RESUMEN
The engagement of a T cell with an antigen-presenting cell (APC) or activating surface results in the formation within the T cell of several distinct actin and actomyosin networks. These networks reside largely within a narrow zone immediately under the T cell's plasma membrane at its site of contact with the APC or activating surface, i.e., at the immunological synapse. Here we review the origin, organization, dynamics, and function of these synapse-associated actin and actomyosin networks. Importantly, recent insights into the nature of these actin-based cytoskeletal structures were made possible in several cases by advances in light microscopy.
Asunto(s)
Actinas/metabolismo , Actomiosina/metabolismo , Células Presentadoras de Antígenos/metabolismo , Citoesqueleto/metabolismo , Sinapsis Inmunológicas/metabolismo , Linfocitos T/metabolismo , Animales , Presentación de Antígeno , Humanos , Activación de LinfocitosRESUMEN
To understand biological processes, it is necessary to reveal the molecular heterogeneity of cells by gaining access to the location and interaction of all biomolecules. Significant advances were achieved by super-resolution microscopy, but such methods are still far from reaching the multiplexing capacity of proteomics. Here, we introduce secondary label-based unlimited multiplexed DNA-PAINT (SUM-PAINT), a high-throughput imaging method that is capable of achieving virtually unlimited multiplexing at better than 15 nm resolution. Using SUM-PAINT, we generated 30-plex single-molecule resolved datasets in neurons and adapted omics-inspired analysis for data exploration. This allowed us to reveal the complexity of synaptic heterogeneity, leading to the discovery of a distinct synapse type. We not only provide a resource for researchers, but also an integrated acquisition and analysis workflow for comprehensive spatial proteomics at single-protein resolution.
Asunto(s)
Proteómica , Imagen Individual de Molécula , ADN , Microscopía Fluorescente/métodos , Neuronas , ProteínasRESUMEN
Neurons build synaptic contacts using different protein combinations that define the specificity, function, and plasticity potential of synapses; however, the diversity of synaptic proteomes remains largely unexplored. We prepared synaptosomes from 7 different transgenic mouse lines with fluorescently labeled presynaptic terminals. Combining microdissection of 5 different brain regions with fluorescent-activated synaptosome sorting (FASS), we isolated and analyzed the proteomes of 18 different synapse types. We discovered â¼1,800 unique synapse-type-enriched proteins and allocated thousands of proteins to different types of synapses (https://syndive.org/). We identify shared synaptic protein modules and highlight the proteomic hotspots for synapse specialization. We reveal unique and common features of the striatal dopaminergic proteome and discover the proteome signatures that relate to the functional properties of different interneuron classes. This study provides a molecular systems-biology analysis of synapses and a framework to integrate proteomic information for synapse subtypes of interest with cellular or circuit-level experiments.
Asunto(s)
Encéfalo , Proteoma , Sinapsis , Animales , Ratones , Encéfalo/metabolismo , Ratones Transgénicos , Proteoma/metabolismo , Proteómica , Sinapsis/metabolismo , Sinaptosomas/metabolismoRESUMEN
Animals with complex nervous systems demand sleep for memory consolidation and synaptic remodeling. Here, we show that, although the Caenorhabditis elegans nervous system has a limited number of neurons, sleep is necessary for both processes. In addition, it is unclear if, in any system, sleep collaborates with experience to alter synapses between specific neurons and whether this ultimately affects behavior. C. elegans neurons have defined connections and well-described contributions to behavior. We show that spaced odor-training and post-training sleep induce long-term memory. Memory consolidation, but not acquisition, requires a pair of interneurons, the AIYs, which play a role in odor-seeking behavior. In worms that consolidate memory, both sleep and odor conditioning are required to diminish inhibitory synaptic connections between the AWC chemosensory neurons and the AIYs. Thus, we demonstrate in a living organism that sleep is required for events immediately after training that drive memory consolidation and alter synaptic structures.
