MAB343 Sigma-AldrichAnti-APP Antibody, APP 643-695 CT fragment, clone 2.F2.19B4

Dysregulated endoplasmic reticulum (ER) calcium (Ca(2+)) signaling is reported to play an important role in Alzheimer disease (AD) pathogenesis. The role of ER Ca(2+) release channels, the ryanodine receptors (RyanRs), has been extensivelys tudied in AD models and RyanR expression and activity are upregulated in the brains of various familial AD (FAD) models.The objective of this study was to utilize a genetic approach to evaluate the importance of RyanR type 3 (RyanR3) in the context of AD pathology.The expression of RyanR3 was also elevated in hippocampus of APPPS1 mice (Thy1-APPKM670/671NL, Thy1-PS1L166P).In young (≤ 3 mo) APPPS1 mice, the deletion of RyanR3 increased hippocampal neuronal network excitability and accelerated AD pathology, leading to mushroom spine loss and increased amyloid accumulation. In contrast, deletion of RyanR3 in older APPPS1 mice (≥ 6 mo) rescued network excitability and mushroom spine loss, reduced amyloid plaque load and reduced spontaneous seizure occurrence.Our data suggests a dual role for RyanR3 in AD pathology. In young AD neurons, RyanR3 protects AD neurons from synaptic and network dysfunction. In older AD neurons, increased RyanR3 activity contributes to pathology. These results imply that blockade of RyanR3 may be beneficial for those in the later stages of the disease, but RyanR activators may be beneficial when used prior to disease onset or in its initial stages. Caffeine is an activator of RyanRs and our results may help to explain a complex epidemiological connection between coffee consumption in mid-life and risk of AD development in old age.

Based on the observations that Grb2 overexpression altered the trafficking route of amyloid-β protein precursor (AβPP) by inhibiting its release via exosomal vesicles, and subsequently increased its endogenous level, in the present study we aimed to elucidate the mechanism of traffic impairment and the role of different Grb2 domains in this process. We found that the N-SH3 domain of Grb2 was involved in the protein vesicular localization. The C-SH3 domain could also form very small puncta, but were not characteristic Grb2 containing vesicles. Vesicles containing the N-SH3-SH2 domain had a mixed population of early and late endosomes but C-SH3-SH2 domain containing vesicles were of early endosomal type. The N-SH3 domain therefore seems to be involved in the maturation of early endosomes to late endosomes. Almost all the features shown by overexpression of full-length type Grb2, for example, entrapment of endogenous AβPP in vesicles, affecting the turnover of AβPP in terms of decrease in exosomal release and increase in endogenous concentration of the protein, could be reproduced by the N-SH3-SH2 domain and, to a very limited extent, by the C-SH3-SH2 domain. The middle SH2 domain alone did not show any involvement in AβPP trafficking. By mutational analysis of both N and C terminal SH3 domains, attempts were made to elucidate the molecular basis of this functional anomaly.

Lifelong latent infections of the trigeminal ganglion by the neurotropic herpes simplex virus type 1 (HSV-1) are characterized by periodic reactivation. During these episodes, newly produced virions may also reach the central nervous system (CNS), causing productive but generally asymptomatic infections. Epidemiological and experimental findings suggest that HSV-1 might contribute to the pathogenesis of Alzheimer's disease (AD). This multifactorial neurodegenerative disorder is related to an overproduction of amyloid beta (Aβ) and other neurotoxic peptides, which occurs during amyloidogenic endoproteolytic processing of the transmembrane amyloid precursor protein (APP). The aim of our study was to identify the effects of productive HSV-1 infection on APP processing in neuronal cells. We found that infection of SH-SY5Y human neuroblastoma cells and rat cortical neurons is followed by multiple cleavages of APP, which result in the intra- and/or extra-cellular accumulation of various neurotoxic species. These include: i) APP fragments (APP-Fs) of 35 and 45 kDa (APP-F35 and APP-F45) that comprise portions of Aβ; ii) N-terminal APP-Fs that are secreted; iii) intracellular C-terminal APP-Fs; and iv) Aβ(1-40) and Aβ(1-42). Western blot analysis of infected-cell lysates treated with formic acid suggests that APP-F35 may be an Aβ oligomer. The multiple cleavages of APP that occur in infected cells are produced in part by known components of the amyloidogenic APP processing pathway, i.e., host-cell β-secretase, γ-secretase, and caspase-3-like enzymes. These findings demonstrate that HSV-1 infection of neuronal cells can generate multiple APP fragments with well-documented neurotoxic potentials. It is tempting to speculate that intra- and extracellular accumulation of these species in the CNS resulting from repeated HSV-1 reactivation could, in the presence of other risk factors, play a co-factorial role in the development of AD.

