Efrat Levy - Academia.edu (original) (raw)

Papers by Efrat Levy

Nature Neuroscience, Jun 1, 2022

Autophagy is markedly impaired in Alzheimer's disease (AD). Here we reveal unique autophagy dysre... more Autophagy is markedly impaired in Alzheimer's disease (AD). Here we reveal unique autophagy dysregulation within neurons in five AD mouse models in vivo and identify its basis using a neuron-specific transgenic mRFP-eGFP-LC3 probe of autophagy and pH, multiplex confocal imaging and correlative light electron microscopy. Autolysosome acidification declines in neurons well before extracellular amyloid deposition, associated with markedly lowered vATPase activity and build-up of Aβ/APP-βCTF selectively within enlarged de-acidified autolysosomes. In more compromised yet still intact neurons, profuse Aβ-positive autophagic vacuoles (AVs) pack into large membrane blebs forming flower-like perikaryal rosettes. This unique pattern, termed PANTHOS (poisonous anthos (flower)), is also present in AD brains. Additional AVs coalesce into peri-nuclear networks of membrane tubules where fibrillar β-amyloid accumulates intraluminally. Lysosomal membrane permeabilization, cathepsin release and lysosomal cell death ensue, accompanied by microglial invasion. Quantitative analyses confirm that individual neurons exhibiting PANTHOS are the principal source of senile plaques in amyloid precursor protein AD models.

bioRxiv (Cold Spring Harbor Laboratory), Jun 21, 2023

Synaptic loss is an early event in the undersupplied but not yet irreversibly injured penumbra ar... more Synaptic loss is an early event in the undersupplied but not yet irreversibly injured penumbra area after an ischemic stroke. Promoting synaptic preservation in this area would likely improve functional neurological recovery. In the present study, we aimed to detect proteins involved in endogenous protection mechanisms of synapses in the penumbra after stroke and to analyse the potential beneficial effect of these candidates for a prospective stroke treatment. For this, we performed Liquid Chromatography coupled to Mass Spectrometry (LC-MS)-based proteomics of synaptosomes isolated from the ipsilateral hemispheres of mice subjected to experimental stroke at different time points (24 h, 4 and 7 days) and compared them to sham-operated mice. Proteomic analyses indicated that among the differentially expressed proteins between the two groups, cystatin C (CysC) was significantly increased at 24 h and 4 days following stroke, before returning to steady-state levels at 7 days, thus indicating a potential transient and intrinsic rescue mechanism attempt of neurons. When CysC was applied to primary neuronal cultures subjected to an in vitro model of ischemic damage, this treatment significantly improved the preservation of synaptic structures. Notably, similar effects were observed when CysC was loaded into brain-derived extracellular vesicles (BDEVs). Finally, when CysC contained in BDEVs was administered intracerebroventricularly to stroked mice, it significantly increased the expression of synaptic markers such as SNAP25, Homer-1, and NCAM in the penumbra area compared to the group supplied with empty BDEVs. Thus, we show that CysC-loaded BDEVs promote synaptic protection after ischemic damage in vitro and in vivo, opening the possibility of a therapeutic use in stroke patients.

Mouse lymphoma cells ($49) that grow in suspension culture were selected for increased tumorigeni... more Mouse lymphoma cells ($49) that grow in suspension culture were selected for increased tumorigenicity through continuous passages in syngeneic BALB/c mice. Developing tumors were classified as high grade malignant lymphoma, small noncleaved type. Variants were selected from these tumorigenic cells that were able to grow as a monolayer attached to their substrate, resembling, in this respect, fibroblastoid cells. Whereas the tumorigenic suspension-growing parental cells were able to induce progressive tumors with an inoculum as low as 100 cells per mouse, the adherent cells were unable to develop as tumors even at an inoculum of 1 x 108 cells per mouse. In addition, mice inoculated once with live adherent cells were immunized against 1 x 107 suspension-growing cells. Involvement of an immune response in the rejection of tumorigenic 49cellswassuggestedby(a)adoptivetransferexperimentsinwhichspleencellsfromimmunizedmiceprotectednaivemiceand(b)theappearanceofantibodiesintheseraofimmunizedsyngeneicmicethatspecificallyrecognizedbothadherentandsuspension−growing49 cells was suggested by (a) adoptive transfer experiments in which spleen cells from immunized mice protected naive mice and (b) the appearance of antibodies in the sera of immunized syngeneic mice that specifically recognized both adherent and suspension-growing 49cellswassuggestedby(a)adoptivetransferexperimentsinwhichspleencellsfromimmunizedmiceprotectednaivemiceand(b)theappearanceofantibodiesintheseraofimmunizedsyngeneicmicethatspecificallyrecognizedbothadherentandsuspension−growing49 cells and detected differences in [35S]methioninelabeled antigens from these cells. Antibodies raised in rabbits against adherent cells recognized three proteins of 34,000, 61,000, and 72,000 apparent molecular weight in radiolabeled adherent cell extracts that are either absent or present in small amounts in extracts of suspension-growing tumorigenic $49 cells. These findings, taken together with our previous report (

