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1.
Immunity ; 2024 Oct 09.
Artículo en Inglés | MEDLINE | ID: mdl-39419029

RESUMEN

The seeded growth of pathogenic protein aggregates underlies the pathogenesis of Alzheimer's disease (AD), but how this pathological cascade is initiated is not fully understood. Sporadic AD is linked genetically to apolipoprotein E (APOE) and other genes expressed in microglia related to immune, lipid, and endocytic functions. We generated a transgenic knockin mouse expressing HaloTag-tagged APOE and optimized experimental protocols for the biochemical purification of APOE, which enabled us to identify fibrillary aggregates of APOE in mice with amyloid-ß (Aß) amyloidosis and in human AD brain autopsies. These APOE aggregates that stained positive for ß sheet-binding dyes triggered Aß amyloidosis within the endo-lysosomal system of microglia, in a process influenced by microglial lipid metabolism and the JAK/STAT signaling pathway. Taking these observations together, we propose a model for the onset of Aß amyloidosis in AD, suggesting that the endocytic uptake and aggregation of APOE by microglia can initiate Aß plaque formation.

2.
Annu Rev Neurosci ; 46: 59-78, 2023 07 10.
Artículo en Inglés | MEDLINE | ID: mdl-37428605

RESUMEN

All mammalian cell membranes contain cholesterol to maintain membrane integrity. The transport of this hydrophobic lipid is mediated by lipoproteins. Cholesterol is especially enriched in the brain, particularly in synaptic and myelin membranes. Aging involves changes in sterol metabolism in peripheral organs and also in the brain. Some of those alterations have the potential to promote or to counteract the development of neurodegenerative diseases during aging. Here, we summarize the current knowledge of general principles of sterol metabolism in humans and mice, the most widely used model organism in biomedical research. We discuss changes in sterol metabolism that occur in the aged brain and highlight recent developments in cell type-specific cholesterol metabolism in the fast-growing research field of aging and age-related diseases, focusing on Alzheimer's disease. We propose that cell type-specific cholesterol handling and the interplay between cell types critically influence age-related disease processes.


Asunto(s)
Envejecimiento , Enfermedad de Alzheimer , Ratones , Humanos , Animales , Anciano , Enfermedad de Alzheimer/metabolismo , Encéfalo/metabolismo , Colesterol/metabolismo , Mamíferos/metabolismo
3.
Nature ; 618(7964): 349-357, 2023 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-37258678

RESUMEN

The incidence of Alzheimer's disease (AD), the leading cause of dementia, increases rapidly with age, but why age constitutes the main risk factor is still poorly understood. Brain ageing affects oligodendrocytes and the structural integrity of myelin sheaths1, the latter of which is associated with secondary neuroinflammation2,3. As oligodendrocytes support axonal energy metabolism and neuronal health4-7, we hypothesized that loss of myelin integrity could be an upstream risk factor for neuronal amyloid-ß (Aß) deposition, the central neuropathological hallmark of AD. Here we identify genetic pathways of myelin dysfunction and demyelinating injuries as potent drivers of amyloid deposition in mouse models of AD. Mechanistically, myelin dysfunction causes the accumulation of the Aß-producing machinery within axonal swellings and increases the cleavage of cortical amyloid precursor protein. Suprisingly, AD mice with dysfunctional myelin lack plaque-corralling microglia despite an overall increase in their numbers. Bulk and single-cell transcriptomics of AD mouse models with myelin defects show that there is a concomitant induction of highly similar but distinct disease-associated microglia signatures specific to myelin damage and amyloid plaques, respectively. Despite successful induction, amyloid disease-associated microglia (DAM) that usually clear amyloid plaques are apparently distracted to nearby myelin damage. Our data suggest a working model whereby age-dependent structural defects of myelin promote Aß plaque formation directly and indirectly and are therefore an upstream AD risk factor. Improving oligodendrocyte health and myelin integrity could be a promising target to delay development and slow progression of AD.


Asunto(s)
Enfermedad de Alzheimer , Péptidos beta-Amiloides , Vaina de Mielina , Placa Amiloide , Animales , Ratones , Enfermedad de Alzheimer/metabolismo , Enfermedad de Alzheimer/patología , Péptidos beta-Amiloides/metabolismo , Modelos Animales de Enfermedad , Vaina de Mielina/metabolismo , Vaina de Mielina/patología , Placa Amiloide/genética , Placa Amiloide/metabolismo , Placa Amiloide/patología , Axones/metabolismo , Axones/patología , Microglía/metabolismo , Microglía/patología , Análisis de Expresión Génica de una Sola Célula , Factores de Riesgo , Progresión de la Enfermedad
4.
Glia ; 72(8): 1374-1391, 2024 08.
Artículo en Inglés | MEDLINE | ID: mdl-38587131