Asunto(s)
Caenorhabditis elegans , Odorantes , Animales , Caenorhabditis elegans/fisiología , Olfato , Sueño/fisiología , Sinapsis/fisiologíaRESUMEN
Dopaminergic projections regulate various brain functions and are implicated in many neuropsychiatric disorders. There are two anatomically and functionally distinct dopaminergic projections connecting the midbrain to striatum: nigrostriatal, which controls movement, and mesolimbic, which regulates motivation. However, how these discrete dopaminergic synaptic connections are established is unknown. Through an unbiased search, we identify that two groups of antagonistic TGF-ß family members, bone morphogenetic protein (BMP)6/BMP2 and transforming growth factor (TGF)-ß2, regulate dopaminergic synapse development of nigrostriatal and mesolimbic neurons, respectively. Projection-preferential expression of their receptors contributes to specific synapse development. Downstream, Smad1 and Smad2 are specifically activated and required for dopaminergic synapse development and function in nigrostriatal vs. mesolimbic projections. Remarkably, Smad1 mutant mice show motor defects, whereas Smad2 mutant mice show lack of motivation. These results uncover the molecular logic underlying the proper establishment of functionally segregated dopaminergic synapses and may provide strategies to treat relevant, projection-specific disease symptoms by targeting specific BMPs/TGF-ß and/or Smads.
Asunto(s)
Cuerpo Estriado , Dopamina , Animales , Ratones , Mesencéfalo , Motivación , Movimiento , SinapsisRESUMEN
Tau (MAPT) drives neuronal dysfunction in Alzheimer disease (AD) and other tauopathies. To dissect the underlying mechanisms, we combined an engineered ascorbic acid peroxidase (APEX) approach with quantitative affinity purification mass spectrometry (AP-MS) followed by proximity ligation assay (PLA) to characterize Tau interactomes modified by neuronal activity and mutations that cause frontotemporal dementia (FTD) in human induced pluripotent stem cell (iPSC)-derived neurons. We established interactions of Tau with presynaptic vesicle proteins during activity-dependent Tau secretion and mapped the Tau-binding sites to the cytosolic domains of integral synaptic vesicle proteins. We showed that FTD mutations impair bioenergetics and markedly diminished Tau's interaction with mitochondria proteins, which were downregulated in AD brains of multiple cohorts and correlated with disease severity. These multimodal and dynamic Tau interactomes with exquisite spatial resolution shed light on Tau's role in neuronal function and disease and highlight potential therapeutic targets to block Tau-mediated pathogenesis.
Asunto(s)
Mitocondrias/metabolismo , Degeneración Nerviosa/metabolismo , Mapas de Interacción de Proteínas , Sinapsis/metabolismo , Proteínas tau/metabolismo , Enfermedad de Alzheimer/genética , Aminoácidos/metabolismo , Biotinilación , Encéfalo/metabolismo , Encéfalo/patología , Núcleo Celular/metabolismo , Progresión de la Enfermedad , Metabolismo Energético , Demencia Frontotemporal/genética , Humanos , Células Madre Pluripotentes Inducidas/metabolismo , Proteínas Mutantes/metabolismo , Mutación/genética , Degeneración Nerviosa/patología , Neuronas/metabolismo , Unión Proteica , Dominios Proteicos , Proteómica , Índice de Severidad de la Enfermedad , Fracciones Subcelulares/metabolismo , Tauopatías/genética , Proteínas tau/químicaRESUMEN
Glioblastomas are incurable tumors infiltrating the brain. A subpopulation of glioblastoma cells forms a functional and therapy-resistant tumor cell network interconnected by tumor microtubes (TMs). Other subpopulations appear unconnected, and their biological role remains unclear. Here, we demonstrate that whole-brain colonization is fueled by glioblastoma cells that lack connections with other tumor cells and astrocytes yet receive synaptic input from neurons. This subpopulation corresponds to neuronal and neural-progenitor-like tumor cell states, as defined by single-cell transcriptomics, both in mouse models and in the human disease. Tumor cell invasion resembled neuronal migration mechanisms and adopted a Lévy-like movement pattern of probing the environment. Neuronal activity induced complex calcium signals in glioblastoma cells followed by the de novo formation of TMs and increased invasion speed. Collectively, superimposing molecular and functional single-cell data revealed that neuronal mechanisms govern glioblastoma cell invasion on multiple levels. This explains how glioblastoma's dissemination and cellular heterogeneity are closely interlinked.
