Lipophorin receptors genetically modulate neurodegeneration caused by reduction of Psn expression in the aging Drosophila brain.

Mutations in the Presenilin (PSEN) genes are the most common cause of early-onset familial Alzheimer's disease (FAD). Studies in cell culture, in vitro biochemical systems, and knockin mice showed that PSEN mutations are loss-of-function mutations, impairing γ-secretase activity. Mouse genetic analysis highlighted the importance of Presenilin (PS) in learning and memory, synaptic plasticity and neurotransmitter release, and neuronal survival, and Drosophila studies further demonstrated an evolutionarily conserved role of PS in neuronal survival during aging. However, molecular pathways that interact with PS in neuronal survival remain unclear. To identify genetic modifiers that modulate PS-dependent neuronal survival, we developed a new DrosophilaPsn model that exhibits age-dependent neurodegeneration and increases of apoptosis. Following a bioinformatic analysis, we tested top ranked candidate genes by selective knockdown (KD) of each gene in neurons using two independent RNAi lines in Psn KD models. Interestingly, 4 of the 9 genes enhancing neurodegeneration in Psn KD flies are involved in lipid transport and metabolism. Specifically, neuron-specific KD of lipophorin receptors, lpr1 and lpr2, dramatically worsens neurodegeneration in Psn KD flies, and overexpression of lpr1 or lpr2 does not alleviate Psn KD-induced neurodegeneration. Furthermore, lpr1 or lpr2 KD alone also leads to neurodegeneration, increased apoptosis, climbing defects, and shortened lifespan. Lastly, heterozygotic deletions of lpr1 and lpr2 or homozygotic deletions of lpr1 or lpr2 similarly lead to age-dependent neurodegeneration and further exacerbate neurodegeneration in Psn KD flies. These findings show that LpRs modulate Psn-dependent neuronal survival and are critically important for neuronal integrity in the aging brain.

Natural antisense transcription of presenilin in sea urchin reveals a possible role for natural antisense transcription in the general control of gene expression during development

One presenilin gene (PSEN) is expressed in the sea urchin embryo, in the vegetal pole of the gastrula and then mainly in cilia cells located around the digestive system of the pluteus, as we recently have reported. PSEN expression must be accurately regulated for correct execution of these two steps of development. While investigating PSEN expression changes in embryos after expansion of endoderm with LiCl or of ectoderm with Zn2+ by whole-mount in situ hybridization (WISH) and quantitative PCR (qPCR), we detected natural antisense transcription of PSEN. We then found that Endo16 and Wnt5, markers of endo-mesoderm, and of Hnf6 and Gsc, markers of ectoderm, are also sense and antisense transcribed. We discuss that general gene expression could depend on both sense and antisense transcription. This mechanism, together with the PSEN gene, should be included in gene regulatory networks (GRNs) that theorize diverse processes in this species. We suggest that it would also be relevant to investigate natural antisense transcription of PSEN in the field of Alzheimer's disease (AD) where the role of human PSEN1 and PSEN2 is well known.

Converging roles of PSENEN/PEN2 and CLN3 in the autophagy-lysosome system.