RESUMEN

Oligodendrocytes and astrocytes are metabolically coupled to neuronal compartments. Pyruvate and lactate can shuttle between glial cells and axons via monocarboxylate transporters. However, lactate can only be synthesized or used in metabolic reactions with the help of lactate dehydrogenase (LDH), a tetramer of LDHA and LDHB subunits in varying compositions. Here we show that mice with a cell type-specific disruption of both Ldha and Ldhb genes in oligodendrocytes lack a pathological phenotype that would be indicative of oligodendroglial dysfunctions or lack of axonal metabolic support. Indeed, when combining immunohistochemical, electron microscopical, and in situ hybridization analyses in adult mice, we found that the vast majority of mature oligodendrocytes lack detectable expression of LDH. Even in neurodegenerative disease models and in mice under metabolic stress LDH was not increased. In contrast, at early development and in the remyelinating brain, LDHA was readily detectable in immature oligodendrocytes. Interestingly, by immunoelectron microscopy LDHA was particularly enriched at gap junctions formed between adjacent astrocytes and at junctions between astrocytes and oligodendrocytes. Our data suggest that oligodendrocytes metabolize lactate during development and remyelination. In contrast, for metabolic support of axons mature oligodendrocytes may export their own glycolysis products as pyruvate rather than lactate. Lacking LDH, these oligodendrocytes can also "funnel" lactate through their "myelinic" channels between gap junction-coupled astrocytes and axons without metabolizing it. We suggest a working model, in which the unequal cellular distribution of LDH in white matter tracts facilitates a rapid and efficient transport of glycolysis products among glial and axonal compartments.


Asunto(s)
Axones , Glucólisis , L-Lactato Deshidrogenasa , Oligodendroglía , Animales , Oligodendroglía/metabolismo , Axones/metabolismo , L-Lactato Deshidrogenasa/metabolismo , L-Lactato Deshidrogenasa/genética , Glucólisis/fisiología , Ratones , Regulación hacia Abajo/fisiología , Ratones Endogámicos C57BL , Lactato Deshidrogenasa 5/metabolismo , Astrocitos/metabolismo , Astrocitos/ultraestructura , Ratones Transgénicos , Isoenzimas/metabolismo , Isoenzimas/genética , Uniones Comunicantes/metabolismo , Uniones Comunicantes/ultraestructura , Ratones Noqueados
5.
Alzheimers Dement ; 20(10): 6776-6792, 2024 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-39212313

RESUMEN

INTRODUCTION: Cellular prion protein (PrPC) was implicated in amyloid beta (Aß)-induced toxicity in Alzheimer's disease (AD), but the precise molecular mechanisms involved in this process are unclear. METHODS: Double transgenic mice were generated by crossing Prnp knockout (KO) with 5xFAD mice, and light-sheet microscopy was used for whole brain tissue analyses. PrPC-overexpressing cells were developed for in vitro studies, and microscopy was used to assess co-localization of proteins of interest. Surface-plasmon resonance (SPR) was used to investigate protein-binding characteristics. RESULTS: In vivo, PrPC levels correlated with reduced lifespan and cognitive and motor function, and its ablation disconnected behavior deficits from Aß levels. Light-sheet microscopy showed that PrPC influenced Aß-plaque burden but not the distribution of those plaques. Interestingly, caveolin-1 (Cav-1) KO neurons significantly reduced intracellular Aß-oligomer (Aßo) uptake when compared to wild-type neurons. DISCUSSION: The findings shed new light on the relevance of intracellular Aßo, suggesting that PrPC and Cav-1 modulate intracellular Aß levels and the Aß-plaque load. HIGHLIGHTS: PrPC expression adversely affects lifespan and behavior in 5xFAD mice. PrPC increases Aß1-40 and Aß1-42 levels and Aß-plaque load in 5xFAD mice. Cav-1 interacts with both PrPC and Aß peptides. Knocking out Cav-1 leads to a significant reduction in intracellular Aß levels.


Asunto(s)
Enfermedad de Alzheimer , Péptidos beta-Amiloides , Caveolina 1 , Proteínas Priónicas , Animales , Humanos , Ratones , Enfermedad de Alzheimer/metabolismo , Enfermedad de Alzheimer/patología , Enfermedad de Alzheimer/genética , Péptidos beta-Amiloides/metabolismo , Encéfalo/metabolismo , Caveolina 1/metabolismo , Caveolina 1/genética , Modelos Animales de Enfermedad , Ratones Noqueados , Ratones Transgénicos , Neuronas/metabolismo , Placa Amiloide/metabolismo , Placa Amiloide/patología , Proteínas Priónicas/metabolismo , Proteínas Priónicas/genética , Proteínas PrPC/metabolismo , Proteínas PrPC/genética
6.
Glia ; 70(11): 2062-2078, 2022 11.
Artículo en Inglés | MEDLINE | ID: mdl-35802021