Asunto(s)
Neoplasias Encefálicas , Glioblastoma , Animales , Astrocitos/patología , Encéfalo/patología , Neoplasias Encefálicas/patología , Glioblastoma/genética , Glioblastoma/patología , Humanos , Ratones , Invasividad Neoplásica , Neuronas/fisiologíaRESUMEN
RTN4-binding proteins were widely studied as "NoGo" receptors, but their physiological interactors and roles remain elusive. Similarly, BAI adhesion-GPCRs were associated with numerous activities, but their ligands and functions remain unclear. Using unbiased approaches, we observed an unexpected convergence: RTN4 receptors are high-affinity ligands for BAI adhesion-GPCRs. A single thrombospondin type 1-repeat (TSR) domain of BAIs binds to the leucine-rich repeat domain of all three RTN4-receptor isoforms with nanomolar affinity. In the 1.65 Å crystal structure of the BAI1/RTN4-receptor complex, C-mannosylation of tryptophan and O-fucosylation of threonine in the BAI TSR-domains creates a RTN4-receptor/BAI interface shaped by unusual glycoconjugates that enables high-affinity interactions. In human neurons, RTN4 receptors regulate dendritic arborization, axonal elongation, and synapse formation by differential binding to glial versus neuronal BAIs, thereby controlling neural network activity. Thus, BAI binding to RTN4/NoGo receptors represents a receptor-ligand axis that, enabled by rare post-translational modifications, controls development of synaptic circuits.
Asunto(s)
Inhibidores de la Angiogénesis/metabolismo , Encéfalo/metabolismo , Neurogénesis , Neuronas/metabolismo , Proteínas Nogo/metabolismo , Receptores Nogo/metabolismo , Receptores Acoplados a Proteínas G/metabolismo , Adipoquinas/metabolismo , Secuencia de Aminoácidos , Animales , Axones/metabolismo , Adhesión Celular , Moléculas de Adhesión Celular Neuronal/metabolismo , Complemento C1q/metabolismo , Dendritas/metabolismo , Glicosilación , Células HEK293 , Células Madre Embrionarias Humanas/metabolismo , Humanos , Ligandos , Ratones Endogámicos C57BL , Red Nerviosa/metabolismo , Polisacáridos/metabolismo , Unión Proteica , Dominios Proteicos , Eliminación de Secuencia , Sinapsis/metabolismo , Transmisión Sináptica/fisiologíaRESUMEN
The specific patterns and functional properties of electrical synapses of a nervous system are defined by the neuron-specific complement of electrical synapse constituents. We systematically examined the molecular composition of the electrical connectome of the nematode C. elegans through a genome- and nervous-system-wide analysis of the expression patterns of the invertebrate electrical synapse constituents, the innexins. We observe highly complex combinatorial expression patterns throughout the nervous system and found that these patterns change in a strikingly neuron-type-specific manner throughout the nervous system when animals enter an insulin-controlled diapause arrest stage under harsh environmental conditions, the dauer stage. By analyzing several individual synapses, we demonstrate that dauer-specific electrical synapse remodeling is responsible for specific aspects of the altered locomotory and chemosensory behavior of dauers. We describe an intersectional gene regulatory mechanism involving terminal selector and FoxO transcription factors mediating dynamic innexin expression plasticity in a neuron-type- and environment-specific manner.