Neurobiology of Aging, 2013

While anti-human-Aβ immunotherapy clears brain β-amyloid plaques in Alzheimer's disease (AD), tar... more While anti-human-Aβ immunotherapy clears brain β-amyloid plaques in Alzheimer's disease (AD), targeting additional brain plaque constituents to promote clearance has not been attempted. Endogenous murine Aβ is a minor β-amyloid plaque component in amyloid precursor protein transgenic AD models, which we show is ~2-8% of the total accumulated Aβ in various human APP transgenic mice. Murine Aβ co-deposits and co-localizes with human Aβ in amyloid plaques and the two Aβ species co-immunoprecipitate together from brain extracts. In the human APP transgenic mice Tg2576, passive immunization for eight weeks with a murine-Aβ-specific antibody reduced β-plaque pathology, robustly decreasing both murine and human Aβ levels. The immunized mice additionally showed improvements in two behavioral assays, odor habituation and nesting behavior. We conclude that passive anti-murine-Aβ immunization clears β-amyloid

Journal of Cell Biology, Oct 1, 1984

Journal of Alzheimer's Disease, Aug 26, 2009

A role for cystatin C (CysC) in the pathogenesis of Alzheimer's disease (AD) has been suggested b... more A role for cystatin C (CysC) in the pathogenesis of Alzheimer's disease (AD) has been suggested by the genetic linkage of a CysC gene (CST3) polymorphism with late-onset AD, the co-localization of CysC with amyloid-β (Aβ) in AD brains, and binding of CysC to soluble Aβ in vitro and in mouse models of AD. This study investigates the binding between Aβ and CysC in the human central nervous system. While CysC binding to soluble Aβ was observed in AD patients and controls, a SDS-resistant CysC/Aβ complex was detected exclusively in brains of neuropathologically normal controls, but not in AD cases. The association of CysC with Aβ in brain from control individuals and in cerebrospinal fluid reveals an interaction of these two polypeptides in their soluble form. The association between Aβ and CysC prevented Aβ accumulation and fibrillogenesis in experimental systems, arguing that CysC plays a protective role in the pathogenesis of AD in humans and explains why decreases in CysC concentration caused by the CST3 polymorphism or by specific presenilin 2 mutations can lead to the development of the disease. Thus, enhancing CysC expression or modulating CysC binding to Aβ have important disease-modifying effects, suggesting a novel therapeutic intervention for AD.

Frontiers in Neuroscience, Dec 12, 2019

Journal of Neuropathology and Experimental Neurology, 2001

Immunohistochemical analysis of brains of patients with Alzheimer disease (AD) revealed that the ... more Immunohistochemical analysis of brains of patients with Alzheimer disease (AD) revealed that the cysteine proteinase inhibitor cystatin C colocalizes with amyloid ␤-protein (A␤) in parenchymal and vascular amyloid deposits. No evidence of cerebral hemorrhage was observed in any of the brains studied. Immunoelectron microscopy demonstrated dual staining of amyloid fibrils with anti-A␤ and anti-cystatin C antibodies. Cystatin C immunoreactivity was also observed in amyloid deposits in the brain of transgenic mice overexpressing human ␤ amyloid precursor protein. Massive deposition of the variant cystatin C in the cerebral vessels of patients with the Icelandic form of hereditary cerebral hemorrhage with amyloidosis is thought to be responsible for the pathological processes leading to stroke. Anti-cystatin C antibodies strongly labeled pyramidal neurons within cortical layers most prone to amyloid deposition in the brains of AD patients. Immunohistochemistry with antibodies against the carboxyl-terminus of A␤ x-42 showed intracellular immunoreactivity in the same neuronal subpopulation. It remains to be established whether the association of cystatin C to A␤ plays a primary role in amyloidogenesis of AD or is a late event in which the protein is bound to the previously formed A␤ amyloid fibrils.