RESUMEN

Hypothalamic astrocytes are particularly affected by energy-dense food consumption. How the anatomical location of these glial cells and their spatial molecular distribution in the arcuate nucleus of the hypothalamus (ARC) determine the cellular response to a high caloric diet remains unclear. In this study, we investigated their distinctive molecular responses following exposure to a high-fat high-sugar (HFHS) diet, specifically in the ARC. Using RNA sequencing and proteomics, we showed that astrocytes have a distinct transcriptomic and proteomic profile dependent on their anatomical location, with a major proteomic reprogramming in hypothalamic astrocytes. By ARC single-cell sequencing, we observed that a HFHS diet dictates time- and cell- specific transcriptomic responses, revealing that astrocytes have the most distinct regulatory pattern compared to other cell types. Lastly, we topographically and molecularly characterized astrocytes expressing glial fibrillary acidic protein and/or aldehyde dehydrogenase 1 family member L1 in the ARC, of which the abundance was significantly increased, as well as the alteration in their spatial and molecular profiles, with a HFHS diet. Together, our results provide a detailed multi-omics view on the spatial and temporal changes of astrocytes particularly in the ARC during different time points of adaptation to a high calorie diet.


Asunto(s)
Astrocitos , Proteómica , Núcleo Arqueado del Hipotálamo/metabolismo , Astrocitos/metabolismo , Dieta Alta en Grasa/efectos adversos , Proteína Ácida Fibrilar de la Glía/genética , Proteína Ácida Fibrilar de la Glía/metabolismo , Hipotálamo/metabolismo
7.
Glia ; 68(3): 600-616, 2020 03.
Artículo en Inglés | MEDLINE | ID: mdl-31664743

RESUMEN

Liver kinase B1 (LKB1) is a ubiquitously expressed kinase involved in the regulation of cell metabolism, growth, and inflammatory activation. We previously reported that a single nucleotide polymorphism in the gene encoding LKB1 is a risk factor for multiple sclerosis (MS). Since astrocyte activation and metabolic function have important roles in regulating neuroinflammation and neuropathology, we examined the serine/threonine kinase LKB1 in astrocytes in a chronic experimental autoimmune encephalomyelitis mouse model of MS. To reduce LKB1, a heterozygous astrocyte-selective conditional knockout (het-cKO) model was used. While disease incidence was similar, disease severity was worsened in het-cKO mice. RNAseq analysis identified Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways enriched in het-cKO mice relating to mitochondrial function, confirmed by alterations in mitochondrial complex proteins and reductions in mRNAs related to astrocyte metabolism. Enriched pathways included major histocompatibility class II genes, confirmed by increases in MHCII protein in spinal cord and cerebellum of het-cKO mice. We observed increased numbers of CD4+ Th17 cells and increased neuronal damage in spinal cords of het-cKO mice, associated with reduced expression of choline acetyltransferase, accumulation of immunoglobulin-γ, and reduced expression of factors involved in motor neuron survival. In vitro, LKB1-deficient astrocytes showed reduced metabolic function and increased inflammatory activation. These data suggest that metabolic dysfunction in astrocytes, in this case due to LKB1 deficiency, can exacerbate demyelinating disease by loss of metabolic support and increase in the inflammatory environment.


Asunto(s)
Astrocitos/metabolismo , Esclerosis Múltiple/metabolismo , Vaina de Mielina/metabolismo , Proteínas Serina-Treonina Quinasas/deficiencia , Proteínas Quinasas Activadas por AMP , Animales , Diferenciación Celular/genética , Supervivencia Celular/fisiología , Modelos Animales de Enfermedad , Encefalomielitis Autoinmune Experimental/genética , Encefalomielitis Autoinmune Experimental/patología , Hígado/metabolismo , Ratones Noqueados , Esclerosis Múltiple/genética , Médula Espinal/patología
8.
Mol Psychiatry ; 24(10): 1489-1501, 2019 10.
Artículo en Inglés | MEDLINE | ID: mdl-29426955