PSENEN/PEN2 is the smallest subunit of the γ-secretase complex, an intramembrane protease that cleaves proteins within their transmembrane domains. Mutations in components of the γ-secretase underlie familial Alzheimer disease. In addition to its proteolytic activity, supplementary, γ-secretase independent, functions in the macroautophagy/autophagy-lysosome system have been proposed. Here, we screened for PSENEN-interacting proteins and identified CLN3. Mutations in CLN3 are causative for juvenile neuronal ceroid lipofuscinosis, a rare lysosomal storage disorder considered the most common neurodegenerative disease in children. As mutations in the PSENEN and CLN3 genes cause different neurodegenerative diseases, understanding shared cellular functions of both proteins might be pertinent for understanding general cellular mechanisms underlying neurodegeneration. We hypothesized that CLN3 modulates γ-secretase activity and that PSENEN and CLN3 play associated roles in the autophagy-lysosome system. We applied CRISPR gene-editing and obtained independent isogenic HeLa knockout cell lines for PSENEN and CLN3. Following previous studies, we demonstrate that PSENEN is essential for forming a functional γ-secretase complex and is indispensable for γ-secretase activity. In contrast, CLN3 does not modulate γ-secretase activity to a significant degree. We observed in PSENEN- and CLN3-knockout cells corresponding alterations in the autophagy-lysosome system. These include reduced activity of lysosomal enzymes and lysosome number, an increased number of autophagosomes, increased lysosome-autophagosome fusion, and elevated levels of TFEB (transcription factor EB). Our study strongly suggests converging roles of PSENEN and CLN3 in the autophagy-lysosome system in a γ-secretase activity-independent manner, supporting the idea of common cytopathological processes underlying different neurodegenerative diseases.Abbreviations: Aß, amyloid-beta; AD, Alzheimer disease; APP, amyloid precursor protein; ATP5MC, ATP synthase membrane subunit c; DQ-BSA, dye-quenched bovine serum albumin; ER, endoplasmic reticulum; GFP, green fluorescent protein; ICC, immunocytochemistry; ICD, intracellular domain; JNCL, juvenile neuronal ceroid lipofuscinosis; KO, knockout; LC3, microtubule associated protein 1 light chain 3; NCL, neuronal ceroid lipofuscinoses; PSEN, presenilin; PSENEN/PEN2: presenilin enhancer, gamma-secretase subunit; TAP, tandem affinity purification; TEV, tobacco etch virus; TF, transferrin; WB, Western blot; WT, wild type.

Selective expression of the neurexin substrate for presenilin in the adult forebrain causes deficits in associative memory and presynaptic plasticity.

Presenilins (PS) form the active subunit of the gamma-secretase complex, which mediates the proteolytic clearance of a broad variety of type-I plasma membrane proteins. Loss-of-function mutations in PSEN1/2 genes are the leading cause of familial Alzheimer's disease (fAD). However, the PS/gamma-secretase substrates relevant for the neuronal deficits associated with a loss of PS function are not completely known. The members of the neurexin (Nrxn) family of presynaptic plasma membrane proteins are candidates to mediate aspects of the synaptic and memory deficits associated with a loss of PS function. Previous work has shown that fAD-linked PS mutants or inactivation of PS by genetic and pharmacological approaches failed to clear Nrxn C-terminal fragments (NrxnCTF), leading to its abnormal accumulation at presynaptic terminals. Here, we generated transgenic mice that selectively recreate the presynaptic accumulation of NrxnCTF in adult forebrain neurons, leaving unaltered the function of PS/gamma-secretase complex towards other substrates. Behavioral characterization identified selective impairments in NrxnCTF mice, including decreased fear-conditioning memory. Electrophysiological recordings in medial prefrontal cortex-basolateral amygdala (mPFC-BLA) of behaving mice showed normal synaptic transmission and uncovered specific defects in synaptic facilitation. These data functionally link the accumulation of NrxnCTF with defects in associative memory and short-term synaptic plasticity, pointing at impaired clearance of NrxnCTF as a new mediator in AD.

Loss of presenilin function enhances tau phosphorylation and aggregation in mice.

Mutations in the presenilin (PS/PSEN) genes encoding the catalytic components of γ-secretase accelerate amyloid-ß (Aß) and tau pathologies in familial Alzheimer's disease (AD). Although the mechanisms by which these mutations affect Aß are well defined, the precise role PS/γ-secretase on tau pathology in neurodegeneration independently of Aß is largely unclear. Here we report that neuronal PS deficiency in conditional knockout (cKO) mice results in age-dependent brain atrophy, inflammatory responses and accumulation of pathological tau in neurons and glial cells. Interestingly, genetic inactivation of presenilin 1 (PS1) or both PS genes in mutant human Tau transgenic mice exacerbates memory deficits by accelerating phosphorylation and aggregation of tau in excitatory neurons of vulnerable AD brain regions (e.g., hippocampus, cortex and amygdala). Remarkably, neurofilament (NF) light chain (NF-L) and phosphorylated NF are abnormally accumulated in the brain of Tau mice lacking PS. Synchrotron infrared microspectroscopy revealed aggregated and oligomeric ß-sheet structures in amyloid plaque-free PS-deficient Tau mice. Hippocampal-dependent memory deficits are associated with synaptic tau accumulation and reduction of pre- and post-synaptic proteins in Tau mice. Thus, partial loss of PS/γ-secretase in neurons results in temporal- and spatial-dependent tau aggregation associated with memory deficits and neurodegeneration. Our findings show that tau phosphorylation and aggregation are key pathological processes that may underlie neurodegeneration caused by familial AD-linked PSEN mutations.

