Papers by Alejandra Alvarez
Progress in Neurobiology, 2021
Memory consolidation requires activation of a gene expression program that allows de novo protein... more Memory consolidation requires activation of a gene expression program that allows de novo protein synthesis. But the molecular mechanisms that favour or restrict that program are poorly understood. The kinase c-Abl can modulate gene expression through transcription factors and chromatin modifiers. Here, we show that c-Abl ablation in the brain improves learning acquisition and memory consolidation in mice. Its absence also affects gene expression profiles in the mouse hippocampus. We found that genes involved in synaptic plasticity and actin cytoskeleton dynamics, such as Arp2 and Thorase, are up-regulated at the mRNA and protein levels in trained c-Abl KO mice and by a chemical-LTP stimulus. Trained c-Abl KO mice also show dendritic spines that are larger than wild-type mice and present at a higher density. These results indicate that c-Abl kinase is an important part of the mechanism that limits or restricts signalling of relevant gene programs involved in morphological and functional spine changes upon neuronal stimulation.
Nanomedicine : nanotechnology, biology, and medicine, Jan 30, 2017
The properties of nanometric materials make nanotechnology a promising platform for tackling prob... more The properties of nanometric materials make nanotechnology a promising platform for tackling problems of contemporary medicine. In this work, gold nanorods were synthetized and stabilized with polyethylene glycols and modified with two kinds of peptides. The D1 peptide that recognizes toxic aggregates of Aβ, a peptide involved in Alzheimer's disease (AD); and the Angiopep 2 that can be used to deliver nanorods to the mammalian central nervous system. The nanoconjugates were characterized using absorption spectrophotometry, dynamic light scattering, and transmission electron microscopy, among other techniques. We determined that the nanoconjugate does not affect neuronal viability; it penetrates the cells, and decreases aggregation of Aβ peptide in vitro. We also showed that when we apply our nanosystem to a Caenorhabditis elegans AD model, the toxicity of aggregated Aβ peptide is decreased. This work may contribute to the development of therapies for AD based on metallic nanopar...
Neural Regeneration Research
Antioxidants
The endoplasmic reticulum is a subcellular organelle key in the control of synthesis, folding, an... more The endoplasmic reticulum is a subcellular organelle key in the control of synthesis, folding, and sorting of proteins. Under endoplasmic reticulum stress, an adaptative unfolded protein response is activated; however, if this activation is prolonged, cells can undergo cell death, in part due to oxidative stress and mitochondrial fragmentation. Here, we report that endoplasmic reticulum stress activates c-Abl tyrosine kinase, inducing its translocation to mitochondria. We found that endoplasmic reticulum stress-activated c-Abl interacts with and phosphorylates the mitochondrial fusion protein MFN2, resulting in mitochondrial fragmentation and apoptosis. Moreover, the pharmacological or genetic inhibition of c-Abl prevents MFN2 phosphorylation, mitochondrial fragmentation, and apoptosis in cells under endoplasmic reticulum stress. Finally, in the amyotrophic lateral sclerosis mouse model, where endoplasmic reticulum and oxidative stress has been linked to neuronal cell death, we demo...
Frontiers in Cell and Developmental Biology, 2022
Niemann-Pick type A (NPA) disease is a fatal lysosomal neurodegenerative disorder caused by the d... more Niemann-Pick type A (NPA) disease is a fatal lysosomal neurodegenerative disorder caused by the deficiency in acid sphingomyelinase (ASM) activity. NPA patients present severe and progressive neurodegeneration starting at an early age. Currently, there is no effective treatment for this disease and NPA patients die between 2 and 3 years of age. NPA is characterized by an accumulation of sphingomyelin in lysosomes and dysfunction in the autophagy-lysosomal pathway. Recent studies show that c-Abl tyrosine kinase activity downregulates autophagy and the lysosomal pathway. Interestingly, this kinase is also activated in other lysosomal neurodegenerative disorders. Here, we describe that c-Abl activation contributes to the mechanisms of neuronal damage and death in NPA disease. Our data demonstrate that: 1) c-Abl is activated in-vitro as well as in-vivo NPA models; 2) imatinib, a clinical c-Abl inhibitor, reduces autophagy-lysosomal pathway alterations, restores autophagy flux, and lower...