Asunto(s)
Caenorhabditis elegans/fisiología , Sinapsis Eléctricas/metabolismo , Plasticidad Neuronal/fisiología , Animales , Caenorhabditis elegans/metabolismo , Proteínas de Caenorhabditis elegans/metabolismo , Conectoma/métodos , Regulación del Desarrollo de la Expresión Génica/genética , Larva/metabolismo , Neuronas/metabolismo , Transducción de Señal , Sinapsis/metabolismo , Factores de Transcripción/metabolismoRESUMEN
Neuromodulators bind to pre- and postsynaptic G protein-coupled receptors (GPCRs), are able to quickly change intracellular cyclic AMP (cAMP) and Ca2+ levels, and are thought to play important roles in neuropsychiatric and neurodegenerative diseases. Here, we discovered in human neurons an unanticipated presynaptic mechanism that acutely changes synaptic ultrastructure and regulates synaptic communication. Activation of neuromodulator receptors bidirectionally controlled synaptic vesicle numbers within nerve terminals. This control correlated with changes in the levels of cAMP-dependent protein kinase A-mediated phosphorylation of synapsin-1. Using a conditional deletion approach, we reveal that the neuromodulator-induced control of synaptic vesicle numbers was largely dependent on synapsin-1. We propose a mechanism whereby non-phosphorylated synapsin-1 "latches" synaptic vesicles to presynaptic clusters at the active zone. cAMP-dependent phosphorylation of synapsin-1 then removes the vesicles. cAMP-independent dephosphorylation of synapsin-1 in turn recruits vesicles. Synapsin-1 thereby bidirectionally regulates synaptic vesicle numbers and modifies presynaptic neurotransmitter release as an effector of neuromodulator signaling in human neurons.
Asunto(s)
Proteínas Quinasas Dependientes de AMP Cíclico/metabolismo , Terminales Presinápticos/metabolismo , Sinapsinas/metabolismo , Transmisión Sináptica , Vesículas Sinápticas/metabolismo , Animales , Células Cultivadas , Células HEK293 , Humanos , Ratones , Ratones Endogámicos C57BL , Neurotransmisores/metabolismo , Receptores de Neurotransmisores/metabolismo , Transducción de SeñalRESUMEN
To decipher dynamic brain information processing, current genetically encoded calcium indicators (GECIs) are limited in single action potential (AP) detection speed, combinatorial spectral compatibility, and two-photon imaging depth. To address this, here, we rationally engineered a next-generation quadricolor GECI suite, XCaMPs. Single AP detection was achieved within 3-10 ms of spike onset, enabling measurements of fast-spike trains in parvalbumin (PV)-positive interneurons in the barrel cortex in vivo and recording three distinct (two inhibitory and one excitatory) ensembles during pre-motion activity in freely moving mice. In vivo paired recording of pre- and postsynaptic firing revealed spatiotemporal constraints of dendritic inhibition in layer 1 in vivo, between axons of somatostatin (SST)-positive interneurons and apical tufts dendrites of excitatory pyramidal neurons. Finally, non-invasive, subcortical imaging using red XCaMP-R uncovered somatosensation-evoked persistent activity in hippocampal CA1 neurons. Thus, the XCaMPs offer a critical enhancement of solution space in studies of complex neuronal circuit dynamics. VIDEO ABSTRACT.
Asunto(s)
Potenciales de Acción/fisiología , Axones/metabolismo , Corteza Cerebral/metabolismo , Hipocampo/metabolismo , Interneuronas/metabolismo , Células Piramidales/metabolismo , Animales , Corteza Cerebral/citología , Femenino , Hipocampo/citología , Interneuronas/citología , Ratones , Ratones Transgénicos , Células Piramidales/citología , Ratas , Ratas Sprague-DawleyRESUMEN
Tumors weakly infiltrated by T lymphocytes poorly respond to immunotherapy. We aimed to unveil malignancy-associated programs regulating T cell entrance, arrest, and activation in the tumor environment. Differential expression of cell adhesion and tissue architecture programs, particularly the presence of the membrane tetraspanin claudin (CLDN)18 as a signature gene, demarcated immune-infiltrated from immune-depleted mouse pancreatic tumors. In human pancreatic ductal adenocarcinoma (PDAC) and non-small cell lung cancer, CLDN18 expression positively correlated with more differentiated histology and favorable prognosis. CLDN18 on the cell surface promoted accrual of cytotoxic T lymphocytes (CTLs), facilitating direct CTL contacts with tumor cells by driving the mobilization of the adhesion protein ALCAM to the lipid rafts of the tumor cell membrane through actin. This process favored the formation of robust immunological synapses (ISs) between CTLs and CLDN18-positive cancer cells, resulting in increased T cell activation. Our data reveal an immune role for CLDN18 in orchestrating T cell infiltration and shaping the tumor immune contexture.