The Journal of Neuroscience, Jan 13, 2010

Alzheimer's disease often results in impaired olfactory perceptual acuity-a potential biomarker o... more Alzheimer's disease often results in impaired olfactory perceptual acuity-a potential biomarker of the disorder. However, the usefulness of olfactory screens to serve as informative indicators of Alzheimer's is precluded by a lack of knowledge regarding why the disease impacts olfaction. We addressed this question by assaying olfactory perception and amyloid-␤ (A␤) deposition throughout the olfactory system in mice that overexpress a mutated form of the human amyloid-␤ precursor protein. Such mice displayed progressive olfactory deficits that mimic those observed clinically-some evident at 3 months of age. Also, at 3 months of age, we observed nonfibrillar A␤ deposition within the olfactory bulb-earlier than deposition within any other brain region. There was also a correlation between olfactory deficits and the spatial-temporal pattern of A␤ deposition. Therefore, nonfibrillar, versus fibrillar, A␤-related mechanisms likely contribute to early olfactory perceptual loss in Alzheimer's disease. Furthermore, these results present the odor cross-habituation test as a powerful behavioral assay, which reflects A␤ deposition and thus may serve to monitor the efficacy of therapies aimed at reducing A␤.

Molecular Psychiatry, Oct 25, 2016

Recent data suggest that intraneuronal accumulation of metabolites of the amyloid β precursor pro... more Recent data suggest that intraneuronal accumulation of metabolites of the amyloid β precursor protein (APP) is neurotoxic. We observed that transgenic mice overexpressing in neurons a human APP gene harboring the APP E693Q (Dutch) mutation have intraneuronal lysosomal accumulation of APP carboxyl-terminal fragments (APP-CTFs) and oligomeric amyloid β (oAβ) but no histological evidence of amyloid deposition. Morphometric quantification using the lysosomal marker protein 2 (LAMP-2) immunolabeling showed higher neuronal lysosomal counts in brain neurons of 12 months old APP E693Q as compared to age-matched non-transgenic littermates, and Western blots showed increased lysosomal proteins including LAMP-2, cathepsin D and LC3. At 24 months of age, these mice also exhibited an accumulation of α-synuclein in the brain, along with increased conversion of LC3-I to LC3-II, an autophagosomal/autolysosomal marker. In addition to lysosomal changes at 12 months of age, these mice developed cholinergic neuronal loss in the basal forebrain, GABAergic neuronal loss in the cortex, hippocampus and basal forebrain, and gliosis and microgliosis in the hippocampus. These findings suggest a role for the intraneuronal accumulation of oAβ and APP-CTFs and resultant lysosomal pathology at early stages of Alzheimer's disease-related pathology. Users may view, print, copy, and download text and data-mine the content in such documents, for the purposes of academic research, subject always to the full Conditions of use:

The Journal of Neuroscience, Nov 2, 2011

The unique vulnerability of the olfactory system to Alzheimer's disease (AD) provides a quintesse... more The unique vulnerability of the olfactory system to Alzheimer's disease (AD) provides a quintessential translational tool for understanding mechanisms of synaptic dysfunction and pathological progression in the disease. Using the Tg2576 mouse model of ␤-amyloidosis, we show that aberrant, hyperactive olfactory network activity begins early in life, before detectable behavioral impairments or comparable hippocampal dysfunction and at a time when amyloid-␤ (A␤) deposition is restricted to the olfactory bulb (OB). Hyperactive odor-evoked activity in the piriform cortex (PCX) and increased OB-PCX functional connectivity emerged at a time coinciding with olfactory behavior impairments. This hyperactive activity persisted until later in life when the network converted to a hyporesponsive state. This conversion was A␤-dependent, because liver-X receptor agonist treatment to promote A␤ degradation rescued the hyporesponsive state and olfactory behavior. These data lend evidence to a novel working model of olfactory dysfunction in AD and, complimentary to other recent works, suggest that disease-relevant network dysfunction is highly dynamic and region specific, yet with lasting effects on cognition and behavior.

Molecular Neurobiology, Mar 22, 2011

This review critically examines progress in understanding the link between Alzheimer's disease (A... more This review critically examines progress in understanding the link between Alzheimer's disease (AD) molecular pathogenesis and behavior, with an emphasis on the impact of amyloid-β. We present the argument that the AD research field requires more multi-faceted analyses into the impacts of Alzheimer's pathogenesis which combine simultaneous molecular-, circuit-, and behavior-level approaches. Supporting this argument is a review of particular research utilizing similar, 'systems-level' methods in mouse models of AD. Related to this, a critique of common physiological and behavioral models is made-highlighting the likely usefulness of more refined and specific tools in understanding the relationship between candidate molecular pathologies and behavioral dysfunction. Finally, we propose challenges for future research which, if met, may greatly extend our current understanding of how AD molecular pathology impacts neural network function and behavior and possibly may lead to refinements in disease therapeutics.