Synapsin-Promoted Caveolin-1 Overexpression Maintains Mitochondrial Morphology and Function in PSAPP Alzheimer's Disease Mice.

Mitochondrial dysfunction plays a pivotal role in the Alzheimer's Disease (AD) pathology. Disrupted mitochondrial dynamics (i.e., fusion/fission balance), which are essential for normal mitochondria structure and function, are documented in AD. Caveolin-1 (Cav-1), a membrane/lipid raft (MLR) scaffolding protein regulates metabolic pathways in several different cell types such as hepatocytes and cancer cells. Previously, we have shown decreased expression of Cav-1 in the hippocampus of 9-month (m) old PSAPP mice, while hippocampal overexpression of neuron-targeted Cav-1 using the synapsin promoter (i.e., SynCav1) preserved cognitive function, neuronal morphology, and synaptic ultrastructure in 9 and 12 m PSAPP mice. Considering the central role of energy production in maintaining normal neuronal and synaptic function and survival, the present study reveals that PSAPP mice exhibit disrupted mitochondrial distribution, morphometry, and respiration. In contrast, SynCav1 mitigates mitochondrial damage and loss and enhances mitochondrial respiration. Furthermore, by examining mitochondrial dynamics, we found that PSAPP mice showed a significant increase in the phosphorylation of mitochondrial dynamin-related GTPase protein (DRP1), resulting in excessive mitochondria fragmentation and dysfunction. In contrast, hippocampal delivery of SynCav1 significantly decreased p-DRP1 and augmented the level of the mitochondrial fusion protein, mitofusin1 (Mfn1) in PSAPP mice, a molecular event, which may mechanistically explain for the preserved balance of mitochondria fission/fusion and metabolic resilience in 12 m PSAPP-SynCav1 mice. Our data demonstrate the critical role for Cav-1 in maintaining normal mitochondrial morphology and function through affecting mitochondrial dynamics and explain a molecular and cellular mechanism underlying the previously reported neuroprotective and cognitive preservation induced by SynCav1 in PSAPP mouse model of AD.

Sex Differences in Cognitive Abilities Among Children With the Autosomal Dominant Alzheimer Disease Presenilin 1 E280A Variant From a Colombian Cohort.