Frontiers in Cellular Neuroscience, 2019
Spine pathology has been implicated in the early onset of Alzheimer's disease (AD), where Aβ-Olig... more Spine pathology has been implicated in the early onset of Alzheimer's disease (AD), where Aβ-Oligomers (AβOs) cause synaptic dysfunction and loss. Previously, we described that pharmacological inhibition of c-Abl prevents AβOs-induced synaptic alterations. Hence, this kinase seems to be a key element in AD progression. Here, we studied the role of c-Abl on dendritic spine morphological changes induced by AβOs using c-Abl null neurons (c-Abl-KO). First, we characterized the effect of c-Abl deficiency on dendritic spine density and found that its absence increases dendritic spine density. While AβOs-treatment reduces the spine number in both wild-type (WT) and c-Abl-KO neurons, AβOs-driven spine density loss was not affected by c-Abl. We then characterized AβOs-induced morphological changes in dendritic spines of c-Abl-KO neurons. AβOs induced a decrease in the number of mushroom spines in c-Abl-KO neurons while preserving the populations of immature stubby, thin, and filopodia spines. Furthermore, synaptic contacts evaluated by PSD95/Piccolo clustering and cell viability were preserved in AβOs-exposed c-Abl-KO neurons. In conclusion, our results indicate that in the presence of AβOs c-Abl participates in synaptic contact removal, increasing susceptibility to AβOs damage. Its deficiency increases the immature spine population reducing AβOs-induced synapse elimination. Therefore, c-Abl signaling could be a relevant actor in the early stages of AD.
Cells, 2021
Niemann-Pick type C disease (NPCD) is a lysosomal storage disorder caused by mutations in the NPC... more Niemann-Pick type C disease (NPCD) is a lysosomal storage disorder caused by mutations in the NPC1 gene. The most affected tissues are the central nervous system and liver, and while significant efforts have been made to understand its neurological component, the pathophysiology of the liver damage remains unclear. In this study, hepatocytes derived from wild type and Npc1−/− mice were analyzed by mass spectrometry (MS)-based proteomics in conjunction with bioinformatic analysis. We identified 3832 proteins: 416 proteins had a p-value smaller than 0.05, of which 37% (n = 155) were considered differentially expressed proteins (DEPs), 149 of them were considered upregulated, and 6 were considered downregulated. We focused the analysis on pathways related to NPC pathogenic mechanisms, finding that the most significant changes in expression levels occur in proteins that function in the pathways of liver damage, lipid metabolism, and inflammation. Moreover, in the group of DEPs, 30% (n =...
Biochimica et Biophysica Acta (BBA) - Gene Regulatory Mechanisms, 2016
Background-Niemann-Pick type C (NPC) disease is a fatal neurodegenerative disorder characterized ... more Background-Niemann-Pick type C (NPC) disease is a fatal neurodegenerative disorder characterized by the accumulation of free cholesterol in lysosomes. There are currently no effective FDA-approved treatments for NPC, although in the last years the inhibition of Histone Deacetylases (HDACs) has emerged as a potential treatment for this disease. However, the molecular mechanisms that deregulate HDACs activity in NPC disease are unknown. Previously our group had shown that the proapoptotic tyrosine kinase c-Abl signaling is activated in NPC neurons. Here, we demonstrate that c-Abl activity increases HDAC2 levels inducing neuronal gene repression of key synaptic genes in NPC models. Results-Our data show that: i) HDAC2 levels and activity are increased in NPC neuronal models and in Npc1-/mice; ii) inhibition of c-Abl or c-Abl deficiency prevents the increase of HDAC2 protein levels and activity in NPC neuronal models; iii) c-Abl inhibition decreases the levels of HDAC2 tyrosine phosphorylation; iv
Nutrients, Jan 30, 2014
Niemann-Pick C (NPC) disease is a fatal neurodegenerative disorder characterized by the accumulat... more Niemann-Pick C (NPC) disease is a fatal neurodegenerative disorder characterized by the accumulation of free cholesterol in lysosomes. We have previously reported that oxidative stress is the main upstream stimulus activating the proapoptotic c-Abl/p73 pathway in NPC neurons. We have also observed accumulation of vitamin E in NPC lysosomes, which could lead to a potential decrease of its bioavailability. Our aim was to determine if dietary vitamin E supplementation could improve NPC disease in mice. NPC mice received an alpha-tocopherol (α-TOH) supplemented diet and neurological symptoms, survival, Purkinje cell loss, α-TOH and nitrotyrosine levels, astrogliosis, and the c-Abl/p73 pathway functions were evaluated. In addition, the effect of α-TOH on the c-Abl/p73 pathway was evaluated in an in vitro NPC neuron model. The α-TOH rich diet delayed loss of weight, improved coordination and locomotor function and increased the survival of NPC mice. We found increased Purkinje neurons and...