Experimental and Molecular Pathology, Feb 1, 2009

Down's syndrome (DS) in humans is caused by trisomy of chromosome 21 (HSA 21). DS patients have a... more Down's syndrome (DS) in humans is caused by trisomy of chromosome 21 (HSA 21). DS patients have a variety of pathologies, including mental retardation and an unusually high incidence of leukemia or lymphoma such as megakaryocytic leukemia. Individuals with DS develop the characteristic neuropathological hallmarks of Alzheimer's disease (AD) in early adulthood, generally by the fourth decade of life. There are several mouse models of DS that have a segmental trisomy of mouse chromosome 16 (MMU 16) with triplicated genes orthologous to HSA 21. These mice display neurodegeneration similar to DS. Although brain pathology in DS models is known, little information is available about other organs. We studied the extraneural pathology in aged DS mice (Ts65Dn, Ts2 and Ts1Cje aged 8 to 24 months) as well as other mouse models of neurodegeneration, including presenilin (PS), amyloid-β precursor protein (APP), and tau (hTau and JNPL) transgenic mice. An increased incidence of peripheral amyloidosis, positive for amyloid A (AA) but not amyloid-β peptide (Aβ), was found in APP over-expressing and tauopathic mice as compared to nontransgenic (ntg) littermates or to DS mouse models. A higher incidence of lymphoma was found in the DS models, including Ts1Cje that is trisomic for a small segment of MMU 16 not including the App gene, but not in the APP over-expressing mice, suggesting that high APP expression is not the cause of lymphoma in DS. The occurrence of lymphomas in mouse DS models is of interest in relation to the increased incidence of malignant conditions in human DS.

PLOS Pathogens, Jul 8, 2015

Recent studies have found that extracellular vesicles (EVs) play an important role in normal and ... more Recent studies have found that extracellular vesicles (EVs) play an important role in normal and disease processes. In the present study, we isolated and characterized EVs from the brains of rhesus macaques, both with and without simian immunodeficiency virus (SIV) induced central nervous system (CNS) disease. Small RNA sequencing revealed increased miR-21 levels in EVs from SIV encephalitic (SIVE) brains. In situ hybridization revealed increased miR-21 expression in neurons and macrophage/microglial cells/nodules during SIV induced CNS disease. In vitro culture of macrophages revealed that miR-21 is released into EVs and is neurotoxic when compared to EVs derived from miR-21-/knockout animals. A mutation of the sequence within miR-21, predicted to bind TLR7, eliminates this neurotoxicity. Indeed miR-21 in EV activates TLR7 in a reporter cell line, and the neurotoxicity is dependent upon TLR7, as neurons isolated from TLR7-/knockout mice are protected from neurotoxicity. Further, we show that EVs isolated from the brains of monkeys with SIV induced CNS disease activates TLR7 and were neurotoxic when compared to EVs from control animals. Finally, we show that EV-miR-21 induced neurotoxicity was unaffected by apoptosis inhibition but could be prevented by a necroptosis inhibitor, necrostatin-1, highlighting the actions of this pathway in a growing number of CNS disorders.

Scientific Reports, Jul 31, 2019

cystatin c (cysc) is implicated in neuroprotection and repair in the nervous system in response t... more cystatin c (cysc) is implicated in neuroprotection and repair in the nervous system in response to diverse neurotoxic conditions. In addition to being secreted from cells in a soluble form, CysC is released by cells in association with extracellular vesicles (EVs), including exosomes. We demonstrate that EVs containing CysC protect cultured cells from starvation-induced death. Moreover, while EVs secreted by CysC-deficient cells were not protective, EVs secreted by CysC-deficient cells treated with exogenous human CysC significantly enhanced the survival of the cells. CysC also plays a role in modulating the secretion of EVs, enhancing secretion of EVs by primary cortical neurons and primary cortical smooth muscle cells. Confirming these in vitro findings, higher EV levels were observed in the brain extracellular space of transgenic mice expressing human CysC as compared to littermate controls. Regulation of cellsecreted EV levels and content in the brain is likely to be essential to maintaining normal brain function. We propose that enhanced EV release could rescue the deleterious effects of dysfunction of the endosomal-lysosomal system in neurodegenerative disorders. Moreover, a higher level of CysC-loaded EVs released from cells in the central nervous system has important protective functions, representing a potential therapeutic tool for disorders of the central nervous system.