Importance: We previously reported that children with the autosomal dominant Alzheimer disease (ADAD) presenilin 1 (PSEN1) E280A variant had early life plasma biomarker findings consistent with amyloid ß overproduction. However, the cognitive functioning of children with this variant has not been characterized vs those without the variant. Objective: To test whether cognitive functioning of children with and without the PSEN1 E280A variant in the same ADAD cohort differed by genetic status (ie, PSEN1 variant) and sex. Design, Setting, and Participants: This cohort study was conducted among 1354 children (including 265 children with the variant) aged 6 to 16 years recruited from the Alzheimer Prevention Initiative Colombia Registry. Participants from the city of Medellín and surrounding suburban areas traveled to the University of Antioquia to undergo all procedures. Participants were administered a Spanish version of the Wechsler Intelligence Scale for Children, Fourth Edition (WISC-IV) to measure general cognitive functioning. Data were analyzed from July through November 2020. Main Outcomes and Measures: Univariate general linear models were used to characterize differences on WISC-IV cognitive performance by genetic status, sex, and the interaction of genetic status with sex. Urbanity, socioeconomic status, and education were entered as covariates. Results: Among 1354 children with ADAD (695 [51.3%] girls; mean [SD] age, 11.64 [2.64] years), there were 265 children with the variant (19.6%) and 1089 children without the variant (80.4%). Children with and without the variant did not differ by demographic variables or performance on WISC-IV indices. Irrespective of genetic status, boys had statistically significantly decreased mean scores on indices for working memory (90.27 [95% CI, 89.21-91.34] vs 92.99 [95% CI, 91.98-93.99]; mean difference = -2.72; P < .001), perceptual reasoning (91.56 [95% CI, 90.47-92.65] vs. 93.27 [95% CI, 91.23-94.30]; mean difference = -1.71; P = .03), and verbal comprehension (88.69 [95% CI, 87.54-89.84] vs. 90.81 [95% CI, 89.73-91.90]; mean difference = -2.12; P = .009) compared with girls. In the interaction between sex and genetic status, boys with the variant had worse mean working memory index performance (88.78 [95% CI, 86.86-90.70]) than girls with the variant (93.75 [95% CI, 91.95-95.55]; mean difference = -4.97; P = .001), as well as boys (91.77 [95% CI, 90.85-92.70]; mean difference = -2.99; P = .04) and girls (92.22 [95% CI, 91.32-93.13]; mean difference = -3.44; P = .009) without the variant. Conclusions and Relevance: This study found that boys with the PSEN1 variant had decreased working memory abilities compared with girls with the variant and boys and girls without the variant, suggesting a sex-specific genetic risk in early life cognitive performance among individuals with the PSEN1 variant. This increased risk of future cognitive difficulties among boys with the variant may have important downstream implications for learning and academic achievement and could be associated with sex differences seen in adulthood on episodic memory measures.

Altered corticostriatal synchronization associated with compulsive-like behavior in APP/PS1 mice.

Mild behavioral impairment (MBI), which can include compulsive behavior, is an early sign of Alzheimer's disease (AD), but its underlying neural mechanisms remain unclear. Here, we show that 3-5-month-old APP/PS1 mice display obsessive-compulsive disorder (OCD)-like behavior. The number of parvalbumin-positive (PV) interneurons and level of high gamma (γhigh) oscillation are significantly decreased in the striatum of AD mice. This is accompanied by enhanced ß-γhigh coupling and firing rates of putative striatal projection neurons (SPNs), indicating decorrelation between PV interneurons and SPNs. Local field potentials (LFPs) simultaneously recorded in prefrontal cortex (PFC) and striatum (Str) demonstrate a decrease in γhigh-band coherent activity and spike-field coherence in corticostriatal circuits of APP/PS1 mice. Furthermore, levels of GABAB receptor (GABABR), but not GABAA receptor (GABAAR), and glutamatergic receptors, were markedly reduced, in line with presymptomatic AD-related behavioral changes. These findings suggest that MBI occurs as early as 3-5 months in APP/PS1 mice and that altered corticostriatal synchronization may play a role in mediating the behavioral phenotypes observed.

Precise regulation of presenilin expression is required for sea urchin early development.

Presenilins (PSENs) are widely expressed across eukaryotes. Two PSENs are expressed in humans, where they play a crucial role in Alzheimer's disease (AD). Each PSEN can be part of the γ-secretase complex, which has multiple substrates, including Notch and amyloid-ß precursor protein (AßPP) - the source of amyloid-ß (Aß) peptides that compose the senile plaques during AD. PSENs also interact with various proteins independently of their γ-secretase activity. They can then be involved in numerous cellular functions, which makes their role in a given cell and/or organism complex to decipher. We have established the Paracentrotus lividus sea urchin embryo as a new model to study the role of PSEN. In the sea urchin embryo, the PSEN gene is present in unduplicated form and encodes a protein highly similar to human PSENs. Our results suggest that PSEN expression must be precisely tuned to control the course of the first mitotic cycles and the associated intracellular Ca2+ transients, the execution of gastrulation and, probably in association with ciliated cells, the establishment of the pluteus. We suggest that it would be relevant to study the role of PSEN within the gene regulatory network deciphered in the sea urchin.