Asunto(s)
Carcinoma Ductal Pancreático , Claudinas , Activación de Linfocitos , Neoplasias Pancreáticas , Linfocitos T Citotóxicos , Animales , Humanos , Ratones , Carcinoma de Pulmón de Células no Pequeñas/inmunología , Carcinoma de Pulmón de Células no Pequeñas/patología , Carcinoma de Pulmón de Células no Pequeñas/metabolismo , Carcinoma Ductal Pancreático/inmunología , Carcinoma Ductal Pancreático/patología , Carcinoma Ductal Pancreático/metabolismo , Línea Celular Tumoral , Claudinas/metabolismo , Claudinas/genética , Regulación Neoplásica de la Expresión Génica/inmunología , Sinapsis Inmunológicas/metabolismo , Sinapsis Inmunológicas/inmunología , Neoplasias Pulmonares/inmunología , Neoplasias Pulmonares/patología , Activación de Linfocitos/inmunología , Linfocitos Infiltrantes de Tumor/inmunología , Microdominios de Membrana/metabolismo , Microdominios de Membrana/inmunología , Ratones Endogámicos C57BL , Neoplasias Pancreáticas/inmunología , Neoplasias Pancreáticas/patología , Linfocitos T Citotóxicos/inmunología , Microambiente Tumoral/inmunologíaRESUMEN
Inflammatory disorders of the CNS are frequently accompanied by synaptic loss, which is thought to involve phagocytic microglia and complement components. However, the mechanisms accounting for aberrant synaptic connectivity in the context of CD8+ T cell-driven neuronal damage are poorly understood. Here, we profiled the neuronal translatome in a murine model of encephalitis caused by CD8+ T cells targeting antigenic neurons. Neuronal STAT1 signaling and downstream CCL2 expression were essential for apposition of phagocytes, ensuing synaptic loss and neurological disease. Analogous observations were made in the brains of Rasmussen's encephalitis patients. In this devastating CD8+ T cell-driven autoimmune disease, neuronal STAT1 phosphorylation and CCL2 expression co-clustered with infiltrating CD8+ T cells as well as phagocytes. Taken together, our findings uncover an active role of neurons in coordinating phagocyte-mediated synaptic loss and highlight neuronal STAT1 and CCL2 as critical steps in this process that are amenable to pharmacological interventions.
Asunto(s)
Neuronas/metabolismo , Fagocitosis/fisiología , Sinapsis/fisiología , Animales , Encéfalo/patología , Linfocitos T CD8-positivos/inmunología , Linfocitos T CD8-positivos/metabolismo , Quimiocina CCL2/genética , Quimiocina CCL2/fisiología , Modelos Animales de Enfermedad , Encefalitis/genética , Encefalitis/inmunología , Encefalitis/fisiopatología , Femenino , Humanos , Inflamación/inmunología , Inflamación/fisiopatología , Masculino , Ratones , Ratones Endogámicos C57BL , Microglía/metabolismo , Enfermedades del Sistema Nervioso/metabolismo , Neuronas/fisiología , Fagocitos/inmunología , Fagocitos/metabolismo , Fagocitosis/inmunología , Fosforilación , Factor de Transcripción STAT1/fisiología , Transcriptoma/genéticaRESUMEN
N-methyl-D-aspartate receptors (NMDARs) play essential roles in memory formation, neuronal plasticity, and brain development, with their dysfunction linked to a range of disorders from ischemia to schizophrenia. Zinc and pH are physiological allosteric modulators of NMDARs, with GluN2A-containing receptors inhibited by nanomolar concentrations of divalent zinc and by excursions to low pH. Despite the widespread importance of zinc and proton modulation of NMDARs, the molecular mechanism by which these ions modulate receptor activity has proven elusive. Here, we use cryoelectron microscopy to elucidate the structure of the GluN1/GluN2A NMDAR in a large ensemble of conformations under a range of physiologically relevant zinc and proton concentrations. We show how zinc binding to the amino terminal domain elicits structural changes that are transduced though the ligand-binding domain and result in constriction of the ion channel gate.