Ageing Research Reviews, Dec 1, 2016

Under normal conditions, the function of catalytically active proteases is regulated, in part, by... more Under normal conditions, the function of catalytically active proteases is regulated, in part, by their endogenous inhibitors, and any change in the synthesis and/or function of a protease or its endogenous inhibitors may result in inappropriate protease activity. Altered proteolysis as a result of an imbalance between active proteases and their endogenous inhibitors can occur during normal aging, and such changes have also been associated with multiple neuronal diseases, including Amyotrophic Lateral Sclerosis (ALS), rare heritable neurodegenerative disorders, ischemia, some forms of epilepsy, and Alzheimer's disease (AD). One of the most extensively studied endogenous inhibitor is the cysteine-protease inhibitor cystatin C (CysC). Changes in the expression and secretion of CysC in the brain have been described in various neurological disorders and in animal models of neurodegeneration, underscoring a role for CysC in these conditions. In the brain, multiple in vitro and in vivo findings have demonstrated that CysC plays protective roles via pathways that depend upon the inhibition of endosomal-lysosomal pathway cysteine proteases, such as cathepsin B (Cat B), via the induction of cellular autophagy, via the induction of cell proliferation, or via the inhibition of amyloid-β (Aβ) aggregation. We review the data demonstrating the protective roles of CysC under conditions of neuronal challenge and the protective pathways induced by CysC under various conditions. Beyond highlighting the essential role that balanced proteolytic activity plays in supporting normal brain aging, these findings suggest that CysC is a therapeutic candidate that can potentially prevent brain damage and neurodegeneration.

Neurochemical Research, Apr 30, 2022

In multiple neurodevelopmental and neurodegenerative disorders, endosomal changes correlate with ... more In multiple neurodevelopmental and neurodegenerative disorders, endosomal changes correlate with changes in exosomes. We examined this linkage in the brain of mice that received cocaine injections for two weeks starting at 2.5 months of age. Cocaine caused a decrease in the number of both neuronal early and late endosomes and exosomes in the brains of male but not female mice. The response to cocaine in ovariectomized females mirrored male, demonstrating that these sex-differences in response to cocaine are driven by hormonal differences. Moreover, cocaine increased the amount of α-synuclein per exosome in the brain of females but did not affect exosomal α-synuclein content in the brain of males, a sex-difference eliminated by ovariectomy. Enhanced packaging of α-synuclein into female brain exosomes with the potential for propagation of pathology throughout the brain suggests a mechanism for the different response of females to chronic cocaine exposure as compared to males. Endosome • Extracellular vesicle • Exosome • Chronic drug exposure • α-synuclein • Cocaine

Neuroscience, Feb 1, 2017

SUMMARYThe abnormal assembly of tau protein in neurons is the pathological hallmark of multiple n... more SUMMARYThe abnormal assembly of tau protein in neurons is the pathological hallmark of multiple neurodegenerative diseases, including Alzheimer’s disease (AD). In addition, assembled tau associates with extracellular vesicles (EVs) in the central nervous system of patients with AD, which is linked to its clearance and prion-like propagation between neurons. However, the identities of the assembled tau species and the EVs, as well as how they associate, are not known. Here, we combined quantitative mass spectrometry, cryo-electron tomography and single-particle cryo-electron microscopy to study brain EVs from AD patients. We found filaments of truncated tau enclosed within EVs enriched in endo-lysosomal proteins. We observed multiple filament interactions, including with molecules that tethered filaments to the EV limiting membrane, suggesting selective packaging. Our findings will guide studies into the molecular mechanisms of EV-mediated secretion of assembled tau and inform the ta...

Annals of the New York Academy of Sciences

Extracellular vesicles (EVs) are small, lipid‐bilayer‐bound particles released by cells that can ... more Extracellular vesicles (EVs) are small, lipid‐bilayer‐bound particles released by cells that can contain important bioactive molecules, including lipids, RNAs, and proteins. Once released in the extracellular environment, EVs can act as messengers locally as well as to distant tissues to coordinate tissue homeostasis and systemic responses. There is a growing interest in not only understanding the physiology of EVs as signaling particles but also leveraging them as minimally invasive diagnostic and prognostic biomarkers (e.g., they can be found in biofluids) and drug‐delivery vehicles. On October 30–November 2, 2022, researchers in the EV field convened for the Keystone symposium “Exosomes, Microvesicles, and Other Extracellular Vesicles” to discuss developing standardized language and methodology, new data on the basic biology of EVs and potential clinical utility, as well as novel technologies to isolate and characterize EVs.