Deposition of Phosphorylated α-Synuclein and Activation of GSK-3ß and PP2A in the PS19 Mouse Model of Tauopathy.

The simultaneous accumulation of multiple pathological proteins, such as hyperphosphorylated tau (hp-tau) and phosphorylated α-synuclein (p-αSyn), has been reported in the brains of patients with various neurodegenerative diseases. We previously demonstrated that hp-tau-dependent p-αSyn accumulation was associated with the activation of GSK-3ß in the brains of P301L tau transgenic mice. To confirm the effects of another mutant tau on p-αSyn accumulation in vivo, we herein examined the brains of PS19 mice that overexpress human P301S mutant tau. Immunohistochemically, hp-tau and p-αSyn aggregates were detected in the same neuronal cells in the cerebrum and brain stem of aged PS19 mice. A semiquantitative analysis showed a positive correlation between hp-tau and p-αSyn accumulation. Furthermore, an activated form of GSK-3ß was detected within cells containing both hp-tau and p-αSyn aggregates in PS19 mice. Western blotting showed a decrease in inactivated PP2A levels in PS19 mice. The present results suggest that the overexpression of human P301S mutant tau induces p-αSyn accumulation that is accompanied by not only GSK-3ß, but also PP2A activation in PS19 mice, and highlight the synergic effects between tau and αSyn in the pathophysiology of neurodegenerative diseases that show the codeposition of tau and αSyn.

Atrophy of lacunosum moleculare layer is important for learning and memory in APP/PS1 transgenic mice.

Changes in the hippocampus are closely associated with learning and memory in Alzheimer's disease; however, it is not clear which morphological and cellular and subcellular changes are essential for learning and memory. Here, we accurately quantitatively studied the hippocampal microstructure changes in Alzheimer's disease model mice and analyzed the relationship between the hippocampal microstructure changes and learning and memory. Ten-month-old male APP/PS1 transgenic mice and age-matched nontransgenic littermate mice were randomly selected. The spatial learning and memory abilities were assessed using the Morris water maze. The volumes of each layer and numbers of neurons, dendritic spines and oligodendrocytes in the hippocampal subregions were investigated using unbiased stereological techniques. The APP/PS1 transgenic mice showed a decline in hippocampus-dependent spatial learning and memory abilities, smaller volumes of each layer (other than stratum radiatum) and fewer numbers of neurons, dendritic spine synapses and mature oligodendrocytes in the hippocampal subregions than nontransgenic mice. In particular, the decline of spatial learning ability was significantly correlated with the atrophy of lacunosum moleculare layer (LMol) and the decrease of hippocampal neurons and mature oligodendrocytes rather than dendritic spines. The CA1-3 fields (including LMol) atrophy was significantly correlated with the decrease both of neurons, dendritic spines and mature oligodendrocytes. However, the dentate gyrus atrophy was significantly correlated with the decrease of neurons and mature oligodendrocytes rather than dendritic spines. The loss of neurons, dendritic spines synapses and mature oligodendrocytes together caused the LMol atrophy and then led to a decline in hippocampus-dependent spatial learning ability in mice with Alzheimer's disease.

Time or place? Dissociation between object-in-place and relative recency in young APPswe/PS1dE9 mice.