RESUMEN

Autoantibodies of the IgG class against N-methyl-D-aspartate-receptor subunit-NR1 (NMDAR1-AB) were considered pathognomonic for anti-NMDAR encephalitis. This view has been challenged by the age-dependent seroprevalence (up to >20%) of functional NMDAR1-AB of all immunoglobulin classes found in >5000 individuals, healthy or affected by different diseases. These findings question a merely encephalitogenic role of NMDAR1-AB. Here, we show that NMDAR1-AB belong to the normal autoimmune repertoire of dogs, cats, rats, mice, baboons, and rhesus macaques, and are functional in the NMDAR1 internalization assay based on human IPSC-derived cortical neurons. The age dependence of seroprevalence is lost in nonhuman primates in captivity and in human migrants, raising the intriguing possibility that chronic life stress may be related to NMDAR1-AB formation, predominantly of the IgA class. Active immunization of ApoE-/- and ApoE+/+ mice against four peptides of the extracellular NMDAR1 domain or ovalbumin (control) leads to high circulating levels of specific AB. After 4 weeks, the endogenously formed NMDAR1-AB (IgG) induce psychosis-like symptoms upon MK-801 challenge in ApoE-/- mice, characterized by an open blood-brain barrier, but not in their ApoE+/+ littermates, which are indistinguishable from ovalbumin controls. Importantly, NMDAR1-AB do not induce any sign of inflammation in the brain. Immunohistochemical staining for microglial activation markers and T lymphocytes in the hippocampus yields comparable results in ApoE-/- and ApoE+/+ mice, irrespective of immunization against NMDAR1 or ovalbumin. These data suggest that NMDAR1-AB of the IgG class shape behavioral phenotypes upon access to the brain but do not cause brain inflammation on their own.


Asunto(s)
Encefalitis Antirreceptor N-Metil-D-Aspartato/inmunología , Trastornos Mentales/inmunología , Receptores de N-Metil-D-Aspartato/inmunología , Adulto , Animales , Autoanticuerpos/inmunología , Barrera Hematoencefálica , Encéfalo/inmunología , Gatos , Perros , Femenino , Humanos , Inmunoglobulina G/genética , Inmunoglobulina G/inmunología , Masculino , Ratones , Proteínas del Tejido Nervioso/inmunología , Proteínas del Tejido Nervioso/metabolismo , Neuronas/inmunología , Primates , Ratas , Receptores de N-Metil-D-Aspartato/metabolismo , Estudios Seroepidemiológicos
9.
Acta Neuropathol ; 138(1): 147-161, 2019 07.
Artículo en Inglés | MEDLINE | ID: mdl-30919030

RESUMEN

Pelizaeus-Merzbacher disease (PMD) is an untreatable and fatal leukodystrophy. In a model of PMD with perturbed blood-brain barrier integrity, cholesterol supplementation promotes myelin membrane growth. Here, we show that in contrast to the mouse model, dietary cholesterol in two PMD patients did not lead to a major advancement of hypomyelination, potentially because the intact blood-brain barrier precludes its entry into the CNS. We therefore turned to a PMD mouse model with preserved blood-brain barrier integrity and show that a high-fat/low-carbohydrate ketogenic diet restored oligodendrocyte integrity and increased CNS myelination. This dietary intervention also ameliorated axonal degeneration and normalized motor functions. Moreover, in a paradigm of adult remyelination, ketogenic diet facilitated repair and attenuated axon damage. We suggest that a therapy with lipids such as ketone bodies, that readily enter the brain, can circumvent the requirement of a disrupted blood-brain barrier in the treatment of myelin disease.


Asunto(s)
Enfermedades Desmielinizantes/patología , Proteína Proteolipídica de la Mielina/metabolismo , Oligodendroglía/fisiología , Enfermedad de Pelizaeus-Merzbacher/patología , Animales , Dieta Cetogénica , Modelos Animales de Enfermedad , Ratones , Oligodendroglía/metabolismo , Organogénesis/fisiología
11.
Biochim Biophys Acta ; 1851(8): 1083-94, 2015 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-25724171

RESUMEN

The largest pool of free cholesterol in mammals resides in myelin membranes. Myelin facilitates rapid saltatory impulse propagation by electrical insulation of axons. This function is achieved by ensheathing axons with a tightly compacted stack of membranes. Cholesterol influences myelination at many steps, from the differentiation of myelinating glial cells, over the process of myelin membrane biogenesis, to the functionality of mature myelin. Cholesterol emerged as the only integral myelin component that is essential and rate-limiting for the development of myelin in the central and peripheral nervous system. Moreover, disorders that interfere with sterol synthesis or intracellular trafficking of cholesterol and other lipids cause hypomyelination and neurodegeneration. This review summarizes recent results on the roles of cholesterol in CNS myelin biogenesis in normal development and under different pathological conditions. This article is part of a Special Issue entitled Brain Lipids.