Arthritis & Rheumatology, 2014
Objective: To define whether anti-ribosomal P autoantibodies (anti-P) from patients with neuropsy... more Objective: To define whether anti-ribosomal P autoantibodies (anti-P) from patients with neuropsychiatric systemic lupus erythematosus (NPSLE) can impair the function of hippocampal neurons that express the neuronal surface P antigen (NSPA) when accessing the brain from the circulation. Methods: Antibodies included anti-P from NPSLE and rabbit-generated anti-P and anti-NSPA. Mice primary hippocampal neurons were analyzed for antibody cell surface binding (double immunofluorescence), intracellular calcium variations (Fura 2-AM) and apoptosis (caspase-3 activation). Hippocampal-dependent spatial flexible memory was tested by water maze in mice 24 h after an intravenous (i.v.) injection of anti-P or anti-NSPA, using lipopolysaccharide (LPS) to permeate the blood brain barrier (BBB). Antibody and apoptosis in hippocampus were studied by immunohistochemistry (IHC) and TUNEL assays. Results: Hippocampal neurons expressed NSPA on the cell surface, as revealed by anti-P and anti-NSPA staining colocalization, and responded to both antibodies incrementing their intracellular calcium levels. Anti-P directly injected by stereotaxis into the hippocampus or added to primary cultures induced neuronal apoptosis. Upon LPS treatment, i.v. injected anti-P impaired memory but did not elicit neuronal apoptosis in hippocampus, being detectable at low amount there. Anti-NSPA antibodies also impaired memory. Conclusions: Anti-P interact with NSPA on the surface of hippocampal neurons leading to apoptotic death or to functional perturbations, likely depending on their concentration. Circulating anti-P can access the hippocampus and impair memory without requiring neuronal death when the BBB is disrupted. NSPA can mediate antibody-driven diffuse brain dysfunction and anti-P might contribute to the frequently observed cognitive impairment in SLE. of 34 John Wiley & Sons Arthritis & Rheumatology
Molecular Neurodegeneration, 2012
Background Neurotrophins and their receptors regulate several aspects of the developing and matur... more Background Neurotrophins and their receptors regulate several aspects of the developing and mature nervous system, including neuronal morphology and survival. Neurotrophin receptors are active in signaling endosomes, which are organelles that propagate neurotrophin signaling along neuronal processes. Defects in the Npc1 gene are associated with the accumulation of cholesterol and lipids in late endosomes and lysosomes, leading to neurodegeneration and Niemann-Pick type C (NPC) disease. The aim of this work was to assess whether the endosomal and lysosomal alterations observed in NPC disease disrupt neurotrophin signaling. As models, we used i) NPC1-deficient mice to evaluate the central cholinergic septo-hippocampal pathway and its response to nerve growth factor (NGF) after axotomy and ii) PC12 cells treated with U18666A, a pharmacological cellular model of NPC, stimulated with NGF. Results NPC1-deficient cholinergic cells respond to NGF after axotomy and exhibit increased levels o...
Journal of Physiology-Paris, 1998
Acetylcholinesterase (AChE) present in Alzheimer plaques is resistant to low pH, anti-ChE inhibit... more Acetylcholinesterase (AChE) present in Alzheimer plaques is resistant to low pH, anti-ChE inhibitors and high substrate concentrations in comparison with the free enzyme. Kinetic and pharmacological studies of AChE-amyloid complexes indicate that steric hindrance by the amyloid over the gorge and the peripheral site of AChE is responsible for these effects. (OElsevier. Paris) Resume-Interactions mobkulaires de I'acetylcholinestkrase avec les plaques skniles. L'ac6tylcholinestkase (AChE), prkente dans les plaques seniles de la maladie d'Alzheimer, est rtkistante au baa pH, aux inhibiteurs et aux hautes concentrations de substrar. Les Ctudeb cinktiques et pharmacologiques des fibres du complexe amyloide-AChE indiquent que l'encombrement stkrique de I'amylo'ide au niveau de la gorge et du site periphktique de 1'AChE est responsable de ces effets. (bElsevier, Paris) AChE / amyloid plaques I AChE-Af3-amyloid fibril complexes / Alzheimer's disease
Journal of Cellular Physiology, 2008
Wnt factors are secreted ligands that affect different aspects of the nervous system behavior lik... more Wnt factors are secreted ligands that affect different aspects of the nervous system behavior like neurodevelopment, synaptogenesis and neurodegeneration. In different model systems, Wnt signaling has been demonstrated to be regulated by heparan sulfate proteoglycans (HSPGs). Whether HSPGs modulate Wnt signaling in the context of neuronal behavior is currently unknown. Here we demonstrate that activation of Wnt signaling with the endogenous ligand Wnt-7a results in an increased of neurite outgrowth in the neuroblastoma N2a cell line. Interestingly, heparin induces glycogen synthase kinase-3b (GSK-3b) inhibition, b-catenin stabilization and morphological differentiation in both N2a cells and in rat primary hippocampal neuronal cultures. We also show that heparin modulates Wnt-3a-induced stabilization of b-catenin. Several extracellular matrix and membrane-attached HSPGs were found to be expressed in both in vitro neuronal models. Changes in the expression of specific HSPGs were observed upon differentiation of N2a cells. Taken together, our findings suggest that HSPGs may modulate canonical Wnt signaling for neuronal morphogenesis.