In order to access beta-secretase (BACE1), and enzyme strongly implicated in the cause of Alzheimer's disease, inhibitors must possess sufficient lipophilicity to traverse two lipid bilayers. Current drug candidates, which are almost totally peptide-derived, are thus inefficient because cell permeability presents a serious limiting factor. In this study, lipophilic alkylated (C(10)-C(5)) flavanones from Sophora flavescens were examined for their inhibitory effects against beta-secretase. Lavandulyl flavanones (1, 2, 5, 6, and 8) showed potent beta-secretase inhibitory activities with IC(50)s of 5.2, 3.3, 8.4, 2.6, and 6.7microM, respectively, while no significant activity was observed in the corresponding hydrated lavandulyl flavanones (4 and 7) and prenylated flavanone (3). As we expected, lavandulyl flavanones reduced Abeta secretion dose-dependently in transfected human embryonic kidney (HEK-293) cells. In kinetic studies, all compounds screened were shown to be noncompetitive inhibitor.

The release of amyloid precursor protein (APP) intracellular domain (AICD) may be triggered by extracellular cues through gamma-secretase-dependent cleavage. AICD binds to Fe65, which may have a role in AICD-dependent signalling; however, the functional ligand has not been characterized. In this study, we have identified TAG1 as a functional ligand of APP. We found that, through an extracellular interaction with APP, TAG1 increased AICD release and triggered Fe65-dependent activity in a gamma-secretase-dependent manner. TAG1, APP and Fe65 colocalized in the neural stem cell niche of the fetal ventricular zone. Neural precursor cells from TAG1-/-, APP-/- and TAG1-/-;APP-/- mice had aberrantly enhanced neurogenesis, which was significantly reversed in TAG1-/- mice by TAG1 or AICD but not by AICD mutated at the Fe65 binding site. Notably, TAG1 reduced normal neurogenesis in Fe65+/+ mice. Abnormally enhanced neurogenesis also occurred in Fe65-/- mice but could not be reversed by TAG1. These results describe a TAG1-APP signalling pathway that negatively modulates neurogenesis through Fe65.

Alzheimer's disease (AD) is characterized by beta-amyloid plaques, tau pathology, cholinergic cell death and inflammation. The aim of this study was to investigate whether beta-amyloid is generated, released and extracellularly deposited in organotypic brain slices. In developing slices, no amyloid-precursor protein (APP) was detectable; however, there was a strong upregulation in aging slices. In such slices, rat beta-amyloid(1-42) and -(1-40) peptides were found using four sequence-specific antibodies. APP and beta-amyloid were expressed in neurons and to a lesser extent in astrocytes. Beta-amyloid was secreted into the medium. Beta-amyloid was located extracellularly when aging slices were incubated with medium at pH 6.0 including apolipoprotein E4 (ApoE4). It is concluded that aging organotypic brain slices express beta-amyloid and that acidosis induces cell death with efflux of beta-amyloid and extracellular depositions, which is triggered by ApoE4. This novel in vitro model may enable us to investigate further the pathological cascade for AD and may be useful to explore future therapeutics.