Asunto(s)
Colesterol/metabolismo , Vaina de Mielina/metabolismo , Enfermedad de Niemann-Pick Tipo C/metabolismo , Enfermedad de Pelizaeus-Merzbacher/metabolismo , Síndrome de Smith-Lemli-Opitz/metabolismo , Animales , Astrocitos/citología , Astrocitos/metabolismo , Membrana Celular/metabolismo , Membrana Celular/ultraestructura , Sistema Nervioso Central/citología , Sistema Nervioso Central/metabolismo , Homeostasis , Humanos , Vaina de Mielina/química , Vaina de Mielina/ultraestructura , Neuronas/citología , Neuronas/metabolismo , Enfermedad de Niemann-Pick Tipo C/patología , Enfermedad de Pelizaeus-Merzbacher/patología , Sistema Nervioso Periférico/citología , Sistema Nervioso Periférico/metabolismo , Síndrome de Smith-Lemli-Opitz/patología , Transmisión Sináptica
12.
J Virol ; 87(19): 10612-27, 2013 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-23885072

RESUMEN

Like all other positive-strand RNA viruses, hepatitis C virus (HCV) induces rearrangements of intracellular membranes that are thought to serve as a scaffold for the assembly of the viral replicase machinery. The most prominent membranous structures present in HCV-infected cells are double-membrane vesicles (DMVs). However, their composition and role in the HCV replication cycle are poorly understood. To gain further insights into the biochemcial properties of HCV-induced membrane alterations, we generated a functional replicon containing a hemagglutinin (HA) affinity tag in nonstructural protein 4B (NS4B), the supposed scaffold protein of the viral replication complex. By using HA-specific affinity purification we isolated NS4B-containing membranes from stable replicon cells. Complementing biochemical and electron microscopy analyses of purified membranes revealed predominantly DMVs, which contained viral proteins NS3 and NS5A as well as enzymatically active viral replicase capable of de novo synthesis of HCV RNA. In addition to viral factors, co-opted cellular proteins, such as vesicle-associated membrane protein-associated protein A (VAP-A) and VAP-B, that are crucial for viral RNA replication, as well as cholesterol, a major structural lipid of detergent-resistant membranes, are highly enriched in DMVs. Here we describe the first isolation and biochemical characterization of HCV-induced DMVs. The results obtained underline their central role in the HCV replication cycle and suggest that DMVs are sites of viral RNA replication. The experimental approach described here is a powerful tool to more precisely define the molecular composition of membranous replication factories induced by other positive-strand RNA viruses, such as picorna-, arteri- and coronaviruses.


Asunto(s)
Hepacivirus/fisiología , Hepatitis C/virología , Membranas Intracelulares/metabolismo , ARN Polimerasa Dependiente del ARN/metabolismo , Proteínas no Estructurales Virales/metabolismo , Replicación Viral , Western Blotting , Carcinoma Hepatocelular/metabolismo , Carcinoma Hepatocelular/patología , Carcinoma Hepatocelular/virología , Cromatografía de Afinidad , Técnica del Anticuerpo Fluorescente , Hepatitis C/metabolismo , Hepatitis C/patología , Humanos , Membranas Intracelulares/virología , Neoplasias Hepáticas/metabolismo , Neoplasias Hepáticas/patología , Neoplasias Hepáticas/virología , ARN Mensajero/genética , ARN Viral/genética , ARN Polimerasa Dependiente del ARN/genética , Reacción en Cadena en Tiempo Real de la Polimerasa , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Células Tumorales Cultivadas , Proteínas no Estructurales Virales/genética
13.
bioRxiv ; 2024 Apr 15.
Artículo en Inglés | MEDLINE | ID: mdl-38659917

RESUMEN

Afferent neurons in developing sensory organs exhibit a prolonged period of burst firing prior to the onset of sensory experience. This intrinsically generated activity propagates from the periphery through central processing centers to promote the survival and physiological maturation of neurons and refine their synaptic connectivity. Recent studies in the auditory system indicate that these bursts of action potentials also trigger metabotropic glutamate receptor-mediated calcium increases within astrocytes that are spatially and temporally correlated with neuronal events; however, it is not known if this phenomenon occurs in other sensory modalities. Here we show using in vivo simultaneous imaging of neuronal and astrocyte calcium activity in awake mouse pups that waves of retinal ganglion cell activity induce spatially and temporally correlated waves of astrocyte activity in the superior colliculus that depend on metabotropic glutamate receptors mGluR5 and mGluR3. Astrocyte calcium transients reliably occurred with each neuronal wave, but peaked more than one second after neuronal events. Despite differences in the temporal features of spontaneous activity in auditory and visual processing regions, individual astrocytes exhibited similar overall calcium activity patterns, providing a conserved mechanism to synchronize neuronal and astrocyte maturation within discrete sensory domains.