Asunto(s)
Complejos Multiproteicos/química , Protones , Receptores de N-Metil-D-Aspartato/química , Zinc/química , Regulación Alostérica , Animales , Microscopía por Crioelectrón , Concentración de Iones de Hidrógeno , Complejos Multiproteicos/genética , Complejos Multiproteicos/metabolismo , Complejos Multiproteicos/ultraestructura , Dominios Proteicos , Ratas , Receptores de N-Metil-D-Aspartato/genética , Receptores de N-Metil-D-Aspartato/metabolismo , Células Sf9 , Spodoptera , Zinc/metabolismoRESUMEN
Synapses are semi-membraneless, protein-dense, sub-micron chemical reaction compartments responsible for signal processing in each and every neuron. Proper formation and dynamic responses to stimulations of synapses, both during development and in adult, are fundamental to functions of mammalian brains, although the molecular basis governing formation and modulation of compartmentalized synaptic assemblies is unclear. Here, we used a biochemical reconstitution approach to show that, both in solution and on supported membrane bilayers, multivalent interaction networks formed by major excitatory postsynaptic density (PSD) scaffold proteins led to formation of PSD-like assemblies via phase separation. The reconstituted PSD-like assemblies can cluster receptors, selectively concentrate enzymes, promote actin bundle formation, and expel inhibitory postsynaptic proteins. Additionally, the condensed phase PSD assemblies have features that are distinct from those in homogeneous solutions and fit for synaptic functions. Thus, we have built a molecular platform for understanding how neuronal synapses are formed and dynamically regulated.
Asunto(s)
Neurogénesis , Plasticidad Neuronal , Densidad Postsináptica , Sinapsis/fisiología , Animales , Encéfalo/fisiología , Homólogo 4 de la Proteína Discs Large/fisiología , Hipocampo/fisiología , Luz , Ratones , Microscopía Confocal , Neuronas/fisiología , Dispersión de Radiación , Transducción de Señal , Transmisión SinápticaRESUMEN
Arc/Arg3.1 is required for synaptic plasticity and cognition, and mutations in this gene are linked to autism and schizophrenia. Arc bears a domain resembling retroviral/retrotransposon Gag-like proteins, which multimerize into a capsid that packages viral RNA. The significance of such a domain in a plasticity molecule is uncertain. Here, we report that the Drosophila Arc1 protein forms capsid-like structures that bind darc1 mRNA in neurons and is loaded into extracellular vesicles that are transferred from motorneurons to muscles. This loading and transfer depends on the darc1-mRNA 3' untranslated region, which contains retrotransposon-like sequences. Disrupting transfer blocks synaptic plasticity, suggesting that transfer of dArc1 complexed with its mRNA is required for this function. Notably, cultured cells also release extracellular vesicles containing the Gag region of the Copia retrotransposon complexed with its own mRNA. Taken together, our results point to a trans-synaptic mRNA transport mechanism involving retrovirus-like capsids and extracellular vesicles.
Asunto(s)
Proteínas del Citoesqueleto/metabolismo , Productos del Gen gag/genética , Cuerpos Multivesiculares/metabolismo , Proteínas del Tejido Nervioso/metabolismo , Terminales Presinápticos/metabolismo , ARN Mensajero/metabolismo , Animales , Transporte Biológico , Células Cultivadas , Proteínas del Citoesqueleto/química , Proteínas del Citoesqueleto/genética , Drosophila , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Productos del Gen gag/química , Proteínas del Tejido Nervioso/química , Proteínas del Tejido Nervioso/genética , Unión Neuromuscular/metabolismo , Plasticidad Neuronal , Péptido Hidrolasas/genética , Péptido Hidrolasas/metabolismo , Terminales Presinápticos/fisiología , Unión Proteica , Dominios Proteicos , Retroelementos/genéticaRESUMEN
Regulated synthesis and movement of proteins between cellular organelles are central to diverse forms of biological adaptation and plasticity. In neurons, the repertoire of channel, receptor, and adhesion proteins displayed on the cell surface directly impacts cellular development, morphology, excitability, and synapse function. The immensity of the neuronal surface membrane and its division into distinct functional domains present a challenging landscape over which proteins must navigate to reach their appropriate functional domains. This problem becomes more complex considering that neuronal protein synthesis is continuously refined in space and time by neural activity. Here we review our current understanding of how integral membrane and secreted proteins important for neuronal function travel from their sites of synthesis to their functional destinations. We discuss how unique adaptations to the function and distribution of neuronal secretory organelles may facilitate local protein trafficking at remote sites in neuronal dendrites to support diverse forms of synaptic plasticity.