We investigated the morphology and biochemistry of the amyloid-beta (Abeta) peptides produced in TgCRND8 Tg mice carrying combined amyloid precursor protein (APP) Swedish (K670M/N671L) and Indiana (V717F) mutations. Histological analyses employing amyloid-specific staining and electron microscopy revealed that the TgCRND8 Tg mice produce an aggressive pathology, evident as early as 3 months of age, that is a composite of core plaques and peculiar floccular diffuse parenchymal deposits. The Abeta peptides were purified using combined FPLC-HPLC, Western blots, and immunoprecipitation methods and characterized by MALDI-TOF/SELDI-TOF mass spectrometry. The C-terminal APP peptides, assessed by Western blot experiments and mass spectrometry, suggested an alteration in the order of secretase processing, yielding a C-terminal fragment pattern that is substantially different from that observed in sporadic Alzheimer's disease (AD). This modified processing pattern generated longer Abeta peptides, as well as those ending at residues 40/42/43, which may partially explain the early onset and destructive nature of familial AD caused by APP mutations. Despite an aggressive pathology that extended to the cerebellum and white matter, these animals tolerated the presence of an imposing amount of Abeta load. Abeta immunization resulted in an impressive 7-fold reduction in the number of amyloid core plaques and, as previously demonstrated, a significant memory recovery. However, given the phylogenetic distance and the differences in APP processing and Abeta chemistry between Tg mice and AD, caution should be applied in projecting mouse therapeutic interventions onto human subjects.

One of the hallmarks of Alzheimer's disease (AD) is the deposition of beta-amyloid (Abeta) peptides in neuritic plaques. Abeta peptides are derived from sequential cleavage of amyloid precursor protein (APP) by beta- and gamma-secretases. beta-APP cleaving enzyme-1 (BACE1) has been shown to be the major beta-secretase and is a primary therapeutic target for AD. We report here novel BACE1 inhibitory peptidomimetics, which are derived from catalytic domains of BACE1 themselves, instead of APP cleavage sites and are structurally modified by myristoylation in N-terminus for efficient cell permeability. The peptides not only inhibited the formation of APPbeta (a soluble N-terminal fragment of APP cleaved by beta-secretase), but also significantly reduced Abeta40 production. Our results suggest a new approach for identifying inhibitory agents for the treatment of AD.

We have analyzed the metabolic pathway of maturation of APP751 in stably transfected 293 cells, in the presence of either of the cysteine protease inhibitors leupeptin or E-64. Metabolic labeling, followed by immunoprecipitation at various times in the chase with a rabbit polyclonal antibody (anti-BX6) specific to the carboxyl-terminal end of amyloid precursor protein (APP), revealed the accumulation of a novel approximately 22-kDa carboxyl-terminal fragment (22-CTF) in the inhibitor-treated cells. This fragment, which was not detectable in untreated cells, was immunoprecipitated by four separate antibodies to the carboxyl-terminal region of APP as well as by polyclonal and monoclonal antibodies specific to the first 16 amino acids of the beta-peptide domain. Antibodies to the amino-terminal end of APP do not, however, recognize the fragment. Co-treatment of the inhibitor-treated cells with either of the lysosomotropic agents chloroquine or ammonium chloride completely blocked the generation of this fragment but did not significantly affect APP maturation or secretion. All, however, slowed the intracellular turnover of the cell-associated, approximately 9-kDa carboxyl-terminal fragment (c-CTF) produced during constitutive secretion. Densitometric analyses of these results suggest that this non-secretory pathway of APP degradation, mediated by cysteine proteases in an intracellular acidic compartment, accounts for approximately 70% of total APP metabolism and that a key processing intermediate in this pathway is a 22-kDa, beta-peptide-containing APP carboxyl-terminal fragment. It is possible that inefficient degradation of such an intermediate leads to the formation of aggregating beta-peptide.

The approximately 120-kilodalton amyloid beta protein precursor (beta APP) is processed into a complex set of 8- to 12-kilodalton carboxyl-terminal derivatives that includes potentially amyloidogenic forms with the approximately 4-kilodalton amyloid beta protein (beta AP) at or near their amino terminus. In order to determine if these derivatives are processed in a secretory pathway or by the endosomal-lysosomal system, (i) deletion mutants that produce the normal set of carboxyl-terminal derivatives and shortened secreted derivatives were analyzed and (ii) the effect of inhibitors of endosomal-lysosomal processing was examined. In the secretory pathway, cleavage of the beta APP occurs at a single site within the beta AP to generate one secreted derivative and one nonamyloidogenic carboxyl-terminal fragment, whereas, in the endosomal-lysosomal system, a complex set of carboxyl-terminal derivatives is produced that includes the potentially amyloidogenic forms.