14.
EMBO Mol Med ; 16(3): 616-640, 2024 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-38383802

RESUMEN

Haplo-insufficiency of the gene encoding the myelin protein PMP22 leads to focal myelin overgrowth in the peripheral nervous system and hereditary neuropathy with liability to pressure palsies (HNPP). Conversely, duplication of PMP22 causes Charcot-Marie-Tooth disease type 1A (CMT1A), characterized by hypomyelination of medium to large caliber axons. The molecular mechanisms of abnormal myelin growth regulation by PMP22 have remained obscure. Here, we show in rodent models of HNPP and CMT1A that the PI3K/Akt/mTOR-pathway inhibiting phosphatase PTEN is correlated in abundance with PMP22 in peripheral nerves, without evidence for direct protein interactions. Indeed, treating DRG neuron/Schwann cell co-cultures from HNPP mice with PI3K/Akt/mTOR pathway inhibitors reduced focal hypermyelination. When we treated HNPP mice in vivo with the mTOR inhibitor Rapamycin, motor functions were improved, compound muscle amplitudes were increased and pathological tomacula in sciatic nerves were reduced. In contrast, we found Schwann cell dedifferentiation in CMT1A uncoupled from PI3K/Akt/mTOR, leaving partial PTEN ablation insufficient for disease amelioration. For HNPP, the development of PI3K/Akt/mTOR pathway inhibitors may be considered as the first treatment option for pressure palsies.


Asunto(s)
Artrogriposis , Enfermedad de Charcot-Marie-Tooth , Neuropatía Hereditaria Motora y Sensorial , Fosfatidilinositol 3-Quinasas , Ratones , Animales , Proteínas Proto-Oncogénicas c-akt , Roedores/metabolismo , Enfermedad de Charcot-Marie-Tooth/genética , Enfermedad de Charcot-Marie-Tooth/patología , Proteínas de la Mielina/genética , Proteínas de la Mielina/metabolismo , Serina-Treonina Quinasas TOR
15.
J Cell Biol ; 223(1)2024 01 01.
Artículo en Inglés | MEDLINE | ID: mdl-38032389

RESUMEN

Nedd4-2 is an E3 ubiquitin ligase in which missense mutation is related to familial epilepsy, indicating its critical role in regulating neuronal network activity. However, Nedd4-2 substrates involved in neuronal network function have yet to be identified. Using mouse lines lacking Nedd4-1 and Nedd4-2, we identified astrocytic channel proteins inwardly rectifying K+ channel 4.1 (Kir4.1) and Connexin43 as Nedd4-2 substrates. We found that the expression of Kir4.1 and Connexin43 is increased upon conditional deletion of Nedd4-2 in astrocytes, leading to an elevation of astrocytic membrane ion permeability and gap junction activity, with a consequent reduction of γ-oscillatory neuronal network activity. Interestingly, our biochemical data demonstrate that missense mutations found in familial epileptic patients produce gain-of-function of the Nedd4-2 gene product. Our data reveal a process of coordinated astrocytic ion channel proteostasis that controls astrocyte function and astrocyte-dependent neuronal network activity and elucidate a potential mechanism by which aberrant Nedd4-2 function leads to epilepsy.


Asunto(s)
Astrocitos , Permeabilidad de la Membrana Celular , Conexina 43 , Ubiquitina-Proteína Ligasas Nedd4 , Canales de Potasio de Rectificación Interna , Animales , Humanos , Ratones , Conexina 43/genética , Mutación Missense , Proteostasis , Canales de Potasio de Rectificación Interna/genética , Ubiquitina-Proteína Ligasas Nedd4/genética , Epilepsia
16.
Nat Neurosci ; 27(9): 1668-1674, 2024 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-39103558

RESUMEN

Amyloid-ß (Aß) is thought to be neuronally derived in Alzheimer's disease (AD). However, transcripts of amyloid precursor protein (APP) and amyloidogenic enzymes are equally abundant in oligodendrocytes (OLs). By cell-type-specific deletion of Bace1 in a humanized knock-in AD model, APPNLGF, we demonstrate that OLs and neurons contribute to Aß plaque burden. For rapid plaque seeding, excitatory projection neurons must provide a threshold level of Aß. Ultimately, our findings are relevant for AD prevention and therapeutic strategies.


Asunto(s)
Enfermedad de Alzheimer , Secretasas de la Proteína Precursora del Amiloide , Péptidos beta-Amiloides , Ácido Aspártico Endopeptidasas , Neuronas , Oligodendroglía , Placa Amiloide , Animales , Humanos , Ratones , Enfermedad de Alzheimer/metabolismo , Enfermedad de Alzheimer/patología , Enfermedad de Alzheimer/genética , Péptidos beta-Amiloides/metabolismo , Precursor de Proteína beta-Amiloide/metabolismo , Precursor de Proteína beta-Amiloide/genética , Secretasas de la Proteína Precursora del Amiloide/metabolismo , Ácido Aspártico Endopeptidasas/metabolismo , Modelos Animales de Enfermedad , Ratones Transgénicos , Neuronas/metabolismo , Neuronas/patología , Oligodendroglía/metabolismo , Oligodendroglía/patología , Placa Amiloide/patología , Placa Amiloide/metabolismo
17.
J Neurosci ; 32(22): 7632-45, 2012 May 30.
Artículo en Inglés | MEDLINE | ID: mdl-22649242