This study tests the predictions of a novel analysis of recognition memory based on a theory of associative learning, according to which recognition comprises two independent underlying processes, one relying on the to-be-recognized item having been experienced recently (self-generated priming), and the other on it being predicted by some other stimulus (retrieval-generated priming). A single experiment examined recognition performance in the amyloid precursor protein (APP)swe/PS1dE9 (APP/PS1) mouse, a double-transgenic model of Alzheimer's disease (AD), and wild type (WT) littermates. Performance on two variants of the spontaneous object recognition (SOR) was compared in 5-month-old APPswe/PS1dE9 (APP/PS1) mice, a double-transgenic model of AD, and their WT littermates, using junk objects. In the relative recency task animals were exposed to object A, and then object B, followed by a test with both A and B. In the object-in-place task the mice were exposed to both A and B, and then tested with two copies of A, occupying the same positions as the preeexposed objects. The WT mice showed a preference for exploring the first-presented object A in the relative recency task, and the copy of A in the "wrong" position (i.e., the one placed where B had been during the preexposure phase) in the object-in-place task. The APP/PS1 mice performed like the WT mice in the relative recency task, but showed a selective impairment in the object-in-place task. We interpret these findings in terms of-Wagner's (Information processing in animals: Memory Mechanisms, 1981, Erlbaum) theory of associative learning, sometimes opponent process (SOP), as a selective deficit in retrieval-generated priming. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Preparation of a Deuterated Membrane Protein for Small-Angle Neutron Scattering.

This chapter outlines a protocol developed to prepare a purified deuterated membrane protein for a small-angle neutron scattering (SANS) experiment. SANS is a noninvasive technique well suited to studying membrane protein solution structures, and deuteration enhances the signal from the protein over the background (Breyton et al., Eur Phys J E Soft Matter 36 (7):71, 2013; Garg et al., Biophys J 101 (2):370-377, 2011). We present our workflow: transformation of our plasmid into E. coli, cell growth and expression of our deuterated protein, membrane isolation, detergent solubilization, protein purification, purity assessment, and final preparation for SANS.

Liraglutide Has Anti-Inflammatory and Anti-Amyloid Properties in Streptozotocin-Induced and 5xFAD Mouse Models of Alzheimer's Disease.

Recent clinical and epidemiological studies support the contention that diabetes mellitus (DM) is a strong risk factor for the development of Alzheimer's disease (AD). The use of insulin cell toxin, streptozotocin (STZ), when injected into the lateral ventricles, develops an insulin resistant brain state (IRBS) and represents a non-transgenic, or sporadic AD model (SAD), with several AD-like neuropathological features. The present study explored the effects of an anti-diabetic drug, liraglutide (LIR), in reversing major pathological hallmarks in the prodromal disease stage of both the 5xFAD transgenic and SAD mouse models of AD. Three-month-old 5xFAD and age-matched wild type mice were given a single intracerebroventricular (i.c.v) injection of STZ or vehicle (saline) and were subsequently treated with LIR, intraperitoneally (IP), once a day for 30 days. The extent of neurodegeneration, Aß plaque load, and key proteins associated with the insulin signaling pathways were measured using Western blot and neuroinflammation (via immunohistological assays) in the cortical and hippocampal regions of the brain were assessed following a series of behavioral tests used to measure cognitive function after LIR or vehicle treatments. Our results indicated that STZ significantly increased neuroinflammation, Aß plaque deposition and disrupted insulin signaling pathway, while 25 nmol/kg LIR, when injected IP, significantly decreased neuroinflammatory responses in both SAD and 5xFAD mice before significant cognitive changes were observed, suggesting LIR can reduce early neuropathology markers prior to the emergence of overt memory deficits. Our results indicate that LIR has neuroprotective effects and has the potential to serve as an anti-inflammatory and anti-amyloid prophylactic therapy in the prodromal stages of AD.

Archaeal roots of intramembrane aspartyl protease siblings signal peptide peptidase and presenilin.