Asunto(s)
Aparato de Golgi/metabolismo , Plasticidad Neuronal/fisiología , Neuronas/citología , Neuronas/metabolismo , Transporte de Proteínas/fisiología , Animales , Compartimento Celular/fisiología , Membrana Celular/metabolismo , Dendritas/metabolismo , Dendritas/fisiología , Retículo Endoplásmico/metabolismo , Endosomas/metabolismo , Proteínas de la Membrana/biosíntesis , Proteínas de la Membrana/metabolismo , Neuronas/fisiología , Sinapsis/metabolismo , Sinapsis/fisiologíaRESUMEN
Childhood neglect and/or abuse can induce mental health conditions with unknown mechanisms. Here, we identified stress hormones as strong inducers of astrocyte-mediated synapse phagocytosis. Using in vitro, in vivo, and human brain organoid experiments, we showed that stress hormones increased the expression of the Mertk phagocytic receptor in astrocytes through glucocorticoid receptor (GR). In post-natal mice, exposure to early social deprivation (ESD) specifically activated the GR-MERTK pathway in astrocytes, but not in microglia. The excitatory post-synaptic density in cortical regions was reduced in ESD mice, and there was an increase in the astrocytic engulfment of these synapses. The loss of excitatory synapses, abnormal neuronal network activities, and behavioral abnormalities in ESD mice were largely prevented by ablating GR or MERTK in astrocytes. Our work reveals the critical roles of astrocytic GR-MERTK activation in evoking stress-induced abnormal behaviors in mice, suggesting GR-MERTK signaling as a therapeutic target for stress-induced mental health conditions.
Asunto(s)
Astrocitos , Fagocitosis , Estrés Psicológico , Animales , Niño , Humanos , Ratones , Astrocitos/metabolismo , Tirosina Quinasa c-Mer/genética , Hormonas/metabolismo , Sinapsis/metabolismo , Estrés Psicológico/metabolismoRESUMEN
AMPA receptors mediate fast excitatory neurotransmission in the mammalian brain and transduce the binding of presynaptically released glutamate to the opening of a transmembrane cation channel. Within the postsynaptic density, however, AMPA receptors coassemble with transmembrane AMPA receptor regulatory proteins (TARPs), yielding a receptor complex with altered gating kinetics, pharmacology, and pore properties. Here, we elucidate structures of the GluA2-TARP γ2 complex in the presence of the partial agonist kainate or the full agonist quisqualate together with a positive allosteric modulator or with quisqualate alone. We show how TARPs sculpt the ligand-binding domain gating ring, enhancing kainate potency and diminishing the ensemble of desensitized states. TARPs encircle the receptor ion channel, stabilizing M2 helices and pore loops, illustrating how TARPs alter receptor pore properties. Structural and computational analysis suggests the full agonist and modulator complex harbors an ion-permeable channel gate, providing the first view of an activated AMPA receptor.
Asunto(s)
Canales de Calcio/química , Receptores AMPA/química , Animales , Microscopía por Crioelectrón , Agonistas de Aminoácidos Excitadores/química , Agonistas de Aminoácidos Excitadores/farmacología , Ácido Kaínico/química , Ácido Kaínico/farmacología , Modelos Moleculares , Ácido Quiscuálico/química , Ácido Quiscuálico/farmacología , Ratas , Receptores AMPA/agonistasRESUMEN
Lipids represent the most abundant molecular type in the brain with a fat content of approximately 60% of the dry brain weight in humans. Despite this fact, little attention has been paid to circumscribe the dynamic role of lipids in brain function and disease. Membrane lipids such as cholesterol, phosphoinositide, sphingolipids, arachidonic acid and endocannabinoids finely regulate both synaptic receptors and ion channels that insure critical neural functions. After a brief introduction on brain lipids and their respective properties, we review here their role in regulating synaptic function and ion channel activity, action potential propagation, neuronal development, functional plasticity and their contribution in the development of neurological and neuropsychiatric diseases. We also provide possible directions for future research on lipid function in brain plasticity and diseases.