RESUMEN

Cholesterol is an essential membrane component enriched in plasma membranes, growth cones, and synapses. The brain normally synthesizes all cholesterol locally, but the contribution of individual cell types to brain cholesterol metabolism is unknown. To investigate whether cortical projection neurons in vivo essentially require cholesterol biosynthesis and which cell types support neurons, we have conditionally ablated the cholesterol biosynthesis in these neurons in mice either embryonically or postnatally. We found that cortical projection neurons synthesize cholesterol during their entire lifetime. At all stages, they can also benefit from glial support. Adult neurons that lack cholesterol biosynthesis are mainly supported by astrocytes such that their functional integrity is preserved. In contrast, microglial cells support young neurons. However, compensatory efforts of microglia are only transient leading to layer-specific neuronal death and the reduction of cortical projections. Hence, during the phase of maximal membrane growth and maximal cholesterol demand, neuronal cholesterol biosynthesis is indispensable. Analysis of primary neurons revealed that neurons tolerate only slight alteration in the cholesterol content and plasma membrane tension. This quality control allows neurons to differentiate normally and adjusts the extent of neurite outgrowth, the number of functional growth cones and synapses to the available cholesterol. This study highlights both the flexibility and the limits of horizontal cholesterol transfer in vivo and may have implications for the understanding of neurodegenerative diseases.


Asunto(s)
Colesterol/biosíntesis , Neuritas/fisiología , Neuronas/citología , Neuronas/metabolismo , Análisis de Varianza , Animales , Animales Recién Nacidos , Anticolesterolemiantes , Apolipoproteínas E/genética , Apolipoproteínas E/metabolismo , Proteínas Bacterianas/genética , Proteínas Bacterianas/metabolismo , Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/genética , Compuestos Bicíclicos Heterocíclicos con Puentes/farmacología , Proteína Quinasa Tipo 2 Dependiente de Calcio Calmodulina/genética , Diferenciación Celular/efectos de los fármacos , Diferenciación Celular/genética , Supervivencia Celular/efectos de los fármacos , Supervivencia Celular/genética , Células Cultivadas , Corteza Cerebral/citología , Corteza Cerebral/embriología , Corteza Cerebral/crecimiento & desarrollo , Colesterol/farmacología , Embrión de Mamíferos , Efrina-A5/farmacología , Potenciales Postsinápticos Excitadores/efectos de los fármacos , Potenciales Postsinápticos Excitadores/genética , Farnesil Difosfato Farnesil Transferasa/genética , Regulación del Desarrollo de la Expresión Génica/genética , Proteína Ácida Fibrilar de la Glía/metabolismo , Conos de Crecimiento/efectos de los fármacos , Conos de Crecimiento/fisiología , Hipocampo/citología , Humanos , Proteínas Luminiscentes/genética , Proteínas Luminiscentes/metabolismo , Ratones , Ratones Transgénicos , Microglía/efectos de los fármacos , Microglía/fisiología , Mutación/genética , Proteínas del Tejido Nervioso/genética , Proteínas del Tejido Nervioso/metabolismo , Vías Nerviosas/citología , Vías Nerviosas/efectos de los fármacos , Vías Nerviosas/embriología , Vías Nerviosas/crecimiento & desarrollo , Neuritas/efectos de los fármacos , Neuritas/ultraestructura , Neuronas/efectos de los fármacos , Técnicas de Placa-Clamp , ARN Mensajero/metabolismo , Transducción de Señal/efectos de los fármacos
18.
Glia ; 61(4): 567-86, 2013 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-23322581

RESUMEN

The formation of central nervous system myelin by oligodendrocytes requires sterol synthesis and is associated with a significant enrichment of cholesterol in the myelin membrane. However, it is unknown how oligodendrocytes concentrate cholesterol above the level found in nonmyelin membranes. Here, we demonstrate a critical role for proteolipids in cholesterol accumulation. Mice lacking the most abundant myelin protein, proteolipid protein (PLP), are fully myelinated, but PLP-deficient myelin exhibits a reduced cholesterol content. We therefore hypothesized that "high cholesterol" is not essential in the myelin sheath itself but is required for an earlier step of myelin biogenesis that is fully compensated for in the absence of PLP. We also found that a PLP-homolog, glycoprotein M6B, is a myelin component of low abundance. By targeting the Gpm6b-gene and crossbreeding, we found that single-mutant mice lacking either PLP or M6B are fully myelinated, while double mutants remain severely hypomyelinated, with enhanced neurodegeneration and premature death. As both PLP and M6B bind membrane cholesterol and associate with the same cholesterol-rich oligodendroglial membrane microdomains, we suggest a model in which proteolipids facilitate myelination by sequestering cholesterol. While either proteolipid can maintain a threshold level of cholesterol in the secretory pathway that allows myelin biogenesis, lack of both proteolipids results in a severe molecular imbalance of prospective myelin membrane. However, M6B is not efficiently sorted into mature myelin, in which it is 200-fold less abundant than PLP. Thus, only PLP contributes to the high cholesterol content of myelin by association and co-transport.