Signal peptides help newly synthesized proteins reach the cell membrane or be secreted. As part of a biological process key to immune response and surveillance in humans, and associated with diseases, for example, Alzheimer, remnant signal peptides and other transmembrane segments are proteolyzed by the intramembrane aspartyl protease (IAP) enzyme family. Here, we identified IAP orthologs throughout the tree of life. In addition to eukaryotes, IAPs are encoded in metabolically diverse archaea from a wide range of environments. We found three distinct clades of archaeal IAPs: (a) Euryarchaeota (eg, halophilic Halobacteriales, methanogenic Methanosarcinales and Methanomicrobiales, marine Poseidoniales, acidophilic Thermoplasmatales, hyperthermophilic Archaeoglobus spp.), (b) DPANN, and (c) Bathyarchaeota, Crenarchaeota, and Asgard. IAPs were also present in bacterial genomes from uncultivated members of Candidate Phylum Radiation, perhaps due to horizontal gene transfer from DPANN archaeal lineages. Sequence analysis of the catalytic motif YD…GXGD (where X is any amino acid) in IAPs from archaea and bacteria reveals WD in Lokiarchaeota and many residue types in the X position. Gene neighborhood analysis in halophilic archaea shows IAP genes near corrinoid transporters (btuCDF genes). In marine Euryarchaeota, a putative BtuF-like domain is found in N-terminus of the IAP gene, suggesting a role for these IAPs in metal ion cofactor or other nutrient scavenging. Interestingly, eukaryotic IAP family members appear to have evolved either from Euryarchaeota or from Asgard archaea. Taken together, our phylogenetic and bioinformatics analysis should prompt experiments to probe the biological roles of IAPs in prokaryotic secretomes.

Trypanosoma cruzi Presenilin-Like Transmembrane Aspartyl Protease: Characterization and Cellular Localization.

The increasing detection of infections of Trypanosoma cruzi, the etiological agent of Chagas disease, in non-endemic regions beyond Latin America has risen to be a major public health issue. With an impact in the millions of people, current treatments rely on antiquated drugs that produce severe side effects and are considered nearly ineffective for the chronic phase. The minimal progress in the development of new drugs highlights the need for advances in basic research on crucial biochemical pathways in T. cruzi to identify new targets. Here, we report on the T. cruzi presenilin-like transmembrane aspartyl enzyme, a protease of the aspartic class in a unique phylogenetic subgroup with T. vivax separate from protozoans. Computational analyses suggest it contains nine transmembrane domains and an active site with the characteristic PALP motif of the A22 family. Multiple linear B-cell epitopes were identified by SPOT-synthesis analysis with Chagasic patient sera. Two were chosen to generate rabbit antisera, whose signal was primarily localized to the flagellar pocket, intracellular vesicles, and endoplasmic reticulum in parasites by whole-cell immunofluorescence. The results suggest that the parasitic presenilin-like enzyme could have a role in the secretory pathway and serve as a target for the generation of new therapeutics specific to the T. cruzi.

Evolutionary History of Alzheimer Disease-Causing Protein Family Presenilins with Pathological Implications.

Presenilin proteins make the catalytic component of γ-secretase, a multiprotein transmembrane protease, and are type II transmembrane proteins. Amyloid protein, Notch, and beta catenin are among more than 90 substrates of Presenilins. Mutations in Presenilins lead to defects in proteolytic cleavage of its substrate resulting in some of the most devastating pathological conditions including Alzheimer disease (AD), developmental disorders, and cancer. In addition to catalytic roles, Presenilin protein is also shown to be involved in many non-catalytic roles, i.e., calcium homeostasis, regulation of autophagy, and protein trafficking, etc. These proteolytic proteins are highly conserved and are present in almost all the major eukaryotic groups. Studies, performed on a wide variety of organisms ranging from human to unicellular dictyostelium, have shown the important catalytic and non-catalytic roles of Presenilins. In this study, we infer the evolutionary patterns and history of Presenilins as well as of other γ-secretase proteins. We show that Presenilins are the most ancient of the γ-secretase proteins and that Presenilins may have their origin in the last common ancestor (LCA) of Eukaryotes. We also demonstrate that Presenilin proteins generally lack diversifying selection during the course of their evolution. Through evolutionary trace analysis, we show that Presenilin protein sites that undergo mutations in Familial Alzheimer disease, are highly conserved in metazoans. Finally, we discuss the evolutionary, physiological, and pathological implications of our findings and propose that the evolutionary profile of Presenilins supports the loss of function hypothesis of AD pathogenesis.

Green Tea Seed Isolated Theasaponin E1 Ameliorates AD Promoting Neurotoxic Pathogenesis by Attenuating Aß Peptide Levels in SweAPP N2a Cells.