BioMetals, 2012
Niemann-Pick type C disease (NPC) is a hereditary neurovisceral atypical lipid storage disorder p... more Niemann-Pick type C disease (NPC) is a hereditary neurovisceral atypical lipid storage disorder produced by mutations in the NPC1 and NPC2 genes. The disease is characterized by unesterified cholesterol accumulation in late endosomal/lysosomal compartments and oxidative stress. The most affected tissues are the cerebellum and the liver. The lysotropic drug U18666A (U18) has been widely used as a pharmacological model to induce the NPC phenotype in several cell culture lines. It has already been reported that there is an increase in copper content in hepatoma Hu7 cells treated with U18. We confirmed this result with another human hepatoma cell line, HepG2, treated with U18 and supplemented with copper in the media. However, in mouse hippocampal primary cultures treated under similar conditions, we did not find alterations in copper content. We previously reported increased copper content in the liver of Npc1 (-/-) mice compared to control animals. Here, we extended the analysis to the copper content in the cerebella, the plasma and the bile of NPC1 deficient mice. We did not observe a significant change in copper content in the cerebella, whereas we found increased copper content in the plasma and decreased copper levels in the bile of Npc1(-/-) mice. Finally, we also evaluated the plasma content of ceruloplasmin, and we found an increase in this primary copper-binding protein in Npc1 (-/-) mice. These results indicate cell-type dependence of copper accumulation in NPC disease and suggest that copper transport imbalance may be relevant to the liver pathology observed in NPC disease.
Biochimica et Biophysica Acta (BBA) - Molecular Basis of Disease, 2012
Niemann-Pick C disease (NPC) is a neuro-visceral lysosomal storage disorder mainly caused by gene... more Niemann-Pick C disease (NPC) is a neuro-visceral lysosomal storage disorder mainly caused by genetic defects in the NPC1 gene. As a result of loss of NPC1 function large quantities of free cholesterol and other lipids accumulate within late endosomes and lysosomes. In NPC livers and brains, the buildup of lipids correlates with oxidative damage; however the molecular mechanisms that trigger it remain unknown. Here we study potential alterations in vitamin E (α-tocopherol, α-TOH), the most potent endogenous antioxidant, in liver tissue and neurons from NPC1 mice. We found increased levels of α-TOH in NPC cells. We observed accumulation and entrapment of α-TOH in NPC neurons, mainly in the late endocytic pathway. Accordingly, α-TOH levels were increased in cerebellum of NPC1 mice. Also, we found decreased mRNA levels of the α-TOH transporter, α-Tocopherol Transfer Protein (α-TTP), in the cerebellum of NPC1 mice. Finally, by subcellular fractionation studies we detected a significant increase in the hepatic α-TOH content in purified lysosomes from NPC1 mice. In conclusion, these results suggest that NPC cells cannot transport vitamin E correctly leading to α-TOH buildup in the endosomal/lysosomal system. This may result in a decreased bioavailability and impaired antioxidant function of vitamin E in NPC, contributing to the disease pathogenesis.