Asunto(s)
Sistema Nervioso Central/fisiología , Colesterol/fisiología , Glicoproteínas de Membrana/fisiología , Proteína Proteolipídica de la Mielina/fisiología , Vaina de Mielina/fisiología , Proteínas del Tejido Nervioso/fisiología , Animales , Línea Celular , Potenciales Evocados Auditivos del Tronco Encefálico/genética , Potenciales Evocados Auditivos del Tronco Encefálico/fisiología , Potenciales Evocados Visuales/genética , Potenciales Evocados Visuales/fisiología , Glicoproteínas de Membrana/genética , Ratones , Proteína Proteolipídica de la Mielina/genética , Vaina de Mielina/genética , Proteínas del Tejido Nervioso/genética , Órgano Vomeronasal/embriología , Órgano Vomeronasal/fisiología
19.
Nat Neurosci ; 26(7): 1218-1228, 2023 07.
Artículo en Inglés | MEDLINE | ID: mdl-37386131

RESUMEN

Axonal degeneration determines the clinical outcome of multiple sclerosis and is thought to result from exposure of denuded axons to immune-mediated damage. Therefore, myelin is widely considered to be a protective structure for axons in multiple sclerosis. Myelinated axons also depend on oligodendrocytes, which provide metabolic and structural support to the axonal compartment. Given that axonal pathology in multiple sclerosis is already visible at early disease stages, before overt demyelination, we reasoned that autoimmune inflammation may disrupt oligodendroglial support mechanisms and hence primarily affect axons insulated by myelin. Here, we studied axonal pathology as a function of myelination in human multiple sclerosis and mouse models of autoimmune encephalomyelitis with genetically altered myelination. We demonstrate that myelin ensheathment itself becomes detrimental for axonal survival and increases the risk of axons degenerating in an autoimmune environment. This challenges the view of myelin as a solely protective structure and suggests that axonal dependence on oligodendroglial support can become fatal when myelin is under inflammatory attack.


Asunto(s)
Encefalomielitis Autoinmune Experimental , Esclerosis Múltiple , Ratones , Animales , Humanos , Vaina de Mielina/metabolismo , Axones/metabolismo , Esclerosis Múltiple/patología , Encefalomielitis Autoinmune Experimental/patología , Factores de Riesgo
20.
Proc Natl Acad Sci U S A ; 106(20): 8350-5, 2009 May 19.
Artículo en Inglés | MEDLINE | ID: mdl-19416849

RESUMEN

Although sufficient cholesterol supply is known to be crucial for neurons in the developing mammalian brain, the cholesterol requirement of neural stem and progenitor cells in the embryonic central nervous system has not been addressed. Here we have conditionally ablated the activity of squalene synthase (SQS), a key enzyme for endogenous cholesterol production, in the neural stem and progenitor cells of the ventricular zone (VZ) of the embryonic mouse brain. Mutant embryos exhibited a reduced brain size due to the atrophy of the neuronal layers, and died at birth. Analyses of the E11.5-E15.5 dorsal telencephalon and diencephalon revealed that this atrophy was due to massive apoptosis of newborn neurons, implying that this progeny of the SQS-ablated neural stem and progenitor cells was dependent on endogenous cholesterol biosynthesis for survival. Interestingly, the neural stem and progenitor cells of the VZ, the primary target of SQS inactivation, did not undergo significant apoptosis. Instead, vascular endothelial growth factor (VEGF) expression in these cells was strongly upregulated via a hypoxia-inducible factor-1-independent pathway, and angiogenesis in the VZ was increased. Consistent with an increased supply of lipoproteins to these cells, the level of lipid droplets containing triacylglycerides with unsaturated fatty acyl chains was found to be elevated. Our study establishes a direct link between intracellular cholesterol levels, VEGF expression, and angiogenesis. Moreover, our data reveal a hitherto unknown compensatory process by which the neural stem and progenitor cells of the developing mammalian brain evade the detrimental consequences of impaired endogenous cholesterol biosynthesis.


Asunto(s)
Apoptosis , Colesterol/biosíntesis , Farnesil Difosfato Farnesil Transferasa/deficiencia , Neovascularización Fisiológica , Neuronas/citología , Células Madre/metabolismo , Factor A de Crecimiento Endotelial Vascular/genética , Animales , Encéfalo/citología , Encéfalo/embriología , Colesterol/deficiencia , Embrión de Mamíferos , Lípidos/análisis , Ratones , Neuronas/metabolismo , Células Madre/citología , Regulación hacia Arriba/genética , Regulación hacia Arriba/fisiología
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