tracellular amyloid accumulation. A group of 3xTg was TMS treated once a day for 1 month chronically. The magnitude of LTP evoked at Schaffer collateral-CA1 pyramidal cell synapses was significantly larger in slices taken from TMS-treated 3xTg mice than in those from unstimulated 3xTg mice. Neural excitability in cingulate cortex pyramidal cells were lower in terms of current-evoked spike frequency, resting membrane potentail and spike half width in slices from the TMS-treated mice. The spike data suggest that large-conductance calcium-activated potassium channels (BK channels) are facilitated by TMS. Thus, TMS alters electrophysi ological properties in the forebrain in plastic manners, some of which might be relevant to TMS-induced cognitive improvement.

Analysis of N-cadherin interacting proteins in Alzheimer's diesase

and 3 6 0.25 year old) were used in this study. Animals were randomly assigned to 2 groups as follows: Group 1 (n1⁄4 6), normal chow and group 2 (n 1⁄4 6), chow supplemented with 2% cholesterol . Cholesterol-treated animals and their matched controls were euthanized 12 weeks later. Results: Cholesterol-enrichded diets inhibit active Akt and m-TOR. Inhibition of Akt is associated with increased levels of GSK3ab, an enzyme that increases bamyloid and phosphorylated tau production. Inhibition of mTOR also causes tau hyperphosphorylation. Conclusions: Our results suggest that cholesterol-enriched diets cause AD-like pathology by mechanisms involving an Akt/mTOR signaling pathway.