Amyloid, 1998
Amyloid fibril formation is believed to be a nucleation-dependent polymerization process which ma... more Amyloid fibril formation is believed to be a nucleation-dependent polymerization process which may be influenced by various other factors with important consequences for the development, prevention or treatment of amyloidosis. We have previously shown that laminin inhibits Aβpeptide fibril formation in vitro Here we present a kinetic study that indicates laminin to be a potent anti-amyloidosis factor, as it not only inhibited Aβ1-40fibril aggregation, but also inhibited the aggregation of the Dutch Aβ1-40 variant, a peptide with a higher capacity to aggregate than the wild-type Aβ1-40. The inhibitory effect of laminin on amyloid fibril formation was not overcome by the addition of pre-formed Aβ fibrils, suggesting that laminin inhibits the fibril elongation process. At the present time, however, we cannot rule out the possibility that laminin also affects the initial nucleation process of Aβ fibril formation. On other hand, laminin was not able to counteract the amyloid fibril formation promoted by acetylcholinesterase (AChE), another component of the amyloid deposits found in AD brains. The effect of laminin may be important as an inhibitor of Aβ amyloidogenesis in vivo, specifically at the level of cerebral blood vessels.
Journal of Neuroscience, 2010
The c-Abl tyrosine kinase is present in mouse brain synapses, but its precise synaptic function i... more The c-Abl tyrosine kinase is present in mouse brain synapses, but its precise synaptic function is unknown. We found that c-Abl levels in the rat hippocampus increase postnatally, with expression peaking at the first postnatal week. In 14 d in vitro hippocampal neuron cultures, c-Abl localizes primarily to the postsynaptic compartment, in which it colocalizes with the postsynaptic scaffold protein postsynaptic density protein-95 (PSD-95) in apposition to presynaptic markers. c-Abl associates with PSD-95, and chemical or genetic inhibition of c-Abl kinase activity reduces PSD-95 tyrosine phosphorylation, leading to reduced PSD-95 clustering and reduced synapses in treated neurons. c-Abl can phosphorylate PSD-95 on tyrosine 533, and mutation of this residue reduces the ability of PSD-95 to cluster at postsynaptic sites. Our results indicate that c-Abl regulates synapse formation by mediating tyrosine phosphorylation and clustering of PSD-95.
Oxidative Medicine and Cellular Longevity, 2012
Niemann-Pick type C (NPC) disease is a neurovisceral atypical lipid storage disorder involving th... more Niemann-Pick type C (NPC) disease is a neurovisceral atypical lipid storage disorder involving the accumulation of cholesterol and other lipids in the late endocytic pathway. The pathogenic mechanism that links the accumulation of intracellular cholesterol with cell death in NPC disease in both the CNS and the liver is currently unknown. Oxidative stress has been observed in the livers and brains of NPC mice and in different NPC cellular models. Moreover, there is evidence of an elevation of oxidative stress markers in the serumof NPC patients. Recent evidence strongly suggests that mitochondrial dysfunction plays an important role in NPC pathogenesis and that mitochondria could be a significant source of oxidative stress in this disease. In this context, the accumulation of vitamin E in the late endosomal/lysosomal compartments in NPC could lead to a potential decrease of its bioavailability and could be another possible cause of oxidative damage. Another possible source of reactiv...
Molecular Cell, 2014
In Alzheimer's disease (AD), there is a decrease in neuronal gene expression induced by HDAC2 inc... more In Alzheimer's disease (AD), there is a decrease in neuronal gene expression induced by HDAC2 increase; however, the mechanisms involved are not fully elucidated. Here, we described how the tyrosine kinase c-Abl increases HDAC2 levels, inducing transcriptional repression of synaptic genes. Our data demonstrate that (1) in neurons, c-Abl inhibition with Imatinib prevents the AbO-induced increase in HDAC2 levels; (2) c-Abl knockdown cells show a decrease in HDAC2 levels, while c-Abl overexpression increases them; (3) c-Abl inhibition reduces HDAC2-dependent repression activity and HDAC2 recruitment to the promoter of several synaptic genes, increasing their expression; (4) c-Abl induces tyrosine phosphorylation of HDAC2, a posttranslational modification, affecting both its stability and repression activity; and (5) treatment with Imatinib decreases HDAC2 levels in a transgenic mice model of AD. Our results support the participation of the c-Abl/HDAC2 signaling pathway in the epigenetic blockade of gene expression in AD pathology.
iScience, 2020
HIGHLIGHTS c-Abl is a TFEB regulator that mediates its tyr phosphorylation c-Abl inhibition promo... more HIGHLIGHTS c-Abl is a TFEB regulator that mediates its tyr phosphorylation c-Abl inhibition promotes TFEB activity independently of mTORC1 c-Abl inhibition reduces cholesterol accumulation in NPC1 models
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Papers by Alejandra Alvarez