Alzheimer's disease (AD) is the most frequent type of dementia affecting memory, thinking and behaviour. The major hallmark of the disease is pathological neurodegeneration due to abnormal aggregation of Amyloid beta (Aß) peptides generated by ß- and γ-secretases via amyloidogenic pathway. Purpose of the current study was to evaluate the effects of theasaponin E1 on the inhibition of Aß producing ß-, γ-secretases (BACE1, PS1 and NCT) and acetylcholinesterase and activation of the non-amyloidogenic APP processing α-secretase (ADAM10). Additionally, theasaponin E1 effects on Aß degrading and clearing proteins neprilysin and insulin degrading enzyme (IDE). The effect of theasaponin E1 on these crucial enzymes was investigated by RT-PCR, ELISA, western blotting and fluorometric assays using mouse neuroblastoma cells (SweAPP N2a). theasaponin E1 was extracted and purified from green tea seed extract via HPLC, and N2a cells were treated with different concentrations for 24 h. Gene and protein expression in the cells were measured to determine the effects of activation and/or inhibition of theasaponin E1 on ß- and γ-secretases, neprilysin and IDE. Results demonstrated that theasaponin E1 significantly reduced Aß concentration by activation of the α-secretase and neprilysin. The activities of ß- and γ-secretase were reduced in a dose-dependent manner due to downregulation of BACE1, presenilin, and nicastrin. Similarly, theasaponin E1 significantly reduced the activity of acetylcholinesterase. Overall, from the results it is concluded that green tea seed extracted saponin E1 possess therapeutic significance as a neuroprotective natural product recommended for the treatment of Alzheimer's disease.

Importance of γ-secretase in the regulation of liver X receptor and cellular lipid metabolism.

Presenilins (PS) are the catalytic components of γ-secretase complexes that mediate intramembrane proteolysis. Mutations in the PS genes are a major cause of familial early-onset Alzheimer disease and affect the cleavage of the amyloid precursor protein, thereby altering the production of the amyloid ß-peptide. However, multiple additional protein substrates have been identified, suggesting pleiotropic functions of γ-secretase. Here, we demonstrate that inhibition of γ-secretase causes dysregulation of cellular lipid homeostasis, including up-regulation of liver X receptors, and complex changes in the cellular lipid composition. Genetic and pharmacological inhibition of γsecretase leads to strong accumulation of cytoplasmic lipid droplets, associated with increased levels of acylglycerols, but lowered cholesteryl esters. Furthermore, accumulation of lipid droplets was augmented by increasing levels of amyloid precursor protein C-terminal fragments, indicating a critical involvement of this γ-secretase substrate. Together, these data provide a mechanism that functionally connects γ-secretase activity to cellular lipid metabolism. These effects were also observed in human astrocytic cells, indicating an important function of γ-secretase in cells critical for lipid homeostasis in the brain.

Interrelationship between Alzheimer's disease and cardiac dysfunction: the brain-heart continuum?

Dementia, a devastating neurological disorder commonly found in the elderly, is characterized by severe cognitive and memory impairment. Ample clinical and epidemiological evidence has depicted a close association between dementia and heart failure. While cerebral blood under perfusion and neurohormonal activation due to the dampened cardiac pump function contribute to the loss of nutrient supply and neuronal injury, Alzheimer's disease (AD), the most common type of dementia, also provokes cardiovascular function impairment, in particular impairment of diastolic function. Aggregation of amyloid-ß proteins and mutations of Presenilin (PSEN) genes are believed to participate in the pathological changes in the heart although it is still debatable with regards to the pathological cue of cardiac anomalies in AD process. In consequence, reduced cerebral blood flow triggered by cardiac dysfunction further deteriorates vascular dementia and AD pathology. Patients with atrial fibrillation, heart failure, and other cardiac anomalies are at a higher risk for cognitive decline and dementia. Conclusion: Due to the increased incidence of dementia and cardiovascular diseases, the coexistence of the two will cause more threat to public health, warranting much more attention. Here, we will update recent reports on dementia, AD, and cardiovascular diseases and discuss the causal relationship between dementia and heart dysfunction.